WO2019096121A1

WO2019096121A1 - Single-domain antibodies and variants thereof against pd-l1

Info

Publication number: WO2019096121A1
Application number: PCT/CN2018/115213
Authority: WO
Inventors: Yafeng Zhang; Shu Wu; Shuai Yang; Chuan-Chu Chou
Original assignee: Nanjing Legend Biotech Co., Ltd.
Priority date: 2017-11-17
Filing date: 2018-11-13
Publication date: 2019-05-23
Also published as: JP2021503455A; EP3710480A4; AU2018366650A1; CN111433224B; EP3710480A1; KR20200106885A; SG11202004144VA; IL274438A; CA3081375A1; US20210221891A1; TW201923083A; CN111433224A; JP7410024B2; US11673954B2

Abstract

Provided are constructs comprising a single-domain antibody (sdAb) moiety that specifically recognizes PD-L1. Also provided are methods of making and using these constructs.

Description

SINGLE-DOMAIN ANTIBODIES AND VARIANTS THEREOF AGAINST PD-L1

SUBMISSION OF SEQUENCE LISTING ON ASCII TEXT FILE

The content of the following submission on ASCII text file is incorporated herein by reference in its entirety: a computer readable form (CRF) of the Sequence Listing (file name: 688096.97 Sequence Listing, date recorded: November 1, 2017, size: 271kb) .

FIELD OF THE INVENTION

The present invention relates to constructs comprising a single-domain antibody (sdAb) moiety that specifically recognizes PD-L1, and methods of making and using thereof.

BACKGROUND OF THE INVENTION

An immune inhibitory receptor that is primarily expressed on activated T and B cells, Programmed Cell Death Receptor 1, also referred to as Programmed Death Receptor 1 (PD-1) , is a member of the immunoglobulin superfamily related to CD28 and cytotoxic T-lymphocyte associated protein-4 (CTLA-4) . PD-1 and like family members are type I transmembrane glycoproteins containing an extracellular Ig Variable-type (V-type) domain that binds its ligands and a cytoplasmic tail that binds signaling molecules. The cytoplasmic tail of PD-1 contains two tyrosine-based signaling motifs, an ITIM (immunoreceptor tyrosine-based inhibition motif) and an ITSM (immunoreceptor tyrosine-based switch motif) .

PD-1 attenuates T-cell responses when bound to Programmed Cell Death Ligand 1, also referred to as Programmed Death Ligand 1 (PD-Ll) , and/or Programmed Cell Death Ligand 2, also referred to as Programmed Death Ligand 2 (PD-L2) . The binding of either of these ligands to PD-1 negatively regulates antigen receptor signaling. Blocking the binding of PD-Ll to PD-1 enhances tumor-specific CD8+ T-cell immunity, while aiding the clearance of tumor cells by the immune system.

As a result, therapeutic targeting PD-1 and other molecules which signal through interactions with PD-1, such as programmed death ligand 1 (PD-L1) and programmed death ligand 2 (PD-L2) are an area of intense interest. The inhibition of PD-L1 signaling has been proposed as a means to enhance T cell immunity for the treatment of cancer (e.g., tumor immunity) and infection, including both acute and chronic (e.g., persistent) infection. However, as an optimal therapeutic directed to a target in this pathway has yet to be commercialized, a significant unmet medical need exists. Anti-PD-L1 antibody therapy has shown promise in a number of cancers, such as melanoma.

Single-chain antibodies (sdAbs) are different from conventional 4-chain antibodies by having a single monomeric antibody variable domain. For example, camelids and sharks produce single-domain antibodies named heavy chain-only antibodies (HCAbs) , which naturally lack light chains. The antigen-binding fragment in each arm of the camelid HCAb has a single heavy chain variable domain (V _HH) , which can exhibit high affinity to an antigen without the aid of a light chain. Camelid V _HH is known as the smallest functional antigen-binding fragment with a molecular weight of approximately 15 kD.

The disclosures of all publications, patents, patent applications and published patent applications referred to herein are hereby incorporated herein by reference in their entirety.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present application provides an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions.

In some embodiments according to any one of the isolated anti-PD-L1 constructs described above, the sdAb moiety specifically recognizing PD-L1 comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300.

In some embodiments according to any one of the isolated anti-PD-L1 constructs described above, the sdAb moiety specifically recognizing PD-L1 comprises any one of the following:

(1) a CDR1 comprising the amino acid sequence of SEQ ID NO: 51, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 151, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 251, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(2) a CDR1 comprising the amino acid sequence of SEQ ID NO: 52, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 152, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 252, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(3) a CDR1 comprising the amino acid sequence of SEQ ID NO: 53, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 153, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 253, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(4) a CDR1 comprising the amino acid sequence of SEQ ID NO: 54, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 154, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 254, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(5) a CDR1 comprising the amino acid sequence of SEQ ID NO: 55, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 155, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 255, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(6) a CDR1 comprising the amino acid sequence of SEQ ID NO: 56, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 156, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 256, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(7) a CDR1 comprising the amino acid sequence of SEQ ID NO: 57, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 157, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 257, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(8) a CDR1 comprising the amino acid sequence of SEQ ID NO: 58, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 158, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 258, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(9) a CDR1 comprising the amino acid sequence of SEQ ID NO: 59, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 159, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 259, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(10) a CDR1 comprising the amino acid sequence of SEQ ID NO: 60, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 160, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 260, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(11) a CDR1 comprising the amino acid sequence of SEQ ID NO: 61, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 161, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 261, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(12) a CDR1 comprising the amino acid sequence of SEQ ID NO: 62, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 162, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 262, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(13) a CDR1 comprising the amino acid sequence of SEQ ID NO: 63, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 163, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 263, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(14) a CDR1 comprising the amino acid sequence of SEQ ID NO: 64, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 164, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 264, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(15) a CDR1 comprising the amino acid sequence of SEQ ID NO: 65, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 165, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 265, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(16) a CDR1 comprising the amino acid sequence of SEQ ID NO: 66, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 166, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 266, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(17) a CDR1 comprising the amino acid sequence of SEQ ID NO: 67, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 167, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 267, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(18) a CDR1 comprising the amino acid sequence of SEQ ID NO: 68, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 168, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 268, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(19) a CDR1 comprising the amino acid sequence of SEQ ID NO: 69, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 169, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 269, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(20) a CDR1 comprising the amino acid sequence of SEQ ID NO: 70, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 170, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 270, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(21) a CDR1 comprising the amino acid sequence of SEQ ID NO: 71, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 171, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 271, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(22) a CDR1 comprising the amino acid sequence of SEQ ID NO: 72, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 172, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 272, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(23) a CDR1 comprising the amino acid sequence of SEQ ID NO: 73, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 173, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 273, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(24) a CDR1 comprising the amino acid sequence of SEQ ID NO: 74, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 174, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 274, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(25) a CDR1 comprising the amino acid sequence of SEQ ID NO: 75, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 175, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 275, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(26) a CDR1 comprising the amino acid sequence of SEQ ID NO: 76, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 176, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 276, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(27) a CDR1 comprising the amino acid sequence of SEQ ID NO: 77, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 177, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 277, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(28) a CDR1 comprising the amino acid sequence of SEQ ID NO: 78, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 178, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 278, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(29) a CDR1 comprising the amino acid sequence of SEQ ID NO: 79, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 179, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 279, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(30) a CDR1 comprising the amino acid sequence of SEQ ID NO: 80, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 180, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 280, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(31) a CDR1 comprising the amino acid sequence of SEQ ID NO: 81, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 181, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 281, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(32) a CDR1 comprising the amino acid sequence of SEQ ID NO: 82, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 182, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 282, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(33) a CDR1 comprising the amino acid sequence of SEQ ID NO: 83, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 183, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 283, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(34) a CDR1 comprising the amino acid sequence of SEQ ID NO: 84, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 184, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 284, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(35) a CDR1 comprising the amino acid sequence of SEQ ID NO: 85, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 185, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 285, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(36) a CDR1 comprising the amino acid sequence of SEQ ID NO: 86, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 186, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 286, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(37) a CDR1 comprising the amino acid sequence of SEQ ID NO: 87, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 187, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 287, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(38) a CDR1 comprising the amino acid sequence of SEQ ID NO: 88, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 188, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 288, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(39) a CDR1 comprising the amino acid sequence of SEQ ID NO: 89, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 189, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 289, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(40) a CDR1 comprising the amino acid sequence of SEQ ID NO: 90, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 190, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 290, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(41) a CDR1 comprising the amino acid sequence of SEQ ID NO: 91, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 191, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 291, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(42) a CDR1 comprising the amino acid sequence of SEQ ID NO: 92, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 192, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 292, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(43) a CDR1 comprising the amino acid sequence of SEQ ID NO: 93, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 193, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 293, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(44) a CDR1 comprising the amino acid sequence of SEQ ID NO: 94, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 194, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 294, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(45) a CDR1 comprising the amino acid sequence of SEQ ID NO: 95, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 195, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 295, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(46) a CDR1 comprising the amino acid sequence of SEQ ID NO: 96, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 196, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 296, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(47) a CDR1 comprising the amino acid sequence of SEQ ID NO: 97, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 197, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 297, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(48) a CDR1 comprising the amino acid sequence of SEQ ID NO: 98, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 198, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 298, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(49) a CDR1 comprising the amino acid sequence of SEQ ID NO: 99, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 199, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 299, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions;

(50) a CDR1 comprising the amino acid sequence of SEQ ID NO: 100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of SEQ ID NO: 200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 300, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions.

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the sdAb moiety specifically recognizing PD-L1 comprises a V _HH domain having an amino acid sequence containing one or more of the following amino acid residues: a-1) an amino acid residue at position 37 selected from the group consisting of F, Y, L, I, and V, preferably F, V or Y; a-2) an amino acid residue at position 44 selected from the group consisting of A, G, E, D, G, Q, R, S, and L, preferably G, E, or Q; a-3) an amino acid residue at position 45 selected from the group consisting of L, R and C, preferably such as L or R; a-4) an amino acid residue at position 103 selected from the group consisting of G, W, R and S, preferably W or R, more preferably W; and a-5) an amino acid residue at position 108 being Q, wherein the positions are according to the Kabat numbering.

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the sdAb moiety specifically recognizing PD-L1 comprises a V _HH domain having an amino acid sequence containing one or more of the following amino acid residues: b-1) an amino acid residue at position 37 selected from the group consisting of F, Y, L, I, and V, preferably F, V or Y; b-2) an amino acid residue at position 44 selected from the group consisting of G, E and Q; b-3) an amino acid residue at position 45 being R or L; b-4) an amino acid residue at position 103 selected from the group consisting of G, W, R and S, preferably W and b-5) an amino acid residue at position 108 selected from the group consisting of Q and L, preferably Q, wherein the positions are according to the Kabat numbering.

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the sdAb moiety specifically recognizing PD-L1 comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof having at least about 80% (such as at least about any of 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) sequence identify to any one of SEQ ID NOs: 288-328. In some embodiments, the sdAb moiety specifically recognizing PD-L1 comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the V _HH domain. In some embodiments, the sdAb moiety specifically recognizing PD-L1 comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400.

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the affinity (K _D, dissociation constant) of the binding between the sdAb moiety specifically recognizing PD-L1 and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-5 M to about 10 ^-12 M, about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) .

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the sdAb moiety specifically recognizing PD-L1 is camelid, chimeric, human, partially humanized, or fully humanized.

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the isolated anti-PD-L1 construct is a heavy chain-only antibody (HCAb) . In some embodiments, the sdAb moiety specifically recognizing PD-L1 is fused to a human IgG1 Fc. In some embodiments, the HCAb is monomeric or dimeric. In some embodiments, the sdAb moiety specifically recognizing PD-L1 comprises the amino acid sequence of SEQ ID NO: 351-400. In some embodiments, the HCAb comprises the amino acid sequence of any one of SEQ ID NOs: 401-440.

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the isolated anti-PD-L1 construct further comprises a second antibody moiety specifically recognizing a second antigen. In some embodiments, the second antibody moiety is a full-length antibody, a Fab, a Fab’, a (Fab’) 2, an Fv, a single chain Fv (scFv) , an scFv-scFv, a minibody, a diabody, a sdAb, or an antibody mimetics. In some embodiments, the anti-PD-L1 construct is monospecific. In some embodiments, the anti-PD-L1 construct is multispecific. In some embodiments, the second antibody moiety is a sdAb. In some embodiments, the second antigen is PD-L1. In some embodiments, the isolated anti-PD-L1 construct comprises three or more sdAbs that specifically recognize PD-L1. In some embodiments, the second antigen is human serum albumin (HSA) . In some embodiments, the sdAb moiety specifically recognizing PD-L1 is amino (N) -terminal and/or carboxyl (C) -terminal to the second antibody moiety. In some embodiments, the sdAb moiety specifically recognizing PD-L1 and the second antibody moiety are optionally connected by a peptide linker (such as SEQ ID NO: 443, 444, or 445) .

In some embodiments according to any one of the isolated anti-PD-L1 construct described above, the isolated anti-PD-L1 construct further comprises a second antibody moiety specifically recognizing a second antigen, wherein the second antibody moiety is a full-length antibody. In some embodiments, the amino (N) -terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the carboxy (C) -terminus of at least one of the heavy chains of the full-length antibody. In some embodiments, the C-terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the N-terminus of at least one of the heavy chains of the full-length antibody. In some embodiments, the full-length antibody specifically recognizes TIGIT. In some embodiments, the full-length antibody specifically recognizes TIM-3. In some embodiments, the full-length antibody specifically recognizes LAG-3. In some embodiments, the sdAb moiety specifically recognizing PD-L1 comprises the amino acid sequence of SEQ ID NO: 351 -400. In some embodiments, the sdAb moiety specifically recognizing PD-L1 and the second antibody moiety are optionally connected by a peptide linker (SEQ ID NO: 443-445) .

Further provided is a second isolated anti-PD-L1 construct that specifically binds to PD-L1 competitively with any one of the isolated anti-PD-L1 construct described above. In some embodiments, the second isolated anti-PD-L1 construct comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions.

Further provided is a pharmaceutical composition comprising any one of the isolated anti-PD-L1 constructs described above, and a pharmaceutical acceptable carrier.

Another aspect of the present application provides a method of treating an individual having a PD-L1-related disease, comprising administering to the individual an effective amount of any one of the pharmaceutical composition described above. In some embodiments, the PD-L1 related disease is cancer. In some embodiments, the cancer is a solid tumor, such as a colon cancer. In some embodiments, the method further comprises administering to the individual an additional cancer therapy, such as surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or a combination thereof. In some embodiments, the PD-L1 related disease is a pathogenic infection. In some embodiments, the pharmaceutical composition is administered systemically, such as intravenously (i. v. ) . In some embodiments, the pharmaceutical composition is administered locally, such as intratumorally. In some embodiments, the individual is a human.

Further provided is an isolated nucleic acid encoding any one of the isolated anti-PD-L1 construct described above. In some embodiments, the isolated nucleic acid encodes an amino acid sequence selected from any one of SEQ ID NOs: 351-400.

Further provided is a vector comprising any one of the isolated nucleic acids described above.

Further provided is an isolated host cell comprising any one of the isolated nucleic acids or vectors described above.

Further provided is a kit comprising any one of the isolated anti-PD-L1 constructs, isolated nucleic acids, vectors, or isolated host cells described above.

Another aspect of the present application provides a method of producing any one of isolated anti-PD-L1 constructs described above, comprising culturing a host cell comprising any one of the isolated nucleic acids or vectors described above, or culturing any one of the isolated host cells described above, under conditions effective to express the encoded anti-PD-L1 construct; and obtaining the expressed anti-PD-L1 construct from said host cell. In some embodiments, the method further comprises producing a host cell comprising any one of the isolated nucleic acids or vectors described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

Figure 1 depicts immune response evaluation of pre-immune serum and immune serum after the 4 ^th and 6 ^th immunization with recombinant PD-L1 ECD protein.

Figure 2 depicts the immune response evaluation of heavy chain antibodies (IgG2 and IgG3) after the 6 ^th immunization (terminal bleed) with recombinant PD-L1 ECD protein; heavy chain antibodies fractionated from pre-immune serum were used as negative controls.

Figures 3A-3N depict the affinity determination of selected sdAbs (AS06617 (Figure 3A) ; AS06618 (Figure 3B) ; AS06628 (Figure 3C) ; AS06682 (Figure 3D) ; AS06686 (Figure 3E) ; AS06703 (Figure 3F) ; AS06730 (Figure 3G) ; AS06750 (Figure 3H) ; AS06775 (Figure 3I) ; AS06778 (Figure 3J) ; AS06791 (Figure 3K) ; AS11947 (Figure 3L) ; AS11948 (Figure 3M) ; and AS12003 (Figure 3N) ) : the PD-L1 was immobilized onto the chip and anti-PD-L1 sdAb was flowed as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM.

Figures 4A-4N depict the affinity determination of selected sdAbs (AS06617 (Figure 4A) ; AS06618 (Figure 4B) ; AS06628 (Figure 4C) ; AS06682 (Figure 4D) ; AS06686 (Figure 4E) ; AS06703 (Figure 4F) ; AS06730 (Figure 4G) ; AS06750 (Figure 4H) ; AS06775 (Figure 4I) ; AS06778 (Figure 4J) ; AS06791 (Figure 4K) ; AS11947 (Figure 4L) ; AS11948 (Figure 4M) ; and AS12003 (Figure 4N) ) : the PD-L1 was immobilized onto the chip and anti-PD-L1 HCAb was flowed as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM.

Figures 5A and 5B depict the relative binding assay of selected anti-PD-L1 HCAbs based FACS using PD-L1 stably expressing cell line:

was used as a positive anti-PD-L1 antibody control.

Figures 6A and 6B depict FACS-based ligand competition assay of selected anti-PD-L1 HCAbs by using PD-L1 expressing stable cell line and biotin-labeled hPD-1/Fc protein:

was used as a positive anti-PD-L1 antibody control.

Figures 7A-7O depict functional activity evaluation of purified sdAbs (AS06617 (Figure 7A) ; AS06618 (Figure 7B) ; AS06628 (Figure 7C) ; AS06682 (Figure 7D) ; AS06686 (Figure 7E) ; AS06703 (Figure 7F) ; AS06730 (Figure 7G) ; AS06750 (Figure 7H) ; AS06775 (Figure 7I) ; AS06778 (Figure 7J) ; AS06791 (Figure 7K) ; AS11947 (Figure 7L) ; AS11948 (Figure 7M) ; AS12003 (Figure 7N) ; and Tecentriq (Figure 7O) ) by PD-L1-based blockade assay:

was used as a positive anti-PD-L1 antibody control.

Figures 8A-8O depict functional activity evaluation of purified top HCAbs (AS06617 (Figure 8A); AS06618 (Figure 8B) ; AS06628 (Figure 8C) ; AS06682 (Figure 8D) ; AS06686 (Figure 8E) ; AS06703 (Figure 8F) ; AS06730 (Figure 8G) ; AS06750 (Figure 8H) ; AS06775 (Figure 8I) ; AS06778 (Figure 8J) ; AS06791 (Figure 8K) ; AS11947 (Figure 8L) ; AS11948 (Figure 8M) ; AS12003 (Figure 8N) ; and Tecentriq (Figure 8O) ) by PD-L1-based blockade assay:

served as a positive anti-PD-L1 antibody control.

Figures 9A-9E depict sdAb sequences alignment of three WT anti-PD-L1 sdAbs and top 1-9 clones after humanization, amino acid differences in the framework regions relative to the human acceptor (best human germline sequence sharing the highest degree of homology with WT sdAb) are shaded in dark grey:

Figure 9A depicts the sdAb sequences alignment of AS06730 (SEQ ID NO: 360) , the top 9 clones after humanization (SEQ ID NOs: 376-384) , and the consensus sequence;

Figure 9B depicts the sdAb sequences alignment of AS06750 (SEQ ID NO: 361) , the top 5 clones (SEQ ID NOs: 385-389) after humanization, and the consensus sequence; and

Figure 9C depicts the sdAb sequences alignment of AS11948 (SEQ ID NO: 372) , the top 9 clones (SEQ ID NOs: 390-398) after humanization, and the consensus sequence;

Figure 9D depicts the sdAb sequences alignment of AS06617 (SEQ ID NO: 351) , the top 1 clone (SEQ ID NO: 399) after humanization, and the consensus sequence;

Figure 9E depicts the sdAb sequences alignment of AS06775 (SEQ ID NO: 365) , the top 1 clone (SEQ ID NO: 400) after humanization, and the consensus sequence.

Figures 10A-10T depict the affinity determination of selected humanized HCAbs along with the parent HCAbs:

Figures 10A-10C (AS06730 (Figure 10A) ; AS06730S (Figure 10B) ; AS06730SVH3a (Figure 10C) ) : The affinity determination was done using PD-L1His being immobilized onto the chip and anti-PD-L1 HCAb as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM;

Figures 10D-10F (AS06730SVH12 (Figure 10D) ; AS06730SVH12M8 (Figure 10E) ; AS06730SVH12M9 (Figure 10F) ) : The affinity determination was done using HCAbs being captured onto the chip by anti-human IgG and PD-L1 His as analyte at concentrations of 0.33, 1, 3, 9 and 27 nM;

Figures 10G-10J (AS06750 (Figure 10G) ; AS06750VH2 (Figure 10H) ; AS06750VH11 (Figure 10I) ; AS06750VH4 (Figure 10J) ) , The affinity determination was done using PD-L1 His being immobilized onto the chip and anti-PD-L1 HCAb as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM;

Figures 10K-10L (AS11948 (Figure 10K) ; AS11948S (Figure 10L) ) : The affinity determination was done using PD-L1 His being immobilized onto the chip and anti-PD-L1 HCAb as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM;

Figures 10M-10O (AS11948SV12 (Figure 10M) ; AS11948SV12M8 (Figure 10N) ; AS11948V12M9 (Figure 10O) ) : The affinity determination was done using HCAbs being captured onto the chip by anti-human IgG and PD-L1 His as analyte at concentrations of 0.33, 1, 3, 9 and 27 nM;

Figures 10P-10Q (AS06617 (Figure 10P) ; AS06617VH11 (Figure 10Q) ) : The affinity determination was done using PD-L1 His being immobilized onto the chip and anti-PD-L1 HCAb as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM;

Figures 10R-10T (AS06775 (Figure 10R) ; AS06775VH11 (Figure 10S) ; AS06775VH4 (Figure 10T) ) : The affinity determination was done using PD-L1 His being immobilized onto the chip and anti-PD-L1 His as analyte at concentrations of 0.11, 0.33, 1, 3, and 9 nM.

Figures 11A-11Q (AS06730 (Figure 11A) ; AS06730S (Figure 11B) ; AS06730SVH3a (Figure 11C) ; AS06730SVH12 (Figure 11D) ; AS06750 (Figure 11E) ; AS06750VH2 (Figure 11F) ; AS06750VH11 (Figure 11G) ; AS06750VH4 (Figure 11H) ; AS11948 (Figure 11I) ; AS11948S (Figure 11J) ; AS11948SVH12 (Figure 11K) ; AS11948SVH12M8 (Figure 11L) ; AS06617 (Figure 11M) ; AS06617VH11 (Figure 11N) ; AS06775 (Figure 11O) ; AS06775VH11 (Figure 11P) ; AS06775VH4 (Figure 11Q) ) depict functional activity evaluation of purified top humanized HCAbs along with the parent HCAbs by PD-L1-based blockade assay.

Figure 12 depicts the in vivo efficacy study of 6 humanized HCAbs (AS06730QVH1, AS06750VH11, AS11948SVH12, AS06617VH11, AS06617VH11, AS11948QVH1 and AS06775VH11) .

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a single-domain antibody (sdAb) specifically recognizing PD-L1 (hereinafter also referred to as “anti-PD-L1 sdAb” ) and its antibody variants, including but not limited to, a larger protein or polypeptide comprising the anti-PD-L1 sdAb, such as a heavy chain-only antibody (HCAb) , or an anti-PD-L1 sdAb fused to a full-length antibody or an antigen-binding fragment thereof, as a new strategy to treat PD-L1-related diseases, such as cancer.

Single-chain antibodies (sdAbs) are different from conventional 4-chain antibodies by having a single monomeric antibody variable domain, such as heavy chain variable domain (V _HH) , which can exhibit high affinity to an antigen without the aid of a light chain. Camelid V _HH is known as the smallest functional antigen-binding fragment with a molecular weight of approximately 15 kD.

Accordingly, one aspect of the present application provides an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1. The isolated anti-PD-L1 construct can be, for example, an anti-PD-L1 sdAb (e.g. natural or humanized) , a polypeptide comprising multiple anti-PD-L1 sdAbs described herein fused together, an HCAb comprising an anti-PD-L1 sdAb described herein fused to a human IgG1 Fc, or an anti-PD-L1 sdAb fused to a full-length antibody, such as an anti-PD-1 antibody, or an anti-PD-L1 antibody, or an antigen-binding fragment thereof. The anti-PD-L1 construct can be monospecific or multispecific, monovalent or multivalent.

Also provided are compositions (such as pharmaceutical compositions) , kits and articles of manufacture comprising the construct comprising an anti-PD-L1 sdAb moiety, methods of making the construct comprising an anti-PD-L1 sdAb moiety, and methods of treating PD-L1 related disease (such as cancer) using the construct comprising an anti-PD-L1 sdAb moiety.

I. Definitions

The terms “Programmed cell death 1 ligand 1, ” “PD-L1, ” “B7 homolog 1 (B7-H1) , ” “PD-L1 antigen” , “PDCD1 ligand 1” and “CD274” (see, e.g., Chemnitz (2004) J. Immunol. 173: 945-954) are used interchangeably, and include variants, isoforms, species homologs of human PD-L1, and analogs having at least one common epitope with PD-L1 (see, e.g., Butte (2008) Mol Immunol. 45: 3567-3572) . Accordingly, the anti-PD-L1 construct of the invention can, in certain cases, cross-react with PD-L1 from species other than human, or other proteins which are structurally related to human PD-L1 (e.g., human PD-L1 homologs) . In other cases, the anti-PD-L1 construct can be completely specific for human PD-L1 and not exhibit species or other types of cross-reactivity.

The term “human PD-L1” refers to human sequence PD-L1, such as the complete amino acid sequence of human PD-L1 having Genbank Accession Number Q9NZQ7. The human PD-L1 sequence can differ from human PD-L1 of Genbank Accession Number Q9NZQ7 by having, for example, conserved mutations or mutations in non-conserved regions and the PD-L1 has substantially the same biological function as the human PD-L1 of Genbank Accession Number Q9NZQ7. For example, a biological function of human PD-L1 is having an epitope in the extracellular domain of PD-L1 that is specifically bound by an anti-PD-L1 construct of the instant disclosure or a biological function of human PD-L1 is modulation of T cell activity.

The term “epitope” means a protein determinant capable of specific binding to an antibody. Epitopes usually consist of chemically active surface groupings of molecules such as amino acids or sugar side chains and usually have specific three dimensional structural characteristics, as well as specific charge characteristics. Conformational and nonconformational epitopes are distinguished in that the binding to the former but not the latter is lost in the presence of denaturing solvents.

The term “Programmed cell death 1 (PD-1) ” as used herein is intended to refer to a cell surface receptor that belongs to the immunoglobulin superfamily and is expressed on T cells and pro-B cells. The amino acid sequences of human B7-1 (CD80) are disclosed at Genbank Accession Numbers NP_005009.

As used herein, “treatment” or “treating” is an approach for obtaining beneficial or desired results including clinical results. For purposes of this invention, beneficial or desired clinical results include, but are not limited to, one or more of the following: alleviating one or more symptoms resulting from the disease, diminishing the extent of the disease, stabilizing the disease (e.g., preventing or delaying the worsening of the disease) , preventing or delaying the spread (e.g., metastasis) of the disease, preventing or delaying the recurrence of the disease, delay or slowing the progression of the disease, ameliorating the disease state, providing a remission (partial or total) of the disease, decreasing the dose of one or more other medications required to treat the disease, delaying the progression of the disease, increasing the quality of life, and/or prolonging survival. Also encompassed by “treatment” is a reduction of pathological consequence of cancer. The methods of the invention contemplate any one or more of these aspects of treatment.

The term “effective amount” used herein refers to an amount of an agent or a combination of agents, sufficient to treat a specified disorder, condition or disease such as ameliorate, palliate, lessen, and/or delay one or more of its symptoms. In reference to cancer, an effective amount comprises an amount sufficient to cause a tumor to shrink and/or to decrease the growth rate of the tumor (such as to suppress tumor growth) or to prevent or delay other unwanted cell proliferation. In some embodiments, an effective amount is an amount sufficient to delay development. In some embodiments, an effective amount is an amount sufficient to prevent or delay recurrence. An effective amount can be administered in one or more administrations. The effective amount of the drug or composition may: (i) reduce the number of cancer cells; (ii) reduce tumor size; (iii) inhibit, retard, slow to some extent and preferably stop cancer cell infiltration into peripheral organs; (iv) inhibit (i.e., slow to some extent and preferably stop) tumor metastasis; (v) inhibit tumor growth; (vi) prevent or delay occurrence and/or recurrence of tumor; and/or (vii) relieve to some extent one or more of the symptoms associated with the cancer.

The term “antibody” or “antibody moiety” is used in the broadest sense and encompasses various antibody structures, including but not limited to monoclonal antibodies, polyclonal antibodies, multispecific antibodies (e.g., bispecific antibodies) , full-length antibodies and antigen-binding fragments thereof, so long as they exhibit the desired antigen-binding activity.

The basic 4-chain antibody unit is a heterotetrameric glycoprotein composed of two identical light (L) chains and two identical heavy (H) chains. An IgM antibody consists of 5 of the basic heterotetramer units along with an additional polypeptide called a J chain, and contains 10 antigen-binding sites, while IgA antibodies comprise from 2-5 of the basic 4-chain units which can polymerize to form polyvalent assemblages in combination with the J chain. In the case of IgGs, the 4-chain unit is generally about 150, 000 Daltons. Each L chain is linked to an H chain by one covalent disulfide bond, while the two H chains are linked to each other by one or more disulfide bonds depending on the H chain isotype. Each H and L chain also has regularly spaced intrachain disulfide bridges. Each H chain has at the N-terminus, a variable domain (V _H) followed by three constant domains (C _H) for each of the α and γchains and four C _H domains for μ and ε isotypes. Each L chain has at the N-terminus, a variable domain (V _L) followed by a constant domain at its other end. The V _L is aligned with the V _H and the C _L is aligned with the first constant domain of the heavy chain (C _H1) . Particular amino acid residues are believed to form an interface between the light chain and heavy chain variable domains. The pairing of a V _H and V _L together forms a single antigen-binding site. For the structure and properties of the different classes of antibodies, see e.g., Basic and Clinical Immunology, 8th Edition, Daniel P. Sties, Abba I. Terr and Tristram G. Parsolw (eds) , Appleton &Lange, Norwalk, Conn., 1994, page 71 and Chapter 6. The L chain from any vertebrate species can be assigned to one of two clearly distinct types, called kappa and lambda, based on the amino acid sequences of their constant domains. Depending on the amino acid sequence of the constant domain of their heavy chains (C _H) , immunoglobulins can be assigned to different classes or isotypes. There are five classes of immunoglobulins: IgA, IgD, IgE, IgG and IgM, having heavy chains designated α, δ, ε, γ and μ, respectively. The γ and α classes are further divided into subclasses on the basis of relatively minor differences in the C _H sequence and function, e.g., humans express the following subclasses: IgG1, IgG2A, IgG2B, IgG3, IgG4, IgA1 and IgA2.

The term “heavy chain-only antibody” or “HCAb” refers to a functional antibody, which comprises heavy chains, but lacks the light chains usually found in 4-chain antibodies. Camelid animals (such as camels, llamas, or alpacas) are known to produce HCAbs.

The term “single-domain antibody” or “sdAb” refers to a single antigen-binding polypeptide having three complementary determining regions (CDRs) . The sdAb alone is capable of binding to the antigen without pairing with a corresponding CDR-containing polypeptide. In some cases, single-domain antibodies are engineered from camelid HCAbs, and their heavy chain variable domains are referred herein as “V _HHs” (Variable domain of the heavy chain of the Heavy chain antibody) . Some V _HHs can also be known as nanobodies. Camelid sdAb is one of the smallest known antigen-binding antibody fragments (see, e.g., Hamers-Casterman et al., Nature 363: 446-8 (1993) ; Greenberg et al., Nature 374: 168-73 (1995) ; Hassanzadeh-Ghassabeh et al., Nanomedicine (Lond) , 8: 1013-26 (2013) ) . A basic V _HH has the following structure from the N-terminus to the C-terminus: FR1-CDR1-FR2-CDR2-FR3-CDR3-FR4, in which FR1 to FR4 refer to framework regions 1 to 4, respectively, and in which CDR1 to CDR3 refer to the complementarity determining regions 1 to 3.

An “isolated” antibody (or construct) is one that has been identified, separated and/or recovered from a component of its production environment (e.g., natural or recombinant) . Preferably, the isolated polypeptide is free of association with all other components from its production environment. Contaminant components of its production environment, such as that resulting from recombinant transfected cells, are materials that would typically interfere with research, diagnostic or therapeutic uses for the antibody, and may include enzymes, hormones, and other proteinaceous or non-proteinaceous solutes. In preferred embodiments, the polypeptide will be purified: (1) to greater than 95%by weight of antibody as determined by, for example, the Lowry method, and in some embodiments, to greater than 99%by weight; (2) to a degree sufficient to obtain at least 15 residues of N-terminal or internal amino acid sequence by use of a spinning cup sequenator; or (3) to homogeneity by SDS-PAGE under non-reducing or reducing conditions using Coomassie Blue or, preferably, silver stain. Isolated antibody (or construct) includes the antibody in situ within recombinant cells since at least one component of the antibody’s natural environment will not be present. Ordinarily, however, an isolated polypeptide, antibody, or construct will be prepared by at least one purification step.

The “variable region” or “variable domain” of an antibody refers to the amino-terminal domains of the heavy or light chain of the antibody. The variable domains of the heavy chain and light chain may be referred to as “V _H” and “V _L” , respectively. These domains are generally the most variable parts of the antibody (relative to other antibodies of the same class) and contain the antigen binding sites. Heavy-chain only antibodies from the Camelid species have a single heavy chain variable region, which is referred to as “V _HH” . V _HH is thus a special type of V _H.

The term “variable” refers to the fact that certain segments of the variable domains differ extensively in sequence among antibodies. The V domain mediates antigen binding and defines the specificity of a particular antibody for its particular antigen. However, the variability is not evenly distributed across the entire span of the variable domains. Instead, it is concentrated in three segments called complementary determining regions (CDRs) or hypervariable regions (HVRs) both in the light-chain and the heavy chain variable domains. The more highly conserved portions of variable domains are called the framework regions (FR) . The variable domains of native heavy and light chains each comprise four FR regions, largely adopting a beta-sheet configuration, connected by three CDRs, which form loops connecting, and in some cases forming part of, the beta-sheet structure. The CDRs in each chain are held together in close proximity by the FR regions and, with the CDRs from the other chain, contribute to the formation of the antigen binding site of antibodies (see Kabat et al., Sequences of Immunological Interest, Fifth Edition, National Institute of Health, Bethesda, Md. (1991) ) . The constant domains are not involved directly in the binding of antibody to an antigen, but exhibit various effector functions, such as participation of the antibody in antibody-dependent cellular toxicity.

The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e., the individual antibodies comprising the population are identical except for possible naturally occurring mutations and/or post-translation modifications (e.g., isomerizations, amidations) that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. In contrast to polyclonal antibody preparations which typically include different antibodies directed against different determinants (epitopes) , each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they are synthesized by the hybridoma culture, uncontaminated by other immunoglobulins. The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by a variety of techniques, including, for example, the hybridoma method (e.g., Kohler and Milstein., Nature, 256: 495-97 (1975) ; Hongo et al., Hybridoma, 14 (3) : 253-260 (1995) , Harlow et al., Antibodies: A Laboratory Manual, (Cold Spring Harbor Laboratory Press, 2 ^nd ed. 1988) ; Hammerling et al., in: Monoclonal Antibodies and T-Cell Hybridomas 563-681 (Elsevier, N. Y., 1981) ) , recombinant DNA methods (see, e.g., U.S. Pat. No. 4,816,567) , phage-display technologies (see, e.g., Clackson et al., Nature, 352: 624-628 (1991) ; Marks et al., J. Mol. Biol. 222: 581-597 (1992) ; Sidhu et al., J. Mol. Biol. 338 (2) : 299-310 (2004) ; Lee et al., J. Mol. Biol. 340 (5) : 1073-1093 (2004) ; Fellouse, Proc. Natl. Acad. Sci. USA 101 (34) : 12467-12472 (2004) ; and Lee et al., J. Immunol. Methods 284 (1-2) : 119-132 (2004) , and technologies for producing human or human-like antibodies in animals that have parts or all of the human immunoglobulin loci or genes encoding human immunoglobulin sequences (see, e.g., WO 1998/24893; WO 1996/34096; WO 1996/33735; WO 1991/10741; Jakobovits et al., Proc. Natl. Acad. Sci. USA 90: 2551 (1993) ; Jakobovits et al., Nature 362: 255-258 (1993) ; Bruggemann et al., Year in Immunol. 7: 33 (1993) ; U.S. Pat. Nos. 5, 545, 807; 5, 545, 806; 5, 569, 825; 5, 625, 126; 5, 633, 425; and 5,661, 016; Marks et al., Bio/Technology 10: 779-783 (1992) ; Lonberg et al., Nature 368: 856-859 (1994) ; Morrison, Nature 368: 812-813 (1994) ; Fishwild et al., Nature Biotechnol. 14: 845-851 (1996) ; Neuberger, Nature Biotechnol. 14: 826 (1996) ; and Lonberg and Huszar, Intern. Rev. Immunol. 13: 65-93 (1995) .

The terms “full-length antibody” , “intact antibody” , or “whole antibody” are used interchangeably to refer to an antibody in its substantially intact form, as opposed to an antibody fragment. Specifically, full-length 4-chain antibodies include those with heavy and light chains including an Fc region. Full-length heavy-chain only antibodies include the heavy chain (such as V _HH) and an Fc region. The constant domains may be native sequence constant domains (e.g., human native sequence constant domains) or amino acid sequence variants thereof. In some cases, the intact antibody may have one or more effector functions.

An “antibody fragment” comprises a portion of an intact antibody, preferably the antigen binding and/or the variable region of the intact antibody. Examples of antibody fragments include, but are not limited to Fab, Fab′, F (ab′) ₂ and Fv fragments; diabodies; linear antibodies (see U.S. Pat. No. 5,641,870, Example 2; Zapata et al., Protein Eng. 8 (10) : 1057-1062 [1995] ) ; single-chain antibody molecules; single-domain antibodies (such as V _HH) , and multispecific antibodies formed from antibody fragments. Papain digestion of antibodies produced two identical antigen-binding fragments, called “Fab” fragments, and a residual “Fc” fragment, a designation reflecting the ability to crystallize readily. The Fab fragment consists of an entire L chain along with the variable region domain of the H chain (V _H) , and the first constant domain of one heavy chain (C _H1) . Each Fab fragment is monovalent with respect to antigen binding, i.e., it has a single antigen-binding site. Pepsin treatment of an antibody yields a single large F (ab′) ₂ fragment which roughly corresponds to two disulfide linked Fab fragments having different antigen-binding activity and is still capable of cross-linking antigen. Fab′fragments differ from Fab fragments by having a few additional residues at the carboxy-terminus of the C _H1 domain including one or more cysteines from the antibody hinge region. Fab′-SH is the designation herein for Fab′in which the cysteine residue (s) of the constant domains bear a free thiol group. F (ab′) ₂ antibody fragments originally were produced as pairs of Fab′fragments which have hinge cysteines between them. Other chemical couplings of antibody fragments are also known.

The Fc fragment comprises the carboxy-terminal portions of both H chains held together by disulfides. The effector functions of antibodies are determined by sequences in the Fc region, the region which is also recognized by Fc receptors (FcR) found on certain types of cells.

The term “constant domain” refers to the portion of an immunoglobulin molecule having a more conserved amino acid sequence relative to the other portion of the immunoglobulin, the variable domain, which contains the antigen-binding site. The constant domain contains the C _H1, C _H2 and C _H3 domains (collectively, CH) of the heavy chain and the CHL (or CL) domain of the light chain.

The “light chains” of antibodies (immunoglobulins) from any mammalian species can be assigned to one of two clearly distinct types, called kappa ( “κ” ) and lambda ( “λ” ) , based on the amino acid sequences of their constant domains.

“Fv” is the minimum antibody fragment which contains a complete antigen-recognition and -binding site. This fragment consists of a dimer of one heavy-and one light-chain variable region domain in tight, non-covalent association. From the folding of these two domains emanate six hypervariable loops (3 loops each from the H and L chain) that contribute the amino acid residues for antigen binding and confer antigen binding specificity to the antibody. However, even a single variable domain (or half of an Fv comprising only three CDRs specific for an antigen) has the ability to recognize and bind antigen, although at a lower affinity than the entire binding site.

“Single-chain Fv” also abbreviated as “sFv” or “scFv” are antibody fragments that comprise the V _H and V _L antibody domains connected into a single polypeptide chain. Preferably, the sFv polypeptide further comprises a polypeptide linker between the V _H and V _L domains which enables the sFv to form the desired structure for antigen binding. For a review of the sFv, see Pluckthun in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994) .

“Functional fragments” of the antibodies described herein comprise a portion of an intact antibody, generally including the antigen binding or variable region of the intact antibody or the Fc region of an antibody which retains or has modified FcR binding capability. Examples of antibody fragments include linear antibody, single-chain antibody molecules and multispecific antibodies formed from antibody fragments.

The term “diabodies” refers to small antibody fragments prepared by constructing sFv fragments (see preceding paragraph) with short linkers (about 5-10 residues) between the V _H and V _L domains such that inter-chain but not intra-chain pairing of the V domains is achieved, thereby resulting in a bivalent fragment, i.e., a fragment having two antigen-binding sites. Bispecific diabodies are heterodimers of two “crossover” sFv fragments in which the V _H and V _L domains of the two antibodies are present on different polypeptide chains. Diabodies are described in greater detail in, for example, EP 404,097; WO 93/11161; Hollinger et al., Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993) .

The monoclonal antibodies herein specifically include “chimeric” antibodies (immunoglobulins) in which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain (s) is (are) identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity (U.S. Pat. No. 4,816,567; Morrison et al., Proc. Natl. Acad. Sci. USA, 81: 6851-6855 (1984) ) . “Humanized antibody” is used as a subset of “chimeric antibodies” .

“Humanized” forms of non-human (e.g., llama or camelid) antibodies are antibodies that contain minimal sequence derived from non-human immunoglobulin. In some embodiments, a humanized antibody is a human immunoglobulin (recipient antibody) in which residues from an CDR (hereinafter defined) of the recipient are replaced by residues from an CDR of a non-human species (donor antibody) such as mouse, rat, rabbit, camel, llama, alpaca, or non-human primate having the desired specificity, affinity, and/or capacity. In some instances, framework ( “FR” ) residues of the human immunoglobulin are replaced by corresponding non-human residues. Furthermore, humanized antibodies can comprise residues that are not found in the recipient antibody or in the donor antibody. These modifications can be made to further refine antibody performance, such as binding affinity. In general, a humanized antibody will comprise substantially all of at least one, and typically two, variable domains, in which all or substantially all of the hypervariable loops correspond to those of a non-human immunoglobulin sequence, and all or substantially all of the FR regions are those of a human immunoglobulin sequence, although the FR regions may include one or more individual FR residue substitutions that improve antibody performance, such as binding affinity, isomerization, immunogenicity, etc. The number of these amino acid substitutions in the FR is typically no more than 6 in the H chain, and in the L chain, no more than 3. The humanized antibody optionally will also comprise at least a portion of an immunoglobulin constant region (Fc) , typically that of a human immunoglobulin. For further details, see, e.g., Jones et al., Nature 321: 522-525 (1986) ; Riechmann et al., Nature 332: 323-329 (1988) ; and Presta, Curr. Op. Struct. Biol. 2: 593-596 (1992) . See also, for example, Vaswani and Hamilton, Ann. Allergy, Asthma &Immunol. 1: 105-115 (1998) ; Harris, Biochem. Soc. Transactions 23: 1035-1038 (1995) ; Hurle and Gross, Curr. Op. Biotech. 5: 428-433 (1994) ; and U.S. Pat. Nos. 6,982,321 and 7,087,409.

A “human antibody” is an antibody that possesses an amino-acid sequence corresponding to that of an antibody produced by a human and/or has been made using any of the techniques for making human antibodies as disclosed herein. This definition of a human antibody specifically excludes a humanized antibody comprising non-human antigen-binding residues. Human antibodies can be produced using various techniques known in the art, including phage-display libraries. Hoogenboom and Winter, J. Mol. Biol., 227: 381 (1991) ; Marks et al., J. Mol. Biol., 222: 581 (1991) . Also available for the preparation of human monoclonal antibodies are methods described in Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p. 77 (1985) ; Boerner et al., J. Immunol., 147 (1) : 86-95 (1991) . See also van Dijk and van de Winkel, Curr. Opin. Pharmacol., 5: 368-74 (2001) . Human antibodies can be prepared by administering the antigen to a transgenic animal that has been modified to produce such antibodies in response to antigenic challenge, but whose endogenous loci have been disabled, e.g., immunized xenomice (see, e.g., U.S. Pat. Nos. 6,075,181 and 6,150,584 regarding XENOMOUSE ^TM technology) . See also, for example, Li et al., Proc. Natl. Acad. Sci. USA, 103: 3557-3562 (2006) regarding human antibodies generated via a human B-cell hybridoma technology.

The term “hypervariable region, ” “HVR, ” or “HV, ” when used herein refers to the regions of an antibody variable domain which are hypervariable in sequence and/or form structurally defined loops. Generally, single-domain antibodies comprise three HVRs (or CDRs) : HVR1 (or CDR1) , HVR2 (or CDR2) , and HVR3 (or CDR3) . HVR3 (or CDR3) displays the most diversity of the three HVRs, and is believed to play a unique role in conferring fine specificity to antibodies. See, e.g., Hamers-Casterman et al., Nature 363: 446-448 (1993) ; Sheriff et al., Nature Struct. Biol. 3: 733-736 (1996) .

The term “Complementarity Determining Region” or “CDR” are used to refer to hypervariable regions as defined by the Kabat system. See Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991) .

A number of HVR delineations are in use and are encompassed herein. The Kabat Complementarity Determining Regions (CDRs) are based on sequence variability and are the most commonly used (Kabat et al., Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991) ) . Chothia refers instead to the location of the structural loops (Chothia and Lesk, J. Mol. Biol. 196: 901-917 (1987) ) . The AbM HVRs represent a compromise between the Kabat HVRs and Chothia structural loops, and are used by Oxford Molecular’s AbM antibody modeling software. The “contact” HVRs are based on an analysis of the available complex crystal structures. The residues from each of these HVRs are noted below in Table 1.

Table 1. HVR delineations.

HVRs may comprise “extended HVRs” as follows: 24-36 or 24-34 (L1) , 46-56 or 50-56 (L2) and 89-97 or 89-96 (L3) in the V _L and 26-35 (H1) , 50-65 or 49-65 (H2) and 93-102, 94-102, or 95-102 (H3) in the V _H. The variable domain residues are numbered according to Kabat et al., supra, for each of these definitions.

The amino acid residues of a single-domain antibody (such as V _HH) are numbered according to the general numbering for VH domains given by Kabat et al. ( “Sequence of proteins of immunological interest” , US Public Health Services, NIH Bethesda, Md., Publication No. 91) , as applied to V _HH domains from Camelids in the article of Riechmann and Muyldermans, J. Immunol. Methods 2000 Jun. 23; 240 (1-2) : 185-195. According to this numbering, FR1 of a V _HH comprises the amino acid residues at positions 1-30, CDR1 of a V _HH comprises the amino acid residues at positions 31-35, FR2 of a V _HH comprises the amino acids at positions 36-49, CDR2 of a V _HH comprises the amino acid residues at positions 50-65, FR3 of a V _HH comprises the amino acid residues at positions 66-94, CDR3 of a V _HH comprises the amino acid residues at positions 95-102, and FR4 of a V _HH comprises the amino acid residues at positions 103-113. In this respect, it should be noted that-as is well known in the art for V _H domains and for V _HH domains-the total number of amino acid residues in each of the CDRs may vary and may not correspond to the total number of amino acid residues indicated by the Kabat numbering (that is, one or more positions according to the Kabat numbering may not be occupied in the actual sequence, or the actual sequence may contain more amino acid residues than the number allowed for by the Kabat numbering) .

The expression “variable-domain residue-numbering as in Kabat” or “amino-acid-position numbering as in Kabat, ” and variations thereof, refers to the numbering system used for heavy-chain variable domains or light-chain variable domains of the compilation of antibodies in Kabat et al., supra. Using this numbering system, the actual linear amino acid sequence may contain fewer or additional amino acids corresponding to a shortening of, or insertion into, a FR or HVR of the variable domain. For example, a heavy-chain variable domain may include a single amino acid insert (residue 52a according to Kabat) after residue 52 of H2 and inserted residues (e.g. residues 82a, 82b, and 82c, etc. according to Kabat) after heavy-chain FR residue 82. The Kabat numbering of residues may be determined for a given antibody by alignment at regions of homology of the sequence of the antibody with a “standard” Kabat numbered sequence.

Unless indicated otherwise herein, the numbering of the residues in an immunoglobulin heavy chain is that of the EU index as in Kabat et al., supra. The “EU index as in Kabat” refers to the residue numbering of the human IgG1 EU antibody.

“Framework” or “FR” residues are those variable-domain residues other than the HVR residues as herein defined.

A “human consensus framework” or “acceptor human framework” is a framework that represents the most commonly occurring amino acid residues in a selection of human immunoglobulin V _L or V _H framework sequences. Generally, the selection of human immunoglobulin V _L or V _H sequences is from a subgroup of variable domain sequences. Generally, the subgroup of sequences is a subgroup as in Kabat et al., Sequences of Proteins of Immunological Interest, 5 ^th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991) . Examples include for the V _L, the subgroup may be subgroup kappa I, kappa II, kappa III or kappa IV as in Kabat et al., supra. Additionally, for the VH, the subgroup may be subgroup I, subgroup II, or subgroup III as in Kabat et al. Alternatively, a human consensus framework can be derived from the above in which particular residues, such as when a human framework residue is selected based on its homology to the donor framework by aligning the donor framework sequence with a collection of various human framework sequences. An acceptor human framework “derived from” a human immunoglobulin framework or a human consensus framework may comprise the same amino acid sequence thereof, or it may contain pre-existing amino acid sequence changes. In some embodiments, the number of pre-existing amino acid changes are 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less.

An “affinity-matured” antibody is one with one or more alterations in one or more CDRs thereof that result in an improvement in the affinity of the antibody for antigen, compared to a parent antibody that does not possess those alteration (s) . In some embodiments, an affinity-matured antibody has nanomolar or even picomolar affinities for the target antigen. Affinity-matured antibodies are produced by procedures known in the art. For example, Marks et al., Bio/Technology 10: 779-783 (1992) describes affinity maturation by V _H-and V _L -domain shuffling. Random mutagenesis of CDR and/or framework residues is described by, for example: Barbas et al. Proc Nat. Acad. Sci. USA 91: 3809-3813 (1994) ; Schier et al. Gene 169: 147-155 (1995) ; Yelton et al. J. Immunol. 155: 1994-2004 (1995) ; Jackson et al., J. Immunol. 154 (7) : 3310-9 (1995) ; and Hawkins et al, J. Mol. Biol. 226: 889-896 (1992) .

As use herein, the term “specifically binds, ” “specifically recognizes, ” or is “specific for” refers to measurable and reproducible interactions such as binding between a target and an antigen binding protein (such as a sdAb) , which is determinative of the presence of the target in the presence of a heterogeneous population of molecules including biological molecules. For example, an antigen binding protein (such as a sdAb) that specifically binds a target (which can be an epitope) is an antigen binding protein (such as a sdAb) that binds this target with greater affinity, avidity, more readily, and/or with greater duration than it binds other targets. In some embodiments, the extent of binding of an antigen binding protein (such as a sdAb) to an unrelated target is less than about 10%of the binding of the antigen binding protein (such as sdAb) to the target as measured, e.g., by a radioimmunoassay (RIA) . In some embodiments, an antigen binding protein (such as a sdAb) that specifically binds a target has a dissociation constant (K _d) of ≤10 ^-5 M, ≤10 ^-6 M, ≤10 ^-7 M, ≤10 ^-8 M, ≤10 ^-9 M, ≤10 ^-10 M, ≤10 ^-11 M, or ≤10 ^-12 M.In some embodiments, an antigen binding protein specifically binds an epitope on a protein that is conserved among the protein from different species. In some embodiments, specific binding can include, but does not require exclusive binding.

The term “specificity” refers to selective recognition of an antigen binding protein (such as a sdAb) for a particular epitope of an antigen. Natural antibodies, for example, are monospecific. The term “multispecific” as used herein denotes that an antigen binding protein has polyepitopic specificity (i.e., is capable of specifically binding to two, three, or more, different epitopes on one biological molecule or is capable of specifically binding to epitopes on two, three, or more, different biological molecules) . “Bispecific” as used herein denotes that an antigen binding protein has two different antigen-binding specificities. Unless otherwise indicated, the order in which the antigens bound by a bispecific antibody listed is arbitrary. That is, for example, the terms “anti-PD-L1/PD-1, ” “anti-PD-1/PD-L1, ” “PD-L1×PD-1, ” “PD-1×PD-L1, ” “PD-1-PD-L1, ” and “PD-L1-PD-1” may be used interchangeably to refer to bispecific antibodies that specifically bind to both PD-L1 and PD-1. The term “monospecific” as used herein denotes an antigen binding protein (such as a sdAb) that has one or more binding sites each of which bind the same epitope of the same antigen.

The term “valent” as used herein denotes the presence of a specified number of binding sites in an antigen binding protein. A natural antibody for example or a full length antibody has two binding sites and is bivalent. As such, the terms “trivalent” , “tetravalent” , “pentavalent” and “hexavalent” denote the presence of two binding site, three binding sites, four binding sites, five binding sites, and six binding sites, respectively, in an antigen binding protein.

“Antibody effector functions” refer to those biological activities attributable to the Fc region (a native sequence Fc region or amino acid sequence variant Fc region) of an antibody, and vary with the antibody isotype. Examples of antibody effector functions include: C1q binding and complement dependent cytotoxicity; Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC) ; phagocytosis; down regulation of cell surface receptors (e.g., B cell receptors) ; and B cell activation. “Reduced or minimized” antibody effector function means that which is reduced by at least 50% (alternatively 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%) from the wild type or unmodified antibody. The determination of antibody effector function is readily determinable and measurable by one of ordinary skill in the art. In a preferred embodiment, the antibody effector functions of complement binding, complement dependent cytotoxicity and antibody dependent cytotoxicity are affected. In some embodiments, effector function is eliminated through a mutation in the constant region that eliminated glycosylation, e.g., “effector-less mutation. ” In one aspect, the effector-less mutation is an N297A or DANA mutation (D265A+N297A) in the C _H2 region. Shields et al., J. Biol. Chem. 276 (9) : 6591-6604 (2001) . Alternatively, additional mutations resulting in reduced or eliminated effector function include: K322A and L234A/L235A (LALA) . Alternatively, effector function can be reduced or eliminated through production techniques, such as expression in host cells that do not glycosylate (e.g., E. coli. ) or in which result in an altered glycosylation pattern that is ineffective or less effective at promoting effector function (e.g., Shinkawa et al., J. Biol. Chem. 278 (5) : 3466-3473 (2003) .

“Antibody-dependent cell-mediated cytotoxicity” or ADCC refers to a form of cytotoxicity in which secreted Ig bound onto Fc receptors (FcRs) present on certain cytotoxic cells (e.g., natural killer (NK) cells, neutrophils and macrophages) enable these cytotoxic effector cells to bind specifically to an antigen-bearing target cell and subsequently kill the target cell with cytotoxins. The antibodies “arm” the cytotoxic cells and are required for killing of the target cell by this mechanism. The primary cells for mediating ADCC, NK cells, express FcγRIII only, whereas monocytes express FcγRI, FcγRII and FcγRIII. Fc expression on hematopoietic cells is summarized in Table 3 on page 464 of Ravetch and Kinet, Annu. Rev. Immunol. 9: 457-92 (1991) . To assess ADCC activity of a molecule of interest, an in vitro ADCC assay, such as that described in U.S. Pat. No. 5,500,362 or 5,821,337 may be performed. Useful effector cells for such assays include peripheral blood mononuclear cells (PBMC) and natural killer (NK) cells. Alternatively, or additionally, ADCC activity of the molecule of interest may be assessed in vivo, e.g., in an animal model such as that disclosed in Clynes et al., PNAS USA 95: 652-656 (1998) .

The term “Fc region” herein is used to define a C-terminal region of an immunoglobulin heavy chain, including native-sequence Fc regions and variant Fc regions. Although the boundaries of the Fc region of an immunoglobulin heavy chain might vary, the human IgG heavy-chain Fc region is usually defined to stretch from an amino acid residue at position Cys226, or from Pro230, to the carboxyl-terminus thereof. The C-terminal lysine (residue 447 according to the EU numbering system) of the Fc region may be removed, for example, during production or purification of the antibody, or by recombinantly engineering the nucleic acid encoding a heavy chain of the antibody. Accordingly, a composition of intact antibodies may comprise antibody populations with all K447 residues removed, antibody populations with no K447 residues removed, and antibody populations having a mixture of antibodies with and without the K447 residue. Suitable native-sequence Fc regions for use in the antibodies described herein include human IgG1, IgG2 (IgG2A, IgG2B) , IgG3 and IgG4.

“Fc receptor” or “FcR” describes a receptor that binds the Fc region of an antibody. The preferred FcR is a native sequence human FcR. Moreover, a preferred FcR is one which binds an IgG antibody (agamma receptor) and includes receptors of the FcγRI, FcγRII, and FcγRIII subclasses, including allelic variants and alternatively spliced forms of these receptors, FcγRII receptors include FcγRIIA (an “activating receptor” ) and FcγRIIB (an “inhibiting receptor” ) , which have similar amino acid sequences that differ primarily in the cytoplasmic domains thereof. Activating receptor FcγRIIA contains an immunoreceptor tyrosine-based activation motif (ITAM) in its cytoplasmic domain. Inhibiting receptor FcγRIIB contains an immunoreceptor tyrosine-based inhibition motif (ITIM) in its cytoplasmic domain. (see M.

Annu. Rev. Immunol. 15: 203-234 (1997) . FcRs are reviewed in Ravetch and Kinet, Annu. Rev. Immunol. 9: 457-92 (1991) ; Capel et al., Immunomethods 4: 25-34 (1994) ; and de Haas et al., J. Lab. Clin. Med. 126: 330-41 (1995) . Other FcRs, including those to be identified in the future, are encompassed by the term “FcR” herein.

The term “Fc receptor” or “FcR” also includes the neonatal receptor, FcRn, which is responsible for the transfer of maternal IgGs to the fetus. Guyer et al., J. Immunol. 117: 587 (1976) and Kim et al., J. Immunol. 24: 249 (1994) . Methods of measuring binding to FcRn are known (see, e.g., Ghetie and Ward, Immunol. Today 18: (12) : 592-8 (1997) ; Ghetie et al., Nature Biotechnology 15 (7) : 637-40 (1997) ; Hinton et al., J. Biol. Chem. 279 (8) : 6213-6 (2004) ; WO 2004/92219 (Hinton et al. ) . Binding to FcRn in vivo and serum half-life of human FcRn high-affinity binding polypeptides can be assayed, e.g., in transgenic mice or transfected human cell lines expressing human FcRn, or in primates to which the polypeptides having a variant Fc region are administered. WO 2004/42072 (Presta) describes antibody variants which improved or diminished binding to FcRs. See also, e.g., Shields et al., J. Biol. Chem. 9 (2) : 6591-6604 (2001) .

“Complement dependent cytotoxicity” or “CDC” refers to the lysis of a target cell in the presence of complement. Activation of the classical complement pathway is initiated by the binding of the first component of the complement system (C1q) to antibodies (of the appropriate subclass) which are bound to their cognate antigen. To assess complement activation, a CDC assay, e.g., as described in Gazzano-Santoro et al., J. Immunol. Methods 202: 163 (1996) , may be performed. Antibody variants with altered Fc region amino acid sequences and increased or decreased C1q binding capability are described in U.S. Pat. No. 6,194,551B1 and WO99/51642. The contents of those patent publications are specifically incorporated herein by reference. See, also, Idusogie et al. J. Immunol. 164: 4178-4184 (2000) .

“Binding affinity” generally refers to the strength of the sum total of non-covalent interactions between a single binding site of a molecule (e.g., an antibody) and its binding partner (e.g., an antigen) . Unless indicated otherwise, as used herein, “binding affinity” refers to intrinsic binding affinity that reflects a 1: 1 interaction between members of a binding pair. Binding affinity can be indicated by K _d, K _off, K _on, or K _a. The term “K _off” , as used herein, is intended to refer to the off rate constant for dissociation of an antibody (or antigen-binding domain) from the antibody/antigen complex, as determined from a kinetic selection set up, expressed in units of s ^-1. The term “K _on” , as used herein, is intended to refer to the on rate constant for association of an antibody (or antigen-binding domain) to the antigen to form the antibody/antigen complex, expressed in units of M ^-1s ^-1. The term equilibrium dissociation constant “K _D” or “K _d” , as used herein, refers to the dissociation constant of a particular antibody-antigen interaction, and describes the concentration of antigen required to occupy one half of all of the antibody-binding domains present in a solution of antibody molecules at equilibrium, and is equal to K _off/K _on, expressed in units of M. The measurement of K _d presupposes that all binding agents are in solution. In the case where the antibody is tethered to a cell wall, e.g., in a yeast expression system, the corresponding equilibrium rate constant is expressed as EC50, which gives a good approximation of K _d. The affinity constant, K _a, is the inverse of the dissociation constant, K _d, expressed in units of M ^-1.

The dissociation constant (K _D or K _d) is used as an indicator showing affinity of antibodies to antigens. For example, easy analysis is possible by the Scatchard method using antibodies marked with a variety of marker agents, as well as by using BiacoreX (made by Amersham Biosciences) , which is an over-the-counter, measuring kit, or similar kit, according to the user's manual and experiment operation method attached with the kit. The K _D value that can be derived using these methods is expressed in units of M (Mols) . An antibody or antigen-binding fragment thereof that specifically binds to a target may have a dissociation constant (K _d) of, for example, ≤10 ^-5 M, ≤10 ^-6 M, ≤10 ^-7 M, ≤10 ^-8 M, ≤10 ^-9 M, ≤10 ^-10 M, ≤10 ^- ¹¹ M, or ≤10 ^-12 M.

Binding specificity of the antibody or antigen-binding domain can be determined experimentally by methods known in the art. Such methods comprise, but are not limited to Western blots, ELISA-, RIA-, ECL-, IRMA-, EIA-, BIAcore-tests and peptide scans.

Half maximal inhibitory concentration (IC ₅₀) is a measure of the effectiveness of a substance (such as an antibody) in inhibiting a specific biological or biochemical function. It indicates how much of a particular drug or other substance (inhibitor, such as an antibody) is needed to inhibit a given biological process (e.g., the binding between PD-L1 and B7-1, or component of a process, i.e. an enzyme, cell, cell receptor or microorganism) by half. The values are typically expressed as molar concentration. IC ₅₀ is comparable to an EC ₅₀ for agonist drug or other substance (such as an antibody) . EC ₅₀ also represents the plasma concentration required for obtaining 50%of a maximum effect in vivo. As used herein, an “IC ₅₀” is used to indicate the effective concentration of an antibody (such as an anti-PD-L1 sdAb) needed to neutralize 50%of the antigen bioactivity (such as PD-L1 bioactivity) in vitro. IC ₅₀ or EC ₅₀ can be measured by bioassays such as inhibition of ligand binding by FACS analysis (competition binding assay) , cell based cytokine release assay, or amplified luminescent proximity homogeneous assay (AlphaLISA) .

“Percent (%) amino acid sequence identity” and “homology” with respect to a peptide, polypeptide or antibody sequence are defined as the percentage of amino acid residues in a candidate sequence that are identical with the amino acid residues in the specific peptide or polypeptide sequence, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent sequence identity, and not considering any conservative substitutions as part of the sequence identity. Alignment for purposes of determining percent amino acid sequence identity can be achieved in various ways that are within the skill in the art, for instance, using publicly available computer software such as BLAST, BLAST-2, ALIGN or MEGALIGN ^TM (DNASTAR) software. Those skilled in the art can determine appropriate parameters for measuring alignment, including any algorithms needed to achieve maximal alignment over the full length of the sequences being compared.

An “isolated” nucleic acid molecule encoding a construct, antibody, or antigen-binding fragment thereof described herein is a nucleic acid molecule that is identified and separated from at least one contaminant nucleic acid molecule with which it is ordinarily associated in the environment in which it was produced. Preferably, the isolated nucleic acid is free of association with all components associated with the production environment. The isolated nucleic acid molecules encoding the polypeptides and antibodies described herein is in a form other than in the form or setting in which it is found in nature. Isolated nucleic acid molecules therefore are distinguished from nucleic acid encoding the polypeptides and antibodies described herein existing naturally in cells. An isolated nucleic acid includes a nucleic acid molecule contained in cells that ordinarily contain the nucleic acid molecule, but the nucleic acid molecule is present extrachromosomally or at a chromosomal location that is different from its natural chromosomal location.

The term “vector, ” as used herein, refers to a nucleic acid molecule capable of propagating another nucleic acid to which it is linked. The term includes the vector as a self-replicating nucleic acid structure as well as the vector incorporated into the genome of a host cell into which it has been introduced. Certain vectors are capable of directing the expression of nucleic acids to which they are operatively linked. Such vectors are referred to herein as “expression vectors. ”

The term “transfected” or “transformed” or “transduced” as used herein refers to a process by which exogenous nucleic acid is transferred or introduced into the host cell. A “transfected” or “transformed” or “transduced” cell is one which has been transfected, transformed or transduced with exogenous nucleic acid. The cell includes the primary subject cell and its progeny.

The terms “host cell, ” “host cell line, ” and “host cell culture” are used interchangeably and refer to cells into which exogenous nucleic acid has been introduced, including the progeny of such cells. Host cells include “transformants” and “transformed cells, ” which include the primary transformed cell and progeny derived therefrom without regard to the number of passages. Progeny may not be completely identical in nucleic acid content to a parent cell, but may contain mutations. Mutant progeny that have the same function or biological activity as screened or selected for in the originally transformed cell are included herein.

“Adjuvant setting” refers to a clinical setting in which an individual has had a history of cancer, and generally (but not necessarily) been responsive to therapy, which includes, but is not limited to, surgery (e.g., surgery resection) , radiotherapy, and chemotherapy. However, because of their history of cancer, these individuals are considered at risk of development of the disease. Treatment or administration in the “adjuvant setting” refers to a subsequent mode of treatment. The degree of risk (e.g., when an individual in the adjuvant setting is considered as “high risk” or “low risk” ) depends upon several factors, most usually the extent of disease when first treated.

“Neoadjuvant setting” refers to a clinical setting in which the method is carried out before the primary/definitive therapy.

The term “pharmaceutical formulation” of “pharmaceutical composition” refers to a preparation that is in such form as to permit the biological activity of the active ingredient to be effective, and that contains no additional components that are unacceptably toxic to a subject to which the formulation would be administered. Such formulations are sterile. A “sterile” formulation is aseptic or free from all living microorganisms and their spores.

It is understood that embodiments of the invention described herein include “consisting” and/or “consisting essentially of” embodiments.

Reference to “about” a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, description referring to “about X” includes description of “X” .

As used herein, reference to “not” a value or parameter generally means and describes “other than” a value or parameter. For example, the method is not used to treat cancer of type X means the method is used to treat cancer of types other than X.

The term “about X-Y” used herein has the same meaning as “about X to about Y. ”

As used herein and in the appended claims, the singular forms “a, ” “or, ” and “the” include plural referents unless the context clearly dictates otherwise.

II. Anti-PD-L1 construct

Anti-PD-L1 single-domain antibody moiety

The isolated anti-PD-L1 construct described herein comprises a single-domain antibody (sdAb) moiety that specifically recognizes PD-L1 (or “anti-PD-L1 sdAb” ) . In some embodiments, the isolated anti-PD-L1 construct is an anti-PD-L1 sdAb.

Single-domain antibodies

Exemplary sdAbs include, but are not limited to, heavy chain variable domains from heavy-chain only antibodies (e.g., V _HH (Variable domain of the heavy chain of the Heavy chain antibody) in Camelidae or V _NAR (Variable domain of the shark New Antigen Receptor) in cartilaginous fish) , binding molecules naturally devoid of light chains, single domains (such as V _H or V _L) derived from conventional 4-chain antibodies, humanized heavy-chain only antibodies, human single-domain antibodies produced by transgenic mice or rats expressing human heavy chain segments, and engineered domains and single domain scaffolds other than those derived from antibodies. The sdAbs may be derived from any species including, but not limited to mouse, rat, human, camel, llama, lamprey, fish, shark, goat, rabbit, and bovine. Single-domain antibodies contemplated herein also include naturally occurring single-domain antibody molecules from species other than Camelidae and sharks.

In some embodiments, the sdAb is derived from a naturally occurring single-domain antigen binding molecule known as heavy chain antibody devoid of light chains (also referred herein as “heavy chain-only antibodies” , or “HCAb” ) . Such single domain molecules are disclosed in WO 94/04678 and Hamers-Casterman, C. et al. (1993) Nature 363: 446-448, for example. For clarity reasons, the variable domain derived from a heavy chain molecule naturally devoid of light chain is known herein as a V _HH to distinguish it from the conventional VH of four chain immunoglobulins. Such a V _HH molecule can be derived from antibodies raised in Camelidae species, for example, camel, llama, vicuna, dromedary, alpaca and guanaco. Other species besides Camelidae may produce heavy chain molecules naturally devoid of light chain, and such V _HHs are within the scope of the present application.

In some embodiments, the sdAb is derived from a variable region of the immunoglobulin found in cartilaginous fish. For example, the sdAb can be derived from the immunoglobulin isotype known as Novel Antigen Receptor (NAR) found in the serum of shark. Methods of producing single domain molecules derived from a variable region of NAR ( "IgNARs" ) are described in WO 03/014161 and Streltsov (2005) Protein Sci. 14: 2901-2909.

In some embodiments, the sdAb is recombinant, CDR-grafted, humanized, camelized, de-immunized and/or in vitro generated (e.g., selected by phage display) . In some embodiments, the amino acid sequence of the framework regions may be altered by “camelization” of specific amino acid residues in the framework regions. Camelization refers to the replacing or substitution of one or more amino acid residues in the amino acid sequence of a (naturally occurring) VH domain from a conventional 4-chain antibody by one or more of the amino acid residues that occur at the corresponding position (s) in a V _HH domain of a heavy chain antibody. This can be performed in a manner known per se, which will be clear to the skilled person, for example on the basis of the further description herein. Such “camelizing” substitutions are preferably inserted at amino acid positions that form and/or are present at the VH-VL interface, and/or at the so-called Camelidae hallmark residues, as defined herein (see for example WO 94/04678, Davies and Riechmann FEBS Letters 339: 285-290, 1994; Davies and Riechmann Protein Engineering 9 (6) : 531-537, 1996; Riechmann J. Mol. Biol. 259: 957-969, 1996; and Riechmann and Muyldermans J. Immunol. Meth. 231: 25-38, 1999) .

In some embodiments, the sdAb is a human sdAb produced by transgenic mice or rats expressing human heavy chain segments. See, e.g., US20090307787A1, U.S. Pat. No. 8,754,287, US20150289489A1, US20100122358A1, and WO2004049794. In some embodiments, the sdAb is affinity matured.

In some embodiments, naturally occurring V _HH domains against a particular antigen or target, can be obtained from (

or immune) libraries of Camelid V _HH sequences. Such methods may or may not involve screening such a library using said antigen or target, or at least one part, fragment, antigenic determinant or epitope thereof using one or more screening techniques known per se. Such libraries and techniques are for example described in WO 99/37681, WO 01/90190, WO 03/025020 and WO 03/035694. Alternatively, improved synthetic or semi-synthetic libraries derived from (

or immune) V _HH libraries may be used, such as V _HH libraries obtained from (

or immune) V _HH libraries by techniques such as random mutagenesis and/or CDR shuffling, as for example described in WO 00/43507.

In some embodiments, the sdAbs are generated from conventional four-chain antibodies. See, for example, EP 0 368 684, Ward et al. (Nature 1989 Oct. 12; 341 (6242) : 544-6) , Holt et al., Trends Biotechnol., 2003, 21 (11) : 484-490; WO 06/030220; and WO 06/003388.

Because of the unique properties of sdAbs, using V _HH domains as single antigen-binding proteins or as antigen-binding domains (i.e. as part of a larger protein or polypeptide) offers a number of significant advantages over the conventional V _H and V _L, scFv and conventional antibody fragments (such as Fab or (Fab’) 2) : 1) only a single domain is required to bind an antigen with high affinity, so there is no need to have a second domain, nor to assure that these two domains are present in the correct spatial conformation and configuration (e.g. no need to pair the heavy chain and light chain during folding, no need to use a specially designed linker such as for scFv) ; 2) V _HH domains and other sdAbs can be expressed from a single gene and require no post-translational folding or modifications; 3) V _HH domains and other sdAbs can be easily engineered into multivalent and/or multispecific formats (such as those described in the present application) ; 4) V _HH domains and other sdAbs are highly soluble and do not have a tendency to aggregate (as with the mouse-derived “dAbs” described by Ward et al., Nature. 1989 Oct 12; 341 (6242) : 544-6) ; 5) V _HH domains and other sdAbs are highly stable against heat, pH, proteases and other denaturing agents or conditions; 6) V _HH domains and other sdAbs are easy and relatively cheap to prepare (even on a large production scale) , such as using microbial fermentation, there is no need to use mammalian expression system (required by production of, for example, conventional antibody fragments) ; 7) V _HH domains and other sdAbs are relatively small (approximately 15 kDa, or 10 times smaller than a conventional IgG) compared to conventional 4-chain antibodies and antigen-binding fragments thereof, thus have high (er) tissue penetration ability, such as for solid tumors and other dense tissues; and 8) V _HH domains and other sdAbs can exhibit so-called “cavity-binding properties” (due to their extended CDR3 loop compared to that of conventional V _H domains) and can therefore access targets and epitopes not accessible to conventional 4-chain antibodies and antigen-binding fragments thereof, for example, it has been shown that V _HH domains and other sdAbs can inhibit enzymes (see for example WO1997049805; Transue et al., Proteins. 1998 Sep 1; 32 (4) : 515-22; Lauwereys et al., EMBO J. 1998 Jul 1; 17 (13) : 3512-20) .

PD-L1

Similar in structure to related B7 family members, PD-L1 protein contains extracellular IgV and IgC domains and a short, cytoplasmic region. PD-L1 has an intracellular domain similar to that of CD28, which lacks intrinsic catalytic activity and contains one YVKM motif able to bind PI3K, PP2A and SHP-2 and one proline-rich motif able to bind SH3 containing proteins.

The amino acid sequence of human PD-L1 is disclosed at Genbank Accession Number Q9NZQ7. The region of amino acids 1-18 is the leader peptide; 19-238 is the extracellular domain; 239-259 is the transmembrane domain; and 260-290 is the cytoplasmic domain.

A particular human PD-L1 sequence will generally be at least 90%identical in amino acids sequence to human PD-L1 of Genbank Accession Number Q9NZQ7 and contains amino acid residues that identify the amino acid sequence as being human when compared to PD-L1 amino acid sequences of other species (e.g., murine) . In some embodiments, a human PD-L1 may be at least about 95%, 96%, 97%, 98%, or 99%identical in amino acid sequence to PD-L1 of Genbank Accession Number Q9NZQ7. In some embodiments, a human PD-L1 sequence will display no more than 10 amino acid differences from the PD-L1 of Genbank Accession Number Q9NZQ7. In some embodiments, the human PD-L1 may display no more than 5, 4, 3, 2, or 1 amino acid difference from the PD-L1 of Genbank Accession Number Q9NZQ7. Percent identity can be determined as described herein. In some embodiments, the anti-PD-L1 sdAb moiety described herein specifically recognizes a PD-L1 polypeptide with 100%amino acid sequence identity to the PD-L1 of Genbank Accession Number Q9NZQ7. In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes a PD-L1 polypeptide comprising an amino acid sequence of SEQ ID NO: 441.

In some embodiments, the anti-PD-L1 sdAb moiety may cross-react with PD-L1 from species other than human, or other proteins which are structurally related to human PD-L1 (e.g., human PD-L1 homologs) . In some embodiments, the anti-PD-L1 sdAb moiety is completely specific for human PD-L1 and not exhibit species or other types of cross-reactivity. In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes a soluble isoform of human PD-L1. In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes a membrane-bound isoform of human PD-L1 (SEQ ID NO: 441) .

In some embodiments, the anti-PD-L1 sdAb moiety described herein specifically recognizes the extracellular domain (ECD) of PD-L1. In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes the N-terminal portion of the PD-L1 extracellular domain (ECD) . In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes the C-terminal portion of the PD-L1 extracellular domain (ECD) . In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes the middle portion of the PD-L1 extracellular domain (ECD) . In some embodiments, the extracellular domain of PD-L1 specifically recognized by the anti-PD-L1 sdAb moiety is at least about 95%, 96%, 97%, 98%, or 99%identical in amino acid sequence to the extracellular domain of the PD-L1 of Genbank Accession Number Q9NZQ7. In some embodiments, the extracellular domain of PD-L1 specifically recognized by the anti-PD-L1 sdAb moiety is 100%identical in amino acid sequence to the extracellular domain of the PD-L1 of Genbank Accession Number Q9NZQ7. In some embodiments, the anti-PD-L1 sdAb moiety specifically recognizes a PD-L1 polypeptide comprising an amino acid sequence of SEQ ID NO: 442.

Antibody affinity

In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-6 M, about 10 ^-6 M to about 10 ^-7 M, about 10 ^-7 M to about 10 ^-8 M, about 10 ^-8 M to about 10 ^-9 M, about 10 ^-9 M to about 10 ^-10 M, about 10 ^-10 M to about 10 ^-11 M, about 10 ^-11 M to about 10 ^- ¹² M, about 10 ^-5 M to about 10 ^-12 M, about 10 ^-6 M to about 10 ^-12 M, about 10 ^-7 M to about 10 ^-12 M, about 10 ^-8 M to about 10 ^-12 M, about 10 ^-9 M to about 10 ^-12 M, about 10 ^-10 M to about 10 ^-12 M, about 10 ^-5 M to about 10 ^-11 M, about 10 ^-7 M to about 10 ^-11 M, about 10 ^-8 M to about 10 ^-11 M, about 10 ^-9 M to about 10 ^-11 M, about 10 ^-5 M to about 10 ^-10 M, about 10 ^-7 M to about 10 ^-10 M, about 10 ^-8 M to about 10 ^-10 M, about 10 ^-5 M to about 10 ^-9 M, about 10 ^-7 M to about 10 ^-9 M, about 10 ^-5 M to about 10 ^-8 M, or about 10 ^-6 M to about 10 ^-8 M.

In some embodiments, the K _on of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ² M ^-1s ^-1 to about 10 ⁴ M ^-1s ^-1, about 10 ⁴ M ^-1s ^-1 to about 10 ⁶ M ^-1s ^-1, about 10 ⁶ M ^-1s ^-1 to about 10 ⁷ M ^-1s ^-1, about 10 ² M ^-1s ^-1 to about 10 ⁷ M ^-1s ^-1, about 10 ³ M ^-1s ^-1 to about 10 ⁷ M ^-1s ^-1, about 10 ⁴ M ^-1s ^-1 to about 10 ⁷ M ^-1s ^-1, about 10 ⁵ M ^-1s ^-1 to about 10 ⁷ M ^-1s ^-1, about 10 ³ M ^-1s ^-1 to about 10 ⁶ M ^-1s ^-1, or about 10 ⁴ M ^-1s ^-1 to about 10 ⁶ M ^-1s ^-1.

In some embodiments, the K _off of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 1 s ^-1 to about 10 ^-2 s ^-1, about 10 ^-2 s ^-1 to about 10 ^-4 s ^-1, about 10 ^-4 s ^-1 to about 10 ^-5 s ^-1, about 10 ^-5 s ^-1 to about 10 ^-6 s ^-1, about 1 s ^-1 to about 10 ^-6 s ^-1, about 10 ^-2 s ^-1 to about 10 ^-6 s ^-1, about 10 ^-3 s ^-1 to about 10 ^-6 s ^-1, about 10 ^-4 s ^-1 to about 10 ^-6 s ^-1, about 10 ^-2 s ^-1 to about 10 ^-5 s ^-1, or about 10 ^-3 s ^-1 to about 10 ^-5 s ^-1.

In some embodiments, the IC ₅₀ of the anti-PD-L1 sdAb moiety is less than 10 nM in an amplified luminescent proximity homogeneous assay (AlphaLISA) with 0.12 nM PD-1 and 0.2 nM PD-L1. In some embodiments, the IC ₅₀ of the anti-PD-L1 sdAb moiety is less than 500 nM in an inhibition of ligand binding by FACS analysis (competition binding assay) , or cell based cytokine release assay. In some embodiments, the IC ₅₀ of the anti-PD-L1 sdAb moiety is less than 1 nM, about 1 nM to about 10 nM, about 10 nM to about 50 nM, about 50 nM to about 100 nM, about 100 nM to about 200 nM, about 200 nM to about 300 nM, about 300 nM to about 400 nM, or about 400 nM to about 500 nM.

Chimeric or humanized antibodies

In some embodiments, the anti-PD-L1 antibody provided herein is a chimeric antibody. Certain chimeric antibodies are described, e.g., in U.S. Patent No. 4,816,567; and Morrison et al., Proc. Natl. Acad. Sci. USA, 81: 6851-6855 (1984) ) . In one example, a chimeric antibody comprises a non-human variable region (e.g., a variable region derived from a camelid species, such as llama) and a human constant region. In a further example, a chimeric antibody is a “class switched” antibody in which the class or subclass has been changed from that of the parent antibody. Chimeric antibodies include antigen-binding fragments thereof.

In some embodiments, a chimeric antibody is a humanized antibody. Typically, a non-human antibody is humanized to reduce immunogenicity to humans, while retaining the specificity and affinity of the parental non-human antibody. Generally, a humanized antibody comprises one or more variable domains in which HVRs, e.g., CDRs, (or portions thereof) are derived from a non-human antibody, and FRs (or portions thereof) are derived from human antibody sequences. A humanized antibody optionally will also comprise at least a portion of a human constant region. In some embodiments, some FR residues in a humanized antibody are substituted with corresponding residues from a non-human antibody (e.g., the antibody from which the HVR residues are derived) , e.g., to restore or improve antibody specificity or affinity.

Humanized antibodies and methods of making them are reviewed, e.g., in Almagro and Fransson, Front. Biosci. 13: 1619-1633 (2008) , and are further described, e.g., in Riechmann et al., Nature 332: 323-329 (1988) ; Queen et al., Proc. Nat’ l Acad. Sci. USA 86: 10029-10033 (1989) ; US Patent Nos. 5,821,337, 7,527,791, 6,982,321, and 7,087,409; Kashmiri et al., Methods 36: 25-34 (2005) (describing SDR (a-CDR) grafting) ; Padlan, Mol. Immunol. 28: 489-498 (1991) (describing “resurfacing” ) ; Dall’A cqua et al., Methods 36: 43-60 (2005) (describing “FR shuffling” ) ; and Osbourn et al., Methods 36:61-68 (2005) and Klimka et al., Br. J. Cancer, 83: 252-260 (2000) (describing the “guided selection” approach to FR shuffling) .

Human framework regions that may be used for humanization include but are not limited to: framework regions selected using the “best-fit” method (see, e.g., Sims et al. J. Immunol. 151: 2296 (1993) ) ; framework regions derived from the consensus sequence of human antibodies of a particular subgroup of light or heavy chain variable regions (see, e.g., Carter et al. Proc. Natl. Acad. Sci. USA, 89: 4285 (1992) ; and Presta et al. J. Immunol., 151: 2623 (1993) ) ; human mature (somatically mutated) framework regions or human germline framework regions (see, e.g., Almagro and Fransson, Front. Biosci. 13: 1619-1633 (2008) ) ; and framework regions derived from screening FR libraries (see, e.g., Baca et al., J. Biol. Chem. 272: 10678-10684 (1997) and Rosok et al., J. Biol. Chem. 271: 22611-22618 (1996) ) .

In some embodiments, the sdAbs are modified, such as humanized, without diminishing the native affinity of the domain for antigen and while reducing its immunogenicity with respect to a heterologous species. For example, the amino acid residues of the antibody variable domain (V _HH) of an llama antibody can be determined, and one or more of the Camelid amino acids, for example, in the framework regions, are replaced by their human counterpart as found in the human consensus sequence, without that polypeptide losing its typical character, i.e. the humanization does not significantly affect the antigen binding capacity of the resulting polypeptide. Humanization of Camelid single-domain antibodies requires the introduction and mutagenesis of a limited amount of amino acids in a single polypeptide chain. This is in contrast to humanization of scFv, Fab', (Fab') 2 and IgG, which requires the introduction of amino acid changes in two chains, the light and the heavy chain and the preservation of the assembly of both chains.

Single-domain antibodies comprising a V _HH domain can be humanized to have human-like sequences. In some embodiments, the FR regions of the V _HH domain used herein comprise at least about any one of 50%, 60%, 70%, 80%, 90%, 95%or more of amino acid sequence homology to human VH framework regions. One exemplary class of humanized V _HH domains is characterized in that the V _HHs carry an amino acid from the group consisting of glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, tyrosine, tryptophan, methionine, serine, threonine, asparagine, or glutamine at position 45, such as, for example, L45 and a tryptophan at position 103, according to the Kabat numbering. As such, polypeptides belonging to this class show a high amino acid sequence homology to human VH framework regions and said polypeptides might be administered to a human directly without expectation of an unwanted immune response therefrom, and without the burden of further humanization.

Another exemplary class of humanized Camelid single-domain antibodies has been described in WO 03/035694 and contains hydrophobic FR2 residues typically found in conventional antibodies of human origin or from other species, but compensating this loss in hydrophilicity by the charged arginine residue on position 103 that substitutes the conserved tryptophan residue present in V _H from double-chain antibodies. As such, peptides belonging to these two classes show a high amino acid sequence homology to human V _H framework regions and said peptides might be administered to a human directly without expectation of an unwanted immune response therefrom, and without the burden of further humanization.

Human antibodies

In some embodiments, the anti-PD-L1 sdAb moiety provided herein is a human antibody. Human antibodies can be produced using various techniques known in the art. Human antibodies are described generally in van Dijk and van de Winkel, Curr. Opin. Pharmacol. 5: 368-74 (2001) and Lonberg, Curr. Opin. Immunol. 20: 450-459 (2008) . Transgenic mice or rats capable of producing fully human single-domain antibodies are known in the art. See, e.g., US20090307787A1, U.S. Pat. No. 8,754,287, US20150289489A1, US20100122358A1, and WO2004049794.

Human antibodies may be prepared by administering an immunogen to a transgenic animal that has been modified to produce intact human antibodies or intact antibodies with human variable regions in response to antigenic challenge. Such animals typically contain all or a portion of the human immunoglobulin loci, which replace the endogenous immunoglobulin loci, or which are present extrachromosomally or integrated randomly into the animal’s chromosomes. In such transgenic mice, the endogenous immunoglobulin loci have generally been inactivated. For review of methods for obtaining human antibodies from transgenic animals, see Lonberg, Nat. Biotech. 23: 1117-1125 (2005) . See also, e.g., U.S. Patent Nos. 6, 075, 181 and 6, 150, 584 describing XENOMOUSE ^TM technology; U.S. Patent No. 5,770,429 describing

technology; U.S. Patent No. 7,041,870 describing K-M

technology, and U.S. Patent Application Publication No. US 2007/0061900, describing

technology) . Human variable regions from intact antibodies generated by such animals may be further modified, e.g., by combining with a different human constant region.

Human antibodies can also be made by hybridoma-based methods. Human myeloma and mouse-human heteromyeloma cell lines for the production of human monoclonal antibodies have been described. (See, e.g., Kozbor J. Immunol., 133: 3001 (1984) ; Brodeur et al., Monoclonal Antibody Production Techniques and Applications, pp. 51-63 (Marcel Dekker, Inc., New York, 1987) ; and Boerner et al., J. Immunol., 147: 86 (1991) . ) Human antibodies generated via human B-cell hybridoma technology are also described in Li et al., Proc. Natl. Acad. Sci. USA, 103: 3557-3562 (2006) . Additional methods include those described, for example, in U.S. Patent No. 7,189,826 (describing production of monoclonal human IgM antibodies from hybridoma cell lines) and Ni, Xiandai Mianyixue, 26 (4) : 265-268 (2006) (describing human-human hybridomas) . Human hybridoma technology (Trioma technology) is also described in Vollmers and Brandlein, Histology and Histopathology, 20 (3) : 927-937 (2005) and Vollmers and Brandlein, Methods and Findings in Experimental and Clinical Pharmacology, 27 (3) : 185-91 (2005) .

Human antibodies may also be generated by isolating Fv clone variable domain sequences selected from human-derived phage display libraries. Such variable domain sequences may then be combined with a desired human constant domain. Techniques for selecting human antibodies from antibody libraries are described below.

One technique for obtaining V _HH sequences directed against a particular antigen or target involves suitably immunizing a transgenic mammal that is capable of expressing heavy chain antibodies (i.e. so as to raise an immune response and/or heavy chain antibodies directed against said antigen or target) , obtaining a suitable biological sample from said transgenic mammal that contains (nucleic acid sequences encoding) said V _HH sequences (such as a blood sample, serum sample or sample of B-cells) , and then generating V _HH sequences directed against said antigen or target, starting from said sample, using any suitable technique known per se (such as any of the methods described herein or a hybridoma technique) . For example, for this purpose, the heavy chain antibody-expressing mice and the further methods and techniques described in WO 02/085945, WO 04/049794 and WO 06/008548 and Janssens et al., Proc. Natl. Acad. Sci. USA. 2006 Oct. 10; 103 (41) : 15130-5 can be used. For example, such heavy chain antibody expressing mice can express heavy chain antibodies with any suitable (single) variable domain, such as (single) variable domains from natural sources (e.g. human (single) variable domains, Camelid (single) variable domains or shark (single) variable domains) , as well as for example synthetic or semi-synthetic (single) variable domains.

Library-derived antibodies

Antibodies of the present application may be isolated by screening combinatorial libraries for antibodies with the desired activity or activities. For example, a variety of methods are known in the art for generating phage display libraries and screening such libraries for antibodies possessing the desired binding characteristics. Such methods are reviewed, e.g., in Hoogenboom et al. in Methods in Molecular Biology 178: 1-37 (O’ Brien et al., ed., Human Press, Totowa, NJ, 2001) and further described, e.g., in the McCafferty et al., Nature 348: 552-554; Clackson et al., Nature 352: 624-628 (1991) ; Marks et al., J. Mol. Biol. 222: 581-597 (1992) ; Marks and Bradbury, in Methods in Molecular Biology 248: 161-175 (Lo, ed., Human Press, Totowa, NJ, 2003) ; Sidhu et al., J. Mol. Biol. 338 (2) : 299-310 (2004) ; Lee et al., J. Mol. Biol. 340 (5) : 1073-1093 (2004) ; Fellouse, Proc. Natl. Acad. Sci. USA 101 (34) : 12467-12472 (2004) ; and Lee et al., J. Immunol. Methods 284 (1-2) : 119-132 (2004) . Methods for constructing single-domain antibody libraries have been described, for example, see U.S. Pat. NO. 7371849.

In certain phage display methods, repertoires of VH and VL genes are separately cloned by polymerase chain reaction (PCR) and recombined randomly in phage libraries, which can then be screened for antigen-binding phage as described in Winter et al., Ann. Rev. Immunol., 12: 433-455 (1994) . Phage typically display antibody fragments, either as single-chain Fv (scFv) fragments or as Fab fragments. Libraries from immunized sources provide high-affinity antibodies to the immunogen without the requirement of constructing hybridomas. Alternatively, the naive repertoire can be cloned (e.g., from human) to provide a single source of antibodies to a wide range of non-self and also self-antigens without any immunization as described by Griffiths et al., EMBO J, 12: 725-734 (1993) . Finally, naive libraries can also be made synthetically by cloning unrearranged V-gene segments from stem cells, and using PCR primers containing random sequence to encode the highly variable CDR3 regions and to accomplish rearrangement in vitro, as described by Hoogenboom and Winter, J. Mol. Biol., 227: 381-388 (1992) . Patent publications describing human antibody phage libraries include, for example: US Patent No. 5,750,373, and US Patent Publication Nos. 2005/0079574, 2005/0119455, 2005/0266000, 2007/0117126, 2007/0160598, 2007/0237764, 2007/0292936, and 2009/0002360.

Antibodies or antibody fragments isolated from human antibody libraries are considered human antibodies or human antibody fragments herein.

Biological activities

The biological activity of anti-PD-L1 sdAb moiety described herein can be determined by measuring its half maximal inhibitory concentration (IC ₅₀) , which is a measure of the effectiveness of an antibody in inhibiting a specific biological or biochemical function (such as inhibiting the binding between PD-L1 and its receptor PD-l) . For example, here IC ₅₀ can be used to indicate the effective concentration of anti-PD-L1 sdAb needed to neutralize 50%of PD-L1 bioactivity in vitro. IC ₅₀ is comparable to an EC ₅₀ for agonist drug or other substance (such as an antibody) . EC ₅₀ also represents the plasma concentration required for obtaining 50%of a maximum effect in vivo. IC ₅₀ or EC ₅₀ can be measured by assays known in the art, for example, bioassays such as inhibition of ligand binding by FACS analysis (competition binding assay) , cell based cytokine release assay, or amplified luminescent proximity homogeneous assay (AlphaLISA) .

For example, the blockade of ligand binding can be studied using flow cytometry (also see Example 1) . CHO cells expressing human PD-L1 can be dissociated from adherent culture flasks and mixed with varying concentrations of anti-PD-L1 sdAb for test, and a constant concentration of labeled-PD-1 protein (such as biotin-labeled hPD-1/Fc protein) . An anti-PD-L1 antibody positive control can be employed, such as

The mixture is equilibrated for 30 minutes at room temperature, washed three times with FACS buffer (PBS containing 1%BSA) . Then, an antibody specifically recognizing the labeled PD-1 protein of constant concentration (such as PE/Cy5 Streptavidin secondary antibody) is added and incubated for 15 minutes at room temperature. Cells are washed with FACS buffer and analyzed by flow cytometry. Data can be analyzed with Prism (GraphPad Software, San Diego, CA) using non-linear regression to calculate IC ₅₀. The results from the competition assay will demonstrate the ability of anti-PD-L1 sdAbs in inhibiting the interaction between labeled-PD-1 and PD-L1.

The biological activity of anti-PD-L1 sdAb moiety can also be tested by PD-L1-based blockade assay for cytokine release (also see Example 1) . PD-1 signaling typically has a greater effect on cytokine production than on cellular proliferation, with significant effects on IFN-γ, TNF-α and IL-2 production. PD-1 mediated inhibitory signaling also depends on the strength of the TCR signaling, with greater inhibition delivered at low levels of TCR stimulation. This reduction can be overcome by costimulation through CD28 (Freeman et al., J. Exp. Med. 192: 1027-34 (2000) ) or the presence of IL-2 (Carter et al., Eur. J. Immunol. 32: 634-43 (2002) ) . Additionally, several studies show a receptor for PD-L1 or PD-L2 that is independent of PD-1. B7.1 has already been identified as a binding partner for PD-L1 (Butte et al., Immunity 27: 111-22 (2007) ) . Chemical crosslinking studies suggest that PD-L1 and B7.1 can interact through their IgV-like domains. B7.1: PD-L1 interactions can induce an inhibitory signal into T cells. As a result, the antagonism of signaling through PD-L1, including blocking PD-L1 from interacting with either PD-1, B7.1 or both, thereby preventing PD-L1 from sending a negative co-stimulatory signal to T-cells and other antigen presenting cells is likely to enhance immunity in response to infection (e.g., acute and chronic) and tumor immunity. In addition, the anti-PD-L1 antibodies of the present invention, may be combined with antagonists of other components of PD-1: PD-L1 signaling, for example, antagonist anti-PD-1 and anti-PD-L2 antibodies. Thus, blockade of PD-L1 pathways by anti-PD-L1 antibodies can be studied using a variety of bioassays that monitor T cell proliferation, IFN-γ release, or IL-2 secretion.

For examples, PD-1 Effector Cells (Jurkat cell stably transfected with human PD-1 protein and NFAT luciferase) and CHO-K1/human CD274 (CHO-K1 stably expressing human CD80) are mixed in wells. Anti-PD-L1 sdAbs are added into each well at different concentrations. No antibody can be used as a background control. Negative control (such as human IgG1) and positive control (such as

) can be employed. After 24-hour incubation in 37℃/5%CO ₂ incubator, medium is taken from each testing well for IL-2 secretion measurement (Cisbio) . EC ₅₀ value for each test antibody is measured, which will reflect the ability of test anti-PD-L1 sdAb in blocking the interaction between PD-1 and PD-L1 on Jurkat cells, thus in inhibiting T-cell IL-2 production.

In some embodiments, the anti-PD-L1 sdAb moiety blocks or antagonizes signals transduced by the PD-L1 ligand. In some embodiments, the anti-PD-L1 sdAb moiety can bind to an epitope on PD-L1 so as to inhibit PD-L1 from interacting with a PD-1. In some embodiments, the anti-PD-L1 sdAb moiety can reduce the binding of PD-L1 to it receptor PD-1 by at least about any of 5%, 10%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 90%, 95%, 99%or 99.9%under conditions in which the ratio of antibody combining site to PD-L1 ligand binding site is greater than 1: 1 and the concentration of antibody is greater than 10 ^-8 M.

In some embodiments, there is provided an anti-PD-L1 sdAb moiety comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions. In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

In some embodiments, the anti-PD-L1 sdAb moiety comprises a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, and the amino acid substitutions are in CDR1 and/or CDR2.

Thus, in some embodiments, there is provided an anti-PD-L1 sdAb moiety comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300. In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

In some embodiments, there is provided an anti-PD-L1 sdAb moiety comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300. In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

The sequences of the CDRs noted herein are provided in Table 15.

The CDRs can be combined in various pair-wise combinations to generate a number of anti-PD-L1 sdAb moieties.

The anti-PD-L1 sdAb moiety may comprise one or more “hallmark residues” in one or more of the FR sequences. In some embodiments, the anti-PD-L1 sdAb moiety may comprise a V _HH domain comprising the amino acid sequence of any one of the following: a-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, L, I, and V (such as Y or such as F) ; a-2) the amino acid residue at position 44 is selected from the group consisting of A, G, E, D, G, Q, R, S, and L (such as G, E, or Q) ; a-3) the amino acid residue at position 45 is selected from the group consisting of L, R and C (such as L or R) ; a-4) the amino acid residue at position 103 is selected from the group consisting of G, W, R and S (such as W or R, or such as W) ; and a-5) the amino acid residue at position 108 is Q; or b-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, L, I, and V (such as Y or such as F) ; b-2) the amino acid residue at position 44 is selected from the group consisting of E and Q; b-3) the amino acid residue at position 45 is R; b-4) the amino acid residue at position 103 is selected from the group consisting of G, W, R and S (such as W ) ; and b-5) the amino acid residue at position 108 is selected from the group consisting of Q and L (such as Q) ; wherein the amino acid position is according to Kabat numbering. It should be noted that these “hallmark residues” at amino acid positions 37, 44, 45, 103 and 108 according to Kabat numbering apply to anti-PD-L1 sdAb moieties of natural V _HH sequences, and can be substituted during humanization. For example, Q at amino acid position 108 according to Kabat numbering can be optionally humanized to L. Other humanized substitutions will be clear to those skilled in the art. For example, potentially useful humanizing substitutions can be determined by comparing the FR sequences of a naturally occurring V _HH with the corresponding FR sequences of one or more closely related human V _H, then introducing one or more of such potentially useful humanizing substitutions into said V _HH using methods known in the art (also as described herein) . The resulting humanized V _HH sequences can be tested for their PD-L1 binding affinity, for stability, for ease and level of expression, and/or for other desired properties. Possible residue substitutions may also come from an antibody V _H domain wherein the VH/VL interface comprises one or more highly charged amino acid residues. The anti-PD-L1 sdAb moiety described herein can be partially or fully humanized. Preferably, the resulting humanized anti-PD-L1 sdAb binds to PD-L1 with K _d, K _on, K _off described herein.

In some embodiments, there is provided an anti-PD-L1 sdAb moiety comprising a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof having at least about 80% (such as at least about any of 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) sequence identify to any one of SEQ ID NOs: 351-400. In some embodiments, there is provided an anti-PD-L1 sdAb moiety comprising a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the V _HH domain. In some embodiments, the anti-PD-L1 sdAb moiety comprising the V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400 or a variant thereof comprises amino acid substitutions in CDRs, such as the CDR1, and/or the CDR2, and/or the CDR3 of any one of SEQ ID NOs: 351-400. In some embodiments, the anti-PD-L1 sdAb moiety comprising the V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400 or a variant thereof comprises CDR1, CDR2, and CDR3 of any one of SEQ ID NOs: 351-400, and the amino acid substitutions are in FRs, such as the FR1, and/or the FR2, and/or the FR3, and/or the FR4 of any one of SEQ ID NOs: 351-400.

In some embodiments, there is provided an anti-PD-L1 sdAb moiety (hereinafter referred to as “competing anti-PD-L1 sdAb moiety” or “competing anti-PD-L1 sdAb” ) that specifically binds to PD-L1 competitively with any one of the anti-PD-L1 sdAb moiety described herein. In some embodiments, competitive binding may be determined using an ELISA assay. For example, in some embodiments, there is provided an anti-PD-L1 sdAb moiety that specifically binds to PD-L1 competitively with an anti-PD-L1 sdAb moiety comprising the amino acid sequence of any one of SEQ ID NOs: 351-400. For another example, in some embodiments, there is provided an anti-PD-L1 sdAb moiety that specifically binds to PD-L1 competitively with an anti-PD-L1 sdAb moiety comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300. In some embodiments, the K _d of the binding between the competing anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the competing anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

Construct comprising the anti-PD-L1 sdAb moiety

The anti-PD-L1 construct comprising the anti-PD-L1 sdAb moiety can be of any possible format.

In some embodiments, the anti-PD-L1 construct comprising the anti-PD-L1 sdAb moiety may further comprise additional polypeptide sequences, such as one or more antibody moieties, or Fc fragment of immunoglobulin. Such additional polypeptide sequences may or may not change or otherwise influence the (biological) properties of the sdAb, and may or may not add further functionality to the sdAb described herein. In some embodiments, the additional polypeptide sequences confer one or more desired properties or functionalities to the sdAb of the present invention. In some embodiments, the anti-PD-L1 construct is a chimeric antigen receptor (CAR) comprising an extracellular antigen binding domain comprising one or more anti-PD-L1 sdAb moiety described herein.

In some embodiments, the additional polypeptide sequences may be a second antibody moiety (such as sdAb, scFv, full-length antibody) that specifically recognizes a second antigen. In some embodiments, the second antigen is not PD-L1. In some embodiments, the second antibody moiety specifically recognizes the same epitope on PD-L1 as the anti-PD-L1 sdAb described herein. In some embodiments, the second antibody moiety specifically recognizes a different epitope on PD-L1 as the anti-PD-L1 sdAb described herein.

In some embodiments, the additional polypeptide sequences may increase the antibody construct half-life, solubility, or absorption, reduce immunogenicity or toxicity, eliminate or attenuate undesirable side effects, and/or confer other advantageous properties to and/or reduce undesired properties of the anti-PD-L1 construct of the invention, compared to the anti-PD-L1 sdAb described herein per se. Some non-limiting examples of such additional polypeptide sequences are serum proteins, such as human serum albumin (see for example WO 00/27435) or haptenic molecules (for example haptens that are recognized by circulating antibodies, see for example WO 98/22141) . It was shown that linking fragments of immunoglobulins (such as V _H domains) to serum albumin or fragments thereof may increase antibody half-life (see e.g. WO 00/27435 and WO 01/077137) . Thus, in some embodiments, the anti-PD-L1 construct of the present invention may comprise an anti-PD-L1 sdAb moiety described herein linked to serum albumin (or to a suitable fragment thereof) , optionally via a suitable linker (such as peptide linker) . In some embodiments, the anti-PD-L1 sdAb moiety described herein can be linked to a fragment of serum albumin at least comprising serum albumin domain III. (see PCT/EP2007/002817) .

Heavy chain-only antibody (HCAb)

In some embodiments, anti-PD-L1 sdAb moiety described herein can be linked to one or more (preferably human) C _H2 and/or C _H3 domains, optionally via a linker sequence, to increase its half-life in vivo.

Thus in some embodiments, the anti-PD-L1 construct is an HCAb (hereinafter referred to as “anti-PD-L1 HCAb” ) comprising an anti-PD-L1 sdAb moiety described herein fused to an Fc fragment of an immunoglobulin, such as IgA, IgD, IgE, IgG, and IgM. In some embodiments, the anti-PD-L1 HCAb comprises an Fc sequence of IgG, such as any of IgG1, IgG2, IgG3, or IgG4. In some embodiments, the Fc fragment is a human Fc. In some embodiments, the Fc fragment is a human IgG1 Fc. In some embodiments, the anti-PD-L1 HCAb is monomeric. In some embodiments, the anti-PD-L1 HCAb is dimeric. In some embodiments, the anti-PD-L1 sdAb moiety and the Fc fragment are optionally connected by a peptide linker. In some embodiments, the peptide linker is a mutated human IgG1 hinge (SEQ ID NO: 445) . In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 443 (GGGGSGGGS) . In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 444 (GGGGSGGGGSGGGGS) .

Thus in some embodiments, there is provided an anti-PD-L1 HCAb comprising a sdAb moiety specifically recognizing PD-L1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions, and wherein the sdAb moiety is fused to an Fc fragment of an immunoglobulin. In some embodiments, there is provided an anti-PD-L1 HCAb comprising a sdAb moiety specifically recognizing PD-L1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions, and wherein the sdAb moiety is fused to an Fc fragment of an immunoglobulin. In some embodiments, the amino acid substitutions are in CDR1 and/or CDR2. In some embodiments, there is provided an anti-PD-L1 HCAb comprising a sdAb moiety specifically recognizing PD-L1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, and wherein the sdAb moiety is fused to an Fc fragment of an immunoglobulin. In some embodiments, the anti-PD-L1 sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of the following: a-1) the amino acid residue at position 44 is selected from the group consisting of A, G, E, D, G, Q, R, S, and L (such as G, E, or Q) ; a-2) the amino acid residue at position 45 is selected from the group consisting of L, R and C (such as L or R) ; a-3) the amino acid residue at position 103 is selected from the group consisting of W, R and S (such as W or R, or such as W) ; and a-4) the amino acid residue at position 108 is Q; b-1) the amino acid residue at position 44 is selected from the group consisting of E and Q; b-2) the amino acid residue at position 45 is R; b-3) the amino acid residue at position 103 is selected from the group consisting of W, R and S (such as W) ; and b-4) the amino acid residue at position 108 is selected from the group consisting of Q and L (such as Q) ; wherein the amino acid position is according to Kabat numbering, and wherein position 108 can be optionally humanized to L when position 108 is Q. In some embodiments, the Fc fragment is a human IgG1 Fc. In some embodiments, the anti-PD-L1 HCAb is monomeric. In some embodiments, the anti-PD-L1 HCAb is dimeric. In some embodiments, the anti-PD-L1 sdAb moiety and the Fc fragment are optionally connected by a peptide linker. In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 443, SEQ ID NO: 444, or SEQ ID NO: 445. In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

In some embodiments, there is provided an anti-PD-L1 HCAb comprising the amino acid sequence of any one of SEQ ID NOs: 401-440.

In some embodiments, there is also provided an anti-PD-L1 HCAb (hereinafter referred to as “competing anti-PD-L1 HCAb” ) that specifically binds to PD-L1 competitively with any one of the anti-PD-L1 HCAb described herein. Competitive binding may be determined using an ELISA assay. For example, in some embodiments, there is provided an anti-PD-L1 HCAb that specifically binds to PD-L1 competitively with an anti-PD-L1 HCAb comprising the amino acid sequence of any one of SEQ ID NOs: 401-440. For another example, in some embodiments, there is provided an anti-PD-L1 HCAb that specifically binds to PD-L1 competitively with an anti-PD-L1 HCAb comprising a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300. In some embodiments, the K _d of the binding between the competing anti-PD-L1 HCAb and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the competing anti-PD-L1 HCAb is camelid, chimeric, human, partially humanized, or fully humanized.

Multivalent and/or multispecific antibodies

In some embodiments, the anti-PD-L1 construct comprises an anti-PD-L1 sdAb moiety described herein fused to one or more other antibody moiety (such as an antibody moiety that specifically recognizes another antigen) . The one or more other antibody moiety can be of any antibody or antibody fragment format, such as a multispecific sdAb (such as bispecific sdAb) , a full-length antibody, a Fab, a Fab’, a (Fab’ ) 2, an Fv, a single chain Fv (scFv) , an scFv-scFv, a minibody, a diabody, or a sdAb. For a review of certain antibody fragments, see Hudson et al. Nat. Med. 9: 129-134 (2003) . For a review of scFv fragments, see, e.g., Pluckthün, in The Pharmacology of Monoclonal Antibodies, vol. 113, Rosenburg and Moore eds., (Springer-Verlag, New York) , pp. 269-315 (1994) ; see also WO 93/16185; and U.S. Patent Nos. 5,571,894 and 5,587,458. For discussion of Fab and F (ab') ₂ fragments comprising salvage receptor binding epitope residues and having increased in vivo half-life, see U.S. Patent No. 5,869,046. For a review of multispecific antibodies, see Weidle et al., Cancer Genomics Proteomics, 10 (1) : 1-18, 2013; Geering and Fussenegger, Trends Biotechnol., 33 (2) : 65-79, 2015; Stamova et al., Antibodies, 1 (2) : 172-198, 2012. Diabodies are antibody fragments with two antigen-binding sites that may be bivalent or bispecific. See, for example, EP 404,097; WO 1993/01161; Hudson et al., Nat. Med. 9: 129-134 (2003) ; and Hollinger et al., Proc. Natl. Acad. Sci. USA 90: 6444-6448 (1993) . Triabodies and tetrabodies are also described in Hudson et al., Nat. Med. 9: 129-134 (2003) . Antibody fragments can be made by various techniques, including but not limited to proteolytic digestion of an intact antibody as well as production by recombinant host cells (e.g. E. coli or phage) , as described herein. In some embodiments, the one or more other antibody moiety is antibody mimetics, which are small engineered proteins comprising antigen-binding domains reminiscent of antibodies (Geering and Fussenegger, Trends Biotechnol., 33 (2) : 65-79, 2015) . These molecules are derived from existing human scaffold proteins and comprise a single polypeptide. Exemplary antibody mimetics that can be comprised within the anti-PD-L1 construct described herein can be, but are not limited to, a designed ankyrin repeat protein (DARPin; comprising 3-5 fully synthetic ankyrin repeats flanked by N-and C-terminal Cap domains) , an avidity multimer (avimer; a high-affinity protein comprising multiple A domains, each domain with low affinity for a target) , or an Anticalin (based on the scaffold of lipocalins, with four accessible loops, the sequence of each can be randomized) .

Techniques for making multispecific antibodies include, but are not limited to, recombinant co-expression of two immunoglobulin heavy chain-light chain pairs having different specificities (see Milstein and Cuello, Nature 305: 537 (1983) ) , WO 93/08829, and Traunecker et al., EMBO J. 10: 3655 (1991) ) , and “knob-in-hole” engineering (see, e.g., U.S. Patent No. 5,731,168) . Multi-specific antibodies may also be made by engineering electrostatic steering effects for making antibody Fc-heterodimeric molecules (WO 2009/089004A1) ; cross-linking two or more antibodies or fragments (see, e.g., US Patent No. 4,676,980, and Brennan et al., Science, 229: 81 (1985) ) ; using leucine zippers to produce bi-specific antibodies (see, e.g., Kostelny et al., J. Immunol., 148 (5) : 1547-1553 (1992) ) ; using “diabody” technology for making bispecific antibody fragments (see, e.g., Hollinger et al., Proc. Natl. Acad. Sci. USA, 90: 6444-6448 (1993) ) ; and using single-chain Fv (sFv) dimers (see, e.g., Gruber et al., J. Immunol., 152: 5368 (1994) ) ; and preparing trispecific antibodies as described, e.g., in Tutt et al. J. Immunol. 147: 60 (1991) ; and creating polypeptides comprising tandem single-domain antibodies (see, e.g., U.S. Patent Application No. 20110028695; and Conrath et al. J. Biol. Chem., 2001; 276 (10) : 7346-50) . Engineered antibodies with three or more functional antigen binding sites, including “Octopus antibodies, ” are also included herein (see, e.g., US 2006/0025576A1) .

Peptide linkers

In some embodiments, the two or more antibody moieties within the anti-PD-L1 construct can be optionally connected by a peptide linker. The length, the degree of flexibility and/or other properties of the peptide linker (s) used in the anti-PD-L1 construct may have some influence on properties, including but not limited to the affinity, specificity or avidity for one or more particular antigens or epitopes. For example, longer peptide linkers may be selected to ensure that two adjacent domains do not sterically interfere with one another. In some embodiment, a peptide linker comprises flexible residues (such as glycine and serine) so that the adjacent domains are free to move relative to each other. For example, a glycine-serine doublet can be a suitable peptide linker.

The peptide linker can be of any suitable length. In some embodiments, the peptide linker is at least about any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 50, 75, 100 or more amino acids long. In some embodiments, the peptide linker is no more than about any of 100, 75, 50, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5 or fewer amino acids long. In some embodiments, the length of the peptide linker is any of about 1 amino acid to about 10 amino acids, about 1 amino acid to about 20 amino acids, about 1 amino acid to about 30 amino acids, about 5 amino acids to about 15 amino acids, about 10 amino acids to about 25 amino acids, about 5 amino acids to about 30 amino acids, about 10 amino acids to about 30 amino acids long, about 30 amino acids to about 50 amino acids, about 50 amino acids to about 100 amino acids, or about 1 amino acid to about 100 amino acids.

The peptide linker may have a naturally occurring sequence, or a non-naturally occurring sequence. For example, a sequence derived from the hinge region of heavy chain only antibodies may be used as the linker. See, for example, WO1996/34103. In some embodiments, the peptide linker is a mutated human IgG1 hinge (SEQ ID NO: 445) . In some embodiments, the peptide linker is a flexible linker. Exemplary flexible linkers include glycine polymers (G) _n, glycine-serine polymers (including, for example, (GS) _n, (GSGGS) _n, (GGGS) _n, and (GGGGS) _n, where n is an integer of at least one) , glycine-alanine polymers, alanine-serine polymers, and other flexible linkers known in the art. In some embodiments, the peptide linker comprises the amino acid sequence of GGGGSGGGS (SEQ ID NO: 443) . In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 444 (GGGGSGGGGSGGGGS) . In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 445 (EPKSSDKTHTSPPSP) .

In some embodiments, the anti-PD-L1 construct comprising an anti-PD-L1 sdAb moiety and one or more other antibody moiety is monospecific. In some embodiments, the anti-PD-L1 construct comprising an anti-PD-L1 sdAb moiety and one or more other antibody moiety is multispecific (such as bispecific) . Multispecific molecules are molecules that have binding specificities for at least two different antigens or epitopes (e.g., bispecific antibodies have binding specificities for two antigens or epitopes) . Multispecific molecules with more than two valencies and/or specificities are also contemplated. For example, trispecific antibodies can be prepared. Tutt et al. J. Immunol. 147: 60 (1991) . It is to be appreciated that one of skill in the art could select appropriate features of individual multispecific molecules described herein to combine with one another to form a multi-specific anti-PD-L1 molecule of the invention.

In some embodiments, the anti-PD-L1 construct is multivalent but monospecific, i.e., the anti-PD-L1 construct comprises an anti-PD-L1 sdAb moiety described herein and at least a second antibody moiety specifically recognizing the same PD-L1 epitope as the anti-PD-L1 sdAb moiety. In some embodiments, the one or more antibody moiety specifically recognizing the same PD-L1 epitope as the anti-PD-L1 sdAb moiety described herein may comprise the same CDRs and/or the same V _HH amino acid sequence as the anti-PD-L1 sdAb moiety. For example, the anti-PD-L1 construct may comprise two or more anti-PD-L1 sdAb moieties described herein, wherein the two or more anti-PD-L1 sdAb moieties are the same. In some embodiments, the anti-PD-L1 sdAb moieties are optionally connected by peptide linker (s) . In some embodiments, the peptide linker comprises the amino acid sequence of any one of SEQ ID NO: 443-445.

In some embodiments, the anti-PD-L1 construct is multivalent and multispecific, i.e., the anti-PD-L1 construct comprises an anti-PD-L1 sdAb moiety described herein and at least a second antibody moiety specifically recognizing a second antigen other than PD-L1, or a different PD-L1 epitope recognized by the anti-PD-L1 sdAb moiety. In some embodiments, the second antibody moiety is a sdAb. In some embodiments, the second antibody moiety specifically recognizes human serum albumin (HSA) . In some embodiments, the sdAb moiety specifically recognizing PD-L1 is N terminal or C terminal to the second antibody moiety. In some embodiments, the anti-PD-L1 construct is trivalent and bispecific. In some embodiments, the anti-PD-L1 construct comprises two anti-PD-L1 sdAbs described herein and a second antibody moiety (such as an anti-HSA sdAb) , wherein the second antibody moiety is in between the two anti-PD-L1 sdAbs. In some embodiments, the antibody moieties are optionally connected by peptide linker (s) . In some embodiments, the peptide linker comprises the amino acid sequence of any one of SEQ ID NO: 443-445.

The monospecific or multispecific anti-PD-L1 construct comprising two or more sdAb moieties specifically recognizing PD-L1 may have increase avidity compared to that of a single anti-PD-L1 sdAb moiety described here.

Bispecific antibodies comprising sdAb fused to full-length antibody

In some embodiments, the anti-PD-L1 construct comprises an anti-PD-L1 sdAb moiety described herein fused to a second antibody moiety, wherein the second antibody moiety is a full-length antibody (such as anti-TIGIT full-length antibody) . The construct comprising bi-specificity against PD-L1 and TIGIT will be hereinafter referred to as “anti-PD-L1/TIGIT antibody” , “anti-PD-L1/TIGIT construct” , or “PD-L1×TIGIT antibody” .

In some embodiments, the anti-PD-L1 construct comprises an anti-PD-L1 sdAb moiety described herein fused to a second antibody moiety, wherein the second antibody moiety is a full-length antibody (such as anti-TIM-3 full-length antibody) . The construct comprising bi-specificity against PD-L1 and TIM-3 will be hereinafter referred to as “anti-PD-L1/TIM-3 antibody” , “anti-PD-L1/TIM-3 construct” , or “PD-L1×TIM-3 antibody” .

In some embodiments, the anti-PD-L1 construct comprises an anti-PD-L1 sdAb moiety described herein fused to a second antibody moiety, wherein the second antibody moiety is a full-length antibody (such as anti-LAG-3 full-length antibody) . The construct comprising bi-specificity against PD-L1 and LAG-3 will be hereinafter referred to as “anti-PD-L1/LAG-3 antibody” , “anti-PD-L1/LAG-3 construct” , or “PD-L1×LAG-3 antibody” .

TIGIT, TIM-3 and LAG-3, similar to PD-L1, are inhibitory immune checkpoint molecules.

In some embodiments, there is provided an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1 and a full length antibody selected from the group consisting of an anti-TIGIT antibody, an anti-TIM-3 antibody, and an anti-LAG-3 antibody, wherein the anti-PD-L1 sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions. In some embodiments, the N terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the C terminus of at least one of the heavy chains of the full-length antibody. In some embodiments, the C terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the N terminus of at least one of the heavy chains of the full-length antibody. In some embodiments, the sdAb moiety specifically recognizing PD-L1 and the full-length antibody are optionally connected by a peptide linker. In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 443-445. In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

In some embodiments, there is provided an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1 and a full length antibody selected from the group consisting of an anti-TIGIT antibody, an anti-TIM-3 antibody, and an anti-LAG-3 antibody, wherein the sdAb comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof having at least about 80% (such as at least about any of 80%, 85%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%) sequence identify to any one of SEQ ID NOs: 351-400. In some embodiments, there is provided an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1 and a full length antibody selected from the group consisting of an anti-TIGIT antibody, an anti-TIM-3 antibody, and an anti-LAG-3 antibody, wherein the sdAb comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the V _HH domain. In some embodiments, the anti-PD-L1 sdAb moiety comprising the V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400 or a variant thereof comprises amino acid substitutions in CDRs, such as the CDR1, and/or the CDR2, and/or the CDR3 of any one of SEQ ID NOs: 351-400. In some embodiments, the anti-PD-L1 sdAb moiety comprising the V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400 or a variant thereof comprises CDR1, CDR2, and CDR3 of any one of SEQ ID NOs: 351-400, and the amino acid substitutions are in FRs, such as the FR1, and/or the FR2, and/or the FR3, and/or the FR4 of any one of SEQ ID NOs: 351-400. In some embodiments, the anti-PD-L1 sdAb moiety comprising the V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400 or a variant thereof comprises amino acid substitutions in both CDRs and FRs. In some embodiments, there is provided an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1 and a full-length antibody selected from the group consisting of an anti-TIGIT antibody, an anti-TIM-3 antibody, and an anti-LAG-3 antibody, wherein the sdAb comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400. In some embodiments, the N terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the C terminus of at least one of the heavy chains of the full-length antibody. In some embodiments, the C terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the N terminus of at least one of the heavy chains of the full-length antibody. In some embodiments, the sdAb moiety specifically recognizing PD-L1 and the full-length antibody are optionally connected by a peptide linker. In some embodiments, the peptide linker comprises the amino acid sequence of SEQ ID NO: 443-445. In some embodiments, the K _d of the binding between the anti-PD-L1 sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M (such as about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M) . In some embodiments, the anti-PD-L1 sdAb moiety is camelid, chimeric, human, partially humanized, or fully humanized.

In some embodiments, there is also provided an anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1 (hereinafter referred to as “competing anti-PD-L1 construct” ) that specifically binds to PD-L1 competitively with any one of the anti-PD-L1/TIGIT constructs, anti-PD-L1/TIM-3 constructs or anti-PD-L1/LAG-3 constructs described herein.

Anti-PD-L1 antibody variants

In some embodiments, amino acid sequence variants of the antibodies provided herein are contemplated. For example, it may be desirable to improve the binding affinity and/or other biological properties of the antibody. Amino acid sequence variants of an antibody may be prepared by introducing appropriate modifications into the nucleic acid sequence encoding the antibody, or by peptide synthesis. Such modifications include, for example, deletions from, and/or insertions into and/or substitutions of residues within the amino acid sequences of the antibody. Any combination of deletion, insertion, and substitution can be made to arrive at the final construct, provided that the final construct possesses the desired characteristics, e.g., antigen-binding.

a) Substitution, insertion, deletion and variants

In some embodiments, antibody variants having one or more amino acid substitutions are provided. Sites of interest for substitutional mutagenesis include the HVRs and FRs. Conservative substitutions are shown in Table 2 under the heading of “Preferred substitutions. ” More substantial changes are provided in Table 2 under the heading of “exemplary substitutions, ” and as further described below in reference to amino acid side chain classes. Amino acid substitutions may be introduced into an antibody of interest and the products screened for a desired activity, e.g., retained/improved antigen binding, decreased immunogenicity, or improved ADCC or CDC.

Table 2. Amino acid substitutions

Original Residue	Exemplary Substitutions	Preferred Substitutions
Ala (A)	Val; Leu; Ile	Val
Arg (R)	Lys; Gln; Asn	Lys
Asn (N)	Gln; His; Asp, Lys; Arg	Gln
Asp (D)	Glu; Asn	Glu
Cys (C)	Ser; Ala	Ser
Gln (Q)	Asn; Glu	Asn
Glu (E)	Asp; Gln	Asp
Gly (G)	Ala	Ala
His (H)	Asn; Gln; Lys; Arg	Arg
Ile (I)	Leu; Val; Met; Ala; Phe; Norleucine	Leu
Leu (L)	Norleucine; Ile; Val; Met; Ala; Phe	Ile
Lys (K)	Arg; Gln; Asn	Arg
Met (M)	Leu; Phe; Ile	Leu
Phe (F)	Trp; Leu; Val; Ile; Ala; Tyr	Tyr
Pro (P)	Ala	Ala
Ser (S)	Thr	Thr
Thr (T)	Val; Ser	Ser
Trp (W)	Tyr; Phe	Tyr
Tyr (Y)	Trp; Phe; Thr; Ser	Phe
Val (V)	Ile; Leu; Met; Phe; Ala; Norleucine	Leu

Amino acids may be grouped according to common side-chain properties:

(1) hydrophobic: Norleucine, Met, Ala, Val, Leu, Ile;

(2) neutral hydrophilic: Cys, Ser, Thr, Asn, Gln;

(3) acidic: Asp, Glu;

(4) basic: His, Lys, Arg;

(5) residues that influence chain orientation: Gly, Pro;

(6) aromatic: Trp, Tyr, Phe.

Non-conservative substitutions will entail exchanging a member of one of these classes for another class.

One type of substitutional variant involves substituting one or more hypervariable region residues of a parent antibody (e.g., a humanized or human antibody) . Generally, the resulting variant (s) selected for further study will have modifications (e.g., improvements) in certain biological properties (e.g., increased affinity, reduced immunogenicity) relative to the parent antibody and/or will have substantially retained certain biological properties of the parent antibody. An exemplary substitutional variant is an affinity matured antibody, which may be conveniently generated, e.g., using phage display-based affinity maturation techniques such as those described herein. Briefly, one or more HVR residues are mutated and the variant antibodies displayed on phage and screened for a particular biological activity (e.g. binding affinity) .

Alterations (e.g., substitutions) may be made in HVRs, e.g., to improve antibody affinity. Such alterations may be made in HVR “hotspots, ” i.e., residues encoded by codons that undergo mutation at high frequency during the somatic maturation process (see, e.g., Chowdhury, Methods Mol. Biol. 207: 179-196 (2008) ) , and/or SDRs (a-CDRs) , with the resulting variant VH or VL being tested for binding affinity. Affinity maturation by constructing and reselecting from secondary libraries has been described, e.g., in Hoogenboom et al. in Methods in Molecular Biology 178: 1-37 (O’ Brien et al., ed., Human Press, Totowa, NJ, (2001) ) In some embodiments of affinity maturation, diversity is introduced into the variable genes chosen for maturation by any of a variety of methods (e.g., error-prone PCR, chain shuffling, or oligonucleotide-directed mutagenesis) . A secondary library is then created. The library is then screened to identify any antibody variants with the desired affinity. Another method to introduce diversity involves HVR-directed approaches, in which several HVR residues (e.g., 4-6 residues at a time) are randomized. HVR residues involved in antigen binding may be specifically identified, e.g., using alanine scanning mutagenesis or modeling. CDR-H3 and CDR-L3 in particular are often targeted.

In some embodiments, substitutions, insertions, or deletions may occur within one or more HVRs so long as such alterations do not substantially reduce the ability of the antibody to bind antigen. For example, conservative alterations (e.g., conservative substitutions as provided herein) that do not substantially reduce binding affinity may be made in HVRs. Such alterations may be outside of HVR “hotspots” or CDRs. In some embodiments of the variant V _HH sequences provided above, each HVR either is unaltered, or contains no more than one, two or three amino acid substitutions.

A useful method for identification of residues or regions of an antibody that may be targeted for mutagenesis is called “alanine scanning mutagenesis” as described by Cunningham and Wells (1989) Science, 244: 1081-1085. In this method, a residue or group of target residues (e.g., charged residues such as Arg, Asp, His, Lys, and Glu) are identified and replaced by a neutral or negatively charged amino acid (e.g., alanine or polyalanine) to determine whether the interaction of the antibody with antigen is affected. Further substitutions may be introduced at the amino acid locations demonstrating functional sensitivity to the initial substitutions. Alternatively, or additionally, a crystal structure of an antigen-antibody complex to identify contact points between the antibody and antigen. Such contact residues and neighboring residues may be targeted or eliminated as candidates for substitution. Variants may be screened to determine whether they contain the desired properties.

Amino acid sequence insertions include amino-and/or carboxyl-terminal fusions ranging in length from one residue to polypeptides containing a hundred or more residues, as well as intrasequence insertions of single or multiple amino acid residues. Examples of terminal insertions include an antibody with an N-terminal methionyl residue. Other insertional variants of the antibody molecule include the fusion to the N-or C-terminus of the antibody to an enzyme (e.g., for ADEPT) or a polypeptide which increases the serum half-life of the antibody.

b) Glycosylation variants

In some embodiments, an anti-PD-L1 construct provided herein is altered to increase or decrease the extent to which the construct is glycosylated. Addition or deletion of glycosylation sites to an antibody may be conveniently accomplished by altering the amino acid sequence such that one or more glycosylation sites is created or removed.

Where the anti-PD-L1 construct comprises an Fc region, the carbohydrate attached thereto may be altered. Native antibodies produced by mammalian cells typically comprise a branched, biantennary oligosaccharide that is generally attached by an N-linkage to Asn297 of the CH2 domain of the Fc region. See, e.g., Wright et al. TIBTECH 15: 26-32 (1997) . The oligosaccharide may include various carbohydrates, e.g., mannose, N-acetyl glucosamine (GlcNAc) , galactose, and sialic acid, as well as a fucose attached to a GlcNAc in the “stem” of the biantennary oligosaccharide structure. In some embodiments, modifications of the oligosaccharide in an anti-PD-L1 construct of the present application may be made in order to create antibody variants with certain improved properties.

In some embodiments, antibody variants are provided having a carbohydrate structure that lacks fucose attached (directly or indirectly) to an Fc region. For example, the amount of fucose in such antibody may be from 1%to 80%, from 1%to 65%, from 5%to 65%or from 20%to 40%. The amount of fucose is determined by calculating the average amount of fucose within the sugar chain at Asn297, relative to the sum of all glycostructures attached to Asn 297 (e.g., complex, hybrid and high mannose structures) as measured by MALDI-TOF mass spectrometry, as described in WO 2008/077546, for example. Asn297 refers to the asparagine residue located at about position 297 in the Fc region (EU numbering of Fc region residues) ; however, Asn297 may also be located about ± 3 amino acids upstream or downstream of position 297, i.e., between positions 294 and 300, due to minor sequence variations in antibodies. Such fucosylation variants may have improved ADCC function. See, e.g., US Patent Publication Nos. US 2003/0157108 (Presta, L. ) ; US 2004/0093621 (Kyowa Hakko Kogyo Co., Ltd) . Examples of publications related to “defucosylated” or “fucose-deficient” antibody variants include: US 2003/0157108; WO 2000/61739; WO 2001/29246; US 2003/0115614; US 2002/0164328; US 2004/0093621; US 2004/0132140; US 2004/0110704; US 2004/0110282; US 2004/0109865; WO 2003/085119; WO 2003/084570; WO 2005/035586; WO 2005/035778; WO2005/053742; WO2002/031140; Okazaki et al. J. Mol. Biol. 336: 1239-1249 (2004) ; Yamane-Ohnuki et al. Biotech. Bioeng. 87: 614 (2004) . Examples of cell lines capable of producing defucosylated antibodies include Lec13 CHO cells deficient in protein fucosylation (Ripka et al. Arch. Biochem. Biophys. 249: 533-545 (1986) ; US Patent Application No. US 2003/0157108 A1, Presta, L; and WO 2004/056312 A1, Adams et al., especially at Example 11) , and knockout cell lines, such as alpha-1, 6-fucosyltransferase gene, FUT8, knockout CHO cells (see, e.g., Yamane-Ohnuki et al. Biotech. Bioeng. 87: 614 (2004) ; Kanda, Y. et al., Biotechnol. Bioeng., 94 (4) : 680-688 (2006) ; and WO2003/085107) .

Anti-PD-L1 construct variants are further provided with bisected oligosaccharides, e.g., in which a biantennary oligosaccharide attached to the Fc region of the antibody is bisected by GlcNAc. Such antibody variants may have reduced fucosylation and/or improved ADCC function. Examples of such antibody variants are described, e.g., in WO 2003/011878 (Jean-Mairet et al. ) ; US Patent No. 6,602,684 (Umana et al. ) ; and US 2005/0123546 (Umana et al. ) . Antibody variants with at least one galactose residue in the oligosaccharide attached to the Fc region are also provided. Such antibody variants may have improved CDC function. Such antibody variants are described, e.g., in WO 1997/30087 (Patel et al. ) ; WO 1998/58964 (Raju, S. ) ; and WO 1999/22764 (Raju, S. ) .

c) Fc region variants

In some embodiments, one or more amino acid modifications may be introduced into the Fc region of the anti-PD-L1 construct provided herein, thereby generating an Fc region variant. The Fc region variant may comprise a human Fc region sequence (e.g., a human IgG1, IgG2, IgG3 or IgG4 Fc region) comprising an amino acid modification (e.g. a substitution) at one or more amino acid positions.

In some embodiments, the present application contemplates an anti-PD-L1 construct variant that possesses some but not all effector functions, which make it a desirable candidate for applications in which the half-life of the anti-PD-L1 construct in vivo is important yet certain effector functions (such as complement and ADCC) are unnecessary or deleterious. In vitro and/or in vivo cytotoxicity assays can be conducted to confirm the reduction/depletion of CDC and/or ADCC activities. For example, Fc receptor (FcR) binding assays can be conducted to ensure that the antibody lacks FcγR binding (hence likely lacking ADCC activity) , but retains FcRn binding ability. The primary cells for mediating ADCC, NK cells, express FcγRIII only, whereas monocytes express FcγRI, FcγRII and FcγRIII. FcR expression on hematopoietic cells is summarized in Table 3 on page 464 of Ravetch and Kinet, Annu. Rev. Immunol. 9: 457-492 (1991) . Non-limiting examples of in vitro assays to assess ADCC activity of a molecule of interest is described in U.S. Patent No. 5,500,362 (see, e.g. Hellstrom, I. et al. Proc. Nat’ l Acad. Sci. USA 83: 7059-7063 (1986) ) and Hellstrom, I et al., Proc. Nat’ l Acad. Sci. USA 82: 1499-1502 (1985) ; 5,821,337 (see Bruggemann, M. et al., J. Exp. Med. 166: 1351-1361 (1987) ) . Alternatively, non-radioactive assays methods may be employed (see, for example, ACTI ^TM non-radioactive cytotoxicity assay for flow cytometry (Cell Technology, Inc. Mountain View, CA; and CytoTox

non-radioactive cytotoxicity assay (Promega, Madison, WI) . Useful effector cells for such assays include peripheral blood mononuclear cells (PBMC) and Natural Killer (NK) cells. Alternatively, or additionally, ADCC activity of the molecule of interest may be assessed in vivo, e.g., in an animal model such as that disclosed in Clynes et al. Proc. Nat’ l Acad. Sci. USA 95: 652-656 (1998) . C1q binding assays may also be carried out to confirm that the antibody is unable to bind C1q and hence lacks CDC activity. See, e.g., C1q and C3c binding ELISA in WO 2006/029879 and WO 2005/100402. To assess complement activation, a CDC assay may be performed (see, for example, Gazzano-Santoro et al., J. Immunol. Methods 202: 163 (1996) ; Cragg, M.S. et al., Blood 101: 1045-1052 (2003) ; and Cragg, M.S. and M.J. Glennie, Blood 103: 2738-2743 (2004) ) . FcRn binding and in vivo clearance/half-life determinations can also be performed using methods known in the art (see, e.g., Petkova, S.B. et al., Int’l. Immunol. 18 (12) : 1759-1769 (2006) ) .

Antibodies with reduced effector function include those with substitution of one or more of Fc region residues 238, 265, 269, 270, 297, 327 and 329 (U.S. Patent No. 6,737,056) . Such Fc mutants include Fc mutants with substitutions at two or more of amino acid positions 265, 269, 270, 297 and 327, including the so-called “DANA” Fc mutant with substitution of residues 265 and 297 to alanine (US Patent No. 7,332,581) .

Certain antibody variants with improved or diminished binding to FcRs are described. (See, e.g., U.S. Patent No. 6,737,056; WO 2004/056312, and Shields et al., J. Biol. Chem. 9 (2) : 6591-6604 (2001) ) .

In some embodiments, an anti-PD-L1 construct variant comprises an Fc region with one or more amino acid substitutions which improve ADCC, e.g., substitutions at positions 298, 333, and/or 334 of the Fc region (EU numbering of residues) .

In some embodiments, alterations are made in the Fc region that result in altered (i.e., either improved or diminished) C1q binding and/or Complement Dependent Cytotoxicity (CDC) , e.g., as described in US Patent No. 6,194,551, WO 99/51642, and Idusogie et al. J. Immunol. 164: 4178-4184 (2000) .

In some embodiments, there is provided an anti-PD-L1 construct (e.g., a HCAb) variant comprising a variant Fc region comprising one or more amino acid substitutions which increase half-life and/or improve binding to the neonatal Fc receptor (FcRn) . Antibodies with increased half-lives and improved binding to the neonatal Fc receptor (FcRn) , which is responsible for the transfer of maternal IgGs to the fetus (Guyer et al., J. Immunol. 117: 587 (1976) and Kim et al., J. Immunol. 24: 249 (1994) ) , are described in US2005/0014934A1 (Hinton et al. ) . Those antibodies comprise an Fc region with one or more substitutions therein which improve binding of the Fc region to FcRn. Such Fc variants include those with substitutions at one or more of Fc region residues: 238, 256, 265, 272, 286, 303, 305, 307, 311, 312, 317, 340, 356, 360, 362, 376, 378, 380, 382, 413, 424 or 434, e.g., substitution of Fc region residue 434 (US Patent No. 7,371,826) .

See also Duncan &Winter, Nature 322: 738-40 (1988) ; U.S. Patent No. 5,648,260; U.S. Patent No. 5,624,821; and WO 94/29351 concerning other examples of Fc region variants.

Anti-PD-L1 constructs (such as HCAb or anti-PD-L1 sdAb fused to a full-length antibody) comprising any of the Fc variants described herein, or combinations thereof, are contemplated.

d) Cysteine engineered antibody variants

In some embodiments, it may be desirable to create cysteine engineered anti-PD-L1 constructs, e.g., “thioMAbs, ” in which one or more residues of an antibody are substituted with cysteine residues. In particular embodiments, the substituted residues occur at accessible sites of the antibody. By substituting those residues with cysteine, reactive thiol groups are thereby positioned at accessible sites of the antibody and may be used to conjugate the antibody to other moieties, such as drug moieties or linker-drug moieties, to create an immunoconjugate, as described further herein. In some embodiments, any one or more of the following residues may be substituted with cysteine: A118 (EU numbering) of the heavy chain; and S400 (EU numbering) of the heavy chain Fc region. Cysteine engineered anti-PD-L1 constructs may be generated as described, e.g., in U.S. Patent No. 7,521,541.

e) Antibody derivatives

In some embodiments, an anti-PD-L1 construct provided herein may be further modified to contain additional nonproteinaceous moieties that are known in the art and readily available. The moieties suitable for derivatization of the antibody include but are not limited to water soluble polymers. Non-limiting examples of water soluble polymers include, but are not limited to, polyethylene glycol (PEG) , copolymers of ethylene glycol/propylene glycol, carboxymethylcellulose, dextran, polyvinyl alcohol, polyvinyl pyrrolidone, poly-1, 3-dioxolane, poly-1, 3, 6-trioxane, ethylene/maleic anhydride copolymer, polyaminoacids (either homopolymers or random copolymers) , and dextran or poly (n-vinyl pyrrolidone) polyethylene glycol, propropylene glycol homopolymers, prolypropylene oxide/ethylene oxide co-polymers, polyoxyethylated polyols (e.g., glycerol) , polyvinyl alcohol, and mixtures thereof. Polyethylene glycol propionaldehyde may have advantages in manufacturing due to its stability in water. The polymer may be of any molecular weight, and may be branched or unbranched. The number of polymers attached to the antibody may vary, and if more than one polymer are attached, they can be the same or different molecules. In general, the number and/or type of polymers used for derivatization can be determined based on considerations including, but not limited to, the particular properties or functions of the antibody to be improved, whether the antibody derivative will be used in a therapy under defined conditions, etc.

In some embodiments, conjugates of an anti-PD-L1 construct and nonproteinaceous moiety that may be selectively heated by exposure to radiation are provided. In some embodiments, the nonproteinaceous moiety is a carbon nanotube (Kam et al., Proc. Natl. Acad. Sci. USA 102: 11600-11605 (2005) ) . The radiation may be of any wavelength, and includes, but is not limited to, wavelengths that do not harm ordinary cells, but which heat the nonproteinaceous moiety to a temperature at which cells proximal to the antibody-nonproteinaceous moiety are killed.

In some embodiments, an anti-PD-L1 construct provided herein (such as anti-PD-L1 sdAb, anti-PD-L1 HCAb, anti-PD-L1/antiCTLA-4 HCAb, anti-PD-L1/TIGIT bispecific antibody, anti-PD-L1/TIM-3 bispecific antibody or anti-PD-L1/LAG-3 bispecific antibody) may be further modified to contain one or more biologically active protein, polypeptides or fragments thereof. “Bioactive” or “biologically active” as used herein means showing biological activity in the body to carry out a specific function. For example, it may mean the combination with a particular biomolecule such as protein, DNA, etc., and then promotion or inhibition of the activity of such biomolecule. In some embodiments, the bioactive protein or fragments thereof have immunostimulatory/immunoregulatory, membrane transport, or enzymatic activities.

In some embodiments, the bioactive protein or fragments thereof that can be fused with the anti-PD-L1 construct described herein is a ligand, such as lymphokines and cellular factors which interact with specific cellular receptor. Lymphokines are low molecular weight proteins which are secreted by T cells when antigens or lectins stimulate T cell growth. Examples of lymphokines include, but are not limited to, interferon-α, interferon-γ, interleukin-1 (IL-1) , interleukin-2 (IL-2) , interleukin-3 (IL-3) , tumor necrosis factor (TNF) , a colony stimulating factor (e.g. CSF-1, G-CSF or GM-CSF) , chemotaxins, macrophage migration inhibitory factor (MIF) , macrophage-activating factor (MAF) , NK cell activating factor, T cell replacing factor, leukocyte-inhibitory factor (LIF) , lymphotoxins, osteoclast-activating factor (OAF) , soluble immune response suppressor (SIRS) , growth-stimulating factor, monocyte growth factor, etc. Cellular factors which may be incorporated into the anti-PD-L1 fusion proteins of the invention include but are not limited to tumor necrosis factor α (TNFα) , interferons (IFNs) , and nerve growth factor (NGF) , etc.

III. Pharmaceutical compositions

Further provided by the present application are pharmaceutical compositions comprising any one of the anti-PD-L1 constructs comprising a sdAb specifically recognizing PD-L1 as described herein (such as anti-PD-L1 sdAb, anti-PD-L1 HCAb, anti-PD-L1/antiCTLA-4 HCAb, anti-PD-L1/TIGIT bispecific antibody, anti-PD-L1/TIM-3 bispecific antibody or anti-PD-L1/LAG-3 bispecific antibody) , and optionally a pharmaceutically acceptable carrier. Pharmaceutical compositions can be prepared by mixing an anti-PD-L1 construct described herein having the desired degree of purity with optional pharmaceutically acceptable carriers, excipients or stabilizers (Remington's Pharmaceutical Sciences 16th edition, Osol, A. Ed. (1980) ) , in the form of lyophilized formulations or aqueous solutions.

The pharmaceutical composition is preferably to be stable, in which the anti-PD-L1 construct comprising anti-PD-L1 sdAb described here essentially retains its physical and chemical stability and integrity upon storage. Various analytical techniques for measuring protein stability are available in the art and are reviewed in Peptide and Protein Drug Delivery, 247-301, Vincent Lee Ed., Marcel Dekker, Inc., New York, N. Y., Pubs. (1991) and Jones, A. Adv. Drug Delivery Rev. 10: 29-90 (1993) . Stability can be measured at a selected temperature for a selected time period. For rapid screening, the formulation may be kept at 40℃ for 2 weeks to 1 month, at which time stability is measured. Where the formulation is to be stored at 2-8℃, generally the formulation should be stable at 30℃ or 40℃ for at least 1 month, and/or stable at 2-8℃ for at least 2 years. Where the formulation is to be stored at 30℃, generally the formulation should be stable for at least 2 years at 30℃, and/or stable at 40℃ for at least 6 months. For example, the extent of aggregation during storage can be used as an indicator of protein stability. In some embodiments, the stable formulation of anti-PD-L1 construct described herein may comprise less than about 10% (preferably less than about 5%) of the anti-PD-L1 construct present as an aggregate in the formulation.

Acceptable carriers, excipients, or stabilizers are nontoxic to recipients at the dosages and concentrations employed, and include buffers, antioxidants including ascorbic acid, methionine, Vitamin E, sodium metabisulfite; preservatives, isotonicifiers (e.g. sodium chloride) , stabilizers, metal complexes (e.g. Zn-protein complexes) ; chelating agents such as EDTA and/or non-ionic surfactants.

Examples of physiologically acceptable carriers include buffers such as phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives (such as octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium chloride, benzethonium chloride; phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol; 3-pentanol; and m-cresol) ; low molecular weight (less than about 10 residues) polypeptide; proteins, such as serum albumin, gelatin, or immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, arginine or lysine; monosaccharides, disaccharides, and other carbohydrates including glucose, mannose, or dextrins; chelating agents such as EDTA; sugars such as sucrose, mannitol, trehalose or sorbitol; salt-forming counterions such as sodium; metal complexes (e.g. Zn-protein complexes) ; and/or nonionic surfactants such as TWEEN ^TM, polyethylene glycol (PEG) , and PLURONICS ^TM or polyethylene glycol (PEG) .

Buffers are used to control the pH in a range which optimizes the therapeutic effectiveness, especially if stability is pH dependent. Buffers are preferably present at concentrations ranging from about 50 mM to about 250 mM. Suitable buffering agents for use in the present application include both organic and inorganic acids and salts thereof. For example, citrate, phosphate, succinate, tartrate, fumarate, gluconate, oxalate, lactate, acetate. Additionally, buffers may comprise histidine and trimethylamine salts such as Tris.

Preservatives are added to retard microbial growth, and are typically present in a range from 0.2%-1.0% (w/v) . The addition of a preservative may, for example, facilitate the production of a multi-use (multiple-dose) formulation. Suitable preservatives for use in the present application include octadecyldimethylbenzyl ammonium chloride; hexamethonium chloride; benzalkonium halides (e.g., chloride, bromide, iodide) , benzethonium chloride; thimerosal, phenol, butyl or benzyl alcohol; alkyl parabens such as methyl or propyl paraben; catechol; resorcinol; cyclohexanol, 3-pentanol, and m-cresol.

Tonicity agents, sometimes known as “stabilizers” are present to adjust or maintain the tonicity of liquid in a composition. When used with large, charged biomolecules such as proteins and antibodies, they are often termed “stabilizers” because they can interact with the charged groups of the amino acid side chains, thereby lessening the potential for inter and intra-molecular interactions. Tonicity agents can be present in any amount between 0.1%to 25%by weight, preferably 1%to 5%, taking into account the relative amounts of the other ingredients. Preferred tonicity agents include polyhydric sugar alcohols, preferably trihydric or higher sugar alcohols, such as glycerin, erythritol, arabitol, xylitol, sorbitol and mannitol.

Additional excipients include agents which can serve as one or more of the following: (1) bulking agents, (2) solubility enhancers, (3) stabilizers and (4) and agents preventing denaturation or adherence to the container wall. Such excipients include: polyhydric sugar alcohols (enumerated above) ; amino acids such as alanine, glycine, glutamine, asparagine, histidine, arginine, lysine, ornithine, leucine, 2-phenylalanine, glutamic acid, threonine, etc. ; organic sugars or sugar alcohols such as sucrose, lactose, lactitol, trehalose, stachyose, mannose, sorbose, xylose, ribose, ribitol, myoinisitose, myoinisitol, galactose, galactitol, glycerol, cyclitols (e.g., inositol) , polyethylene glycol; sulfur containing reducing agents, such as urea, glutathione, thioctic acid, sodium thioglycolate, thioglycerol, α-monothioglycerol and sodium thio sulfate; low molecular weight proteins such as human serum albumin, bovine serum albumin, gelatin or other immunoglobulins; hydrophilic polymers such as polyvinylpyrrolidone; monosaccharides (e.g., xylose, mannose, fructose, glucose; disaccharides (e.g., lactose, maltose, sucrose) ; trisaccharides such as raffinose; and polysaccharides such as dextrin or dextran.

Non-ionic surfactants or detergents (also known as “wetting agents” ) are present to help solubilize the therapeutic agent as well as to protect the therapeutic protein against agitation-induced aggregation, which also permits the formulation to be exposed to shear surface stress without causing denaturation of the active therapeutic protein or antibody. Non-ionic surfactants are present in a range of about 0.05 mg/ml to about 1.0 mg/ml, preferably about 0.07 mg/ml to about 0.2 mg/ml.

Suitable non-ionic surfactants include polysorbates (20, 40, 60, 65, 80, etc. ) , polyoxamers (184, 188, etc. ) ,

polyols,

polyoxyethylene sorbitan monoethers (

-20,

-80, etc. ) , lauromacrogol 400, polyoxyl 40 stearate, polyoxyethylene hydrogenated

castor oil

10, 50 and 60, glycerol monostearate, sucrose fatty acid ester, methyl celluose and carboxymethyl cellulose. Anionic detergents that can be used include sodium lauryl sulfate, dioctyle sodium sulfosuccinate and dioctyl sodium sulfonate. Cationic detergents include benzalkonium chloride or benzethonium chloride.

In order for the pharmaceutical compositions to be used for in vivo administration, they must be sterile. The pharmaceutical composition may be rendered sterile by filtration through sterile filtration membranes. The pharmaceutical compositions herein generally are placed into a container having a sterile access port, for example, an intravenous solution bag or vial having a stopper pierceable by a hypodermic injection needle.

The route of administration is in accordance with known and accepted methods, such as by single or multiple bolus or infusion over a long period of time in a suitable manner, e.g., injection or infusion by subcutaneous, intravenous, intraperitoneal, intramuscular, intra-arterial, intralesional or intraarticular routes, topical administration, inhalation or by sustained release or extended-release means. In some embodiments, the pharmaceutical composition is administered locally, such as intratumorally.

Sustained-release preparations may be prepared. Suitable examples of sustained-release preparations include semi-permeable matrices of solid hydrophobic polymers containing the antagonist, which matrices are in the form of shaped articles, e.g. films, or microcapsules. Examples of sustained-release matrices include polyesters, hydrogels (for example, poly (2-hydroxyethyl-methacrylate) , or poly (vinylalcohol) ) , polylactides (U.S. Pat. No. 3,773,919) , copolymers of L-glutamic acid and. ethyl-L-glutamate, non-degradable ethylene-vinyl acetate, degradable lactic acid-glycolic acid copolymers such as the LUPRON DEPOT ^TM (injectable microspheres composed of lactic acid-glycolic acid copolymer and leuprolide acetate) , and poly-D- (-) -3-hydroxybutyric acid.

The pharmaceutical compositions herein may also contain more than one active compound as necessary for the particular indication being treated, preferably those with complementary activities that do not adversely affect each other. Alternatively, or in addition, the composition may comprise a cytotoxic agent, chemotherapeutic agent, cytokine, immunosuppressive agent, or growth inhibitory agent. Such molecules are suitably present in combination in amounts that are effective for the purpose intended.

The active ingredients may also be entrapped in microcapsules prepared, for example, by coacervation techniques or by interfacial polymerization, for example, hydroxymethylcellulose or gelatin-microcapsules and poly- (methylmethacylate) microcapsules, respectively, in colloidal drug delivery systems (for example, liposomes, albumin microspheres, microemulsions, nano-particles and nanocapsules) or in macroemulsions. Such techniques are disclosed in Remington's Pharmaceutical Sciences 18th edition.

In some embodiments, the pharmaceutical composition is contained in a single-use vial, such as a single-use sealed vial. In some embodiments, the pharmaceutical composition is contained in a multi-use vial. In some embodiments, the pharmaceutical composition is contained in bulk in a container. In some embodiments, the pharmaceutical composition is cryopreserved.

IV. Methods of treating PD-L1 related diseases

The anti-PD-L1 construct comprising sdAb specifically recognizing PD-L1 as described herein (such as anti-PD-L1 sdAb, anti-PD-L1 HCAb, anti-PD-L1/antiCTLA-4 HCAb, anti-PD-L1/TIGIT bispecific antibody, anti-PD-L1/TIM-3 bispecific antibody or anti-PD-L1/LAG-3 bispecific antibody) , and the compositions (such as pharmaceutical compositions) thereof are useful for a variety of applications, such as in diagnosis, molecular assays, and therapy.

One aspect of the invention provides a method of treating a PD-L1 related disease or a condition in an individual in need thereof, comprising administering to the individual an effective amount of a pharmaceutical composition comprising the anti-PD-L1 construct described herein. In some embodiments, the PD-L1 related disease is cancer. In some embodiments, the PD-L1 related disease is pathogenic infection, such as viral infection.

The present invention contemplates, in part, protein constructs (such as anti-PD-L1 sdAb, anti-PD-L1 HCAb, anti-PD-L1/antiCTLA-4 HCAb, anti-PD-L1/TIGIT bispecific antibody, anti-PD-L1/TIM-3 bispecific antibody or anti-PD-L1/LAG-3 bispecific antibody) , nucleic acid molecules and/or vectors encoding thereof, host cells comprising nucleic acid molecules and/or vectors encoding thereof, that can be administered either alone or in any combination with another therapy, and in at least some aspects, together with a pharmaceutically acceptable carrier or excipient. In some embodiments, prior to administration of the anti-PD-L1 construct, they may be combined with suitable pharmaceutical carriers and excipients that are well known in the art. The compositions prepared according to the disclosure can be used for the treatment or delaying of worsening of cancer.

In some embodiments, there is provided a method of treating cancer comprising administering to the individual an effective amount of a pharmaceutical composition comprising an isolated anti-PD-L1 construct comprising a single-domain antibody (sdAb) moiety specifically recognizing PD-L1 (such as anti-PD-L1 sdAb, anti-PD-L1 HCAb, anti-PD-L1/antiCTLA-4 HCAb, anti-PD-L1/TIGIT bispecific antibody, anti-PD-L1/TIM-3 bispecific antibody or anti-PD-L1/LAG-3 bispecific antibody) . In some embodiments, the cancer is a solid tumor (such as colon cancer) . In some embodiments, the pharmaceutical composition is administered systemically (such as intravenously) . In some embodiments, the pharmaceutical composition is administered locally (such as intratumorally) . In some embodiments, the method further comprises administering to the individual an additional cancer therapy (such as surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or a combination thereof) . In some embodiments, the individual is a human. In some embodiments, the method of treating cancer has one or more of the following biological activities: (1) killing cancer cells (including bystander killing) ; (2) inhibiting proliferation of cancer cells; (3) inducing immune response in a tumor; (4) reducing tumor size; (5) alleviating one or more symptoms in an individual having cancer; (6) inhibiting tumor metastasis; (7) prolonging survival; (8) prolonging time to cancer progression; and (9) preventing, inhibiting, or reducing the likelihood of the recurrence of a cancer. In some embodiments, the method of killing cancer cells mediated by the pharmaceutical composition described herein can achieve a tumor cell death rate of at least about any of 40%, 50%, 60%, 70%, 80%, 90%, 95%, or more. In some embodiments, the method of killing cancer cells mediated by the pharmaceutical composition described herein can achieve a bystander tumor cell (uninfected by the oncolytic VV) death rate of at least about any of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or more. In some embodiments, the method of reducing tumor size mediated by the pharmaceutical composition described herein can reduce at least about 10% (including for example at least about any of 20%, 30%, 40%, 60%, 70%, 80%, 90%, or 100%) of the tumor size. In some embodiments, the method of inhibiting tumor metastasis mediated by the pharmaceutical composition described herein can inhibit at least about 10% (including for example at least about any of 20%, 30%, 40%, 60%, 70%, 80%, 90%, or 100%) of the metastasis. In some embodiments, the method of prolonging survival of an individual (such as a human) mediated by the pharmaceutical composition described herein can prolongs the survival of the individual by at least any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, or 24 months. In some embodiments, the method of prolonging time to cancer progression mediated by the pharmaceutical composition described herein can prolongs the time to cancer progression by at least any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 weeks.

The methods described herein are suitable for treating a variety of cancers, including both solid cancer and liquid cancer. The methods are applicable to cancers of all stages, including early stage cancer, non-metastatic cancer, primary cancer, advanced cancer, locally advanced cancer, metastatic cancer, or cancer in remission. The methods described herein may be used as a first therapy, second therapy, third therapy, or combination therapy with other types of cancer therapies known in the art, such as chemotherapy, surgery, hormone therapy, radiation, gene therapy, immunotherapy (such as T-cell therapy) , bone marrow transplantation, stem cell transplantation, targeted therapy, cryotherapy, ultrasound therapy, photodynamic therapy, radio-frequency ablation or the like, in an adjuvant setting or a neoadjuvant setting (i.e., the method may be carried out before the primary/definitive therapy) . In some embodiments, the method is used to treat an individual who has previously been treated. In some embodiments, the cancer has been refractory to prior therapy. In some embodiments, the method is used to treat an individual who has not previously been treated.

In some embodiments, the method is suitable for treating cancers with aberrant PD-L1 expression, activity and/or signaling include, by way of non-limiting example, melanoma, prostate cancer, lung cancer, colon cancer, gastric cancer, ovarian cancer, breast cancer, and glioblastoma.

Thus in some embodiments, there is provided a method of treating an immunotherapy-responsive solid tumor (such as carcinoma or adenocarcinoma, such as cancers with aberrant PD-L1 expression, activity and/or signaling) , comprising administering to the individual an effective amount of a pharmaceutical composition comprising an isolated anti-PD-L1 construct comprising a sdAb moiety specifically recognizing PD-L1 (such as anti-PD-L1 sdAb, anti-PD-L1 HCAb, anti-PD-L1/antiCTLA-4 HCAb, anti-PD-L1/TIGIT bispecific antibody, anti-PD-L1/TIM-3 bispecific antibody or anti-PD-L1/LAG-3 bispecific antibody) . In some embodiments, the cancer is a solid tumor (such as colon cancer) . In some embodiments, the pharmaceutical composition is administered systemically (such as intravenously) . In some embodiments, the pharmaceutical composition is administered locally (such as intratumorally) . In some embodiments, the method further comprises administering to the individual an additional cancer therapy (such as surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or a combination thereof) . In some embodiments, the individual is a human. In some embodiments, the method of treating cancer has one or more of the following biological activities: (1) killing cancer cells (including bystander killing) ; (2) inhibiting proliferation of cancer cells; (3) inducing immune response in a tumor; (4) reducing tumor size; (5) alleviating one or more symptoms in an individual having cancer; (6) inhibiting tumor metastasis; (7) prolonging survival; (8) prolonging time to cancer progression; and (9) preventing, inhibiting, or reducing the likelihood of the recurrence of a cancer. In some embodiments, the method of killing cancer cells mediated by the pharmaceutical composition described herein can achieve a tumor cell death rate of at least about any of 40%, 50%, 60%, 70%, 80%, 90%, 95%, or more. In some embodiments, the method of killing cancer cells mediated by the pharmaceutical composition described herein can achieve a bystander tumor cell (uninfected by the oncolytic VV) death rate of at least about any of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or more. In some embodiments, the method of reducing tumor size mediated by the pharmaceutical composition described herein can reduce at least about 10% (including for example at least about any of 20%, 30%, 40%, 60%, 70%, 80%, 90%, or 100%) of the tumor size. In some embodiments, the method of inhibiting tumor metastasis mediated by the pharmaceutical composition described herein can inhibit at least about 10% (including for example at least about any of 20%, 30%, 40%, 60%, 70%, 80%, 90%, or 100%) of the metastasis. In some embodiments, the method of prolonging survival of an individual (such as a human) mediated by the pharmaceutical composition described herein can prolongs the survival of the individual by at least any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 18, or 24 months. In some embodiments, the method of prolonging time to cancer progression mediated by the pharmaceutical composition described herein can prolongs the time to cancer progression by at least any of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 weeks.

In some embodiments, the method is suitable for treating cancers with aberrant PD-1 or PD-L1/PD-L2 expression, activity and/or signaling include, by way of non-limiting example, hematological cancer and/or solid tumors. Some cancers whose growth may be inhibited using the antibodies of the invention include cancers typically responsive to immunotherapy. Non-limiting examples of other cancers for treatment include melanoma (e.g., metastatic malignant melanoma) , renal cancer (e.g. clear cell carcinoma) , prostate cancer (e.g. hormone refractory prostate adenocarcinoma) , breast cancer, colon cancer and lung cancer (e.g. non-small cell lung cancer) . Additionally, the invention includes refractory or recurrent malignancies whose growth may be inhibited using the antibodies of the invention. Examples of other cancers that may be treated using the antibodies of the invention include bone cancer, pancreatic cancer, skin cancer, cancer of the head or neck, cutaneous or intraocular malignant melanoma, uterine cancer, ovarian cancer, rectal cancer, cancer of the anal region, stomach cancer, testicular cancer, uterine cancer, carcinoma of the fallopian tubes, carcinoma of the endometrium, carcinoma of the cervix, carcinoma of the vagina, carcinoma of the vulva, Hodgkin's Disease, non-Hodgkin's lymphoma, cancer of the esophagus, cancer of the small intestine, cancer of the endocrine system, cancer of the thyroid gland, cancer of the parathyroid gland, cancer of the adrenal gland, sarcoma of soft tissue, cancer of the urethra, cancer of the penis, chronic or acute leukemias including acute myeloid leukemia, chronic myeloid leukemia, acute lymphoblastic leukemia, chronic lymphocytic leukemia, solid tumors of childhood, lymphocytic lymphoma, cancer of the bladder, cancer of the kidney or ureter, carcinoma of the renal pelvis, neoplasm of the central nervous system (CNS) , primary CNS lymphoma, tumor angiogenesis, spinal axis tumor, brain stem glioma, pituitary adenoma, Kaposi's sarcoma, epidermoid cancer, squamous cell cancer, T-cell lymphoma, environmentally induced cancers including those induced by asbestos, and combinations of said cancers. The present invention is also useful for treatment of metastatic cancers, especially metastatic cancers that express PD-L1 (Iwai et al. (2005) Int. Immunol. 17: 133-144) .

Thus, in some embodiments, there is provided a method of treating an immunotherapy-responsive solid tumor (such as carcinoma or adenocarcinoma, such as cancers with aberrant PD-L1 expression, activity and/or signaling, and/or aberrant TIGIT, TIM-3 and LAG-3 expression, activity and/or signaling) , comprising administering to the individual an effective amount of a pharmaceutical composition comprising an isolated anti-PD-L1 construct comprising a single-domain antibody (sdAb) moiety specifically recognizing PD-L1 fused to a TIGIT, TIM-3 or LAG-3 full-length antibody. In some embodiments, there is provided a method of treating an immunotherapy-responsive solid tumor (such as carcinoma or adenocarcinoma, such as cancers with aberrant PD-L1 expression, activity and/or signaling, and/or aberrant TIGIT, TIM-3, LAG-3 expression, activity and/or signaling) , comprising administering to the individual an effective amount of a pharmaceutical composition comprising an isolated anti-PD-L1 construct comprising a single-domain antibody (sdAb) moiety specifically recognizing PD-L1 fused to a TIGIT, TIM-3 or LAG-3 full-length antibody.

In some embodiments, the method described herein is suitable for treating a colorectal cancer, such as adenocarcinoma, gastrointestinal carcinoid tumor, gastrointestinal stromal tumor, Leiomyosarcoma, melanoma, or squamous cell carcinoma.

Dosages and desired drug concentrations of pharmaceutical compositions of the present application may vary depending on the particular use envisioned. The determination of the appropriate dosage or route of administration is well within the skill of an ordinary artisan. Animal experiments provide reliable guidance for the determination of effective doses for human therapy. Interspecies scaling of effective doses can be performed following the principles laid down by Mordenti, J. and Chappell, W. “The Use of Interspecies Scaling in Toxicokinetics, ” In Toxicokinetics and New Drug Development, Yacobi et al., Eds, Pergamon Press, New York 1989, pp. 42-46.

When in vivo administration of the anti-PD-L1 construct comprising an anti-PD-L1 sdAb moiety described herein are used, normal dosage amounts may vary from about 10 ng/kg up to about 100 mg/kg of mammal body weight or more per day, preferably about 1 mg/kg/day to 10 mg/kg/day, such as about 1-3 mg/kg/day, about 2-4 mg/kg/day, about 3-5 mg/kg/day, about 4-6 mg/kg/day, about 5-7 mg/kg/day, about 6-8 mg/kg/day, about 6-6.5 mg/kg/day, about 6.5-7 mg/kg/day, about 7-9 mg/kg/day, or about 8-10 mg/kg/day, depending upon the route of administration. It is within the scope of the present application that different formulations will be effective for different treatments and different disorders, and that administration intended to treat a specific organ or tissue may necessitate delivery in a manner different from that to another organ or tissue. Moreover, dosages may be administered by one or more separate administrations, or by continuous infusion. For repeated administrations over several days or longer, depending on the condition, the treatment is sustained until a desired suppression of disease symptoms occurs. However, other dosage regimens may be useful. The progress of this therapy is easily monitored by conventional techniques and assays.

In some embodiments, the pharmaceutical composition is administered for a single time (e.g. bolus injection) . In some embodiments, the pharmaceutical composition is administered for multiple times (such as any of 2, 3, 4, 5, 6, or more times) . If multiple administrations, they may be performed by the same or different routes and may take place at the same site or at alternative sites. The pharmaceutical composition may be administered twice per week, 3 times per week, 4 times per week, 5 times per week, daily, daily without break, once per week, weekly without break, once per 2 weeks, once per 3 weeks, once per month, once per 2 months, once per 3 months, once per 4 months, once per 5 months, once per 6 months, once per 7 months, once per 8 months, once per 9 months, once per 10 months, once per 11 months, or once per year. The interval between administrations can be about any one of 24h to 48h, 2 days to 3 days, 3 days to 5 days, 5 days to 1 week, 1 week to 2 weeks, 2 weeks to 1 month, 1 month to 2 months, 2 month to 3 months, 3 months to 6 months, or 6 months to a year. Intervals can also be irregular (e.g. following tumor progression) . In some embodiments, there is no break in the dosing schedule. In some embodiments, the pharmaceutical composition is administered every 4 days for 4 times. The optimal dosage and treatment regime for a particular patient can readily be determined by one skilled in the art of medicine by monitoring the patient for signs of disease and adjusting the treatment accordingly.

The pharmaceutical compositions of the present application, including but not limited to reconstituted and liquid formulations, are administered to an individual in need of treatment with the anti-PD-L1 construct described herein, preferably a human, in accord with known methods, such as intravenous administration as a bolus or by continuous infusion over a period of time, by intramuscular, intraperitoneal, intracerobrospinal, subcutaneous, intravenous (i. v. ) , intra-articular, intrasynovial, intrathecal, oral, topical, or inhalation routes. A reconstituted formulation can be prepared by dissolving a lyophilized anti-PD-L1 construct described herein in a diluent such that the protein is dispersed throughout. Exemplary pharmaceutically acceptable (safe and non-toxic for administration to a human) diluents suitable for use in the present application include, but are not limited to, sterile water, bacteriostatic water for injection (BWFI) , a pH buffered solution (e.g. phosphate-buffered saline) , sterile saline solution, Ringer's solution or dextrose solution, or aqueous solutions of salts and/or buffers.

In some embodiments, the pharmaceutical compositions are administered to the individual by subcutaneous (i.e. beneath the skin) administration. For such purposes, the pharmaceutical compositions may be injected using a syringe. However, other devices for administration of the pharmaceutical compositions are available such as injection devices; injector pens; auto-injector devices, needleless devices; and subcutaneous patch delivery systems.

In some embodiments, the pharmaceutical compositions are administered to the individual intravenously. In some embodiments, the pharmaceutical composition is administered to an individual by infusion, such as intravenous infusion. Infusion techniques for immunotherapy are known in the art (see, e.g., Rosenberg et al., New Eng. J. of Med. 319: 1676 (1988) ) .

V. Methods of preparation

The anti-PD-L1 construct (such as anti-PD-L1 single-domain antibodies) described herein may be prepared using any methods known in the art or as described herein. Also see Examples 1-2.

Methods of preparing single-domain antibodies have been described. See, for example, Els Pardon et al, Nature Protocol, 2014; 9 (3) : 674. Single-domain antibodies (such as V _HHs) may be obtained using methods known in the art such as by immunizing a Camelid species (such as camel or llama) and obtaining hybridomas therefrom, or by cloning a library of single-domain antibodies using molecular biology techniques known in the art and subsequent selection by ELISA with individual clones of unselected libraries or by using phage display.

For recombinant production of the single-domain antibodies, the nucleic acids encoding the single-domain antibodies are isolated and inserted into a replicable vector for further cloning (amplification of the DNA) or for expression. DNA encoding the single-domain antibody is readily isolated and sequenced using conventional procedures (e.g., by using oligonucleotide probes that are capable of binding specifically to genes encoding the heavy and light chains of the antibody) . Many vectors are available. The choice of vector depends in part on the host cell to be used. Generally, preferred host cells are of either prokaryotic or eukaryotic (generally mammalian) origin.

EMBODIMENTS

The invention provides also the following non-limiting embodiments.

Embodiment 1 is an isolated anti-PD-L1 construct comprising a single-domain antibody (sdAb) moiety specifically recognizing PD-L1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 amino acid substitutions.

Embodiment 2 is the isolated anti-PD-L1 construct of embodiment 1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions.

Embodiment 3 is the isolated anti-PD-L1 construct of any one of embodiments 1-2, wherein the sdAb moiety comprises any one of the following:

(1) a CDR1 comprising the amino acid sequence of SEQ ID NO: 51; a CDR2 comprising the amino acid sequence of SEQ ID NO: 151; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 251; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(2) a CDR1 comprising the amino acid sequence of SEQ ID NO: 52; a CDR2 comprising the amino acid sequence of SEQ ID NO: 152; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 252; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(3) a CDR1 comprising the amino acid sequence of SEQ ID NO: 53; a CDR2 comprising the amino acid sequence of SEQ ID NO: 153; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 253; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(4) a CDR1 comprising the amino acid sequence of SEQ ID NO: 54; a CDR2 comprising the amino acid sequence of SEQ ID NO: 154; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 254; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(5) a CDR1 comprising the amino acid sequence of SEQ ID NO: 55; a CDR2 comprising the amino acid sequence of SEQ ID NO: 155; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 255; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(6) a CDR1 comprising the amino acid sequence of SEQ ID NO: 56; a CDR2 comprising the amino acid sequence of SEQ ID NO: 156; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 256; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(7) a CDR1 comprising the amino acid sequence of SEQ ID NO: 57; a CDR2 comprising the amino acid sequence of SEQ ID NO: 157; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 257; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(8) a CDR1 comprising the amino acid sequence of SEQ ID NO: 58; a CDR2 comprising the amino acid sequence of SEQ ID NO: 158; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 258; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(9) a CDR1 comprising the amino acid sequence of SEQ ID NO: 59; a CDR2 comprising the amino acid sequence of SEQ ID NO: 159; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 259; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(10) a CDR1 comprising the amino acid sequence of SEQ ID NO: 60; a CDR2 comprising the amino acid sequence of SEQ ID NO: 160; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 260; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(11) a CDR1 comprising the amino acid sequence of SEQ ID NO: 61; a CDR2 comprising the amino acid sequence of SEQ ID NO: 161; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 261; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(12) a CDR1 comprising the amino acid sequence of SEQ ID NO: 62; a CDR2 comprising the amino acid sequence of SEQ ID NO: 162; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 262; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(13) a CDR1 comprising the amino acid sequence of SEQ ID NO: 63; a CDR2 comprising the amino acid sequence of SEQ ID NO: 163; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 263; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(14) a CDR1 comprising the amino acid sequence of SEQ ID NO: 64; a CDR2 comprising the amino acid sequence of SEQ ID NO: 164; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 264; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(15) a CDR1 comprising the amino acid sequence of SEQ ID NO: 65; a CDR2 comprising the amino acid sequence of SEQ ID NO: 165; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 265; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(16) a CDR1 comprising the amino acid sequence of SEQ ID NO: 66; a CDR2 comprising the amino acid sequence of SEQ ID NO: 166; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 266; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(17) a CDR1 comprising the amino acid sequence of SEQ ID NO: 67; a CDR2 comprising the amino acid sequence of SEQ ID NO: 167; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 267; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(18) a CDR1 comprising the amino acid sequence of SEQ ID NO: 68; a CDR2 comprising the amino acid sequence of SEQ ID NO: 168; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 268; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(19) a CDR1 comprising the amino acid sequence of SEQ ID NO: 69; a CDR2 comprising the amino acid sequence of SEQ ID NO: 169; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 269; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(20) a CDR1 comprising the amino acid sequence of SEQ ID NO: 70; a CDR2 comprising the amino acid sequence of SEQ ID NO: 170; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 270; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(21) a CDR1 comprising the amino acid sequence of SEQ ID NO: 71; a CDR2 comprising the amino acid sequence of SEQ ID NO: 171; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 271; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(22) a CDR1 comprising the amino acid sequence of SEQ ID NO: 72; a CDR2 comprising the amino acid sequence of SEQ ID NO: 172; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 272; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(23) a CDR1 comprising the amino acid sequence of SEQ ID NO: 73; a CDR2 comprising the amino acid sequence of SEQ ID NO: 173; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 273; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(24) a CDR1 comprising the amino acid sequence of SEQ ID NO: 74; a CDR2 comprising the amino acid sequence of SEQ ID NO: 174; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 274; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(25) a CDR1 comprising the amino acid sequence of SEQ ID NO: 75; a CDR2 comprising the amino acid sequence of SEQ ID NO: 175; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 275; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(26) a CDR1 comprising the amino acid sequence of SEQ ID NO: 76; a CDR2 comprising the amino acid sequence of SEQ ID NO: 176; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 276; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(27) a CDR1 comprising the amino acid sequence of SEQ ID NO: 77; a CDR2 comprising the amino acid sequence of SEQ ID NO: 177; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 277; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(28) a CDR1 comprising the amino acid sequence of SEQ ID NO: 78; a CDR2 comprising the amino acid sequence of SEQ ID NO: 178; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 278; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(29) a CDR1 comprising the amino acid sequence of SEQ ID NO: 79; a CDR2 comprising the amino acid sequence of SEQ ID NO: 179; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 279; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(30) a CDR1 comprising the amino acid sequence of SEQ ID NO: 80; a CDR2 comprising the amino acid sequence of SEQ ID NO: 180; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 280; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(31) a CDR1 comprising the amino acid sequence of SEQ ID NO: 81; a CDR2 comprising the amino acid sequence of SEQ ID NO: 181; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 281; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(32) a CDR1 comprising the amino acid sequence of SEQ ID NO: 82; a CDR2 comprising the amino acid sequence of SEQ ID NO: 182; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 282; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(33) a CDR1 comprising the amino acid sequence of SEQ ID NO: 83; a CDR2 comprising the amino acid sequence of SEQ ID NO: 183; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 283; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(34) a CDR1 comprising the amino acid sequence of SEQ ID NO: 84; a CDR2 comprising the amino acid sequence of SEQ ID NO: 184; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 284; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(35) a CDR1 comprising the amino acid sequence of SEQ ID NO: 85; a CDR2 comprising the amino acid sequence of SEQ ID NO: 185; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 285; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(36) a CDR1 comprising the amino acid sequence of SEQ ID NO: 86; a CDR2 comprising the amino acid sequence of SEQ ID NO: 186; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 286; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(37) a CDR1 comprising the amino acid sequence of SEQ ID NO: 87; a CDR2 comprising the amino acid sequence of SEQ ID NO: 187; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 287; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(38) a CDR1 comprising the amino acid sequence of SEQ ID NO: 88; a CDR2 comprising the amino acid sequence of SEQ ID NO: 188; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 288; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(39) a CDR1 comprising the amino acid sequence of SEQ ID NO: 89; a CDR2 comprising the amino acid sequence of SEQ ID NO: 189; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 289; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(40) a CDR1 comprising the amino acid sequence of SEQ ID NO: 90; a CDR2 comprising the amino acid sequence of SEQ ID NO: 190; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 290; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions; and

(41) a CDR1 comprising the amino acid sequence of SEQ ID NO: 91; a CDR2 comprising the amino acid sequence of SEQ ID NO: 191; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 291; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(42) a CDR1 comprising the amino acid sequence of SEQ ID NO: 92; a CDR2 comprising the amino acid sequence of SEQ ID NO: 192; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 292; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(43) a CDR1 comprising the amino acid sequence of SEQ ID NO: 93; a CDR2 comprising the amino acid sequence of SEQ ID NO: 193; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 293; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(44) a CDR1 comprising the amino acid sequence of SEQ ID NO: 94; a CDR2 comprising the amino acid sequence of SEQ ID NO: 194; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 294; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(45) a CDR1 comprising the amino acid sequence of SEQ ID NO: 95; a CDR2 comprising the amino acid sequence of SEQ ID NO: 195; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 295; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(46) a CDR1 comprising the amino acid sequence of SEQ ID NO: 96; a CDR2 comprising the amino acid sequence of SEQ ID NO: 196; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 296; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(47) a CDR1 comprising the amino acid sequence of SEQ ID NO: 97; a CDR2 comprising the amino acid sequence of SEQ ID NO: 197; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 297; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(48) a CDR1 comprising the amino acid sequence of SEQ ID NO: 98; a CDR2 comprising the amino acid sequence of SEQ ID NO: 198; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 298; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(49) a CDR1 comprising the amino acid sequence of SEQ ID NO: 99; a CDR2 comprising the amino acid sequence of SEQ ID NO: 199; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 299; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

(50) a CDR1 comprising the amino acid sequence of SEQ ID NO: 100; a CDR2 comprising the amino acid sequence of SEQ ID NO: 200; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 300; or a variant thereof comprising up to about 3 amino acid substitutions in the CDR regions;

Embodiment 4 is the isolated anti-PD-L1 construct of any one of embodiments 1-3, wherein the sdAb moiety comprises a V _HH domain having the amino acid sequence containing:

a-1) an amino acid residue at position 37 selected from the group consisting of F, Y, L, I, and V, preferably Y and V, and more preferably F;

a-2) an amino acid residue at position 44 selected from the group consisting of A, G, E, D, G, Q, R, S, and L, preferably Q and G, and more preferably E;

a-3) an amino acid residue at position 45 selected from the group consisting of L, R, and C;

a-4) an amino acid residue at position 103 selected from the group consisting of W, R, G, and S; and

a-5) an amino acid residue at position 108 being Q,

wherein each of the amino acid positions is according to the Kabat numbering.

Embodiment 5 is the isolated anti-PD-L1 construct of embodiment 4, wherein the sdAb moiety comprises a V _HH domain having the amino acid sequence containing:

a-1) the amino acid residue at position 37 selected from the group consisting of F, Y, L, I, and V, preferably Y and V, and more preferably F;

a-2) the amino acid residue at position 44 selected from the group consisting of G, E and Q;

a-3) the amino acid residue at position 45 selected from the group consisting of L and R;

a-4) the amino acid residue at position 103 selected from the group consisting of W, G, and R; and

a-5) the amino acid residue at position 108 being Q.

Embodiment 6 is the isolated anti-PD-L1 construct of embodiment 5, wherein the sdAb moiety comprises a V _HH domain having the amino acid sequence containing:

a-1) the amino acid residue at position 37 selected from the group consisting of F, Y, and V;

a-4) the amino acid residue at position 103 being W or G; and

a-5) the amino acid residue at position 108 being Q, which is optionally humanized to L.

Embodiment 7 is the isolated anti-PD-L1 construct of any one of embodiments 1-3, wherein the sdAb moiety comprises a V _HH domain having the amino acid sequence containing:

b-1) an amino acid residue at position 37 selected from the group consisting of F, Y, L, I, and V, preferably Y and V, and more preferably F

b-2) an amino acid residue at position 44 selected from the group consisting of E, Q and G;

b-3) an amino acid residue at position 45 being R;

b-4) an amino acid residue at position 103 selected from the group consisting of W, R, and S; and

b-5) an amino acid residue at position 108 selected from the group consisting of Q and L,

wherein each of the amino acid positions is according to Kabat numbering.

Embodiment 8 is the isolated anti-PD-L1 construct of embodiment 7, wherein the sdAb moiety comprises a VHH domain having the amino acid sequence containing:

b-1) the amino acid residue at position 37 selected from the group consisting of F, Y, L, I, and V;

b-2) the amino acid residue at position 44 selected from the group consisting of E, G and Q;

b-3) the amino acid residue at position 45 being R;

b-4) the amino acid residue at position 103 being W or G; and

b-5) the amino acid residue at position 108 being Q, which is optionally humanized to L.

Embodiment 9 is the isolated anti-PD-L1 construct of any one of embodiments 1-8, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof having at least about 80%, at least about 90%, or at least about 95%sequence identity to any one of SEQ ID NOs: 351-400.

Embodiment 10 is the isolated anti-PD-L1 construct of embodiment 9, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof comprising up to about 3 amino acid substitutions in the V _HH domain.

Embodiment 11 is the isolated anti-PD-L1 construct of any one of embodiments 1-10, wherein the K _D of the binding between the sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M, about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M.

Embodiment 12 is the isolated anti-PD-L1 construct of any one of embodiments 1-11, wherein the sdAb moiety specifically recognizing PD-L1 is camelid, chimeric, human, partially humanized, or fully humanized.

Embodiment 13 is the isolated anti-PD-L1 construct of any one of embodiments 1-12, wherein the isolated anti-PD-L1 construct is a heavy chain-only antibody (HCAb) .

Embodiment 14 is the isolated anti-PD-L1 construct of embodiment 13, wherein the sdAb moiety that specifically recognizes PD-L1 is fused to a human IgG1 Fc.

Embodiment 15 is the isolated anti-PD-L1 construct of embodiment 13 or 14, wherein the HCAb is monomeric or dimeric.

Embodiment 16 is the isolated anti-PD-L1 construct of any one of embodiments 13-15, wherein the sdAb moiety specifically recognizing PD-L1 comprises the amino acid sequence of any one of SEQ ID NOs: 351-400.

Embodiment 17 is the isolated anti-PD-L1 construct of any one of embodiments 13-15, wherein the HCAb comprises the amino acid sequence of any one of SEQ ID NOs: 401-440.

Embodiment 18 is the isolated anti-PD-L1 construct of any one of embodiments 1-13, wherein the isolated anti-PD-L1 construct further comprises a second antibody moiety specifically recognizing a second antigen.

Embodiment 19 is the isolated anti-PD-L1 construct of embodiment 18, wherein the second antibody moiety is a full-length antibody, a Fab, a Fab’, a (Fab’) 2, an Fv, a single chain Fv (scFv) , an scFv-scFv, a minibody, a diabody, a sdAb, or an antibody mimetics.

Embodiment 20 is the isolated anti-PD-L1 construct of embodiment 18 or 19, wherein the anti-PD-L1 construct is monospecific or multispecific.

Embodiment 21 is the isolated anti-PD-L1 construct of any one of embodiments 18-20, wherein the second antibody moiety is a sdAb.

Embodiment 22 is the isolated anti-PD-L1 construct of any one embodiments 18-21, wherein the second antigen is PD-L1.

Embodiment 23 is the isolated anti-PD-L1 construct of embodiment 22, wherein the isolated anti-PD-L1 construct comprises three or more sdAbs that specifically recognize PD-L1.

Embodiment 24 is the isolated anti-PD-L1 construct of embodiment 22 or 23, wherein the second antibody comprises an amino acid sequence of any one of SEQ ID NOs: 351-400.

Embodiment 25 is the isolated anti-PD-L1 construct of any one of embodiments 18-21, wherein the second antigen is human serum albumin (HSA) .

Embodiment 26 is the isolated anti-PD-L1 construct of any one of embodiments 18-21, wherein the second antigen is CTLA-4, and the second antibody is anti-CTLA-4 sdAb.

Embodiment 27 is the isolated anti-PD-L1 construct of any one of embodiments 18-26, wherein the sdAb moiety specifically recognizing PD-L1 is amino (N) -terminal and/or carboxy (C) -terminal to the second antibody moiety.

Embodiment 28 is the isolated anti-PD-L1 construct of any one embodiments 18-21, wherein the second antibody moiety is a full-length antibody.

Embodiment 29 is the isolated anti-PD-L1 construct of claim 28, wherein the amino (N) -terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the carboxy (C) -terminus of at least one of the heavy chains of the full-length antibody.

Embodiment 30 is the isolated anti-PD-L1 construct of claim 28, wherein the C-terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the N-terminus of at least one of the heavy chains of the full length antibody.

Embodiment 31 is the isolated anti-PD-L1 construct of any one of embodiments 28-30, wherein the full-length antibody specifically recognizes a polypeptide selected from the group consisting of TIGIT, TIM-3, and LAG-3.

Embodiment 32 is the isolated anti-PD-L1 construct of any one of embodiments 28-30, wherein the PD-L1 specifically recognized by the sdAb moiety comprises the amino acid sequence of SEQ ID NO: 441 or SEQ ID NO: 442.

Embodiment 33 is the isolated anti-PD-L1 construct of any one of embodiments 28-30, wherein the sdAb moiety specifically recognizing PD-L1 and the second antibody moiety are optionally connected by a peptide linker.

Embodiment 34 is the isolated anti-PD-L1 construct of embodiment 33, wherein the peptide linker comprises the amino acid sequence of SEQ ID NO: 443-445.

Embodiment 35 is a second isolated anti-PD-L1 construct that specifically binds to PD-L1 competitively with the isolated anti-PD-L1 construct of any one of embodiments 1-34.

Embodiment 36 is the second isolated anti-PD-L1 construct of embodiment 35, wherein the second isolated anti-PD-L1 construct comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 amino acid substitutions.

Embodiment 37 is a pharmaceutical composition comprising the isolated anti-PD-L1 construct of any one of embodiments 1-36 and a pharmaceutical acceptable carrier.

Embodiment 38 is a method of treating an individual having a PD-L1-related disease in a subject in need thereof, comprising administering to the subject an effective amount of the pharmaceutical composition of embodiment 37.

Embodiment 39 is the method of embodiment 38, wherein the PD-L1 related disease is cancer.

Embodiment 40 is the method of embodiment 39, wherein the cancer is a solid tumor.

Embodiment 41 is the method of embodiment 39 or 40, wherein the cancer is a colon cancer.

Embodiment 42 is the method of any one of embodiments 39-41, further comprising administering to the individual an additional cancer therapy.

Embodiment 43 is the method of embodiment 42, wherein the additional cancer therapy is surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or a combination thereof.

Embodiment 44 is the method of embodiment 38, wherein the PD-L1 related disease is a pathogenic infection.

Embodiment 45 is the method of any one of embodiments 38-44, wherein the pharmaceutical composition is administered systemically or locally.

Embodiment 46 is the method of embodiment 45, wherein the pharmaceutical composition is administered intravenously.

Embodiment 47 is the method of embodiment 45, wherein the pharmaceutical composition is administered intratumorally.

Embodiment 48 is the method of any one of embodiments 38-47, wherein the individual is a human.

EXAMPLES

The examples below are intended to be purely exemplary of the invention and should therefore not be considered to limit the invention in any way. The following examples and detailed description are offered by way of illustration and not by way of limitation.

Example 1: Generation of anti-PD-L1 sdAbs

Immunization

Two llamas were immunized with recombinant PD-L1 ECD protein under all current animal welfare regulations. For immunization, the antigen was formulated as an emulsion with CFA (primary immunization) or IFA (boost immunization) . The antigen was administered by double-spot injections intramuscularly at the neck. Each animal received two injections of the emulsion, containing 100 μg of PD-L1 ECD and 4 subsequent injections containing 50 μg of antigen at weekly intervals. At different time points during immunization, 10 ml blood samples were collected from the animal and sera were prepared. The induction of an antigen specific humoral immune response was verified using the serum samples in an ELISA-based experiment with immobilized PD-L1 ECD protein (Figures 1 and 2) . Five days after the last immunization, a blood sample of 300 ml was collected. Peripheral blood lymphocytes (PBLs) , as the genetic source of the llama heavy chain immunoglobulins (HCAbs) , were isolated from the 300 ml blood sample using a Ficoll-Paque gradient (Amersham Biosciences) , yielding 1×10 ⁹ PBLs. The maximal diversity of antibodies is expected to be equal to the number of sampled B-lymphocytes, which is about 10%of the number of PBLs (1×10 ⁸) . The fraction of heavy-chain antibodies in llama is up to 20%of the number of B-lymphocytes. Therefore, the maximal diversity of HCAbs in the 300 ml blood sample is calculated as 2×10 ⁷ different molecules.

Library construction

RNA extracted from PBLs and lymph node was used as starting material for RT-PCR to amplify sdAb encoding gene fragments. These fragments were cloned into an in-house phagemid vector. In frame with the sdAb coding sequence, the vector coded for a C-terminal (His) 6 tag. The library size is more than 1×10 ⁹. The library phage was prepared according to a standard protocol and stored after filter sterilization at 4℃ for further use.

Selections and high-throughput screening

Selections were carried out with the above libraries using solid panning as well as cell-based panning. Only a single round of selection was performed for both conditions. Each selection output was analyzed for enrichment factor (#phage present in eluate relative to control) , diversity and percentage of PD-L1 positive clones (ELISA) . Based on these parameters the best selections were chosen for further analysis. To this end, the output from each selection was recloned as a pool into a soluble expression vector for high-throughput screening. In frame with the sdAb coding sequence, the vector coded for a C-terminal (His) 6 tag. Colonies were picked and grown in 96 deep well plates (1 ml volume) and induced by adding IPTG and 0.1%Triton for sdAb expression in the supernatant.

The supernatant was analyzed for their ability to bind to PD-L1 ECD protein (by ELISA) and PD-L1 stable cell line (by FACS) . The positive binders were sequenced and the unique clones were selected for further characterization.

The unique clones were grown in 2XYT medium and induced by IPTG for sdAb expression in the supernatant. The supernatant of unique binders were analyzed for their ability to inhibit PD-L1-PD-1 interaction. To this end, the supernatant was incubated with PD-L1 ECD protein, then the complex was added to PD-1 stable cell line for binding evaluation. sdAbs with negative signal on PD-1 cell line are considered as PD-L1 inhibitors.

All potential inhibitors were selected for off-rate analysis by surface plasmon resonance (SPR) on a BIAcore T200 instrument. The dissociation phase was used to calculate the k _off values for each individual sdAb.

sdAb production

The His6-tagged sdAbs were purified from periplasmic extracts by

The NTA resin was processed according to the manufacturer's instructions. Periplasmic extracts prepared were incubated with the resin for 30 min at RT on a rotator. The resin was washed with PBS and transferred to a column. The packed resin was washed with 15 mM Imidazole. sdAbs were eluted from the column using 150 mM Imidazole. The eluted fractions were analyzed by spotting on Hybond Membrane and visualized with Ponceau. Fractions containing protein were pooled and dialyzed against PBS. Dialyzed protein was collected, filter sterilized, concentration determined and stored at -20℃.

To determine the purity, protein samples were analyzed on a 12%SDS-PAGE gel. 10 μl Laemmli sample buffer was added to 10 μl (2 μg) purified protein, then the sample was heated for 10 minutes at 95℃, cooled and loaded onto a 12%SDS-PAGE gel. The gel was processed according to general procedures and stained with Coomassie Brilliant Blue (CBB) .

HCAb production

The HCAb constructs were generated by fusion sdAbs with human Fc region. The maxiprep of the HCAb constructs were prepared for CHO-K1 cell transient expression and purification. The expressed HCAbs were purified by chromatography through a column containing Protein A agarose resin followed by a size exclusion column.

To determine the purity, protein samples were analyzed on a 12%SDS-PAGE gel. 10 μl Laemmli sample buffer was added to 10 μl (2 μg) purified protein, then the sample was heated for 10 minutes at 95℃, cooled and loaded onto a 12%SDS-PAGE gel. The gel was processed according to general procedures and stained with Coomassie Brilliant Blue (CBB) . The purity of purified HCAbs are >85%. The data were summarized in Table 20.

Table 20. Summary of HCAb purification

sdAb affinity determination and HCAb affinity determination

Affinity constant (K _d) of each sdAbs and HCAbs was determined by surface plasmon resonance (SPR) on a BIAcore T200 instrument. Briefly, PD-L1 His was amine-coupled to a CM5 sensor chip at a density of no higher than 100 RU. Anti-PD-L1 sdAbs or anti-PD-L1 HCAbs were injected at 5 different concentrations between 0.33 and 27 nM. Flow rate was 30 μl/min in all experiments. Association and dissociation phases were 5 and 10 min, respectively. The chip was regenerated using Glycine/HCl pH 1.5. Binding curves at different concentrations of sdAbs and HCAbs were used to calculate the kinetic parameters k _on, k _off and K _D (Figures 3A-3N and Figures 4A-4N) . The kinetics data were summarized in Table 3 and Table 4.

Table 3 affinity determination of sdAbs against PD-L1

Table 4 affinity determination of HCAbs against PD-L1

*kd is outside the limits that can be measured by Biacore T200

Target binding assays

The ability of the purified antigen binding proteins to bind PD-L1 is determined using Surface Plasmon Resonance method (e.g.,

) , an enzyme-linked immunosorbent assay, a Fluorescence-Assisted Cell Sorting method (FACS) , or a combination thereof. The analyses can be performed on PD-L1 transfected cells.

CHO-K1 cells expressing human PD-L1 were dissociated from adherent culture flasks and mixed with varying concentrations of antibodies and a constant concentration of anti-PD-L1 sdAbs or HCAbs (in a 96-well plate) .

was used as an anti-PD-L1 antibody positive control. The antibody and cell incubation was equilibrated for 30 minutes at room temperature, washed three times with FACS buffer (PBS containing 1%BSA) . FITC conjugated anti-human IgG secondary antibody was then added and incubated for 15 minutes at room temperature. Cells were washed again with FACS buffer and analyzed by flow cytometry. Data were analyzed with Prism (GraphPad Software, San Diego, CA) using non-linear regression, and EC ₅₀ values were calculated (Figures 5A and 5B) .

Inhibition of ligand binding by FACS analysis

Blockade of ligand binding was studied using flow cytometry. For anti-PD-L1 HCAbs evaluation, CHO-K1 cells expressing human PD-L1 were dissociated from adherent culture flasks and mixed with varying concentrations of antibodies and a constant concentration of biotin-labeled hPD-1/Fc protein (both in a 96-well plate) .

was used as an anti-PD-L1 antibody positive control. The mixture was equilibrated for 30 minutes at room temperature, washed three times with FACS buffer (PBS containing 1%BSA) . PE/Cy5 Streptavidin secondary antibody was then added and incubated for 15 minutes at room temperature. Cells were washed again with FACS buffer and analyzed by flow cytometry. Data were analyzed with Prism (GraphPad Software, San Diego, CA) using non-linear regression, and IC ₅₀ values were calculated. As can be seen from Figures 6A and 6B, the competition assays demonstrated the ability of most anti-PD-L1 HCAbs in efficiently inhibiting PD-L1-PD-1 interactions at low concentrations (1-10 μg/ml) , the IC ₅₀ of most HCAbs are comparable to

PD-L1-based blockade assay

CHO-K1 stable expressing PD-L1 cells and Jurkat effector cells are used to assess PD-1 blockade for anti-PD-L1 sdAbs and HCAbs evaluation. The effector cells contain a luciferase construct that is induced upon disruption of the PD-1/PD-L1 receptor-ligand interaction, such as when the PD-L1 cells are mixed with effector cells expressing PD-1. Thus, efficacy of inhibiting PD-L1 on CHO-K1 stable cells by anti-PD-L1 sdAbs and HCAbs can be assessed by measuring luciferase reporter activity. The assay is performed as follows.

On day one, PD-L1 cells are thawed in a 37℃ water bath until cells are just thawed (about 3-4 minutes) , and 0.5 mL of thawed cells is transferred to 14.5 mL cell recovery medium (10%FBS/F-12) . The cell suspension is mixed well by gently inverting the tube 1-2 times. The cell suspension is then transferred to a sterile reagent reservoir, and dispensed into assay plates with 25 μL of cell suspension per well. 100 μL of assay medium is added per well as blank control. 100 μL of cell recovery medium is added per well for wells serving as blank control. The plates are then lidded and incubated overnight in a CO ₂ incubator at 37℃.

On the day of assay, fresh assay buffer (RPMI 1640 + 1%FBS) is prepared. An eight-point serial dilution is performed in assay buffer for each of the control anti-PD-L1 antibody (e.g.,

) , sdAbs or HCAbs. The starting concentration and dilution scheme is optimized to achieve full dose-response curves. The assay plates containing PD-L1 cells are retrieved from the CO ₂ incubator. 95μl of medium is removed per well from all the wells. 40 μL of serial dilutions of the control anti-PD-L1 antibody, or the antigen binding protein, is added per well to wells containing PD-L1 cells. 80 μL assay buffer is added per well to the blank control wells for each plate.

Next, PD-1 effector Cells are thawed in a 37℃ water bath until cells are just thawed (about 3-4 minutes) . The cell suspension is gently mixed in the vial by pipetting up and down, and 0.5 mL of the cells is added to 5.9 mL assay buffer. The cell suspension is mixed well by gently inverting the tube 1-2 times. The cell suspension is then transferred to a sterile reagent reservoir, and 40 μL of the cell suspension is dispensed to each well containing the PD-1 cells and control antibody or bispecific antigen binding protein. The plates are lidded and incubated for six hours at 37℃ in a CO ₂ incubator.

The Luciferase Assay System is reconstituted by transferring one bottle of Buffer to the bottle containing Substrate. The system is stored at room temperature and shielded from light for same day use. After 6 hours induction, assay plates are removed from the CO ₂ incubator and equilibrated at ambient temperature for 5-10 min. 80 μL of reagent is added to each well. The plates are incubated for 5-10 min at ambient temperature. Luminescence is measured in

Discover System (Promega, Madison, WI) or a plate reader with glow-type luminescence reading capabilities.

Luminescence is expressed as Relative Light Unit (RLU) . The RLU values of wells having diluted antibody or bispecific antigen binding protein is normalized to the RLU of no antibody or bispecific antigen binding protein control to provide Fold of Luciferase Induction. Data is graphed as RLU versus Log ₁₀ of concentration of antibody or bispecific antigen binding protein and as Fold of Induction versus Log ₁₀ concentration of antibody or bispecific antigen binding protein. The data is fitted to a curve and EC ₅₀ of each bispecific antigen binding proteins and the control anti-PD-1 antibody is determined using curve fitting software such as GraphPad Prism (Figures 7A to 7O and Figures 8A to 8O, Tables 5 and 6) .

Ta ble 5 EC ₅₀ of PD-L1-based blockade assay for sdAbs

Sample	AS06617 sdAb	AS06618 sdAb	AS06628 sdAb	AS06682 sdAb	AS06686 sdAb
EC ₅₀ (M)	6.38E-08	4.45E-08	2.42E-08	4.20E-08	3.52E-07
Sample	AS06703 sdAb	AS06730 sdAb	AS06750 sdAb	AS06775 sdAb	AS06778 sdAb
EC ₅₀ (M)	1.50E-08	1.72E-08	3.36E-08	7.55E-08	2.01E-08
Sample	AS06791 sdAb	AS11947 sdAb	AS11948 sdAb	AS12003 sdAb	Tecentriq
EC ₅₀ (M)	3.65E-08	7.72E-08	2.52E-08	9.62E-08	5.92E-09

Table 6 EC ₅₀ of PD-L1-based blockade assay for HCAbs

Sample	AS06617 HCAb	AS06618 HCAb	AS06628 HCAb	AS06682 HCAb	AS06686 HCAb
EC ₅₀ (M)	6.20E-09	6.45E-09	5.88E-09	6.66E-09	7.37E-09
Sample	AS06703 HCAb	AS06730 HCAb	AS06750 HCAb	AS06775 HCAb	AS06778 HCAb
EC ₅₀ (M)	5.59E-09	6.791E-09	9.98E-09	5.8E-09	5.54E-09
Sample	AS06791 HCAb	AS11947 HCAb	AS11948 HCAb	AS12003 HCAb	Tecentriq
EC ₅₀ (M)	5.82E-09	7.55E-09	5.80E-09	9.34E-09	5.92E-09

Example 2: anti-PD-L1 sdAb humanization

Five anti-PD-L1 sdAbs (AS06730, AS06750, AS11948, AS06617 and AS06675) were selected for humanization. Protein sequences of wildtype camelid sdAb was aligned with the 5 closest human germline sequences sharing the highest degree of homology. The best human germline sequence was selected as human acceptor. Homology model was made. According to the model analysis data, residues potentially critical for antigen binding or antibody scaffold formation were left untouched while the rest were selected for conversion into the human counterpart. Initially a panel of four sequence optimized variants was generated (stage 1) . These variants were analyzed for a number of parameters and the results obtained were used to design a second set of sdAbs (stage 2) . For each wildtype sdAb, 1-9 humanized sdAbs were designed for binding, stability and functional evaluation, and their sequence alignments are shown in Figures 9A-9E.

Humanized HCAb production

Affinity ranking of humanized HCAbs

Binding kinetics of each humanized HCAb to PD-L1 are determined using recombinant human PD-L1 His protein (R&D System) coated on a CM5 (Biacore) sensor chip. Each antigen binding protein is flowed over the antigen-coated chip, using surface plasmon resonance. Alternatively, each antigen binding protein is captured on a CM5 sensor chip, over which human PD-1-His protein is applied. Only the binding affinity of humanized clones comparable to that of the parent HCAbs were selected for further characterization (Tables 7-11) .

Table 7 affinity ranking of humanized sdAbs (AS06730)

Table 8 affinity ranking of humanized sdAbs (AS06750)

Table 9 affinity ranking of humanized sdAbs (AS11948)

Table 10 affinity ranking of humanized sdAbs (AS06617)

Table 11 affinity ranking of humanized sdAbs (AS06775)

Affinity determination

AS06730S, AS06730SVH3a, AS06730SVH12, AS06730AVH12M8, AS06730SVH12M9, AS06750VH2, AS06750VH11, AS06750VH4, AS11948S, AS11948SVH12, AS11948SV12M8, AS11948SV12M9, AS06617VH11, AS06775VH11 and AS06775VH4 were selected for affinity determination. Affinity constant (K _d) of each HCAbs was determined by surface plasmon resonance (SPR) on a BIAcore T200 instrument. Briefly, for most of HCAbs affinity determination, PD-L1 His was amine-coupled to a CM5 sensor chip at a density of no higher than 100 RU. Anti-PD-L1 HCAbs were injected at 5 different concentrations between 0.11 nM and 27 nM. Flow rate was 30 μl/min in all experiments. Association and dissociation phases were 5 and 10 min, respectively. The chip was regenerated using Glycine/HCl pH 1.5. For AS06730SVH12, AS06730SVH12M8, AS06730VH12M9, AS11948SV12, AS11948SV12M8 and AS11948SV12M9 HCAbs affinity determination, anti-PD-L1 HCAbs were captured on a CM5 sensor chip at a density of no higher than 100 RU by anti-human IgG antibody. Anti-PD-L1 His was injected at 5 different concentrations between 0.33 and 27 nM. Flow rate was 30 μl/min in all experiments. Association and dissociation phases were 5 min. Binding curves at different concentrations of HCAbs were used to calculate the kinetic parameters k _on, k _off and K _d (Figures 10A-10T) . The kinetics data were summarized in Table 12 and Table 13.

Table 12. Affinity parameters of humanized HCAbs

Table 13. Affinity parameters of humanized HCAbs

PD-L1 based blockade assay

PD-L1 based blockade assay was performed as described in Example 1. As can be seen from Figures 11A-11Q, all the selected humanized anti-PD-L1 HCAbs are comparable to

in inhibiting the binding between PD-L1 and PD-1. The EC ₅₀ data was summarized in Table 14.

Table 14 EC ₅₀ of PD-L1-based blockade assay for HCAbs

In vivo activity of humanized HCAbs

In the studies presented here, the efficacy of PD-L1 HCAb blockade against murine tumor model was investigated. Inhibition of the PD-L1 interaction is proposed to exert a therapeutic effect by restoring anti-tumor CD8+ T cell responses, thus the preclinical efficacy study was conducted in syngeneic murine tumor model in which the immune system of the host is fully intact. The human PD-1 transgenic mice was used.

In this study, mice were inoculated subcutaneously in the right flank with 1×10 ⁶ human PD-L1 overexpression MC38 colon carcinoma cells. When tumors reached a mean volume of ～ 100 mm ³, mice were sorted into treatment groups (n=5) (defined as study day 0) . 6 humanized HCAbs tested in this study were listed: AS06730QVH1, AS06750VH11, AS11948SVH12, AS06617VH11, AS06617VH11, AS11948QVH1 and AS06775VH11. Groups were administered benchmark antibody MEDI4736 (10 mg/kg) or humanized HCAbs (5.33 mg/kg) intravenously

days

0, 2, 5, 7, 9 and 12. A control group was treated with 10 ml/kg of PBS. Tumors were measured twice weekly for the study duration. All treatment groups demonstrated significant efficacy (P<0.050) when compared to the control group (Figure 12) . These observations support that anti-PD-L1 therapy as an effective strategy for driving anti-tumor CD8+ T cell responses.

Table 15: CDRs of isolated sdAbs

sdAb	ID	CDR1	ID	CDR2	ID	CDR3
AS06617	51	GRTFISYAVG	151	GIRWNGIHTDYADSVKG	251	HRTIATIPEKYEYEY
AS06618	52	GRTFLSYAVG	152	GIRWSGGYTDYAEAVKG	252	HRTIATIPEKYEYEY
AS06624	53	GRTFLTYALG	153	GVSWSGSGTKYADSVKG	253	QISAIVPISAHEYEY
AS06628	54	GRTFITYAIG	154	AINWSGSMTSYADSVKG	254	HRGAIAPMTQSVYDY

AS06639	55	GRTFITYAIG	155	AINWSGSMTSYADSVKG	255	HRGAIAPMTQSVYDT
AS06682	56	GRTFLSYAVG	156	GIRWSGEHTDYAASVKG	256	HTTIATIPKKYEYEY
AS06686	57	GRTFLTYALG	157	GVSWSGSSTKYADSVKG	257	QISAIVPISAHEYQY
AS06703	58	GRTFITYAIG	158	AINWSGSMTSYADSVKG	258	HLGAIAPMSQSVYDY
AS06709	59	GRTFLSYAVG	159	GIRWSGGSTDYSDSVKG	259	HRTIATIPEKYEYEY
AS06730	60	GRTFITYAIG	160	AINWSGSMTSYADSVKG	260	HRGAIAPIAQSVYTN
AS06750	61	GRTFLTYAVG	161	GIRWSGGYTDYADSVKG	261	HRTIATIPEKYEYEY
AS06752	62	GRTFLTYAVG	162	GIRWSGESTDYAESVKG	262	HRTIATIPEKYYYEY
AS06763	63	GRPVSSAVMG	163	RLTSSATSTFYAESVKG	263	DVPGTKIWSIQTPDRYNY
AS06766	64	GRTLTGLLIG	164	IISWTYGSTNYADSVKG	264	RDVAVAKYDS
AS06775	65	GRTFLTLAVG	165	GIRWSGSGTDYADSVKG	265	HTTIATIPEKYEYEY
AS06778	66	GRTFITYAMG	166	AISWSGSSTYSADSVKG	266	EVSARTGEHLPKLMGDY
AS06786	67	GRTFLTLAVG	167	GIRWSGSGTDYADSVKG	267	HTTIATIPEKYEYEY
AS06791	68	GRTFITYAIG	168	AINWSGSMTSYADSVKG	268	HRGAIAPMTQSVYDY
AS06808	69	GRTFSRYAMG	169	TSTGSGGLTSYANSVKG	269	NRYNSDSRYMSSYDW
AS06810	70	GRTFLSYAVG	170	GIRWSGLHTDYADSVKG	270	HRTIATIPEKYEYEY
AS11947	71	GRTFISYAVG	171	GIRWNGISTDYTDSVKG	271	HRTIATIPNKYEYDH
AS11948	72	GRTFVTYGMG	172	AINWSGSMTSYGDSVKG	272	ALGAVVYTTREPYTY
AS12003	73	GRTFLSYAVG	173	GIRWSGGSTDYADSVKG	273	HRTIATVPNKYEYDT
AL22863	74	VSSFSINDMG	174	TIAS-GGSTNYADSVKG	274	DFRDWTRRRYSY
AL23474	75	GRTFSNYTMA	175	VVSRGGGATDYADSVKG	275	GTDLSYYYSTKKWAY
AS06730S	76	GRTFITYAIG	176	AISWSGSMTSYADSVKG	276	HRGAIAPIAQSVYTN
AS06730Q	77	GRTFITYAIG	177	AIQWSGSMTSYADSVKG	277	HRGAIAPIAQSVYTN
AS06730QVH1	78	GRTFITYAIG	178	AIQWSGSMTSYADSVKG	278	HRGAIAPIAQSVYTN
AS06730QVH2	79	GRTFITYAIG	179	AIQWSGSMTSYADSVKG	279	HRGAIAPIAQSVYTN
AS06730QVH3a	80	GRTFITYAIG	180	AIQWSGSMTSYADSVKG	280	HRGAIAPIAQSVYTN
AS06730SVH12	81	GRTFITYAIG	181	AISWSGSMTSYADSVKG	281	HRGAIAPIAQSVYTN
AS06730SVH12M8	82	GRTFITYAIG	182	AISWSGSITSYADSVKG	282	HRGAIAPIAQSVYTN
AS06730SVH12M9	83	GRTFITYAIG	183	AISWSGSLTSYADSVKG	283	HRGAIAPIAQSVYTN
AS06750VH1	84	GRTFLTYAVG	184	GIRWSGGYTDYADSVKG	284	HRTIATIPEKYEYEY
AS06750VH2	85	GRTFLTYAVG	185	GIRWSGGYTDYADSVKG	285	HRTIATIPEKYEYEY
AS06750VH3	86	GRTFLTYAVG	186	GIRWSGGYTDYADSVKG	286	HRTIATIPEKYEYEY
AS06750VHa	87	GRTFLTYAVG	187	GIRWSGGYTDYADSVKG	287	HRTIATIPEKYEYEY
AS06750VH11	88	GRTFLTYAVG	188	GIRWSGGYTDYADSVKG	288	HRTIATIPEKYEYEY
AS11948A	89	GRTFVTYGMG	189	AIAWSGSMTSYGDSVKG	289	ALGAVVYTTREPYTY
AS11948S	90	GRTFVTYGMG	190	AISWSGSMTSYGDSVKG	290	ALGAVVYTTREPYTY
AS11948Q	91	GRTFVTYGMG	191	AIQWSGSMTSYGDSVKG	291	ALGAVVYTTREPYTY
AS11948QVH1	92	GRTFVTYGMG	192	AIQWSGSMTSYGDSVKG	292	ALGAVVYTTREPYTY
AS11948QVH2	93	GRTFVTYGMG	193	AIQWSGSMTSYGDSVKG	293	ALGAVVYTTREPYTY
AS11948QVHa	94	GRTFVTYGMG	194	AIQWSGSMTSYGDSVKG	294	ALGAVVYTTREPYTY
AS11948SVH12	95	GRTFVTYGMG	195	AISWSGSMTSYGDSVKG	295	ALGAVVYTTREPYTY
AS11948SVH12M8	96	GRTFVTYGMG	196	AISWSGSITSYGDSVKG	296	ALGAVVYTTREPYTY
AS11948SVH12M9	97	GRTFVTYGMG	197	AISWSGSLTSYGDSVKG	297	ALGAVVYTTREPYTY
AS06617VH11	98	GRTFISYAVG	198	GIRWSGIHTDYADSVKG	298	HRTIATIPEKYEYEY
AS06775VH11	99	GRTFLTLAVG	199	GIRWSGSGTDYADSVKG	299	HTTIATIPEKYEYEY
AS06775VH4	100	GRTFLTYAVG	200	GIRWSGGYTDYADSVKG	300	HRTIATIPEKYEYEY

ID: SEQ ID NO

Table 16:

Framework Regions

1 and 2

sdAb	ID	FR-1	ID	FR-2
AS06617	1	DVQLVESGGGLVQAGDSLRLSCAAS	101	WFRQAPGSEREFVA
AS06618
	2	EVQLVESGGRLVRAGDSLRLSCAAS	102	WFRQAPGTEREFVA
AS06624
	3	QVQLVESGGGLVQAGGSLRLACSAS	103	WFRQAPGKEREFVA
AS06628
	4	QVQLVESGGGLVQAGGSLRLSCAAS	104	WFRQAPGKEREFVT
AS06639
	5	AVQLVESGGGLVQAGGSLRLSCAAS	105	WFRQAPGKEREFVS
AS06682	6	AVQLVESGGGLVQAGDSLRLSCTAS	106	WFRQAPGTEREFVA
AS06686
	7	AVQLVESGGGLVQAGDSLRLACAAS	107	WFRQAPGKEREFVA
AS06703
	8	EVQLVESGGGLVRAGGSLRLSCAAS	108	WFRQAPGKEREFVT

AS06709	9	EVQLVESGGGLVQAGDSLRLSCTAS	109	WFRQAPGTEREFVA
AS06730
	10	QVQLVESGGGLVQAGGSLRLSCAAS	110	WFRQAPGKEREFVS
AS06750	11	AVQLVESGGGLVQAGDSLRLSCTAS	111	WFRQAPGTEREFVA
AS06752	12	EVQLVESGGGLVQAGDSLRLSCAAS	112	WFRQAPGTEREFVA
AS06763	13	QVQLVESGGGLVQAGGSLRLSCAVS	113	WFRQAPGKEREFVG
AS06766	14	EVQLVESGGGLVQAGGSLSLSCAVS	114	WFRQAPGKERELVA
AS06775
	15	QVQLVESGGGLVQAGDSLRLSCAAS	115	WFRQAPGTEREFVA
AS06778	16	QVQLVESGGGLVQAGGSLKLSCAAS	116	WFRQAPGKERELVA
AS06786	17	QVQLVESGGGLVQAGDSLRLSCAAS	117	WFRQAPGTEREFVA
AS06791	18	QVQLVESGGGLVQAGGSLRLSCAAS	118	WFRQAPGKEREFVT
AS06808	19	QVKLEESGGGLVQAGGSLRLSCVAS	119	WFRQAPGKEREFVS
AS06810
	20	AVQLVESGGGLVQAGDSLRLSCAAS	120	WFRQAPGTEREFVA
AS11947	21	DVQLVESGGGLVQAGDSLRLTCSAS	121	WFRQAPGTEREFVA
AS11948	22	EVQLVESGGGLVQAGDSLRLSCVAS	122	WFRQAPGKEREFVA
AS12003	23	EVQLVESGGGLVQAGDSLRLSCAAS	123	WFRQAPGTEREFVA
AL22863	24	QVKLEESGGGLVQVGDSLRLSCAAS	124	WYRQAPGKQRELVA
AL23474
	25	QVKLEESGGGLVQVGDSLRLSCAAS	125	WFRQFPGKEREFVA
AS06730S	26	QVQLVESGGGLVQAGGSLRLSCAAS	126	WFRQAPGKEREFVS
AS06730Q	27	QVQLVESGGGLVQAGGSLRLSCAAS	127	WFRQAPGKEREFVS
AS06730QVH1	28	EVQLVESGGGLVQPGGSLRLSCAAS	128	WVRQAPGKGLEWVS
AS06730QVH2	29	EVQLVESGGGLVQPGGSLRLSCAAS	129	WFRQAPGKGLEWVS
AS06730QVH3a
	30	EVQLVESGGGLVQPGGSLRLSCAAS	130	WFRQAPGKGLEFVS
AS06730SVH12	31	EVQLVESGGGLVQPGGSLRLSCAAS	131	WFRQAPGKGREFVS
AS06730SVH12M8	32	EVQLVESGGGLVQPGGSLRLSCAAS	132	WFRQAPGKGREFVS
AS06730SVH12M9	33	EVQLVESGGGLVQPGGSLRLSCAAS	133	WFRQAPGKGREFVS
AS06750VH1	34	EVQLVESGGGLVQPGGSLRLSCAAS	134	WVRQAPGKGLEWVS
AS06750VH2
	35	EVQLVESGGGLVQPGGSLRLSCAAS	135	WFRQAPGKGLEWVA
AS06750VH3	36	EVQLVESGGGLVQPGGSLRLSCAAS	136	WFRQAPGKGLEFVA
AS06750VHa	37	EVQLVESGGGLVQPGGSLRLSCTAS	137	WFRQAPGKGLEFVA
AS06750VH11	38	EVQLVESGGGLVQPGGSLRLSCAAS	138	WFRQAPGKGREFVS
AS11948A	39	EVQLVESGGGLVQAGDSLRLSCVAS	139	WFRQAPGKEREFVA
AS11948S
	40	EVQLVESGGGLVQAGDSLRLSCVAS	140	WFRQAPGKEREFVA
AS11948Q	41	EVQLVESGGGLVQAGDSLRLSCVAS	141	WFRQAPGKEREFVA
AS11948QVH1	42	EVQLVESGGGLVQPGGSLRLSCAAS	142	WVRQAPGKGLEWVS
AS11948QVH2	43	EVQLVESGGGLVQPGGSLRLSCAAS	143	WFRQAPGKGLEFVA
AS11948QVHa	44	EVQLVESGGGLVQPGGSLRLSCVAS	144	WFRQAPGKGREFVS
AS11948SVH12
	45	EVQLVESGGGLVQPGGSLRLSCAAS	145	WFRQAPGKGREFVS
AS11948SVH12M8	46	EVQLVESGGGLVQPGGSLRLSCAAS	146	WFRQAPGKGREFVS
AS11948SVH12M9	47	EVQLVESGGGLVQPGGSLRLSCAAS	147	WFRQAPGKGREFVS
AS06617VH11	48	EVQLVESGGGLVQPGGSLRLSCAAS	148	WFRQAPGKGREFVS
AS06775VH11	49	EVQLVESGGGLVQPGGSLRLSCAAS	149	WFRQAPGKGREFVS
AS06775VH4
	50	EVQLVESGGGLVQPGGSLRLSCAAS	150	WFRQAPGKGLEFVS

ID: SEQ ID NO; FR: Framework region

Table 17:

Framework Regions

3 and 4

sdAb	ID	FR-3	ID	FR-4
AS06617	201	RFTISRDNAKNTVTLEMTSLKPEDTAVYYCAA	301	WGQGTQVTVSS
AS06618	202	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	302	WGQGTQVTVSS
AS06624	203	RFTISRDNAKNTVYMQMNSLKPEDTAVYYCAA	303	WGQGTQVTVSS
AS06628	204	RFTISRDNNKNMVYLQMNSLKPEDTAVYYCAA	304	WGQGTQVTVSS
AS06639	205	RFTISRDNAKNTVYLQMNGLKPEDTAVYYCAA	305	WGQGTQVTVSS
AS06682	206	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	306	WGQGTQVTVSS
AS06686	207	RFTISRDNAKNTVYMQMNSLKPEDTAVYYCAA	307	WGQGTQVTVSS
AS06703	208	RFTISRDNNKNTVYLQMNSLKPEDTALYYCAA	308	WGQGTQVTVSS
AS06709	209	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	309	WGQGTQVTVSS
AS06730	210	RFTISRDNAKNTVYLQMNGLKPEDTAVYYCAA	310	WGQGTQVTVSS
AS06750	211	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	311	WGQGTQVTVSS
AS06752	212	RFTISRDDTKNTVYLQMNSLKPEDTAVYYCAA	312	WGQGTQVTVSS

AS06763	213	RFTISRDNAKNTVYLQMNNLKPEDTAVYYCAA	313	WGQGTQVTVSS
AS06766	214	RFTISRDNAKNTVLLQMNSLKPEDTAVYYCSA	314	WGQGTQVTVSS
AS06775	215	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	315	WGRGTQVTVSS
AS06778	216	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	316	WGQGTQVTVSS
AS06786	217	RFTISRDNAANTVYLQMNSLKPEDTAVYYCAA	317	WGQGTQVTVSS
AS06791	218	RFTISRDNAKNTVYLQINGLKSEDTAVYYCAA	318	WGQGTQVTVSS
AS06808	219	RFTISRDNAKNTVYLQMNNLKPEDTAIYYCAA	319	WGQGTQVTVSS
AS06810	220	RFTISRDNAKNTVYLQMNSLKPEDTAIYYCAA	320	WGQGTQVTVSS
AS11947	221	RFTISRDNAKNTVYLQMNSLKPEDTAIYYCAA	321	WGQGTQVTVSS
AS11948	222	RFAISRDNAKNTVYLQMNSLKPEDTAVYYCAA	322	WGRGTQVTVSS
AS12003	223	RFTISRDNAKNTVYLQMNSLKPEDTAVYYCAA	323	WGQGTQVTVSS
AL22863	224	RFTISRDNVKNTVYLQMNGLKPEDTAVYYCNA	324	WGQGTQVTVSS
AL23474	225	RFTISRDNAKNTMYLQMNSLKTEDTAVYYCAA	325	WGQGTQVTVSS
AS06730S	226	RFTISRDNAKNTVYLQMNGLKPEDTAVYYCAA	326	WGQGTQVTVSS
AS06730Q	227	RFTISRDNAKNTVYLQMNGLKPEDTAVYYCAA	327	WGQGTQVTVSS
AS06730QVH1	228	RFTISRDNSKNTLYLQMNSLRAEDTAVYYCAK	328	WGQGTLVTVSS
AS06730QVH2	229	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	329	WGQGTLVTVSS
AS06730QVH3a	230	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	330	WGQGTLVTVSS
AS06730SVH12	231	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	331	WGQGTLVTVSS
AS06730SVH12M8	232	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	332	WGQGTLVTVSS
AS06730SVH12M9	233	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	333	WGQGTLVTVSS
AS06750VH1	234	RFTISRDNSKNTLYLQMNSLRAEDTAVYYCAK	334	WGQGTLVTVSS
AS06750VH2	235	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	335	WGQGTLVTVSS
AS06750VH3	236	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	336	WGQGTLVTVSS
AS06750VHa	237	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	337	WGQGTLVTVSS
AS06750VH11	238	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	338	WGQGTLVTVSS
AS11948A
	239	RFAISRDNAKNTVYLQMNSLKPEDTAVYYCAA	339	WGRGTQVTVSS
AS11948S	240	RFAISRDNAKNTVYLQMNSLKPEDTAVYYCAA	340	WGRGTQVTVSS
AS11948Q	241	RFAISRDNAKNTVYLQMNSLKPEDTAVYYCAA	341	WGRGTQVTVSS
AS11948QVH1	242	RFTISRDNSKNTLYLQMNSLRAEDTAVYYCAK	342	WGQGTLVTVSS
AS11948QVH2	243	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	343	WGQGTLVTVSS
AS11948QVHa	244	RFTISRDNSKNTVYLQMNSLRAEDTAVYYCAA	344	WGQGTLVTVSS
AS11948SVH12	245	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	345	WGQGTLVTVSS
AS11948SVH12M8	246	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	346	WGQGTLVTVSS
AS11948SVH12M9	247	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	347	WGQGTLVTVSS
AS06617VH11	248	RFTISRDNSKNTLYLQMNSLRAEDTAVYYCAA	348	WGQGTLVTVSS
AS06775VH11	249	RFTISRDNAKNTLYLQMNSLRPEDTAVYYCAA	349	WGQGTLVTVSS
AS06775VH4	250	RFTISRDNSKNTLYLQMNSLRAEDTAVYYCAA	350	WGQGTLVTVSS

ID: SEQ ID NO; FR: Framework region

Table 18: sdAbs

ID: SEQ ID NO

Table 19: HCAbs

Claims

An isolated anti-PD-L1 construct comprising a single-domain antibody (sdAb) moiety specifically recognizing PD-L1, wherein the sdAb moiety comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 amino acid substitutions.
The isolated anti-PD-L1 construct of claim 1, wherein the sdAb moiety comprises any one of the following:

(1) a CDR1 comprising the amino acid sequence of SEQ ID NO: 51; a CDR2 comprising the amino acid sequence of SEQ ID NO: 151; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 251; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(2) a CDR1 comprising the amino acid sequence of SEQ ID NO: 52; a CDR2 comprising the amino acid sequence of SEQ ID NO: 152; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 252; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(3) a CDR1 comprising the amino acid sequence of SEQ ID NO: 53; a CDR2 comprising the amino acid sequence of SEQ ID NO: 153; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 253; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(4) a CDR1 comprising the amino acid sequence of SEQ ID NO: 54; a CDR2 comprising the amino acid sequence of SEQ ID NO: 154; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 254; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(5) a CDR1 comprising the amino acid sequence of SEQ ID NO: 55; a CDR2 comprising the amino acid sequence of SEQ ID NO: 155; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 255; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(6) a CDR1 comprising the amino acid sequence of SEQ ID NO: 56; a CDR2 comprising the amino acid sequence of SEQ ID NO: 156; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 256; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(7) a CDR1 comprising the amino acid sequence of SEQ ID NO: 57; a CDR2 comprising the amino acid sequence of SEQ ID NO: 157; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 257; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(8) a CDR1 comprising the amino acid sequence of SEQ ID NO: 58; a CDR2 comprising the amino acid sequence of SEQ ID NO: 158; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 258; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(9) a CDR1 comprising the amino acid sequence of SEQ ID NO: 59; a CDR2 comprising the amino acid sequence of SEQ ID NO: 159; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 259; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(10) a CDR1 comprising the amino acid sequence of SEQ ID NO: 60; a CDR2 comprising the amino acid sequence of SEQ ID NO: 160; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 260; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(11) a CDR1 comprising the amino acid sequence of SEQ ID NO: 61; a CDR2 comprising the amino acid sequence of SEQ ID NO: 161; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 261; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(12) a CDR1 comprising the amino acid sequence of SEQ ID NO: 62; a CDR2 comprising the amino acid sequence of SEQ ID NO: 162; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 262; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(13) a CDR1 comprising the amino acid sequence of SEQ ID NO: 63; a CDR2 comprising the amino acid sequence of SEQ ID NO: 163; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 263; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(14) a CDR1 comprising the amino acid sequence of SEQ ID NO: 64; a CDR2 comprising the amino acid sequence of SEQ ID NO: 164; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 264; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(15) a CDR1 comprising the amino acid sequence of SEQ ID NO: 65; a CDR2 comprising the amino acid sequence of SEQ ID NO: 165; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 265; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(16) a CDR1 comprising the amino acid sequence of SEQ ID NO: 66; a CDR2 comprising the amino acid sequence of SEQ ID NO: 166; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 266; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(17) a CDR1 comprising the amino acid sequence of SEQ ID NO: 67; a CDR2 comprising the amino acid sequence of SEQ ID NO: 167; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 267; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(18) a CDR1 comprising the amino acid sequence of SEQ ID NO: 68; a CDR2 comprising the amino acid sequence of SEQ ID NO: 168; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 268; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(19) a CDR1 comprising the amino acid sequence of SEQ ID NO: 69; a CDR2 comprising the amino acid sequence of SEQ ID NO: 169; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 269; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(20) a CDR1 comprising the amino acid sequence of SEQ ID NO: 70; a CDR2 comprising the amino acid sequence of SEQ ID NO: 170; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 270; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(21) a CDR1 comprising the amino acid sequence of SEQ ID NO: 71; a CDR2 comprising the amino acid sequence of SEQ ID NO: 171; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 271; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(22) a CDR1 comprising the amino acid sequence of SEQ ID NO: 72; a CDR2 comprising the amino acid sequence of SEQ ID NO: 172; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 272; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(23) a CDR1 comprising the amino acid sequence of SEQ ID NO: 73; a CDR2 comprising the amino acid sequence of SEQ ID NO: 173; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 273; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(24) a CDR1 comprising the amino acid sequence of SEQ ID NO: 74; a CDR2 comprising the amino acid sequence of SEQ ID NO: 174; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 274; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(25) a CDR1 comprising the amino acid sequence of SEQ ID NO: 75; a CDR2 comprising the amino acid sequence of SEQ ID NO: 175; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 275; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(26) a CDR1 comprising the amino acid sequence of SEQ ID NO: 76; a CDR2 comprising the amino acid sequence of SEQ ID NO: 176; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 276; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(27) a CDR1 comprising the amino acid sequence of SEQ ID NO: 77; a CDR2 comprising the amino acid sequence of SEQ ID NO: 177; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 277; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(28) a CDR1 comprising the amino acid sequence of SEQ ID NO: 78; a CDR2 comprising the amino acid sequence of SEQ ID NO: 178; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 278; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(29) a CDR1 comprising the amino acid sequence of SEQ ID NO: 79; a CDR2 comprising the amino acid sequence of SEQ ID NO: 179; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 279; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(30) a CDR1 comprising the amino acid sequence of SEQ ID NO: 80; a CDR2 comprising the amino acid sequence of SEQ ID NO: 180; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 280; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(31) a CDR1 comprising the amino acid sequence of SEQ ID NO: 81; a CDR2 comprising the amino acid sequence of SEQ ID NO: 181; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 281; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(32) a CDR1 comprising the amino acid sequence of SEQ ID NO: 82; a CDR2 comprising the amino acid sequence of SEQ ID NO: 182; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 282; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(33) a CDR1 comprising the amino acid sequence of SEQ ID NO: 83; a CDR2 comprising the amino acid sequence of SEQ ID NO: 183; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 283; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(34) a CDR1 comprising the amino acid sequence of SEQ ID NO: 84; a CDR2 comprising the amino acid sequence of SEQ ID NO: 184; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 284; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(35) a CDR1 comprising the amino acid sequence of SEQ ID NO: 85; a CDR2 comprising the amino acid sequence of SEQ ID NO: 185; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 285; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(36) a CDR1 comprising the amino acid sequence of SEQ ID NO: 86; a CDR2 comprising the amino acid sequence of SEQ ID NO: 186; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 286; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(37) a CDR1 comprising the amino acid sequence of SEQ ID NO: 87; a CDR2 comprising the amino acid sequence of SEQ ID NO: 187; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 287; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(38) a CDR1 comprising the amino acid sequence of SEQ ID NO: 88; a CDR2 comprising the amino acid sequence of SEQ ID NO: 188; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 288; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(39) a CDR1 comprising the amino acid sequence of SEQ ID NO: 89; a CDR2 comprising the amino acid sequence of SEQ ID NO: 189; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 289; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(40) a CDR1 comprising the amino acid sequence of SEQ ID NO: 90; a CDR2 comprising the amino acid sequence of SEQ ID NO: 190; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 290; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(41) a CDR1 comprising the amino acid sequence of SEQ ID NO: 91; a CDR2 comprising the amino acid sequence of SEQ ID NO: 191; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 291; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(42) a CDR1 comprising the amino acid sequence of SEQ ID NO: 92; a CDR2 comprising the amino acid sequence of SEQ ID NO: 192; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 292; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(43) a CDR1 comprising the amino acid sequence of SEQ ID NO: 93; a CDR2 comprising the amino acid sequence of SEQ ID NO: 193; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 293; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(44) a CDR1 comprising the amino acid sequence of SEQ ID NO: 94; a CDR2 comprising the amino acid sequence of SEQ ID NO: 194; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 294; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(45) a CDR1 comprising the amino acid sequence of SEQ ID NO: 95; a CDR2 comprising the amino acid sequence of SEQ ID NO: 195; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 295; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(46) a CDR1 comprising the amino acid sequence of SEQ ID NO: 96; a CDR2 comprising the amino acid sequence of SEQ ID NO: 196; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 296; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(47) a CDR1 comprising the amino acid sequence of SEQ ID NO: 97; a CDR2 comprising the amino acid sequence of SEQ ID NO: 197; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 297; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(48) a CDR1 comprising the amino acid sequence of SEQ ID NO: 98; a CDR2 comprising the amino acid sequence of SEQ ID NO: 198; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 298; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(49) a CDR1 comprising the amino acid sequence of SEQ ID NO: 99; a CDR2 comprising the amino acid sequence of SEQ ID NO: 199; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 299; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions;

(50) a CDR1 comprising the amino acid sequence of SEQ ID NO: 100; a CDR2 comprising the amino acid sequence of SEQ ID NO: 200; and a CDR3 comprising the amino acid sequence of SEQ ID NO: 300; or a variant thereof comprising up to about 3 (such as about any of 1, 2, or 3) amino acid substitutions in the CDR regions.
The isolated anti-PD-L1 construct of any one of claims 1-2, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of the following:

a-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, L, I, and V; preferably Y and V, more preferably F

a-2) the amino acid residue at position 44 is selected from the group consisting of A, G, E, D, G, Q, R, S, and L; preferably Q and G, more preferably E

a-3) the amino acid residue at position 45 is selected from the group consisting of L, R, and C;

a-4) the amino acid residue at position 103 is selected from the group consisting of W, R, G, and S; and

a-5) the amino acid residue at position 108 is Q; or

b-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, L, I, and V; preferably Y and V, more preferably F

b-2) the amino acid residue at position 44 is selected from the group consisting of E, Q and G;

b-3) the amino acid residue at position 45 is R;

b-4) the amino acid residue at position 103 is selected from the group consisting of W, R, and S; and

b-5) the amino acid residue at position 108 is selected from the group consisting of Q and L,wherein the amino acid position is according to Kabat numbering.
The isolated anti-PD-L1 construct of claim 3, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of the following:

a-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, L, I, and V; preferably Y and V, more preferably F

a-2) the amino acid residue at position 44 is selected from the group consisting of G, E and Q;

a-3) the amino acid residue at position 45 is selected from the group consisting of L and R;

a-4) the amino acid residue at position 103 is selected from the group consisting of W, G, and R; and

a-5) the amino acid residue at position 108 is Q; or

b-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, L, I, and V;

b-2) the amino acid residue at position 44 is selected from the group consisting of E, G and Q;

b-3) the amino acid residue at position 45 is R;

b-4) the amino acid residue at position 103 is W; and G;

b-5) the amino acid residue at position 108 is Q;

wherein the amino acid position is according to Kabat numbering, and wherein Q at position 108 can be optionally humanized to L.
The isolated anti-PD-L1 construct of claim 4, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of the following:

a-1) the amino acid residue at position 37 is selected from the group consisting of F, Y, and V;

a-2) the amino acid residue at position 44 is selected from the group consisting of G, E and Q;

a-3) the amino acid residue at position 45 is selected from the group consisting of L and R;

a-4) the amino acid residue at position 103 is W; and G

a-5) the amino acid residue at position 108 is Q; or

wherein the amino acid position is according to Kabat numbering, and wherein Q at position 108 can be optionally humanized to L.
The isolated anti-PD-L1 construct of any one of claims 1-5, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof having at least about 80%, at least about 90%, or at least about 95%sequence identity to any one of SEQ ID NOs: 351-400.
The isolated anti-PD-L1 construct of claim 6, wherein the sdAb moiety comprises a V _HH domain comprising the amino acid sequence of any one of SEQ ID NOs: 351-400, or a variant thereof comprising up to about 3 amino acid substitutions in the V _HH domain.
The isolated anti-PD-L1 construct of any one of claims 1-7, wherein the K _d of the binding between the sdAb moiety and PD-L1 is about 10 ^-5 M to about 10 ^-12 M, about 10 ^-7 M to about 10 ^-12 M, or about 10 ^-8 M to about 10 ^-12 M.
The isolated anti-PD-L1 construct of any one of claims 1-8, wherein the sdAb moiety specifically recognizing PD-L1 is camelid, chimeric, human, partially humanized, or fully humanized.
The isolated anti-PD-L1 construct of any one of claims 1-9, wherein the isolated anti-PD-L1 construct is a heavy chain-only antibody (HCAb) .
The isolated anti-PD-L1 construct of claim 90, wherein the sdAb moiety that specifically recognizes PD-L1 is fused to a human IgG1 Fc.
The isolated anti-PD-L1 construct of claim 90 or 101, wherein the HCAb is monomeric or dimeric.
The isolated anti-PD-L1 construct of any one of claims 10-12, wherein the sdAb moiety specifically recognizing PD-L1 comprises the amino acid sequence of any one of SEQ ID NOs: 351-400.
The isolated anti-PD-L1 construct of any one of claims 10-12, wherein the HCAb comprises the amino acid sequence of any one of SEQ ID NOs: 401-440.
The isolated anti-PD-L1 construct of any one of claims 1-9, wherein the isolated anti-PD-L1 construct further comprises a second antibody moiety specifically recognizing a second antigen.
The isolated anti-PD-L1 construct of claim 15, wherein the second antibody moiety is a full-length antibody, a Fab, a Fab’ , a (Fab’ ) 2, an Fv, a single chain Fv (scFv) , an scFv-scFv, a minibody, a diabody, a sdAb, or an antibody mimetics.
The isolated anti-PD-L1 construct of claim 15 or 16, wherein the anti-PD-L1 construct is monospecific or multispecific.
The isolated anti-PD-L1 construct of any one of claims 15-17, wherein the second antibody moiety is a sdAb.
The isolated anti-PD-L1 construct of any one of claims 15-18, wherein the second antigen is PD-L1.
The isolated anti-PD-L1 construct of claim 19, wherein the isolated anti-PD-L1 construct comprises three or more sdAbs that specifically recognize PD-L1.
The isolated anti-PD-L1 construct of claim 19 or 20, wherein the second antibody comprises an amino acid sequence of any one of SEQ ID NOs: 351-400.
The isolated anti-PD-L1 construct of any one of claims 15-18, wherein the second antigen is human serum albumin (HSA) .
The isolated anti-PD-L1 construct of any one of claims 15-18, wherein the second antigen is CTLA-4, and the second antibody is anti-CTLA-4 sdAb.
The isolated anti-PD-L1 construct of any one of claims 15-23, wherein the sdAb moiety specifically recognizing PD-L1 is amino (N) -terminal and/or carboxy (C) -terminal to the second antibody moiety.
The isolated anti-PD-L1 construct of any one of claims 15-21, wherein the second antibody moiety is a full-length antibody.
The isolated anti-PD-L1 construct of claim 25, wherein the amino (N) -terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the carboxy (C) -terminus of at least one of the heavy chains of the full-length antibody.
The isolated anti-PD-L1 construct of claim 25, wherein the C-terminus of the sdAb moiety specifically recognizing PD-L1 is fused to the N-terminus of at least one of the heavy chains of the full-length antibody.
The isolated anti-PD-L1 construct of any one of claims 25-27, wherein the full-length antibody specifically recognizes a polypeptide selected from the group consisting of TIGIT, TIM-3, and LAG-3.
The isolated anti-PD-L1 construct of any one of claims 25-28, wherein the PD-L1 specifically recognized by the sdAb moiety comprises the amino acid sequence of SEQ ID NO: 441-442.
The isolated anti-PD-L1 construct of any one of claims 25-28, wherein the sdAb moiety specifically recognizing PD-L1 and the second antibody moiety are optionally connected by a peptide linker.
The isolated anti-PD-L1 construct of claim 280, wherein the peptide linker comprises the amino acid sequence of SEQ ID NO: 443-445.
A second isolated anti-PD-L1 construct that specifically binds to PD-L1 competitively with the isolated anti-PD-L1 construct of any one of claims 1-31.
The second isolated anti-PD-L1 construct of claim 32, wherein the second isolated anti-PD-L1 construct comprises a CDR1 comprising the amino acid sequence of any one of SEQ ID NOs: 51-100, or a variant thereof comprising up to about 3 amino acid substitutions; a CDR2 comprising the amino acid sequence of any one of SEQ ID NOs: 151-200, or a variant thereof comprising up to about 3 amino acid substitutions; and a CDR3 comprising the amino acid sequence of any one of SEQ ID NOs: 251-300, or a variant thereof comprising up to about 3 amino acid substitutions.
A pharmaceutical composition comprising the isolated anti-PD-L1 construct of any one of claims 1-33, and a pharmaceutical acceptable carrier.
A method of treating an individual having a PD-L1-related disease comprising administering to the individual an effective amount of the pharmaceutical composition of claim 34.
The method of claim 35, wherein the PD-L1 related disease is cancer.
The method of claim 36, wherein the cancer is a solid tumor.
The method of claim 36 or 37, wherein the cancer is a colon cancer.
The method of any one of claims 36-38, further comprising administering to the individual an additional cancer therapy.
The method of claim 39, wherein the additional cancer therapy is surgery, radiation, chemotherapy, immunotherapy, hormone therapy, or a combination thereof.
The method of claim 35, wherein the PD-L1 related disease is a pathogenic infection.
The method of any one of claims 35-41, wherein the pharmaceutical composition is administered systemically or locally.
The method of claim 42, wherein the pharmaceutical composition is administered intravenously.
The method of claim 42, wherein the pharmaceutical composition is administered intratumorally.
The method of any one of claims 35-44, wherein the individual is a human.