WO2020109428A1

WO2020109428A1 - Therapeutic compounds, nanoparticles and uses thereof

Info

Publication number: WO2020109428A1
Application number: PCT/EP2019/082810
Authority: WO
Inventors: John Porter; Yao Ding
Original assignee: Midatech Ltd
Priority date: 2018-11-29
Filing date: 2019-11-27
Publication date: 2020-06-04
Also published as: GB201819430D0

Abstract

The present invention comprising a maytansinoid covalently bonded to a linker group, wherein the linker group is covalently bonded to a ligand group having a cyclic polythiol moiety. Also provided are nanoparticles and conjugates, including antibody-drug conjugates, comprising the compound. Furthermore, pharmaceutical compositions comprising the compounds, nanoparticles, and conjugates are provided. Also disclosed are uses of the compounds, nanoparticles, conjugates and pharmaceutical compositions in methods of treatment of proliferative disorders, including cancer.

Description

THERAPEUTIC COMPOUNDS, NANOPARTICLES AND USES THEREOF [ 1 ] Field of the Invention

[2] The present invention relates to compounds, nanoparticles linked to the compounds, conjugates comprising the compounds and a

targeting agent, for example for the targeted delivery of the compounds to specific tissue types or locations, particularly for use in medicine, and includes methods for treatment of proliferative disorders such as cancer. Pharmaceutical compositions, processes for production of the compounds and nanoparticles and methods for their use are also disclosed.

[ 3 ] Background to the Invention

[4] The present invention is directed at compounds, compositions and products, and methods of making and administering such compounds, compositions and products, including for the treatment of mammals and particularly humans.

[5] Drug delivery poses several significant challenges, particularly with regard to the site of action. In the case of treatment of certain tumours, for example, there remains a need for delivery systems that are able to target anti-cancer drugs to the tumour site, while minimizing off-target effects.

[6] Cancer is a condition where cells in a specific part of the body grow and reproduce uncontrollably. In 2015 alone cancer caused around 8.8 million deaths worldwide with over 200 types of cancers that affect humans. Cancers are divided into groups according to the type of cell they start from - carcinomas, lymphomas, leukaemias, brain tumours and sarcomas. Often, underlying diseases complicate conventional cancer therapies. Currently, in such situations, surgical resection is the major treatment option for cancer if the tumour is resectable. However, it is often difficult to completely remove a tumour using surgery. Therefore, targeted drug delivery is of crucial interest due to both improvement of efficacy of approved chemotherapeutics and reducing their side effects (Shi B. et al . , J. Histochem. Cytochem. , 2013, Vol. 61, pp. 901-909) .

[7] US5208020 describes a cytotoxic agent comprising one or more maytansinoids linked to a cell binding agent, a method for killing selected cell populations comprising contacting a cell population with said agent and an I7-methyl-alanine-containing ester of

maytansinol or an analogue of maytansinol.

[8] US2015359903 describes linker compounds containing a disulfide group and maytansine-derived cytotoxic compounds for forming CBA- drug conjugates and conjugates so formed.

[9] US2014142253 describes a dithiolane based thiol modifier for labelling and stronger immobilization of bio-molecules on solid surfaces .

[10] US2017037076 describes a 1 , 2-dithiolane functionalized

nucleoside phosphoramidites and corresponding solid supports. The 1 , 2-dithiolane moiety can also be functionalized at the various positions of the nucleobase and sugar part.

[11] W02017/012591 describes a complex having a metallic

nanoparticle, plural linker conjugates and plural polyethylene glycols (PEGs) , wherein the linker conjugate comprises a pH- sensitive linker and an antibody. The linker links to the metallic nanoparticle through the sulphur atoms of 1 , 2-dithiolane groups, and the PEGs directly link to the metallic nanoparticle.

[12] WO2017/075495 describes conjugates of an active agent such as DM1 attached to a targeting moiety, such as a somatostatin receptor binding moiety, via a linker, and particles comprising such

conjugates. Methods of making, formulating and administering the conjugates are also described.

[13] US2016143914 describes nanoparticles for drug-delivery of cytotoxic anti-cancer compounds. The nanoparticle comprises a maytansinoid and an acetylated polysaccharide-polyethylene glycol conjugate. Methods of treatment are also described.

[14] US4307016 describes demethylmaytansinoids are produced from maytansinoids by means of enzymic transformation. The

demethylmaytansinoids are allegedly useful as antifungal,

antiprotozoal or antitumor agents.

[15] US2004039176 describes a method of making conjugates of cell binding agents and small molecule drugs comprising reacting a cell binding agent with a bifunctional cross-linking moiety to thereby provide the cell binding agent with a reactive disulfide group and then reacting the modified cell binding agent with a small molecule drug comprising a free thiol group. Bifunctional cross-linking moieties are also described.

[16] W02017/003940 describes nanoparticles and microparticles, and pharmaceutical formulations thereof, containing conjugates of an active agent such as maytansinoid attached to a targeting moiety, such as a somatostatin receptor binding moiety, via a linker.

Methods of making the conjugates, the particles, and the

formulations thereof are provided. Methods of administering the formulations to a subject in need thereof are provided.

[17] One problem with compounds for the treatment of disease is that they must show the required potency without causing harmful side effects. That is to say, they must have a good therapeutic window. Another problem is the stability of such compounds when they are used as part of a delivery system to target the site of action. That is to say, a therapeutically effective amount of the drug must survive transport to the site of action. Both of these problems must be addressed where a targeted delivery system is provided.

[18] There remains an unmet need for further compounds,

nanoparticles and conjugate delivery systems and for methods of delivering bioactive agents to a specific tissue or location in a subject, including for the targeted treatment of cancer. The present invention addresses these and other needs.

[ 19 ] Brief Description of the Invention

[20] Broadly, the present invention relates to compounds, tumour targeting nanoparticles thereof and conjugates thereof wherein the compound has a maytansinoid and a cyclic polythiol moiety.

[21] In a first aspect of the invention, there is provided a compound comprising a maytansinoid covalently bonded to a linker group, wherein the linker group is covalently bonded to a ligand group having a cyclic polythiol moiety.

[22] As described in detail herein, the cyclic polythiol containing compound has been found to (a) exhibit an up to 17-fold improvement in in vivo tumour growth reduction compared to the equivalent monothiol containing compound and (b) improve animal survival (i.e. better tolerability vs the equivalent monothiol compound) .

[23] In some cases, the cyclic polythiol is a cyclic disulfide.

[24] In some instances, the cyclic polythiol is saturated.

[25] In some cases, the ligand group is of the following formula;

wherein Z is CR⁵ or N; R³, R⁴, R⁵ and R⁶ are independently one of a hydrogen atom, a methyl group, an ethyl group, a propyl group or an isopropyl group; q is an integer of 0, 1, 2, 3, 4, 5 or 6, and m and n are independently an integer of 0, 1, 2, 3, 4 or 5 and m + n equals 0, 1, 2, 3, 4 or 5. [26] In some instances, the ligand group is of the following formula;

and R³, R⁴, R⁵, R⁶, q, m and n are as defined above.

[27] In some instances, the cyclic polythiol is selected from one of 1 , 2-dithiolane (5-membered) , 1,2-dithiane ( 6-membered) , 1,2- dithiopane (7-membered) and 1 , 2-dithiocane (8-membered) .

[28] In some instances, the cyclic polythiol is unsubstituted.

[29] In some cases, the linker group is an amino acid-derived linker group of the following formula:

wherein R¹ and R² are each independently a hydrogen atom or a naturally occurring amino acid side chain.

[30] In some cases, R¹ is a methyl group and R² is a hydrogen atom.

[31] In some instances, the linker group is of the following formula :

and R¹ is as defined above.

[32] In some cases, the linker group is covalently bonded to the 3- OH position of the maytansinoid via an ester bond. [33] In some instances, the linker group is covalently bonded to the ligand group via an amide bond.

[34] In some instances, the compound is of the following formula;

wherein each X is independently a hydrogen atom or methyl group; Y is a hydrogen atom, fluorine atom, chlorine atom, bromine atom or iodine atom; Z is CR⁵ or N; R³, R⁴, R⁵ and R⁶ are independently one of a hydrogen atom, a methyl group, an ethyl group, a propyl group or an isopropyl group, q is an integer of 0, 1, 2, 3, 4, 5 or 6, and m and n are independently an integer of 0, 1, 2, 3, 4 or 5 and m + n equals 0, 1, 2, 3, 4 or 5.

[35] In some instances, the compound is of the following formula;

wherein X, Y, R³, R⁴, R⁵, R⁶, q, m and n are as defined above.

[36] In some cases, the compound is of one of the following

formulae : wherein the alanine derived linker group stereochemistry is (S) , (R) or racemic and the cyclic disulphide stereochemistry is (S) , (R) or racemic .

[37] In some instances, the alanine derived linker group

stereochemistry is (S) and the cyclic disulphide stereochemistry (S) , (R) or racemic.

[38] In some instances, the alanine derived linker group

stereochemistry is (S) and the cyclic disulphide stereochemistry (R) or racemic.

[39] In some cases, the compound is of one of the following

formulae :

[40] In a second aspect of the invention, there is provided a nanoparticle comprising a core comprising a metal and/or a

semiconductor and a plurality of ligands covalently linked to the core, wherein said ligands comprise (i) at least one compound of the first aspect of the invention as a polydentate ligand; (ii)

optionally at least one targeting ligand (e.g. a tumour-targeting ligand) ; and (iii) at least one dilution ligand.

[41] As described in detail herein, the nanoparticle according to the present invention has been found to (a) exhibit an up to 22-fold greater reduction in in vivo tumour growth compared to the

equivalent monothiol compound-containing nanoparticle, (b) improve animal survival (i.e. better tolerability vs the equivalent

monothiol containing nanoparticle) , (c) enable otherwise lethal doses of the maytansinoid to be administered (i.e. even higher doses vs both delivery of free DM1 and the equivalent monothiol containing nanoparticle) and (d) facilitate greater tumour delivery (i.e.

higher tumour concentration vs both delivery of free DM1 and the equivalent monothiol compound) .

[42] In some cases, the at least one dilution ligand comprises one or more of an ethylene glycol (EG) moiety, a polyethyleneglycol (PEG) moiety, glutathione, a carbohydrate, and

HS- (CH2) _v- (OCH2CH2) _w-COOH, where v and w are independently between 1 and 30, optionally between 2 and 10, 6 and 10, or 20 and 60 (such as HS- (CH₂₎ 2- (EG) ₈-COOH) .

[43] In some instances, the targeting ligand may be a tumour targeting ligand selected from: lactose, FGF-4 (fibroblast growth factor 4), c-Met (hepatocyte growth factor receptor), a glypican-3 binding agent (e.g. a glypican-3 binding peptide as disclosed in US8388937, in particular SEQ ID NO: 1 or 10 as disclosed therein, or an anti-glypican-3 antibody) , an alpha-fetoprotein (AFP) receptor binding agent (e.g. an AFP receptor binding peptide as disclosed in US2012/0270238 or an anti-AFP receptor antibody), and an ASGPR binding agent (e.g. galactose, N-acetylgalactosamine , lactose, glucose, mannose, or a glycomimetic ligand such as disclosed in Mamidyala et al . , J. Am. Chem. Soc . , 2012, Vol . 1334, No. 4, pp. 1978-1981) . In some cases the tumour-targeting ligand may also be an antibody or binding fragment thereof, e.g. a Fab fragment (fragment antigen-binding) , single domain antibody / nanobody directed at a liver or hepatocyte target such as glypican-3, ASGPR, FGF-4, c-Met, AFP or other tumour-expressed protein or tumour-expressed receptor.

[44] In some cases the targeting ligand may comprise a cyclic RGD- containing peptide, such as a cyclic RGD peptide disclosed in Shi et al . , Biophys Rep., 2016, Vol. 2, No. 1, pp . 1-20, DOI

10.1007/s41048-016-0021-8, incorporated herein by reference.

[45] In some cases, the targeting ligand (e.g. tumour-targeting ligand) may be covalently linked to the core via a first linker, said first linker having a chain length of 2 to 50 atoms.

[46] In some instances, the first linker comprises a

group — (CH2) _r— and/or - (OCH2CH2) _s- , wherein r and s are independently > 1.

[47] In some cases, the first linker is bound to the core via a terminal sulphur atom.

[48] In some instances, the first linker is bound to the core via two terminal sulphur atoms .

[49] In some instances, the at least one dilution ligand comprises HS- (CH₂₎ 1-10- (EG) 1-10-COOH (i.e. one to ten ethylene units and one to ten ethylene glycol units, e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10) . [50] In some cases, the at least one dilution ligand comprises HS- (CH₂) _1-4- (OCH₂CH₂) 6-I_O-COOH . Preferably, the at least one dilution ligand comprises HS- (CH₂) _2-3- (OCH₂CH₂) _7-9-COOH .

[51] In some instances, the at least one dilution ligand comprises:

[52] In some cases, the dilution ligand may be, or derived from, a monosaccharide or a disaccharide. In particular the dilution ligand may have the structure of formula 1, 2, 3, 4 or 5 :

wherein the dilution ligand is bound to the core via the terminal thiol group. Optionally, the monosaccharide, disaccharide or derivative thereof is one or more of the a-D, b-D, a-L and b-L stereoisomers, such as the a-D stereoisomer of one or more of formulae 1, 2, 3, 4 or 5, preferably the a-D stereoisomer of formula

3.

[53] In some cases, the plurality of ligands comprise at least one carbohydrate ligand (e.g. a galactose ligand) and at least one bidentate ligand of the following formulae;

wherein the bidentate ligand is bound to the nanoparticle core by two thiol groups and the alanine derived linker group

stereochemistry is (S) , (R) or racemic and the dithiol chain stereochemistry is (S) , (R) or racemic and at least one dilution ligand. As described in the examples herein, one of the linker group enantiomers displayed improved efficacy as a free compound and as a nanoparticle ligand against an array of cancer cell lines in vitro. In some embodiments, the compound of the first aspect of the invention or the nanoparticle of the second aspect of the invention or the conjugate of the third aspect of the invention may have the alanine derived linker group stereochemistry which displays the greater potency against a cancer cell line. For example, the alanine derived linker group stereochemistry that exhibits the lowest IC50 in an assay as described in Method 3 or Method 4 of the Examples herein. [54] In some instances, the alanine derived linker group stereochemistry is (S) and the dithiol chain stereochemistry is (S) , (R) or racemic.

[55] In some cases, the alanine derived linker group stereochemistry is (S) and the dithiol chain stereochemistry is (R) or racemic.

[56] In some instances, the at least one bidentate ligand is of one of the following formulae:

wherein the bidentate ligand is bound to the nanoparticle core by two thiol groups .

[57] In some cases, the core comprises at metal selected from the group consisting of: Au, Ag, Cu, Pt, Pd, Fe, Co, Gd, Zn or any combination thereof. In particular, the core may be of gold.

[58] In some instances, the diameter of the core is in the range 1 nm to 10 nm, such as 2-6 nm.

[59] In some cases, the diameter of the nanoparticle including its ligands is in the range 3 nm to 50 nm.

[60] In some instances, the nanoparticle has the following general structure : wherein the alanine derived linker group stereochemistry is (S) , (R) or racemic and the dithiol chain stereochemistry is (S) , (R) or racemic .

[61] In some instances, the alanine derived linker group

stereochemistry is (S) and the dithiol chain stereochemistry is (S) , (R) or racemic. [62] In some cases, the alanine derived linker group stereochemistry is (S) and the dithiol chain stereochemistry is (R) or racemic.

[63] In some cases, the total number of ligands bound to the core is 20 or more including at least one maytansinoid . The number of maytansinoid ligands may, for example, be in the range 3 to 8 per nanoparticle core, such as 4 to 6 per core or around 5 maytansinoid ligands per core. The number of alpha-galactose-containing ligands and/or (EG) sCOOH-containing ligands will typically be higher, such as more than 10 or more than 20. In some cases, the number of alpha-galactose-containing ligands and/or (EG) sCOOH-containing ligands will be not more than 50, such as not more than 25 or even not more than 20 per core. In some instances, the ligands may be in the following proportions (which may be determined, e.g., by NMR and/or by input proportion during synthesis); Alpha-Galactose 45-50% / 17-20 per core, (EG) s-COOH 45-50% / 17-20 per core and

maytansinoid 10-15% / 4.5-6 per core.

[64] In a third aspect of the invention, there is provided a

conjugate comprising a compound according to the first aspect of the invention and a targeting agent.

[65] In some cases, the targeting agent comprises an antibody, an antibody fragment, a peptide or an aptamer. In some cases, the targeting agent may comprise a peptidic tumour targeting agent as disclosed in Brown, Curr. Pharm. Des . , 2010, Vol . 16, No. 9, pp. 1040-1054, incorporated herein by reference.

[66] In some instances, the targeting agent comprises an antibody or an antibody fragment that selectively binds a tumour antigen. In particular, the targeting agent may comprise a tumour-targeting antibody disclosed in Scott et al., Cancer Immun., 2012, Vol. 12, p. 14, incorporated herein by reference. In some embodiments the targeting agent comprises a therapeutic antibody. In particular, the therapeutic antibody may exhibit antibody-dependent cellular cytotoxicity (ADCC) and/or complement-dependent cytotoxicity (CDC) effector function in vivo in a mammalian subject (e.g. in a human subject) and/or in an appropriate in vitro assay. Suitable assays for determining ADCC and CDC effector function are known in the art. See, for example, ADCC assay (SC1544) and CDC assay (SC1545) services provided by GenScript®, NJ, USA, and non-radioactive assays described in Rossignol et al . , mAbs, 2017, 9(3) : 521-535, doi :

10.1080/19420862.2017.1286435.

[67] In some embodiments the compound is conjugated to the targeting agent via a suitable linker. The linker may (or may not) comprise a cleavable portion. In particular, when the targeting agent comprises an antibody or an antibody fragment the linker may comprise a cleavable (e.g. protease cleavable) portion so that the antibody-drug conjugate of the invention may be internalised by a cell (e.g. a cancer cell) and the compound of the invention cleaved from the antibody, thereby releasing the cytotoxic compound of the invention to kill the cancer cell and/or other cancer cells in the vicinity. A variety of linkers are known for use in therapeutic antibody-drug conjugates and may find use in accordance with the conjugates of the present invention (see, for example, the linkers described in Bargh et al . , Chem. Soc . Rev., 2019, 48, 4361-4374, doi : 10.1039/C8CS00676H - the contents of which are expressly incorporated herein by reference) .

[68] In a fourth aspect of the invention, there is provided a pharmaceutical composition comprising a compound according to the first aspect of the invention, a nanoparticle according to the second aspect of the invention or a conjugate according to the third aspect of the invention and at least one pharmaceutically acceptable carrier or diluent.

[69] In some cases, the pharmaceutical composition is a sustained release formulation and wherein at least a portion of the compound, the nanoparticle or the conjugate is encapsulated in a biocompatible polymer .

[70] In some instances, the sustained release formulation is in the form of a microparticle, a microsphere, a bead or a film.

[71] In some cases, the composition is in injectable form.

[72] In a fifth aspect of the invention there is provided a compound according to the first aspect of the invention, a nanoparticle according the second aspect of the invention, a conjugate according to the third aspect of the invention, or a pharmaceutical

composition according to the fourth aspect of the invention for use in medicine. [73] In a sixth aspect of the invention there is provided a compound according to the first aspect of the invention, a nanoparticle according the second aspect of the invention, a conjugate according to the third aspect of the invention, or a pharmaceutical

composition according to the fourth aspect of the invention for use in the treatment of a proliferative disorder (e.g. a cancer) .

[74] In some cases, the proliferative disorder is cancer.

[75] In some instances, the cancer is a carcinoma.

[76] In some cases, the cancer is selected from renal cancer, ovarian cancer, skin cancer, lung cancer, pancreatic cancer, liver cancer, head and neck cancer and brain cancer.

[77] In some instances, the cancer is selected from hepatocellular carcinoma (HCC) , glioma, melanoma, epidermal carcinoma, non-small cell lung cancer (NSCLC) , pancreatic adenocarcinoma, renal

adenocarcinoma and ovarian adenocarcinoma.

[78] In some instances, the cancer is selected from hepatoblastoma, cholangiocarcinoma, cholangiocellular cystadenocarcinoma,

angiosarcoma, hemangioendothelioma, embryonal sarcoma, fibrosarcoma, leiomyosarcoma and rhabdomyosarcoma.

[79] In some cases, the compound, nanoparticle, conjugate or composition for use is administered concurrently, sequentially or separately with a second anti-cancer agent. In particular cases, said second anti-cancer agent may comprise a kinase inhibitor (e.g. protein tyrosine kinase inhibitor) , such as Sorafenib (NEXAVAR (RTM) ) , Regorafenib (STIVARGA (RTM) ) , and/or Lenvatinib (LENVIMA (RTM) ) . In particular cases, said second anti-cancer agent may comprise a monoclonal antibody, such as an anti-PD-1 monoclonal antibody (e.g. Nivolumab (OPDIVO (RTM))), an anti-CTLA4 monoclonal antibody (e.g. ipilumumab (Yervoy (RTM))), and anti-PD-Ll monoclonal antibody (e.g. atezolizumab (Tecentriq (RTM)), an antibody that binds CD223, an antibody that binds TIM-3, or an antibody that binds OX-40. Combination therapy employing a compound, nanoparticle, conjugate or composition of the present invention together (e.g. sequential administration) with a second anti-cancer agent, such as Sorafenib, may exhibit superior clinical efficacy in comparison to either agent administered alone. It is contemplated that the combination therapy may comprise intravenous administration of a pharmaceutical composition comprising the compound, nanoparticle, conjugate or composition of the present invention and oral

administration of a second anti-cancer agent, such as a kinase inhibitor as mentioned above.

[80] In some instances, the second anti-cancer agent comprises a kinase inhibitor selected from the group consisting of: Sorafenib, Regorafenib and Lenvatinib.

[81] In a seventh aspect of the invention there is provided a method of treating a proliferative disease (e.g. a cancer) in a mammalian subject, comprising administering a compound according to the first aspect of the invention, a nanoparticle according to the second aspect of the invention, a conjugate according to the third aspect of the invention or a pharmaceutical composition according to the fourth aspect of the invention to the subject in need of therapy.

[82] In some cases, the proliferative disease is a cancer.

[83] In some instances, the cancer is a carcinoma.

[84] In some instances, the cancer is selected from renal cancer, ovarian cancer, skin cancer, lung cancer, pancreatic cancer, liver cancer, head and neck cancer and brain cancer.

[85] In some cases, the cancer is selected from hepatocellular carcinoma (HCC) , glioma, melanoma, epidermal carcinoma, non-small cell lung cancer (NSCLC) , pancreatic adenocarcinoma, renal

adenocarcinoma and ovarian adenocarcinoma. [86] In some instances, the cancer is selected from hepatoblastoma, cholangiocarcinoma, cholangiocellular cystadenocarcinoma,

[87] In some cases, the compound, nanoparticle, conjugate or pharmaceutical composition is administered concurrently,

sequentially or separately with a second anti-cancer agent. In particular cases, said second anti-cancer agent may comprise a kinase inhibitor (e.g. protein tyrosine kinase inhibitor), such as Sorafenib (NEXAVAR (RTM) ) , Regorafenib (STIVARGA (RTM) ) , and/or Lenvatinib (LENVIMA (RTM)) . In particular cases, said second anti cancer agent may comprise a monoclonal antibody, such as an anti-PD- 1 monoclonal antibody (e.g. Nivolumab (OPDIVO (RTM))), an anti-CTLA4 monoclonal antibody (e.g. ipilumumab (Yervoy (RTM))), and anti-PD-Ll monoclonal antibody (e.g. atezolizumab (Tecentriq (RTM)), an antibody that binds CD223, an antibody that binds TIM-3, or an antibody that binds OX-40. Combination therapy employing a

compound, nanoparticle, conjugate or composition of the present invention together (e.g. sequential administration) with a second anti-cancer agent, such as Sorafenib, may exhibit superior clinical efficacy in comparison to either agent administered alone. It is contemplated that the combination therapy may comprise intravenous administration of a pharmaceutical composition comprising the compound, nanoparticle, conjugate or composition of the present invention and oral administration of a second anti-cancer agent, such as a kinase inhibitor as mentioned above.

[88] In some instances, the second anti-cancer agent comprises a kinase inhibitor selected from the group consisting of: Sorafenib, Regorafenib and Lenvatinib.

[89] In certain cases, the method of treatment of said cancer (e.g. a liver cancer such as HCC) in a mammalian subject may comprise administering said nanoparticle or said pharmaceutical composition in combination with transarterial chemoembolization (TACE) therapy. [90] In an eighth aspect of the invention, there is provided use of a compound according to the first aspect of the invention, a nanoparticle according to the second aspect of the invention, a conjugate according to the third aspect of the invention or a pharmaceutical composition according to the fourth aspect of the invention in the preparation of a medicament for use in a method according to the seventh aspect of the invention.

[91] In a ninth aspect of the invention there is provided an article of manufacture comprising a compound according to a first aspect of the invention, a nanoparticle according to a second aspect of the invention, a conjugate according to a third aspect of the invention or a pharmaceutical composition according to a fourth aspect of the invention, a container for housing the compound, nanoparticle, conjugate or pharmaceutical composition and an insert or label.

[92] In some cases, the insert and/or label provides instructions, dosage and/or administration information relating to the use of the nanoparticle or pharmaceutical composition in the treatment of a proliferative disorder in a mammalian subject (e.g. in the treatment of a cancer) .

[93] The present invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or is stated to be expressly avoided. These and further aspects and embodiments of the invention are described in further detail below and with reference to the accompanying examples and figures.

[ 94 ] Brief Description of the Figures

[95] Figure 1 shows the IC50 values of the compounds maytansinoid DM1 (DM1), DM1- (S-Ala) -rac-LA and DM1- (S-Ala) -R-LA on 786-0 (renal cell adenocarcinoma), D2780 (ovarian endometrioid adenocarcinoma), D375 (malignant melanoma), A431 (epidermoid carcinoma), A549 (carcinoma), ACHN (renal cell adenocarcinoma) , BXPC-3 (pancreatic

adenocarcinoma) , HEP3B (hepatocellular carcinoma) and U87MG (glioblastoma) cell lines. DM1- (S-Ala) -S-LA and DM1- (R-Ala) -S-LA are also shown for HEP3B and U87MG cell lines only.

[96] Figure 2 shows the IC50 values of the nanoparticles

corresponding to the compounds of Figure 1, namely maytansinoid DM1- GNP (DM1-GNP) , DM1- (S-Ala) -rac-LA-GNP and DM1- (S-Ala) -R-LA-GNP on 786-0 (renal cell adenocarcinoma), A2780 (ovarian endometrioid adenocarcinoma) , A375 (malignant melanoma) , A431 (epidermoid carcinoma), A549 (carcinoma), ACHN (renal cell adenocarcinoma), BXPC-3 (pancreatic adenocarcinoma) , HEP3B (hepatocellular carcinoma) and U87MG (glioblastoma) cell lines. DM1- (S-Ala) -S-LA-GNP and DM1- (R-Ala) -S-LA-GNP are also shown for HEP3B and U87MG cell lines only.

[97] Figure 3 shows the effect of various compounds on tubulin polymerisation monitored in a fluorescence-based assay. In

particular DM1, DM1- (S-Ala) -rac-LA, DM1- (R-Ala) -rac-LA, DM1- (S-Ala) - R-LA and DM1- (R-Ala) -R-LA appear to inhibit tubulin polymerisation. Paclitaxel seems to improve tubulin polymerisation with most of the polymerisation occurring before the plate could read in the

fluorimeter .

[98] Figure 4a shows the tolerability of the compound DM1 in mice by the percentage bodyweight change over the course of intravenous treatments at various dosage amounts and frequencies.

[99] Figure 4b shows the tolerability of the compound DM1- (S-Ala) -R- LA in mice by the percentage bodyweight change over the course of intravenous treatments at various dosage amounts and frequencies.

[100] Figure 4c shows the tolerability of the nanoparticle DM1-GNP by the percentage bodyweight change over the course of intravenous treatments at various dosage amounts and frequencies.

[101] Figure 4d shows the tolerability of the nanoparticle DM1- (S- Ala) -R-LA-GNP by the percentage bodyweight change over the course of intravenous treatments at various dosage amounts and frequencies, at various dosage amounts and frequencies. The maximum tolerated dose (MTD) of DM1 (900 pg/kg) and DM1-GNP (1250 pg/kg) are each lower than the DM1- (S-Ala) -R-LA (1350 pg/kg) maximum feasible dose and the DM1- (S-Ala) -R-LA-GNP maximum tolerated dose (>2700 pg/kg) . The DM1- (S-Ala)-R-LA maximum tolerated does could not be determined due to solubility issues.

[102] Figure 5a shows and compares the tumour volume (mm³) over the course of intravenous treatment with DM1- (S-Ala) -R-LA and DM1- (S- Ala) -R-LA-GNP at a 1350 pg/kg weekly dose and DM1- (S-Ala) -R-LA-GNP at a 2700 pg/kg weekly dose.

[103] Figure 5b shows the free DM1- (S-Ala) -R-LA at a weekly dose of 1350 pg/kg has improved survival rates over the vehicle alone. DM1- (R-Ala) -R-LA-GNP at a weekly dose of 1350 pg/kg shows an improved survival rate over the free DM1- (S-Ala) -R-LA. DM1- (S-Ala) -R-LA-GNP at a weekly dose of 2700 pg/kg shows an improved survival rate over a weekly dose of 1350 pg/kg. The 2700 pg/kg dose is not possible with free DM1- (S-Ala) -R-LA compound due to solubility issues.

[104] At around 30 days after treatment, the order of tumour volume (mm³) from smallest to largest is DM1- (S-Ala) -R-LA-GNP at a weekly dose of 2700 pg/kg, DM1- (S-Ala) -R-LA-GNP at a weekly dose of 1350 pg/kg, DM1- (S-Ala) -R-LA and the vehicle alone. Not only does DM1- (S- Ala) -R-LA reduce tumour growth alone, but bound to a gold

nanoparticle as DM1- (S-Ala) -R-LA-GNP it reduces tumour growth even more. The higher dose of DM1- (S-Ala) -R-LA-GNP reduces tumour growth the most.

[105] Detailed description of the invention

[106] In describing the present invention, the following terms will be employed, and are intended to be defined as indicated below.

[107] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the

invention in diverse forms thereof.

[108] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[109] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[110] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[111] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word "comprise" and "include", and variations such as "comprises", "comprising", and "including" will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[112] It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent "about," it will be understood that the particular value forms another embodiment. The term "about" in relation to a numerical value is optional and means for example +/- 10%.

[113] Compounds

[114] As used herein, unless states otherwise, "compound" refers to the compound having a maytansinoid group, linker group and ligand group wherein the ligand group comprises a cyclic polythiol. The maytansinoid group of the compound is therapeutically active. A maytansinoid is a chemical derivative of maytansine. Maytansinoids are tubulin inhibitors, meaning that they inhibit the assembly of microtubules by binding to tubulin. Tubulin inhibitors are useful in the treatment of proliferative diseases, such as cancer.

[115] The linker group of the compound is the part of the compound between the maytansinoid group and the ligand group. It functions to provide space between the active maytansinoid group and the linker group. The linker group and the ligand group of the compound thereby form a physical extension to the maytansinoid. It is thought that the linker group extends the ligand group into a pocket of the tubulin where the cyclic polysulfide group binds. Indeed, in silico modelling of maytansine bound to tubulin (pdb: 4TV8) shows that DM1 and DM1- (R-Ala) -R-LA bound to tubulin have the linker group

extending the ligand group into a pocket of the tubulin (data not shown) . Virtual screening of maytansinoid-linker-polythiol

analogues shows that many polythiol-containing maytansinoid

analogues exhibit similarly advantageous binding to the tubulin pocket .

[116] In particular, the following polythiol structures are

specifically contemplated ligand structures herein based, at least in part, on the above-described in silico modelling: 1, Upok add analog ties

[117] Practically, the linker group can comprise any atoms such as H, N, C, S and 0. In certain instances, the linker group is an amino-acid derived linker group having a naturally occurring amino acid side chain. That is to say, if the linker group is derived from the amino acid alanine (Ala) , for example, then the side chain is methyl . [118] The ligand group of the compound has a cyclic polysulfide group. Firstly, as mentioned above, it is thought that such a cyclic group has a confirmation that is particularly suited to sit in or bind to a pocket of the tubulin adjacent to the binding site/pocket of the linked maytansinoid. Secondly, it is thought that the polysulfide nature of the ligand group allows the compound to bind to a nanoparticle as a polydentate ligand. Compared to

monothiol/monodentate ligands, the polythiol/polydentate ligands demonstrate a stronger binding constant/affinity for nanoparticles. [119] One problem with the corresponding monothiol compounds is that displacement of the compound occurs more readily before reaching the site of action. This premature dissociation means that the delivery efficiency is potentially lower because there is only a small increase in the amount of additional compound delivered to the site of action before the minimum toxic concentration is reached in vivo.

[120] Furthermore, the presence of a monothiol makes the measurement of the free drug in vivo very challenging because the monothiol is readily metabolised (see, e.g., Shen, Drug Metabolism Letters, 2015, 9, 119-131) and readily reacts with plasma proteins. It is also thought that these metabolites are themselves therapeutically active compounds and so a complex system is formed that is difficult to monitor and inherently introduces unwanted risks.

[121] By contrast, the cyclic polythiol compounds are less readily displaced before reaching the site of action. This decrease in premature dissociation means that the delivery efficiency is improved because there is a larger increase in the amount of additional compound delivered to the site of action before the minimum toxic concentration is reached in vivo.

[122] Furthermore, after dissociating from the nanoparticle in vivo, the free polythiol reforms a cyclic polythiol that is not as readily metabolised or as reactive towards plasma proteins as the

corresponding monothiol compound. Because the formation of

metabolites is slower, the measured concentration of the cyclic polythiol compound in vivo more accurately represents both the amount of dissociated compound and the amount of free active compounds .

[123] As used herein, unless states otherwise, "cyclic polythiol" refers to a chemical moiety having two or more sulfur atoms in a ring. Where compounds of the present invention containing a cyclic polythiol are used as a ligand in a nanoparticle of the present invention, the disulphide bonds of the cyclic polythiols are instead in their reduced form to give free thiol groups that readily co ordinate the core of the nanoparticle.

[124] Preferably, the cyclic polythiol is a heterocycle. The cyclic polythiol includes other atoms such as one or more of H, C, N and 0. The cyclic polythiol may be substituted with one or more small hydrocarbon chains, such as methyl, ethyl, propyl, isopropyl, butyl and isobutyl. The cyclic polythiol or any small hydrocarbon chains may be substituted with one or more additional free thiol groups . It is envisaged that one or more additional free thiol groups would further increase the binding constant by increasing the denticity of the compound to, for example, give a tridentate or tetradentate ligand etc. Such groups could also form additional cyclic polythiols and/or interchangeably for sulfide bridges with any other of the thiols that make up the cyclic polythiol thereby forming structural isomers of the compound.

[125] Tumour-targeting ligands

[126] The tumour-targeting ligand binds, couples to or interacts with a receptor, marker, protein or antigen present at, in or on tumour cells (in some cases also healthy cells, in other cases only or predominantly cancer cells) . In binding or otherwise being attracted to a tumour, the tumour-targeting ligand assists with targeting the nanoparticle of the invention to the site of intended action .

[127] The tumour-targeting ligand is covalently linked to the nanoparticle core (directly or more commonly via a linker) and therefore acts to cause the nanoparticle, including its payload, to associate with or otherwise come into contact with the tumour with greater frequency, for longer duration and/or at higher

concentration than would be the case for the nanoparticle in the absence of the tumour-targeting ligand. As used herein the term "tumour-targeting ligand" specifically includes not only ligands that actively target tumours, but also includes ligands that passively target the tumour and/or which aid passive uptake by healthy cells and/or tumour cells. [128] Examples of tumour-targeting ligands include: cyclic RGD peptides (such as cyclic RGD peptide discussed above), galactose (e.g. alpha-galactose), lactose, FGF-4 (fibroblast growth factor 4), c-Met (hepatocyte growth factor receptor) , a glypican-3 binding agent (e.g. a glypican-3 binding peptide as disclosed in US8388937 (including specifically the peptides of SEQ ID NOs : 1, 2, 3, 4, 5,

6, 7 and 10 therein, which are expressly incorporated herein by reference) or an anti-glypican-3 antibody) , an alpha-fetoprotein (AFP) receptor binding agent (e.g. an AFP receptor binding peptide as disclosed in US2012/0270238 or an anti-AFP receptor antibody), and an ASGPR binding agent (e.g. galactose, N-acetylgalactosamine, lactose, glucose, mannose, or a glycomimetic ligand such as

disclosed in Mamidyala et al . , J. Am. Chem. Soc . , 2012, Vol. 1334, No. 4, pp. 1978-1981) . The tumour-targeting ligand may also be an antibody or binding fragment thereof, e.g. a Fab fragment (fragment antigen-binding) , single domain antibody / nanobody directed at a liver or hepatocyte target such as glypican-3, ASGPR, FGF-4, c-Met, AFP or other tumour-expressed protein or tumour-expressed receptor.

[129] Nanoparticles

[130] As used herein, "nanoparticle" refers to a particle having a nanomeric scale, and is not intended to convey any specific shape limitation. In particular, "nanoparticle" encompasses nanospheres, nanotubes, nanoboxes, nanoclusters, nanorods and the like. In certain embodiments the nanoparticles and/or nanoparticle cores contemplated herein have a generally polyhedral or spherical geometry. References to "diameter" of a nanoparticle or a

nanoparticle core a generally taken to mean the longest dimension of the nanoparticle or nanoparticle core, respectively. For

nanoparticles having a substantially polyhedral or spherical geometry, the shortest dimension across the particle will typically be within 50% of the longest dimension across the particle and may be, e.g., within 25% or 10%.

[131] Nanoparticles comprising a plurality of carbohydrate- containing ligands have been described in, for example, WO 2002/032404, WO 2004/108165, WO 2005/116226, WO 2006/037979, WO 2007/015105, WO 2007/122388, WO 2005/091704 (the entire contents of each of which is expressly incorporated herein by reference) and such nanoparticles may find use in accordance with the present invention .

[132] As used herein, "corona" refers to a layer or coating, which may partially or completely cover the exposed surface of the nanoparticle core. The corona includes a plurality of ligands covalently attached to the core of the nanoparticle. Thus, the corona may be considered to be an organic layer that surrounds or partially surrounds the metallic core. In certain embodiments the corona provides and/or participates in passivating the core of the nanoparticle. Thus, in certain cases the corona may include a sufficiently complete coating layer substantially to stabilise the core. In certain cases the corona facilitates solubility, such as water solubility, of the nanoparticles of the present invention.

[133] Nanoparticles are small particles, e.g. clusters of metal or semiconductor atoms, that can be used as a substrate for

immobilising ligands.

[134] Preferably, the nanoparticles have cores having mean diameters between 0.5 and 50 nm, more preferably between 0.5 and 10 nm, more preferably between 0.5 and 5 nm, more preferably between 0.5 and 3 nm and still more preferably between 0.5 and 2.5 nm. When the ligands are considered in addition to the cores, preferably the overall mean diameter of the particles is between 2.0 and 50 nm, more preferably between 3 and 10 nm and most preferably between 2 and 4 nm or between 4 and 5 nm. The mean diameter can be measured using techniques well known in the art such as transmission electron microscopy .

[135] The core material can be a metal or semiconductor and may be formed of more than one type of atom. Preferably, the core material is a metal selected from Au, Fe or Cu. Nanoparticle cores may also be formed from alloys including Au/Fe, Au/Cu, Au/Gd, Au/Fe/Cu, Au/Fe/Gd and Au/Fe/Cu/Gd, and may be used in the present invention. Preferred core materials are Au and Fe, with the most preferred material being Au . The cores of the nanoparticles preferably comprise between about 100 and 500 atoms (e.g. gold atoms) to provide core diameters in the nanometre range. A core of 4 nm mean diameter typically has about 2,000 gold atoms and a core of 10 nm mean diameter typically has about 31,000 atoms. Other particularly useful core materials are doped with one or more atoms that are NMR active, allowing the nanoparticles to be detected using NMR, both in vitro and in vivo. Examples of NMR active atoms include Mn⁺², Gd⁺³, Eu⁺², Cu⁺², V⁺², Co⁺², Ni⁺², Fe⁺², Fe⁺³ and lanthanides²³, or the quantum dots .

[136] Nanoparticle cores comprising semiconductor compounds can be detected as nanometre scale semiconductor crystals are capable of acting as quantum dots, that is they can absorb light thereby exciting electrons in the materials to higher energy levels, subsequently releasing photons of light at frequencies

characteristic of the material. An example of a semiconductor core material is cadmium selenide, cadmium sulphide, cadmium tellurium. Also included are the zinc compounds such as zinc sulphide.

[137] In some embodiments, the nanoparticle or its ligand comprises a detectable label. The label may be an element of the core of the nanoparticle or the ligand. The label may be detectable because of an intrinsic property of that element of the nanoparticle or by being linked, conjugated or associated with a further moiety that is detectable. Preferred examples of labels include a label which is a fluorescent group, a radionuclide, a magnetic label or a dye.

Fluorescent groups include fluorescein, rhodamines or tetramethyl rhodamine, Texas-Red, Cy3, Cy5, etc., and may be detected by excitation of the fluorescent label and detection of the emitted light using Raman scattering spectroscopy (Y.C. Cao, R. Jin, C. A. Mirkin, Science 2002, 297: 1536-1539) .

[138] In some embodiments, the nanoparticles may comprise a

radionuclide for use in detecting the nanoparticle using the radioactivity emitted by the radionuclide, e.g. by using PET, SPECT, or for therapy, i.e. for killing target cells. Examples of

radionuclides commonly used in the art that could be readily adapted for use in the present invention include ^99mTc, which exists in a variety of oxidation states although the most stable is TcO^4-; ³²P or ³³P; ⁵⁷Co; ⁵⁹Fe; ⁶⁷Cu which is often used as Cu²⁺ salts; ⁶⁷Ga which is commonly used a Ga³⁺ salt, e.g. gallium citrate; ⁶⁸Ge; ⁸²Sr; "Mo;

¹⁰³Pd; ^ulIn which is generally used as In³⁺ salts; ¹²⁵I or ¹³¹I which is generally used as sodium iodide; ¹³⁷Cs; ¹⁵³Gd; ¹⁵³Sm; ¹⁵⁸Au; ¹⁸⁶Re; ²⁰¹T1 generally used as a T1⁺ salt such as thallium chloride; ³⁹Y³⁺; ⁷¹Lu³⁺; and ²⁴Cr²⁺. The general use of radionuclides as labels and tracers is well known in the art and could readily be adapted by the skilled person for use in the aspects of the present invention. The radionuclides may be employed most easily by doping the cores of the nanoparticles or including them as labels present as part of ligands immobilised on the nanoparticles.

[139] Actives

[140] As used herein the term "biologically active agent" or

"bioactive agent" is intended to encompass drugs and pro-drugs that exert an effect on a biological system, preferably a therapeutic effect. Class of active agent contemplated herein include small molecule organic compounds, peptides, polypeptides and nucleic acids. An exemplary class of therapeutic agent is an anti-cancer agent, such as a cytotoxic compound, an anti-proliferative agent or an anti-angiogenic agent.

[141] Particular examples include chemotherapeutic agents, e.g. a maytansinoid (e.g. maytansinoid DM1 or maytansinoid DM4),

doxorubicin, temozolomide, irinotecan, carmustine, platinum ( IV) , platinum ( II ) , camptothecin, docetaxel, sorafenib, maytansine, monomethyl auristatin E (MMAE) , pyrrolobenzodiazepines and a histone deacetylase (HDAC) inhibitor (e.g. panobinostat) .

[ 142 ] Administration and treatment

[143] The compounds, nanoparticles and compositions of the invention may be administered to patients by any number of different routes, including enteral or parenteral routes. Parenteral administration includes administration by the following routes: intravenous, cutaneous or subcutaneous, nasal, intramuscular, intraocular, transepithelial , intraperitoneal and topical (including dermal, ocular, rectal, nasal, inhalation and aerosol), and rectal systemic routes .

[144] Administration be performed e.g. by injection, including depot inj ection .

[145] The compounds, nanoparticles and conjugates of the invention may be formulated as pharmaceutical compositions that may be in the forms of solid or liquid compositions. Such compositions will generally comprise a carrier of some sort, for example a solid carrier or a liquid carrier such as water, petroleum, animal or vegetable oils, mineral oil or synthetic oil. Physiological saline solution, or glycols such as ethylene glycol, propylene glycol or polyethylene glycol may be included. Such compositions and preparations generally contain at least 0.1 wt% of the compound.

[146] For intravenous, cutaneous or subcutaneous injection, or injection at the site of affliction, the active ingredient will be in the form of a parenterally acceptable aqueous solution or liquid which is pyrogen-free and has suitable pH, isotonicity and

stability. Those of relevant skill in the art are well able to prepare suitable solutions using, for example, solutions of the compounds or a derivative thereof, e.g. in physiological saline, a dispersion prepared with glycerol, liquid polyethylene glycol or oils .

[147] In addition to one or more of the compounds, optionally in combination with other active ingredient, the compositions can comprise one or more of a pharmaceutically acceptable excipient, carrier, buffer, stabiliser, isotonicising agent, preservative or anti-oxidant or other materials well known to those skilled in the art. Such materials should be non-toxic and should not interfere with the efficacy of the active ingredient. The precise nature of the carrier or other material may depend on the route of administration, e.g., intravenous injection.

[148] Preferably, the pharmaceutically compositions are given to an individual in a prophylactically effective amount or a

therapeutically effective amount (as the case may be, although prophylaxis may be considered therapy) , this being sufficient to show benefit to the individual. Typically, this will be to cause a therapeutically useful activity providing benefit to the individual. The actual amount of the compounds administered, and rate and time- course of administration, will depend on the nature and severity of the condition being treated. Prescription of treatment, e.g.

decisions on dosage etc., is within the responsibility of general practitioners and other medical doctors, and typically takes account of the disorder to be treated, the condition of the individual patient, the site of delivery, the method of administration and other factors known to practitioners. Examples of the techniques and protocols mentioned above can be found in Handbook of

Pharmaceutical Additives, 2nd Edition (eds. M. Ash and I. Ash), 2001 (Synapse Information Resources, Inc., Endicott, New York, USA);

Remington's Pharmaceutical Sciences, 20th Edition, 2000, pub.

Lippincott, Williams & Wilkins; and Handbook of Pharmaceutical Excipients, 2nd edition, 1994. By way of example, and the

compositions are preferably administered to patients in dosages of between about 0.01 and 100 mg of active compound per kg of body weight, and more preferably between about 0.5 and lOmg/kg of body weight. One benefit of the tumour targeting of the nanoparticles and conjugates of the present invention is that a therapeutically effective dose of the active "payload" may be lower in comparison with the effective dose of the same active when administered as a free drug, e.g., by systematic administration.

[149] The following is presented by way of example and is not to be construed as a limitation to the scope of the claims. [150] Examples

[151] Method 1- Synthesis of DMl- (S-Ala) - (R) -LA

[152] A three step synthesis of DMl- (S-Ala) - (R) -LA includes an amide coupling of lipoic acid to N-methyl-L-alaninate, hydrolysis of the methyl ester and esterification with a maytansinol.

[153] 1.1 Preparation of methyl N- ( (5- (R) -1 , 2-dithiolan-3-yl) pentanoyl) -N-methyl-L-alaninate

[154] A solution of (R) -lipoic acid (4.00 g, 19.4 mmol) in dry DCM (20 mL) was cooled to 0°C and treated with EDCI (4.09 g, 21.3 mmol), HOBT (2.88 g, 21.3 mmol) and DIPEA (5.01 g, 38.8 mmol) and the reaction mixture was stirred for 10 min at 0°C. A solution of methyl N-methyl- L-alaninate (3.28 g, 21.3 mmol) was added and the reaction allowed to warm to room temperature and stirred for 16 hr. After this time TLC (1:1 hexane/EtOAc) showed the reaction was complete.

[155] Water (200mL) was added and the product was extracted with DCM (2xl00mL) . The combined organic layers were dried (MgSCb) and concentrated in vacuo to give an oil that was purified by chromatography (SiCh, hexane/EtOAc, 20/1 to 5/1) to give the title compound as a yellow oil .

^!H NMR (400 MHz, CDC1₃) d 5.23 (q, J = 7.3 Hz, 1H) , 4.11 (q, J = 7.1

Hz, 1H) , 3.57 (s, 3H) , 3.57 (m, 1H) , 3.22 - 3.04 (m, 2H) , 2.92 (s,

3H) , 2.51 - 2.25 (m, 3H) , 2.03 (s, 1H) , 1.97 - 1.84 (m, 1H) , 1.76 - 1.61 (m, 1H) , 1.48 (m, 2H) , 1.37 (d, J = 7.3 Hz, 3H) , 1.24 (t, J = 7.1 Hz, 1H) . [156] 1.2 Preparation of N- ( (5- (R) -1 , 2-dithiolan-3-yl) pentanoyl) -N- me hyl-L-alanine

[157] A solution of NaOH (1.16 g, 29.1 mmol) in water (15 mL) was added to a solution of methyl N- ( (5- (R) -1, 2-dithiolan-3-yl) pentanoyl) -N- methyl-L-alaninate (7.40 g, 24.2 mmol) in MeOH (45 mL) at room temperature and stirred for 16 h.

[158] The reaction was concentrated in vacuo and partitioned between water (50 mL) and ethyl acetate (50 mL) . The pH of the mixture was adjusted to pH 3-4 by the addition of 1 M HC1. The aqueous layer was extracted with ethyl acetate (50 mL x 2) and the organic layers concentrated in vacuo to give the title compound as a yellow oil, (4.00 g, 13.7 mmol, 56.7%) .

[159] ^!HNMR (400 MHz CDCI3) : 7.52-7.28 (m, 1H) , 5.23-5.13 (m, 1H) , 3.58

(t, J = 8.0 Hz, 1H) , 3.19-3.13 (m, 2H) , 2.97 (s, 3H) , 2.46-2.38 (m, 1H) , 2.38-2.36 (m, 2H) , 1.72-1.70 (m, 1H) , 1.69-1.67 (m, 4H) , 1.50-

1.48 (m, 2H) , 1.42 (d, J = 7.2 Hz, 3H) ; MS: m/z 292 (MH+) ; HPLC: rt 3.53 min

[160] 1.3 Preparation of (1⁴S , 1⁶S , 3²S , 3³S , 2R, 4S , 10E, 12E, 14R) -8⁶- chloro-14-hydroxy-8⁵ , 14-dimethoxy-3³ ,2,7, 10-tetramethyl-l² , 6-dioxo-7- aza-1 (6,4) -oxazinana-3 (2 ,3) -oxirana-8 (1,3)- benzenacyclotetradecaphane-10 , 12-dien-4-yl N- ( (5- (R) -1 , 2-dithiolan- 3-yl) pentanoyl) -N-methyl-alaninate [161] DCC (690 mg, 3.34 mmol) was added to a solution of N- ( (5- (R) - 1 , 2-dithiolan-3-yl ) pentanoyl ) -IV-methyl-L-alanine (928 mg, 3.19 mmol) and maytansinol (300 mg, 530 umol) in DCM (10 mL) .

[162] After stirring for 1 minute ZnCl2 (1 M solution in DCM, 663 uL) was added and the mixture stirred at room temperature for 24 hr. Water (10 mL) was added and the mixture extracted with DCM (2 x 10 mL) . The combined organic layers were dried (MgS04) and concentrated in vacuo. Separation of the diastereomeric mixture was performed by preparative- TLC (dichloromethane/methanol=20/ 1 ) to give the title compound (1⁴S, 1⁶S, 3²S, 3³S, 2R, 4S, 10E, 12E, 14R) - 8⁶-chloro-l 4-hydroxy- 8⁵, 14- dimethoxy-3³, 2,7, 10-tetramethyl-l², 6-dioxo-7-aza-l (6, 4) -oxazinana- 3 (2,3) -oxirana-8 (1,3) -benzenacyclotetradecaphane-10 , 12-dien-4-yl N

N- ( (5- (R) -1, 2-dithiolan-3-yl ) pentanoyl) -I7-methyl-D-alaninate as a white solid (0.05 g, 56.1 umol, 10.6% yield) .

[163] ²H NMR: (400 MHz, CDC1₃) : 6.80-6.85 (m, 2H) , 6.40-6.47 (m, 1H) ,

6.21-6.28 (m, 2H) , 5.82-5.89 (m, 1H) , 5.33 (d, J = 8.41 Hz, 1H) ,

5.01-5.06 (m, 1H) , 4.02-4.96 (m, 1H) , 4.31 (t, J = 11.35 Hz, 1H) ,

4.00 (s, 3H) , 3.58-3.63 (m, 1H) , 3.51 (d, J = 12.72 Hz, 1H) , 3.44

(d, J = 9.39 Hz, 1H) , 3.35 (s, 3H) , 3.11-3.23 (m, 7H) , 3.03 (s, 3H) , 2.80-2.92 (m, 3H) , 2.63-2.70 (m, 1H) , 2.37-2.51 (m, 4H) , 2.19-2.23 (m, 1H) , 1.90-1.95 (m, 1H) , 1.63-1.81 (m, 11H) , 1.46-1.51(m, 7H) ,

1.25-1.36 (m, 6H) , 0.88 (s, 3H) ; MS: m/z 840 (MH⁺) ; HPLC: rt 3.59 min

[164] and [165] (1⁴S, 1⁶S, 3²S, 3³S, 2R, 4S, 10E, 12E, 14R) - 8⁶-chloro-l 4-hydroxy- 8⁵, 14- dimethoxy-3³, 2,7, 10-tetramethyl-l², 6-dioxo-7-aza-l (6, 4) -oxazinana- 3 (2,3) -oxirana-8 (1,3) -benzenacyclotetradecaphane-10 , 12-dien-4-yl N N- ( (5- (R) -1, 2-dithiolan-3-yl ) pentanoyl) -I7-methyl-L-alaninate as a white solid (0.05 g, 56.9 umol, 10.7% yield) .

[166] ⁴H NMR: (400 MHz, CDC13 ) : 6.83 (s, 1H) , 6.73 (d, J = 10.76 Hz,

1H) , 6.67 (s, 1H) , 6.40-6.46 (m, 1H) , 5.63-5.69 (m, 1H) , 5.37-5.38 (m, 1H) , 4.76-4.79 (m, 1H) , 4.29 (t, J = 11.15 Hz, 1H) , 3.99 (s,

3H) , 3.66 (d, J = 12.72 Hz, 1H) , 3.5 (d, J = 9 Hz, 1H) , 3.40-3.44

(m, 2H) , 3.36 (s, 3H) , 3.2 (s, 3H) , 3.01-3.17 (m, 4H) , 2.84 (s, 3H) , 2.58-2.65 (m, 1H) , 2.32-2.44 (m, 2H) , 2.16-2.26 (m, 2H) , 1.78-1.88 (m, 1H) , 1.50-1.73 (m, 8H) , 1.36-1.48 (m, 3H) , 1.20-1.31 (m, 7H) ,

0.81 (s, 3H) ; MS: m/z 840 (MH⁺) ; HPLC : rt 3.74 min

[167] Method 2 - Functionalisation of gold nanoparticle to form

[DM1- (S-Ala) - (R) -LA] - [C2-cc-Galactose] - [PEG_sCOOH] @Au nanoparticles

[168] 0.34 mL of a 2.39 uM solution in DMSO of

(1⁴S, 1⁶S, 3²S, 3³S, 2R, 4S, 10E, 12E, 14R) - 8⁶-chloro-l 4-hydroxy- 8⁵, 14- dimethoxy-3³, 2,7, 10-tetramethyl-l², 6-dioxo-7-aza-l (6, 4) -oxazinana- 3 (2,3) -oxirana-8 (1,3) -benzenacyclotetradecaphane-10 , 12-dien-4-yl N

N- ( (5- (R) -1, 2-dithiolan-3-yl ) pentanoyl) -I7-methyl-L-alaninate and

4.47 uL of a 0.2 M solution in water of TCEP were stirred at 37°C for 2 h. 40 uL DMSO, 222 pL of Milli-Q water and 393 uL of gold nanoparticle solution were added and the mixture was stirred at 500 rpm for 1 h at room temperature. The dark brown solution was washed with 15% DMSO (1 mL x 3), followed by Milli-Q water wash (1 mL x 5) . The concentrated dark GNP solutions were hard spun at 13.3G for 5 min twice. The supernatant was collected, passed through a 0.2 pm filter, and stored at 4 ° C [169] Method 3 - Investigating in vitro cyctotoxicity

[170] The following method was performed using sterile technique in a cell culture hood.

[171] The cell lines prepared using this method were 786-0 (renal cell adenocarcinoma), D2780 (ovarian endometrioid adenocarcinoma), D375 (malignant melanoma), A431 (epidermoid carcinoma), A549

(carcinoma) , ACHN (renal cell adenocarcinoma) , BXPC-3 (pancreatic adenocarcinoma) , HEP3B (hepatocellular carcinoma) and U87MG

(glioblastoma) .

[172] Cells were suspended in "complete" Eagle's MEM media (MEM (Sigma M4655) + 1 mM Sodium Pyruvate (Sigma S8636) + lx MEM Non- essential amino acids (Sigma M7145) + 10% FBS) to achieve a

concentration of 5xl0⁴ cells (or lxlO⁵ cells/ml for Hep3B) . One 96- well plate required 20 ml cell suspension (22 ml including losses on reservoirs) . 200m1 of cell suspension was dispensed into each well of a flat bottom 96 well tissue culture treated plate. The plate was covered with a 'sticky' sterile gas permeable 96 well plate cover (Excel Scientific AeraSeal BS-25 (Sterile) Sigma-Aldrich Cat. #

A9224) and the plate lid retained for later use. The cells were incubated at 37°C, 5% CO2, overnight.

[173] The next day, a dilution series of the compounds (DM1, DM1- (S- Ala) -rac-LA, DM1- (R-Ala) -rac-LA, DM1- (S-Ala) -R-LA and DM1- (R-Ala) -R- LA) was prepared. > 30 mΐ of the compounds in DMSO was prepared at lOOx the top final assay concentration. 6 additional points can be generated by serial dilution (10 mΐ previous dilution + 20 mΐ DMSO) . The final 8^th point consists of 100% DMSO (or the solvent used to dissolve the compound) . The final dilution into complete DMEM was performed in a sterile 8x6 deep well dispensing plate. For each of the points in the dilution series 15 mΐ of the lOOx DMSO dilution was added to 1485 mΐ complete DMEM and mixed by pipetting up and down several times . [174] The media was removed from the cells by aspiration and then 200 mΐ of the appropriate concentration of each compound was added in complete DMEM to the appropriate wells. Each concentration point was be performed in triplicate. The plate was covered with an

AeraSeal gas permeable cover. The cells were incubated at 37 °C, 5% CO2, for 72 hrs.

[175] To develop the plate, the stock of 10 mg/ml MTT reagent was diluted in DMSO 1 in 20 with phenol red free complete MEM (Phenol Red free MEM (Fisher 51200-046) + 1 mM Sodium Pyruvate (Sigma S8636) + lx MEM Non-essential amino acids (Sigma M7145) + 10% FBS) . The treatment media was removed from the treatment plate. 100 mΐ 0.5 mg/ml MTT containing media was added to each well of the plate and resealed with an AeraSeal. The plate was incubated at 37 °C for 1 hr in the TC incubator (humid environment + 5% CO2) . After incubation, the media was removed and replaced with 200 mΐ/well DMSO. The original lid was placed on the plate and shaken at 700 rpm on an orbital shaker for > 10 min until the purple oxidised MTT reagent was dissolved.

[176] The lid was removed and the absorbance of the plate wells was read on an absorbance plate reader at 595nm using the precise measurement setting without path length correction. Absorbance readings were background subtracted by subtracting the Asgs_nm of wells containing only 200 mΐ DMSO (no MTT reagent, can take measurements from a clean 96-well TC plate) .

[177] Data was analysed by non-linear curve fitting in GraphPad Prism 7.

[178] Equation 1 was fitted to all the titrations at the different time points using GraphPad Prism 7. The Hill constant and IC50 were constrained so that they were the same in all of the time points while the top and bottom constants were allowed to vary between the time points .

[179] The minimum percentage cell viability for a given incubation time can be calculated using equation 2. 100 (2)

[180] The results are provided in Table 1.

[181] Table 1 MTT assays using compounds against selected cell lines .

[182] DMl- (S-Ala) -rac-LA and DMl- (S-Ala) -R-LA compounds showed improved IC50 values compared to DMl versus all of the tested cell lines .

[183] Both DMl- (S-Ala) -rac-LA and DMl- (S-Ala) -R-LA showed particular efficacy against the A431 cell line (epidermoid carcinoma) .

[184] In some cases, DMl- (S-Ala) -rac-LA was more effective than DM1- (S-Ala) -R-LA, such as against BXPC-3 (pancreatic adenocarcinoma) .

[185] In other cases DMl- (S-Ala) -R-LA was more effective than DM1- (S-Ala) -rac-LA, such as against 786-0 (renal cell adenocarcinoma) .

[186] DMl- (S-Ala) -R-LA and DMl- (S-Ala) -S-LA show similar efficacy against HEP3B and U87MG indicating that the stereochemistry of the lipoic acid derived group may not be important in the free compound of the present invention.

[187] The examples of Method 3 are also shown graphically in

Figure 1.

[188] Method 4 - Investigating in vitro and in vivo activity and tolerability of [DMl] - [C2-cc-Galactose] - [ (EG) _sCOOH] @Au nanoparticles

[189] The same method described in Method 3 was followed except that a dilution series of the corresponding nanoparticles (DM1-GNP, DM1- (S-Ala) -rac-LA-GNP and DMl- (S-Ala) -R-LA-GNP) was prepared and used. The results are provided in Table 2 below. [190] Table 2 - MTT assays using nanoparticles against selected cell lines .

[191] DM1- (S-Ala) -rac-LA-GNP and DM1- (S-Ala) -R-LA-GNP compounds showed improved IC50 values compared to DM1-GNP versus all of the tested cell lines.

[192] Both DM1- (S-Ala) -rac-LA and DM1- (S-Ala) -R-LA showed particular efficacy against the HEP3B cell line (hepatocellular carcinoma) .

[193] In some cases, DM1- (S-Ala) -rac-LA-GNP was more effective than DM1- (S-Ala) -R-LA-GNP, such as against A549 (carcinoma) .

[194] In other cases DM1- (S-Ala) -R-LA-GNP was more effective than DM1- (S-Ala) -rac-LA-GNP, such as against U87MG (glioblastoma) .

[195] D Ml- (S-Ala) -R-LA-GNP shows even more improved efficacy against HEP3B and U87MG over DM1-GNP than DM1- (S-Ala) -S-LA-GNP indicating that the R stereochemistry of the lipoic acid derived group is preferred in the nanoparticle of the present invention.

[196] The results are also shown graphically in Figure 2.

[197] Method 5 - Investigating the effect on tubulin polymerisation

[198] This method was carried out using a tubulin polymerisation kit (Cat. # BK011P) from Cytoskeleton, Inc. Tubulin polymerisation is followed by fluorescence enhancement due to the incorporation of a fluorescent reporter into microtubules as polymerisation occurs.

[199] 330 mM (llx) compound in DMSO was prepared. Buffer 1 (80 mM

PIPES, pH 6.9, 2 mM MgCl2, 0.5 mM EGTA, 10 mM "fluorescent reporter" (possibly DAPI, Bonne et al . JBC 260, 2819)) and 100 mM GTP aliquots were defrosted on ice. An aliquot of 9.1 mg/ml tubulin was defrosted in a room temperature water bath before being placed on ice. Tubulin Glycerol (Cushion) Buffer (80 mM PIPES, pH 6.9, 2 mM MgCl2, 0.5 mM EGTA, 60% (v/v) glycerol) was also kept on ice. [200] 5 mΐ/well compound (or control) in DMSO was dispensed into the appropriate wells of a black ½-area polystyrene Corning Costar 96- well plate (Cat. # 3686) . Assay buffer consisting of 205 mΐ Buffer 1, 150 mΐ Tubulin Glycerol Buffer, 4.4 mΐ 100 mM GTP and 85 mΐ 9.1 mg/ml tubulin stock was prepared and 50 mΐ of this solution

dispensed into each of the relent wells of the 96-well plate.

[201] The plate was sealed with a clear plate seal and read in a BMG FLUOstar Omega (top optic, 61 cycles, 60 s between each cycle, 20 flashes per well, excitation 355 nm, emission 460 nm, gain 925, 500 rpm double orbital shaking 1 s before first cycle, plate temperature 37 °C) .

[202] The results are shown in Figure 2.

[203] Method 6 - Tolerability of compounds in mice

[204] 6-8-week-old female NOD/SCID mice (Beijing HFK Bioscience Co., LTD.) were injected weekly by intravenous injection, with test compounds 10 mΐ/g at the drug concentrations illustrated in Figure

3.

[205] All the procedures related to animal handling, care, and treatment in the studies were performed according to the guidelines approved by the Institutional Animal Care and Use Committee (IACUC) of WuXi AppTec following the guidance of the Association for

Assessment and Accreditation of Laboratory Animal Care (AAALAC) .

[206] Animals were checked daily for any effects of treatment on normal behaviour such as; mobility, food and water consumption (visual only), body weight gain/loss, eye/hair matting and any other abnormal effects. Death and observed clinical signs were recorded based on the numbers of animals within each subset.

[207] The relative change of body weights (%) was calculated based on animal weight on the first day of dosing. Data points represent percent group mean change in BW. Error bars represent standard error of the mean (SEM) . Maximum tolerated dose (MTD) was defined by > 15% body weight loss or general significant loss in overall body condition .

[208] The results are shown graphically in Figures 4a-d and 5a-b.

[209] Figures 4a-d shows the tolerability of the compounds in mice by the percentage bodyweight change over the course of intravenous treatments with the compounds DM1 and DM1- (S-Ala) -R-LA and the nanoparticles DM1-GNP and DM1- (S-Ala) -R-LA-GNP at various dosage amounts and frequencies.

[210] The maximum tolerated dose (MTD) of DM1 (900 pg/kg) and DM1- GNP (1250 pg/kg) are each lower than the DM1- (S-Ala) -R-LA (1350 pg/kg) maximum tolerated dose and the DM1- (S-Ala) -R-LA-GNP maximum tolerated dose (>2700 pg/kg) .

[211] It is apparent that the highest dose of DM1 (top left graph, open circles) did not follow the entire course of the treatment because the end-point of general significant loss in overall body condition was reached.

[212] Figure 5a shows and compares the tumour volume (mm³) over the course of intravenous treatment with DM1- (S-Ala) -R-LA and DM1- (S- Ala) -R-LA-GNP at a 1350 pg/kg weekly dose and DM1- (S-Ala) -R-LA-GNP at a 2700 pg/kg weekly dose.

[213] Figure 5b shows the free DM1- (S-Ala) -R-LA at a weekly dose of 1350 pg/kg has improved survival rates over the vehicle alone. DM1- (S-Ala) -R-LA-GNP at a weekly dose of 1350 pg/kg shows an improved survival rate over the free DM1- (S-Ala) -R-LA. DM1- (S-Ala) -R-LA-GNP at a weekly dose of 2700 pg/kg shows an improved survival rate over a weekly dose of 1350 pg/kg. The 2700 pg/kg dose was not possible with free DM1- (S-Ala) -R-LA compound due to solubility issues. [214] At around 30 days after treatment, the order of tumour volume (mm³) from smallest to largest is DM1- (S-Ala) -R-LA-GNP at a weekly dose of 2700 pg/kg, DM1- (S-Ala) -R-LA-GNP at a weekly dose of 1350 pg/kg, DM1- (S-Ala) -R-LA and the vehicle alone. Not only does DM1- (S- Ala) -R-LA reduce tumour growth alone, but bound to a gold

nanoparticle as DM1- (S-Ala) -R-LA-GNP it reduces tumour growth even more. The higher dose of DM1- (S-Ala) -R-LA-GNP reduces tumour growth the most. -oqo-

[215] All references cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.

[216] The specific embodiments described herein are offered by way of example, not by way of limitation. Any sub-titles herein are included for convenience only, and are not to be construed as limiting the disclosure in any way.

Claims

1. A compound comprising a maytansinoid covalently bonded to a linker group, wherein the linker group is covalently bonded to a ligand group having a cyclic polythiol moiety.

2. A compound according to claim 1 wherein the cyclic polythiol is a cyclic disulfide.

3. A compound according to any one of the preceding claims

wherein the cyclic polythiol is saturated.

4. A compound according to any one of the preceding claims

wherein the ligand group is of the following formula;

wherein;

Z is CR⁵ or N,

R³, R⁴, R⁵ and R⁶ are independently one of a hydrogen atom, a methyl group, an ethyl group, a propyl group or an isopropyl group,

q is an integer of 0, 1, 2, 3, 4, 5 or 6, and m and n are independently an integer of 0, 1, 2, 3,

4 or 5 and m + n equals 0, 1, 2, 3, 4 or 5.

5. A compound according to claim 4 wherein the ligand group is of the following formula;

and R³, R⁴, R⁵, R⁶, q, m and n are as defined above.

6. A compound according to any one of the preceding claims wherein the cyclic polythiol is selected from one of 1,2- dithiolane, 1 , 2-dithiane, 1 , 2-dithiopane and 1 , 2-dithiocane .

7. A compound according to any one of the preceding claims

wherein the cyclic polythiol is unsubstituted.

8. A compound according to any one of the preceding claims

wherein the linker group is an amino acid-derived linker group of the following formula:

wherein;

R¹ and R² are each independently a hydrogen atom or a naturally occurring amino acid side chain.

9. A compound according to claim 8 wherein R¹ is a methyl group and R² is a hydrogen atom.

10. A compound according to claim 8 or claim 9 wherein the linker group is of the following formula:

and R¹ is a hydrogen atom or a naturally occurring amino acid side chain.

11. A compound according to any one of the preceding claims

wherein the linker group is covalently bonded to the 3-OH position of the maytansinoid via an ester bond.

12. A compound according to any one of the preceding claims

wherein the linker group is covalently bonded to the ligand group via an amide bond.

13. A compound according to claim 1 of the following formula;

each X is independently a hydrogen atom or methyl group,

Y is a hydrogen atom, fluorine atom, chlorine atom, bromine atom or iodine atom,

Z is CR⁵ or N,

4 or 5 and m + n equals 0, 1, 2, 3, 4 or 5.

14. A compound according to claim 13 of the following formula;

wherein X, Y, R³, R⁴, R⁵, R⁶, q, m and n are as defined above .

15. A compound according to claim 1 of one of the following formulae :

wherein the alanine derived linker group stereochemistry is (S) , (R) or racemic and the cyclic disulphide

stereochemistry is (S) , (R) or racemic.

16. A compound according to claim 15 wherein the alanine derived linker group stereochemistry is (S) and the cyclic disulphide stereochemistry (S) , (R) or racemic.

17. A compound according to claim 16 wherein the alanine derived linker group stereochemistry is (S) and the cyclic disulphide stereochemistry (R) or racemic.

18. A compound according to claim 1 of one of the following

formulae :

19. A nanoparticle comprising:

a core comprising a metal and/or a semiconductor; and

a plurality of ligands covalently linked to the core,

wherein said ligands comprise:

(i) at least one compound of any one of claims 1 to 16 as a polydentate ligand;

(ii) optionally at least one targeting ligand; and

(iii) at least one dilution ligand.

20. A nanoparticle according to claim 19 wherein the at least one dilution ligand comprises one or more of an ethylene glycol (EG) moiety, a polyethyleneglycol (PEG) moiety, glutathione, a carbohydrate and HS- (CH_{2) v}- (OCH₂CH_{2) w}-COOH, where v and w are independently between 1 and 30, optionally between 6 and 10, or between 20 and 60.

21. The nanoparticle according to claim 19 or claim 20, wherein the targeting ligand comprises a tumour-targeting ligand.

22. The nanoparticle according any one of claims 19 to 21, wherein the targeting ligand is covalently linked to the core via a first linker, said first linker having a chain length of 2 to 50 atoms.

23. The nanoparticle according to claim 22, wherein said first

linker comprises a group -(CH2)_r~ and/or - (OCH2CH2) _s- , wherein r and s are independently ³ 1.

24. The nanoparticle according to any one of claims 20 to 24,

wherein said first linker is bound to the core via a terminal sulphur atom.

25. The nanoparticle according to any one of claims 19 to 24,

wherein said first linker is bound to the core via two terminal sulphur atoms .

26. The nanoparticle according to any one of claims 19 to 25,

wherein the at least one dilution ligand comprises HS- (CH2) 1- 10- (EG) 1-10-COOH or comprises a carbohydrate.

27. The nanoparticle according to any one of claims 19 to 26,

wherein the at least one dilution ligand comprises HS- (CH2) 1- 4- (OCH2CH2) 6-_IO-COOH.

28. The nanoparticle according to any one of claims 19 to 27,

wherein the at least one dilution ligand comprises:

29. The nanoparticle according to any one of claims 19 to 28, wherein said plurality of ligands comprise:

at least one galactose ligand; and

at least one bidentate ligand of the following formulae; wherein the bidentate ligand is bound to the nanoparticle core by two thiol groups and the alanine derived linker group stereochemistry is (S) , (R) or racemic and the dithiol chain stereochemistry is (S) , (R) or racemic, and

at least one dilution ligand.

30. The nanoparticle according to claim 29 wherein the alanine

derived linker group stereochemistry is (S) and the dithiol chain stereochemistry is (S) , (R) or racemic.

31. The nanoparticle according to claim 29 wherein the alanine

derived linker group stereochemistry is (S) and the dithiol chain stereochemistry is (R) or racemic.

32. The nanoparticle according to any one of claims 19 to 31

wherein the at least one bidentate ligand is of one of the following formulae: core by two thiol groups .

33. The nanoparticle according to any one of claims 19 to 32,

wherein the core comprises at metal selected from the group consisting of: Au, Ag, Cu, Pt, Pd, Fe, Co, Gd, Zn or any combination thereof.

34. The nanoparticle according to claim 33, wherein the core

comprises Au .

35. The nanoparticle according to any one of claims 19 to 34,

wherein the diameter of the core is in the range 1 nm to 10 nm .

36. The nanoparticle according to any one of claims 19 to 35,

wherein the diameter of the nanoparticle including its ligands is in the range 3 nm to 50 nm.

37. A nanoparticle according to claim 19 having the following structure :

wherein the alanine derived linker group stereochemistry is (S) , (R) or racemic and the dithiol chain stereochemistry is (S) , (R) or racemic.

38. A nanoparticle according to claim 37 wherein the alanine

39. A nanoparticle according to claim 38 wherein the alanine

40. A nanoparticle according to any one of claims 19 to 39 wherein the total number of ligands bound to the core is 20 or more including at least one maytansinoid .

41. A conjugate comprising a compound according to any one of claims 1 to 18 and a targeting agent.

42. A conjugate according to claim 41 wherein the targeting agent comprises an antibody, an antibody fragment, a peptide or an aptamer .

43. A conjugate according to claim 42 wherein the targeting agent comprises an antibody or an antibody fragment that selectively binds a tumour antigen.

44. A conjugate according to any one of claims 41 to 43, wherein the targeting agent comprises a therapeutic antibody.

45. A conjugate according to claim 44, wherein the therapeutic antibody exhibits antibody-dependent cellular cytotoxicity (ADCC) and/or complement-dependent cytotoxicity (CDC) effector function in vivo in a mammalian subject.

46. A conjugate according to any one of the preceding claims,

wherein said compound is conjugated to said targeting agent via a linker.

47. A conjugate according to claim 46, wherein the targeting agent comprises an antibody or an antibody fragment and wherein the linker comprises a cleavable portion.

48. A pharmaceutical composition comprising a compound according to any one of claims 1 to 18 a nanoparticle according to any one of claims 20 to 40 or a conjugate according to any one of claims 41 to 47, and at least one pharmaceutically acceptable carrier or diluent.

49. A pharmaceutical composition according to claim 48, wherein the pharmaceutical composition is a sustained release

formulation and wherein at least a portion of the compound, the plurality of nanoparticles or the conjugate are encapsulated in a biocompatible polymer.

50. A pharmaceutical composition according to claim 49, wherein the sustained release formulation is in the form of a

microparticle, a microsphere, a bead or a film.

51. A pharmaceutical composition according to any one of claims 48 to 50, wherein the composition is in injectable form.

52. A compound according to any one of claims 1 to 18, a

nanoparticle according to any one of claims 19 to 40, a conjugate according to any one of claims 41 to 47, or a composition according to any one of claims 48 to 51 for use in medicine .

53. A compound according to any one of claims 1 to 18, a

nanoparticle according to any one of claims 19 to 40, a conjugate according to any one of claims 41 to 47, or a composition according to any one of claims 48 to 51 for use in the treatment of a proliferative disorder.

54. A compound, nanoparticle, conjugate or composition for use according to claim 53 wherein the proliferative disorder is a cancer .

55. A compound, nanoparticle, conjugate or composition for use according to claim 54 wherein the cancer is a carcinoma.

56. A compound, nanoparticle, conjugate or composition for use according to claim 54 wherein the cancer is selected from renal cancer, ovarian cancer, skin cancer, lung cancer, pancreatic cancer, liver cancer, head and neck cancer and brain cancer.

57. A compound, nanoparticle, conjugate or composition for use according to claim 54 wherein the cancer is selected from hepatocellular carcinoma (HCC) , glioma, melanoma, epidermal carcinoma, non-small cell lung cancer (NSCLC) , pancreatic adenocarcinoma, renal adenocarcinoma and ovarian

adenocarcinoma .

58. A compound, nanoparticle, conjugate or composition for use according to claim 54 wherein the cancer is selected from: hepatoblastoma, cholangiocarcinoma, cholangiocellular

cystadenocarcinoma, angiosarcoma, hemangioendothelioma, embryonal sarcoma, fibrosarcoma, leiomyosarcoma and

rhabdomyosarcoma .

59. The compound, nanoparticle, conjugate or composition for use according to any one of claims 53 to 58, wherein said

compound, nanoparticle, conjugate or composition is

administered concurrently, sequentially or separately with a second anti-cancer agent.

60. The compound, nanoparticle, conjugate or composition for use according to claim 59, wherein said second anti-cancer agent comprises a kinase inhibitor selected from the group

consisting of: Sorafenib, Regorafenib and Lenvatinib.

61. A method of treating a proliferative disease in a mammalian subject, comprising administering a compound according to any one of claims 1 to 18, a nanoparticle according to any one of claims 19 to 40, a conjugate according to any one of claims 41 to 47 or a pharmaceutical composition according to any one of claims 48 to 51 to the subject in need of therapy.

62. A method according to claim 61 wherein the proliferative

disease is a cancer.

63. The method according to claim 62, wherein the cancer is a

carcinoma .

64. The method according to claim 62, wherein the cancer is selected from renal cancer, ovarian cancer, skin cancer, lung cancer, pancreatic cancer, liver cancer, head and neck cancer and brain cancer.

65. The method according to claim 62, wherein the cancer is

selected from hepatocellular carcinoma (HCC) , glioma, melanoma, epidermal carcinoma, non-small cell lung cancer (NSCLC) , pancreatic adenocarcinoma, renal adenocarcinoma and ovarian adenocarcinoma.

66. The method according to claim 62, wherein said cancer is

selected from: hepatoblastoma, cholangiocarcinoma,

cholangiocellular cystadenocarcinoma, angiosarcoma,

hemangioendothelioma, embryonal sarcoma, fibrosarcoma, leiomyosarcoma and rhabdomyosarcoma.

67. The method according to any one of claims 61 to 66, wherein said compound, nanoparticle, conjugate or composition is administered concurrently, sequentially or separately with a second anti-cancer agent.

68. The method according to claim 67, wherein said second anti cancer agent comprises a kinase inhibitor selected from the group consisting of: Sorafenib, Regorafenib and Lenvatinib.

69. Use of a compound according to any one of claims 1 to 18, a nanoparticle according to any one of claims 19 to 40, a conjugate according to any one of claims 41 to 47 or a pharmaceutical composition according to any one of claims 48 to 51 in the preparation of a medicament for use in a method according to any one of claims 61 to 68.

70. An article of manufacture comprising:

a compound according to any one of claims 1 to 18, a nanoparticle according to any one of claims 19 to 40, a conjugate according to any one of claims 41 to 47 or a pharmaceutical composition according to any one of claims 48 to 51;

a container for housing the compound, nanoparticle, conjugate or pharmaceutical composition; and

an insert or label .

71. The article of manufacture according to claim 70, wherein the insert and/or label provides instructions, dosage and/or administration information relating to the use of the

nanoparticle or pharmaceutical composition in the treatment of a cancer in a mammalian subject.