AU644139B2 - Target-specific, cytotoxic, recombinant pseudomonas exotoxin - Google Patents

Description

OPI DATE 24/07/91 APPLN. ID 72424 91 PCT AOJP DATE 05/09/91 PCT NUMBER PCT/US90/07421 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT) (51) International Patent Classification 5 International Publication Number: WO 91/09949 C12N 15/31, A61K 37/02 Al C07K 13/00 (43) International Publication Date: 11 July 1991 (11.07.91) (21) International Application Number: PCT/US90/07421 (74) Agents: HOLMAN, John, Clarke et al.; Fleit, Jacobson, Cohn, Price, Holman Stern, The Jenifer Building, 400 (22) International Filing Date: 27 December 1990 (27.12.90) Seventh Street, Washington, DC 20004 (US).

Priority data: (81) Designated States: AT (European patent), AU, BE (Euro- 459,635 2 January 1990 (02.01.90) US pean patent), CA, CH (European patent), DE (European patent), DK (European patent), ES (European patent), FR (European patent), GB (European patent), GR (71) Applicant: THE UNITED STATES OF AMERICA, as re- (European patent), IT (European patent), JP, LU (Europresented by THE SECRETARY, U.S. DEPARTMENT n pant), NL (European patent), SE (European pa- OF COMMERCE [US/US]; 5285 Port Royal Road, Springfield, VA 22151 (US).

(72)Inventors: PASTAN, Ira 11710 Beall Mountain Road, Published Potomac, MD 20854 CHAUDHARY, Vijay 1001 With international search report.

Rockville Pike, #1207, Rockville, MD 20852 FITZ- GERALD, David 1731 Ladd Street, Silver Spring, MD 20960 (US).

(54) Title: TARGET-SPECIFIC, CYTOTOXIC, RECOMBINANT PSEUDOMONAS EXOTOXIN (57) Abstract A target-specific, cytc'oxic, recombinant Pseudomonas exotoxin is described. Such toxins are made by inserting specific recognition molecules at specific cloning sites in at least domain III at the carboxyl terminus of the PE molecule. Various modifications ol' the carboxyl terminus of the PE molecule to increase cytotoxicity are set forth, WO 91/09949 P(7r/U'S90/07421 TARGET-SPECIFIC, CYTOTOXIC, RECOMBINANT PSEUDOMONAS EXOTOXIN The present invention is related generally to the making of improved recombinant immunotoxins. More particularly, the present invention is related tu the construction of a recombinant Pseudomonas exotoxin (rPE) with specific cloning sites for the insertion of recognition molecules at least at the carboxyl end of the PE to achieve target-directed cytotoxicity.

BACKGROUND OF THE INVENTION The mechanism by which protein toxins kill cells is quite complex. Many toxins bind to receptors on the surface of mammalian cells, are internalized by endocytosis, translocate to the cytosol and, there, exert an enzymatic activity that kills the target cell.

Accordingly, these toxins have separate domains for cell binding, translocation and an enzymatic activity that inactivates an essential cellular function.

Pseudomonas exotoxin A (PE) is a single polypeptide chain of 613 amino acids. X-ray crystallographic studies and mutational analysis of the PE molecule have shown that PE consists of three domains: an amino terminal cell receptor binding domain (Domain a middle translocation domain (Domain II); and a carboxyl terminal activity domain (Domain III). Domain III catalyzes the ADP ribosylation and inactivation of elongation Factor 2(EF-2) which inhibits protein synthesis and leads to cell death. Mutational analysis of Domain I has :'evealed that Lysine 5 7 plays a major role in receptor binding. Similarly glutamic acid 553 Tyr~sine 481 and histidine 426 have been shown to be important for ADP-ribosylation activity. Recently mutational analysis of domain II has shown zhat certain portions of this domain are absolutely required for the SUBSTrUTE

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WO 91/09949 PCT/US90/07421' 2 cytotoxicity of PE.

While constructing various chimeric toxins in which growth factors were fused to a form of PE (PE40) which was devoid of domain I, it was observed that the recombinant fusion proteins, made by attaching TGFa, interleukin-2 or interleukin-4 at the carboxyl end of had poor cytotoxic activity. Hence, an examination of the role of the carboxyl terminus of the PE molecule (domain III) was undertaken.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to determine the role of the carboxyl terminus of the PE molecule in its cytotoxic action.

It is another object of the present invention to identify specific regions at the carboxyl terminus of the PE molecule for the insertion of recognition molecules for selective killing of target cells.

It is a further object of the present invention to provide an improved, target-specific, cytotoxic recombinant PE molecule, wherein the improvement comprises the insertion of target-specific recognition molecule at least in domain III at the carboxyl terminus of the PE molecule.

A still further object of the present invention is to modify the oarboxyl end of the PE to increase the potency of the chimeric toxin.

It is yet another object oi the present invention to make cytotoxic PE with two recognition molecules (target ligands) wherein either the same recognition molecule is placed at two different termini, such as the amino terminus and near the carboxyl terminus, for enhanced cellular binding, or two different recognition SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 3 elements are'inserted, one each at two different regions of the PE molecule, to enable more effective binding of the.resulting PE molecule to the cell surface having two or more different entities, such as antigens, receptors and the like to which said recognition elements could bind.

It is an additional object of the present invention to provide a recombinant PE having repeat carboxyl end cytotoxic sequences for enhanced cytocidal activity.

Various other objects and advantages will become evident from the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and many of the attendant advantages of the invention will be better understood upon a reading of the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 demonstrates cytotoxicity of PE and PE mutants on Swiss cells. Various dilutions of PE proteins were made in PBS containing 0.2% human serum albumin and added to IxlO 5 Swiss 3T3 calls in 24-well plates. Sixteen hours later the cells were pulse labeled with 3H-leucine and TCA precipitable cell associated radioactivity was determined as a measure of protein synthesis. The results are expressed as percent of control where no toxin was added. PE; 0-0 PEA613; D--D PEA612,613; and 6-- PEA 611-613. All the assays were done in duplicate and repeated twice.

Figure 2 shows the results of competition for the cellular uptake of recombinant PE. Swiss 3T3 mouse SUBSTITUTE

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WO 91/09949 PCT/US90/07421 4 cells were incubated with 400 ng 3 H-PE (specific activity 3.5x10 5 DPM/ig) and increasing concentrations of purified mutant proteins for one hour at 37'C. Cell monolayers were washed and cell-associated radicactivity was determined. PE; A--A PEglu57; A PE 612,613; -0 PE 613; PEgly276; PE 609-613; PE A609- 613+598-613.

Figure 3 shows immunofluorescence detection of binding and internalization of Pseudomonas exotoxin and its recombinant variants in Swiss 3T3 cells. Swiss 3T3 cells were incubated at 37°C for 30 minutes in the absence of toxin or in the presence of 10 gg/ml of native Pseudomonas exotoxin (PE) recombinant PE gly 5 7 or recombinant PE 612,613 Following this incubation, the cells were fixed in formaldehyde and further incubated in the continuous presence of saponin. The cells were incubated with mouse monoclonal anti PE (M40-1) (10 Ag/ml), followed by affinity-purified rhodamine-labeled goat anti-mouse IgG pg/ml). (Mags x 400; bar 10 Mm).

DETAILED DESCRIPTION OF THE INVENTION The above and various other objects and advantages of the present invention are achieved by a cytotoxic recombinant Pseudomonas exotoxin (rPE) having a recognition molecule inserted at least in domain III at the carboxyl terminus of the PE for selective killing of target cells recognized by said recognition molecule without substantial cytotoxicity to other cells not recognized by said recognition molecule, and by a rPE with modified "cytotoxic sequence" with increased cell killing activity.

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WO 91/09949 PCT/US90/07421 Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned hereunder are incorporated herein by reference. Unless mentioned otherwise, the techniques employed or contemplated herein are standard methodologies well known to one of ordinary skill in the art. The materials, methods and examples are illustrative only and not limiting.

The term "recognition molecule" as defined herein means those molecules or ligands which recognize only target cells desired to be killed. Examples of such recognition molecules are antibodies or portions thereof that can recognize the target cells, growth factors, lymphokines, cytokines, hormones and the like which specifically bind to molecules on the surface of the target cells.

The term "cytotoxic sequence" as used herein means those variety of amino acid sequences at the carboxyl end of the PE, the presence of which is a prerequisite for the cytocidal activity of the toxin and the repeat sequences of which may determine the level of cytotoxicity. The examples of such sequences are KDEL, RDELK and the like as will become apparent from the various embodiments of the sequences discussed herein below.

SUBSTITUTE SHEET PC/US90/07421 W0 91/09949 6 MATERIALS AND METHODS Materials Unless mentioned otherwise, the materials and reagents used herein were obtained from commefcial sources. Polymerization Chain Reaction (PCR) kit, Gene Amp Kit, was obtained from Perkin Elmer-Cetus, Norwalk,

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Mutants and Plasmid Constructions Mutants were created by :ligonucleotide directed mutagenesis using plasmid pVC45f+T as described by Jinno et al, 1988, J. Biol. Chem. 263, 132C3-13207 and Jinno et al, 1989, J. Biol. Chem. 264, 15953-15959 or using polymerase chain reaction (PCR) as describel below. pVC45f+T carries a PE gene under a T7 promoter and also contains a T7 transcriptional terminator and a fl phage origin. The PE gene also contains an OmpA signal sequence which is cleaved upon secretion of PE into the periplasm leaving a 3 amino acid (ala asn leu) extension at the amino terminus (Chaudhary et al, 1988, Proc. Natl. Acad. Sci. USA 85, 2939-2943). For PCR mutagenesis, two oligonucleotides and a 1.0 Kb Sall- EcoRI fragment of pVC45f+T were employed. One oligonucleotide was the same as nucleotides 2216-2236 of the PE gene (Gray et al, 1984, Proc. Natl. Acad.

Sci. USA 81, 2645-2649), Other oligonucleotides were complementary to the 3' end of the coding sequence PE gene, contained desired mutations and created an EcoRI site after the stop codon. Other unique restriction sites were also created without changing amino acids to identify the mutants. A 30 cycle PCR was performed with denaturation at 94'C for 2 minutes, annealing at for 1 min and polymerization at 72C for 3 min with SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 7 seconds extension per cycle using a gene amplification thermal cycler (Perkin Elmer Cetus).

After the PCR, amplified fragment was cut with EcoRI and BamHI, it was purified using low melting point agarose. PCR fragments were ligated with a 4.5 Kb dephosphoylated EcoRI-BamHI fragment of Mutants were identified by unique restriction sites which were created during mutagenesis and finally confirmed -by sequencing by Snager's dideoxy-chain termination procedure using Sequenase (US Biochemical Corp.).

pVC4915f+T This plasmid contains two mutations; Codon 608, CCG and 609, CGC were changed to CCC and GGG, respectively.

This mutation results in glycine at 609 in place of arginine and creates a Smal site between codons 608 and 609. This plasmid was used to clone various carboxyl terminal fragments of PE. pVC4975f+T: A 1 Kb BamHI- PstI fragment of pVC8 (Wozniak et al, 1988, Proc. Natl.

Acad. Sci. USA 85, 8880-8884) was restricted with Narl, treated with T4 DNA polymerase to make blunt ends followed by EcoRI, and a 286bp fragment was ligated to a 4.9 Kb dephophorylated SmaI-EcoRI fragment of pVC4915f+T. pVC4985f+T: A 1 Kb BamHI-PstI fragment of pVC8 was restricted with Hinfl, treated with T4 DNA polymerase followed by EcoRI and a 237bp fragment was ligated to the 4.9 Kb Smal-EcoRI fragment of pVC4995f+T: A synthetic oligonucleotide duplex VK192/193 (not shown), containing codons 598-613 of PE with a stop codon and an EcoRI compatible 3' end, was ligated to the 4.9 Kb SmaI-EcoRI fragment of pVC4915f+T. pVC4715f+T: This plasmid was created by SUBSTITUTE

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WO 91/09949 PCT/US90/07421 8 PCR mutagenesis and contains restriction sites Stul, Ndel, Smal, EcoRV and EcoRI within the 3' end of the PE gene and encodes amino acids RPHMPGDILK in place of PREDLK at 608 to 613. These unique sites were later used to make insertions and to attach various DNA segments encoding carboxyl terminal portions of PE.

pVC47195f+T This was created by ligating oligonucleotide duplex VK191/192 to a 4.9 Kb EcoRV-EcoRI fragment of pVC4715f+T. The carboxyl terminus of this PE mutant contains amino acids RPHMPGDPDYASQPGKPPREDLK in place of amino acids 608-613.(PREDLK) of PE.

Plasmids for the insertion of receptor binding domains in the carboxyl end of PE Plasmid pVC4715f+T consists of DNA sequences encoding PE from amino acids 1 to 607 followed by a polylinker that contains Stul, Ndel; Smal, EcoRV and AflI sites as well as encodes amino acids RPHMPGDILK.

These sequence are under T7 promoter control and also contain shine-Dalgarno region and signal sequence from OmpA of E. coli. Plasmid pVC 4715/4E f+T is similar to pVC 4715 f+T, but also contains mutations in the receptor binding domain of PE (Domain These mutations are Lys 57 Glu, His 2 4 6 249 -Glu and Arg 247 Glu.

Plasmid pVC 47195/f+T is similar to pVC4715 f+T but contains a polylinker with Stul, Ndel, Smal sites encoding amino acids RPHMPGI followed by the last 16 codons of PE that encode PDYASQPGKPPREDLK. Plasmid pVC 47195/4# f+T contains insertions of a cDNA encoding transforming growth factor a in the Ndel site of plasmids pVC 4715f+T and 4715/4Ef+T respectively.

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WO 91/09949 PCT/US90/07421 9 Plasmids pVC47395f+T and pVC 47195/4Ef+T are derived from 47195f+T and pVC 47195f+T by inserting TGFa sequences into the Ndel site. Plasmid pVC 47355/4Ef+t was derived from pVC47395/4Ef+T by deleting 6 amino acids, inserting TGFa and following it with 10 amino acids of the PE carboxyl end.

A deposit of pVC49415f+t and pVC47355/4Ef+t has been made at the ATCC, Rockville, MD., on December 28, 1989 under accession numbers 68198 and 68199, respectively. The deposit shall be viably maintained, replacing if it becomes non-viable during the life of the patent, for a period of 30 years from the date of the deposit, for 5 years from the last date of request for a sample of the deposit, whichever is longer, and upon issuance of the patent made available to the public without restriction in accordance with the provisions of the law. The Commissioner of the Patents and Trademarks, upon request, shall have access to the deposit.

Protein Expression and Purification Cultures of E. coli strain BL21 (?DE3) containing various plasmids were grown to OD650 of 0.6-0.8 and induced with 1 mM isopropyl-thiogalactoside for minutes at 37*C. Periplasmic fractions were prepared as described by Chaudhary et al, supra. By virtue of having an OmpA signal sequence, more than 90% of each of the expressed toxin proteins were secreted into the periplasm. These proteins have a residual ala asn leu sequence at the amino end left behind after the processing of the OmpA signal sequence. Periplasmic fractions were assayed for ADP ribosylation activity and cytotoxicity. Later PE mutants were purified using SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 a MonoQ anion exchange column (HR5/5) attached to a Pharmacia FPLC system. PE and mutant proteins eluted at NaC1 concentrations of 0.22-0.26M. Upon SDS-PAGE the toxins were more than 90% pure. Proteir concentration was measured by the Bradford assay Reagent (BioRad.Richmond, CA) using boviie serum albumin as a standard.

ADP Ribosylation and Cytotoxicity Assays ADP ribosylation activity was assayed after the activation of PE and mutant proteins with 4M urea and mM DTT unless otherwise st ted (Collier et al, 1971, J. Biol. Chem. 246, 1496-1503). Cytotoxicity of PE mutants was determined by adding various dilu ,.ons of periplasmic proteins or purified proteins to 1 x 105 Swiss 3T3 cells in 24-2311 plates as described by Jinno et al, (1988) supra, and Jinno et al, (1989) supra.

ADP-ribosylation and cytotoxic activities of recombinant PE and native PE (from Swiss Serum and Vaccine Institute, Berne, Switzerland) were indistinguishable.

Toxin Binding and Internalization The ability of various mutant PE proteins to compete the binding of 3 H-labelled PE on Swios cells as well as internalization of various mutant PE derivatives as studied by immunofluorescence has been described by Jinno et al, (1989), sup'a.

Preparation of Target-SpeAific immunotoxins PE expression vectors with the cloning sites in the carboxyl end of PE to produce selective cytotoxic molecules are illustrated here with TGFa, a recognition molecule which recognizes only EGF receptor bearing cells. These cloning sites were used 'o insert TGFa SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 11 near the carboxyl end of PE which produced a very active molecule that killed EGF receptor bearing cells when the insertion was followed by the last 10 amino acids of PE (Table The details of the procedure are now described.

RESULTS

The role of sequences at the carboxyl end of PE was determined by making a series of carboxyl terminal deletion mutants that removed 1,2,3,7,8,11,14 and 24 amino acids. Removal of two or more amino acids eliminated cytotoxicity without affecting ADP ribosylation activity (Table 1, Fig. In fact, even eleven amino acids (603-613) could be removed without any loss of ADP ribosylation activity. However, removal of 14 amino acids resulted in a protein with low, but measurable, ADP ribosylation activity (600- 613) and removal of 24 amino acids (590-613) produced an enzymatically inactive protein. These results indicate that particular sequences at the carboxyl end of PE have a role in toxin action that are not required for ADP ribosylation activity.

The role of the carboxyl terminal sequences in toxin action was defined by creating a series of internal deletions and substitutions (Table These mutations began at amino acid 602 so that ADP ribosylating activity Would not be affected and extended to position 611. It was found that several small deletions encompassing amino acids 601-604 and 606-608 did not reduce cytotoxicity. Furthermore, two substitutions which altered amino acids 603-608 as well as two other substitutions within amino acids 606-608 of PE did not reduce cytotoxicity. Therefore, the SUBSTITUTE SHEET WO 91/09949 PCr/US90/07421 12 sequence of amino acide in positions 602-608 did not appear to be important for cytotoxicity. However, deletions which removed arginine at 609 (pVC 49215 and pVC 49255) greatly reduced the cytotoxic action of PE.

These results, together with the experiments in Table 1 showing that deletion of amino acids 612 and 613 abolish cytotoxicity, focused our attention on amino acids 609-613 which are situated at the carboxyl terminus of PE.

The role of arginine 609 was studied by either deleting it or replacing it with several different amino acids. Replacement of arginine at 609 with another basic amino acid, lysine, retained the cytotoxic activity of PE (Table However, deleting arginine at 609 (pVC 49115) or replacing it with glycine, glutamic acid or leucine reduced cytotoxocity about 6-10-fold. Thus, a basic amino acid appears to be important at position 609.

To study the sequence specificity of the last five amino acids of PE, several other mutant molecules were then constructed. In two of these, the order of the acidic amino acids at positions 610 and 611 was reversed and lysine 613 deleted (Table 4, pVC 49415 and pVC 49425). These molecules were fully active whether or not position 609 was a lysine or an arginine. A molecule was also created with a leuc.ae at position 609 and an arginine at 612 (pVC 494J5) that Tas inactive.

Although deletion of the terminal amino acid lysine at 613 did not affect cytotoxicity, it was suspected that other mutatAons in this position might affect cytotoxicity in a negative manner because of the low SUBSTITUTE SHEET WO91/09949 PCT/US90/07421 13 activity of various chimeric toxins in which the ligand was placed in peptide linkage at the carboxyl terminus of PE. Therefore, lysine 613 was converted to glutamine, asparagine or aspartate. All these mutations produced a less cytotoxic molecule (Table Addition 'f 6 or 11 amino acids to the carboxyl terminus of PE also produced a less cytotoxic molecule (data not shown). However, replacement of lys 613 with the basic amino acid, arginine, did not decrease cytotoxicity. Thus, positions 609 and 613 both require a basic amino acid for full cytotoxic activity. There are two other lysine residues at the carboxyl end of PE; these are situated at positions 590 and 606. Both of these lysines could be converted to the uncharged amino ac.d glutamine without a decrease in cytotoxicity, indicating that a positively charged amino acid was not required at position 590 or 606 (Table Having shown the importance of particular amino ac:Lds at the carboxyl terminus of PE, it was determined that the five carboxyl terminal amino acids could be separated from the ADP ribosylation domain to regenerate an active toxin. As shown in Table 6, a fully active cytotoxic molecule could be generated from PEA609-613 (which is not cytotoxic) by the addition of amino acids 551-613, 567-613 or 598-613 of an intact PE to the carboxyl terminus of PEA 609-613. Thus, the distance'between the ADP ribosylation domain which ends around amino acid 600 and the essential amino acids at positions 609-613 was not critical and could be substantially increased without a decrease in cytotoxicity. Also shown in Table 6 is a PE molecule SUBSTITUTE

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WO 91/09949 PCT/US90/07421 14 with the carboxyl terminus of RPHMPGDILK in place of PREDLK. This molecule, in which arg 609 and asp 61 1 were altered, was not cytotoxic. But attaching the last 16 amino acids of an intact PE molecule to give a carboxyl terminus of RPHMPGDPDYASQPGKPPREDLK restored cytotoxicity to this molecule.

Furtbarmore, constructs were made in which a cDNA TGFa was inserted at the carboxyl end of PE with an inactive carboxyl terminus (Table A pVC 47315/4Ef+T) and an active carboxyl terminus (Table A, pVC 47355f+T and pVC 47395f+T). The constructs with good car'*oxyl termini were more than 50 times as cytotoxic to cells with EGF receptors (TGFa binds to the EGF receptor) as the ones with the bad carboxyl ends. This clearly indicates that for the highest cytotoxic activity, a suitable carboxyl end is an essential requirement.

Altogether the data presented herein demonstrate that the cytotoxic activity of a PE molecule that is inactive due to a deletion or modification within the carboxyl end can be restored by attaching an intact carboxyl end. Hence, it is now possible to create active chimeric molecules by inserting a binding ligand such as TGFa at 608 within the carboxyl end of PE thus retaining the last five amino acids as REDLK.

Although it has been previously demonstrated that domain I of PE is the region responsible for cell binding, it was important to show that the mutations at the carboxyl end of PE that decreased cytotoxicity did not also somehow decrease cell binding. To test this, the ability of various mutant forms of PE to compete for the uptake of [3]-PE was evaluated. As shown in Figure 2. several PE mutants that had decreased SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 cytotoxicity due to mutations at the carboxyl terminus of PE were just as able to compete for the uptake of 3 H]-PE as authentic wild type of PE. In this competition assay, PE40 which has a deletion of domain I and Peglu 57 were inactive as previously described (Jinno et al, supra).

These uptake results were confirmed using a fluorescence assay that measured the internalization of PE and various mutant PE molecules (Figure In this assay, cells are incubated with various toxins for minutes to allow binding and internalization into endocytic vesicles. Molecules with a point mutation in domain I (PEglu 57 or PE40 were not internalized. In contract, all the other PE molecules, whether or not they contained mutations at the carboxyl end of domain III, were found to have bound and internalized into endocytic vesicles and other elements in the trans- Golgi system in the perinuclear area of the cells (Figure 3, Panel B and These results clearly show that decreased cytotoxicity of carboxyl terminal mutants is not due to decreased receptor binding or cellular uptake of PE molecules.

In summary, the results presented herein clearly show that mutations at the carboxyl end of PE and particularly in the last five amino acids of PE result in a molecule with full ADP ribosylation activity, but greatly reduced cytotoxicity. The data show that the amino acid sequence at the carboxyl end of PE is Arg, Glu, Asp, Leu, Lys (REDLK, Table The arginine at 609 can be replaced by lysine but non basic amino acids cannot be tolerated (Table Lysine at 613 is not essential and can be deleted without loss of cytotoxic SUBSTITUTE

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WO 91/09949 PCT/US90/07421 16 activity (Table but it cannot be replaced with a non-basic amino acid (Table Thus, having either ArgGluAspLeu or LysGluAspLeuLys at the carboxyl terminus produced a fully cytotoxic molecule (Table 4).

A search of the literature for similar sequences that were present in other molecules and performed a specific biological function revealed that the sequence which retains newly formed proteins within the endoplasmic reticulum is LysAspGluLeu (Munro et al, 1987, Cell 48, 899-907). Therefore, several other mutant molecules were constructed, one of which contained the exact sequence previously described as being responsible for the retention of the protein in the lumen of the endoplasmic reticulum (Table It was found that a molecule ending with LysAspGluLeu (KDEL) was fully cytotoxic. Also a molecule ending in ArgAspGluLeu (RDEL) but not leuAspGluArg (LDER) was fully active. These findings indicate that the successful entry of PE into the cytosol from a- 6ndocytic compartment requires interaction with the similar cellular component that helps retain proteins made by the cells within the endoplasmic reticulum.

These findings also suggest that the sequence at the carboxyl end of PE acts as some type of recognjiion sequence to assist translocation of PE from endocytic compartment into the cytosol. C' 94 sequences that perform the same function we Ikewise increase the activity.

Of further significance was the finding that because the cell targeting ligands can be inserted at two cloning regions in the PE molecule (at the amino terminus as previously described or near the carboxyl SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 17 end as described herein), the same or different targeting ligands can be inserted at these two regions thereby increasing either cell binding, cytotoxicity or both. Different targeting molecules at each of the two cloning regions would enable the chimeric toxin to bind to two different types of receptors present on the same cell. This is important because some antigens on target cells do not internalize well and are, therefore, poor targets for immunotoxins. But, if the toxin also binds to another antigen that is well internalized, specific cell killing is increased greatly.

It was further discovered during the modificational study of the carboxyl end of the PE that if the REDLK (single letter amino acid code) sequence is replaced with KDEL, the resulting molecule is about two fold more active. Even more spectacular was the finding that a molecule with three repeats of KDEL in place of REDLK, was three times as active (Table B) indicating that by adding KDEL or equivalent repeat sequences, chimeric toxins with enhanced cytotoxicity can be produced.

In short, the present invention for the first time shows that? 1. An appropriate carboxyl end sequence is absolutely required for cytotoxicity of the PE; 2. Deletion of as few as two amino acids from the carboxyl end of PE yields a molecule that contains full ADP ribosylation and receptor binding activity, but is nontoxic to target cells (Table 1); 3. Mutational analyses indicate that PE should possess a positively charged amino acid at 609, negatively SUBSTITUTE SHEET WO 91/09949 PCT/US90/07421 18 charged amino acids at 610 and 611 and a leucine at 612; 4. Lysine at 613 can be deleted but cannot be substituted with several other amino acid residues; 5. Addition of random amino acid residues at the carboxyl end of PE produce relatively inactive molecules (data not shown).

6. Addition of at least 10 carboxyl end amino acids of PE to the PE molecules that are not cytotoxic due to mutations in the carboxyl end, restores full cytotoxic activity (Table 4); 7. Different targeting ligands at different ends (amino and carboxyl) provide the flexibility of producing better binding and cytocidal PE molecules; and 8. Repeat "cytotoxic sequences" multiply the cytotoxicity in appropriate cases.

Of course, other target-specific immunotoxins are made similar to the method described herein supra by using appropriate recognition molecules, toxins and cytotoxic sequences including such modified recombinants as TGFa-PE40 and the like.

It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

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TABLE 1: Deletion analysis 0 of the carboxyl terminus of PE ADP ribosylation Cytotoxicity activity Mutants amino acids present 1-589 590- 1-599 600- 1-602 603- 1-605 606- 1-606 607- 1-610 611- 1-611 612, 1-612 613 1-613 amino acids deleted 513 513 513 513 513 513 513 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 100 100 *0 100 100 100 100 100 100 Legend to Table 1. Mutant PE proteins were expressed in E. coli using T7 promoter based vector (Studier and Moffatt, 1986) and purified from the periplasm. All proteins contain a 3 amino acid (ala asn leu) extention at the amino terminus remaining after the processing of the OmpA signal sequence.

These amino acids were not considered when assigning residues-numbers to the above mutant proteins. Cytotoxicity was determined by assaying inhibition of protein synthesis on Swiss 3T3 mouse cells. All results are expressed as percent of the activity obtained with recombinant full lerjth PE molecules. All the assays were done in duplicate and at least 2 separate clones were tested.

o TABLE 2: Internal deletions and substitutions within the carboxyl terminus of PE S Location of the amino acids in PE Plasmid 6 6 .6 6 6 6 6 6 6 6 6 6 6 Cytotoxicity pVC 0 0 0 0 0 0 0 0 0 1 1 1 1 1 2 3 4 5 6 7 8 9 0 1 2 3 A S Q P G K P P R E D L K 100 49215 A L K <0.1 49235 A G K P P R E D L K 100 49245 A S Q P G R E D L K 100 C 49255 A S Q P G E D L K 0.3 S4955 A S Q P G P K P R E D L K .100 S4935 A S G S H L A A R E D L K 100 S4955 A S E G K S S G R E D L K 100 C 49315 A S Q P G MM MR ED L K 100 m Mutant PE proteins were expressed in E. coli and purified from the periplasm.

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I ADP ribosylation activities of all the mutants were indistinguishable from the m MT full length PE.

4 Amino acids within the carboxyl end of PE (601-613) are shown as single letter code. The substitutions have been underlined.

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21 Table 3: Mutations at position~ 609 of PE Plasmid Mutant Cytotoxicity (pVC) Proteins of PE) 49115 PEA 609 12 49125 PELys 6 9 100 4915 pEgl1 49135. l6 16 49155 PEleu 0 mutant PE proteins were expressed in E. coli and purified from the periplasia. Substitutions are shown as replacement amino acids (also see Tables 1 and 2).

SUBSTITUTE SHEET Table 4: Plasmids (pVC) Sequence specificity of last 5 amino acids of

PE

Location of the amino acid in PE Cytotoxicity of PE) 609 610 611 612 R E D L 49125 K E D L 4215 R E D L 49415 K D E L 49425 R' D E L 49435 L D E R For details see legend to Tables 1 and 2.

613 100 100 100 100 100 <0.03 Table 5: Mutation of the lysines residues 590,606 and 613 in the carboxyl.

terminal domain of PE Mutants Cytotoxicity ADP-ribosylation of PE) (96 PEA 613 100 PEarg 613 100 PEqln 613 1 iEglu 613 1 PEasn 613 PEg ln 60 6 100 PEgln 590 100 Pgn590,606,613 1 Pgn590,606 ar613 100 Analyses-were per-Aeormed as described in Tables 1 and 2.

of PE) 100 100 100 100 100 100 100 100 100 Table 6: Addition ol various portions of PE carboxyl terminus to PE A609-613 Plasmid Mutant Cytotoxicety ADP-ribosylation (pvc) Proteins (%of PE) activity of PE) 4905 PE A 609-613 <0.1 100 4975 PEA609-613+551-613 100 100 4985 PEZS69-613+567--613 100 100 4995 PEA6O9-613+598-613 100 100 4715 PEA609-613 RPHIMPGDILK <0.1 100 47195 PEA 608-613 RPHMPGD+598-613 50 100 i

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Legend to Table 6. A plasmid pVC4915 with a SinaI site between codons 608 and 609 7-

W,

of PE was created and various portions of the carboxyl terminus were attached U1 &aEter codon 608. p-VC4995 was constructed using synthetic oligonucleotides. The C~j last 16 amliio acids (598-613) of PE consists of PDYASQPGKPPREDLK (also see Table

CD

1 and A means the deletion of amino acids following the symblol. C

CO,

Table A: Cvtotoxic activity on A431 cells of various carbo-n termina insertions of TGF into PE.

Plasmid Protein' I IDs (n/ml)b b pVC47315/4Ef+T PEl-CO7RPHMA (TGFa)AHIMPGDILK pVC47395/,-Ef+T PEI-6O7RPHMA(TGFa) AHMPGIPDYASOPGKPPREDLK PVC47355/4Ef+T PE -!-Z7RPHMA (TGFalAI4PGKPPREDLK a Fusion protei, ;ere partially purified from periplasm. SDS-PAGE indicated that the fusion proteins were 20-30% pure. Residues xrormally present in PE are underlined.

nb

ID

5 0 is the concentration of fusion protein (estimated as total protein C 5 ED concentration) that is required to inhibit protein 'synthesis by 50 percent

CD

as compared to control where no toxin was added. Protein synthe%,is was measured by 3H--leucine incorporation.

m m

-I

Mc M0 M0 0! Table B Cytotoxic activity on Sviss ;TI cells of various PE derivative Plasmid Protein!- ID__ 50__ bnkio pVC 45f+T PEl-608REDLK 1.6 PVC 49415f+T PEI-608DE1 0.76 pDS_49445f+T PEl-608KDELYDELKDEL 0.55 aPE proteins were purifiedI on M~ono colur-r and were approximately pure.

co b Same as Table

C

ID

H

C

M

ITn

Claims (25)

1. A cytotoxic recombinant Pseudomonas exotoxic (PE) having a first recognition molecule inserted in domain III adjacent to the caboxyl terminus of domain III, the resulting PE being selectively cytotoxic only to target cells recognized by said recognition molecule.

2. The PE of claim 1 wherein a second recognition molecule is inserted in a region other than said carboxyl terminus.

3. The PE of clrim 2 wherein said first and second recognition molecules are the same or different.

4. The PE of claim 1 or claim 2 wherein said recognition molecule is an antibody or a portion of an antibody which recognizes said target cells. The PE of claim 1 or claim 2 wherein said recognition molecule is selected from the group consisting of a growth factor, lymphokine, cytokine and a hormone.

6. The PE of any one of claims 1 to 5 wherein said recognition molecule is inserted after amino acid 607. S7. The PE of any one of clairs 1 to 6 wherein said carboxyl terminus has only the last 10 amino acid residues of PE following insertion at 607 and deletion of 608- S" 20 613.

8. The PE of any one of claims 1 to 7 wherein the amino acid after residue 608 comprises a cytotoxi', sequence KEDL, RDELK or repeat thereof.

9. The PE of claim 8 wherein the amino acid after residue (08 comprises a cytotoxic sequence KDELKDEL.

10. The PE of claim 8 wherein the cytotoxic sequence after residue 608 is KDELKDELKDEL.

11. The PE of claim 8 wherein the repeat cytotoxic sequence yields a rPE molecule with enhanced cytotoxicity compared to a molecule without the repeat sequence.

12. A composition, comprising a cytotoxic amount of the PE of any one of claims 1 to 11 and a pharmaceutically acceptable carrier.

13. A method for killing target cells, comprising contacting cells targeted to be 930812p:\oper\jw,72424-91.clm,27 I. r d^ -28- killed, with a cytotoxic amount of the PE of any one of claims 1 to 11.

14. A method for producing target-specific cytotoxic PE molecule, comprising inserting at least a first target-specific recognition molecule in domain III at the carboxyl terminus of the PE molecule.

15. The method of claim 14 further comprising replacing amino acid residues after 608 with the sequence KDEL or repeats thereof.

16. The method of claim 15 further comprising the step of inserting a second recognition molecule in a region other than said carboxyl terminus of the PE molecule.

17. The method of claim 16 wherein said second recognition molecule is the same as or different from said first recognition molecule.

18. The method of claim 17 wherein the second recognition molecule is inserted at the amino terminus of the PE molecule.

19. A composition comprising a recombinant Pseudomonas exotoxin (PE) molecule having a recognition molecule for binding a target cell and a carboxyl terminal sequence of from about 4 to about 16residues which permits translocation of the PE molecule into the target cell cytosol, the recognition molecule being S. inserted in domain III after about residue 603 of the PE molecule. t. 20. The composition of claim 19, wherein the carboxyl terminal sequence 20 comprises, in a direction from the amino terminus to the carboxyl terminus, the following amino acid residues: R-R2-R3R4-(Rs)n wherein, R 1 is a positively charged amino acid residue; R 2 is a negatively charged amino acid residue; R 3 is a negatively charged amino acid residue; R 4 is L; and R 5 is a positively charged amino acid residue; and wherein n is zero or'l.

21. The composition of claim 20, wherein R 1 is selected from the group consisting of R and K.

22. The composition of claim 20, wherein R 2 is selected from the group consisting S92't.2,p:\oper\nmw,7242491.clm,28 -29- of E and D.

23. The composition of claim 20, wherein R 3 is selected from the group consisting of D and E.

24. The composition of claim 20, wherein n is 1 and R 5 is selected from the group consisting of K and R. The composition of claim 19, wherein the carboxyl terminal sequence is selected from the group consisting of REDLK, KEDLK, REDLR, REDL, and KDEL.

26. The composition of claim 19, wherein the carboxyl terminal sequence is KDELKDELKDEL.

27. The composition of claim 19, wherein the recognition molecule is TGFa.

28. A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a recombinant Pseudomonas exotoxin (PE) molecule having a recognition molecule for binding a target cell and a carboxyl terminal sequence of from about 4 to about 16 residues which permits translocation of the PE molecule into the target cell cytosol, the recognition molecule being inserted in domain III after about residue 603 of the PE molecule.

29. The composition of claim 28, wherein the carboxyl terminal sequence :comprises, in a direction from the amino terminus to the carboxyl terminus, the following amino acid residues: R-R 2 -R'-R(Rs)n wherein, R 1 is a positively charged amino acid residue; S" R 2 is a negatively charged amino acid residue; R 3 is a negatively charged amino acid residue; R 4 is L; and :,ii R 5 is a positively charged amino acid residue; and wherein n is zero e or 1. r) 930812,p:\opcr\jmw,72424-91.dm,29 "N 30 The composition of claim 28, wherein the carboxyl terminal residues are selected from the group consisting of REDLK, KCEDLK, REDLRZ, REDL, and KDEL. DATED this 18th day of August, 1993. Tfhe United States of America, as represented by The Secretary, U.S. Department of Commerce By its Patent Attorneys Davies Collison Cave 4444 44 4 4, 44 4444 4 *4 44 4. ,.4 4 4* 4* 44 4 4 4 44 *4 930818,p:'koper\mw,7.2491.clm,30