Chimeric polypeptide assembly and methods of making and using the same
The present invention relates to bispecific chimeric polypeptide assembly compositions comprising bulking moieties linked to binding domains by cleavable release segments that, when cleaved are capable of concurrently binding effector T cells with targeted tumor or cancer cells and effecting cytolysis of the tumor cells or cancer cells. The invention also provides compositions and methods of making and using the cleavable chimeric polypeptide assembly compositions.
1. A method of treating prostate cancer in a subject in need thereof, comprising intravenously administering to the subject a therapeutically effective amount of a chimeric polypeptide assembly,
wherein the chimeric polypeptide assembly comprises a bispecific antibody comprising
i. a first antibody binding domain having binding specificity to PSMA, wherein the first antibody binding domain is a Fab, and
ii. a second antibody binding domain having binding specificity to CD3, wherein the second binding domain comprises an scFv,
wherein the second antibody binding domain is attached to a bulking moiety via a linker comprising a peptidyl release segment that is capable of being cleaved by at least one mammalian protease, and wherein the bulking moiety (i) reduces the ability of the second antibody binding domain to bind CD3 and (ii) comprises an albumin binding domain;
wherein cleavage of the peptidyl release segment by the at least one mammalian protease converts the chimeric polypeptide assembly into an activated bispecific antibody,
wherein the activated bispecific antibody is capable of effecting at least a 10-fold greater amount of cell lysis of tumor cells compared to the chimeric polypeptide assembly, when cell lysis is measured in an in vitro assay comprising the tumor cells and a population of human peripheral blood mononuclear cells (PBMCs) comprising T cells.
2. The method of claim 1 , wherein, in the in vitro assay:
(a) the PBMCs are isolated from one or more healthy donors by ficoll density gradient centrifugation from either whole blood or from a lymphocyte-enriched buffy coat preparation;
(b) the PBMCs are resuspended and cultured in RPMI-1640/10% FCS/25 mmol/mL HEPES at 37° C. in a 5% CO 2 humidified incubator until use in the in vitro assay;
(c) the cell density of the tumor cells is 2.5×10 5 cells/mL and the cell density of the PBMCs is 1×10 6 cells/mL in the in vitro assay;
(d) the tumor cells and the PBMCs are co-cultured in assay medium comprised of phenol red-free RPMI and 5% FCS; and/or
(e) cell lysis is measured by a lactate dehydrogenase (LDH) release assay, a caspase 3/7 assay, or FACS-based analysis.
3. The method of claim 2 , wherein, in the in vitro assay, an effector cell to tumor cell ratio of 5:1 is present in the assay medium.
4. The method of claim 1 , wherein the tumor cells have arisen from prostate cells.
5. The method of claim 3 , wherein the tumor cells have arisen from prostate cells.
6. The method of claim 1 , wherein the CD3 is CD3 epsilon.
7. The method of claim 1 , wherein binding affinity of the first antibody binding domain to PSMA, if measured by a K d constant in an in vitro assay, is at least one order of magnitude greater compared to lower binding affinity of the second antibody binding domain to CD3.
8. The method of claim 1 , wherein the prostate cancer is metastatic.
9. The method of claim 1 , wherein the chimeric polypeptide assembly has been produced by a process comprising expression of the chimeric polypeptide assembly by a cultured mammalian host cell followed by purification of the chimeric polypeptide assembly.
10. The method of claim 1 , wherein the at least one mammalian protease comprises MMP-2, MMP-7, MMP-9, MMP-13, MMP-14, Urokinase (uPA), or matriptase.