Characterization of Site-Specifically Conjugated Monomethyl Auristatin E- and Duocarmycin-Based Anti-PSMA Antibody-Drug Conjugates for Treatment of PSMA-Expressing Tumors.

Abstract

Prostate cancer (PCa) is the most common cancer in men worldwide. In general, PCa responds poorly to chemotherapy. Therefore, antibody-drug conjugates (ADCs) have been developed to specifically deliver highly cytotoxic drugs to the tumor. Because the prostate-specific membrane antigen (PSMA) is overexpressed in PCa, it represents a promising target for ADC-based therapies. The aim of this study was to evaluate the therapeutic efficacy of site-specifically conjugated duocarmycin- and monomethyl auristatin E (MMAE)-based anti-PSMA ADCs with drug-to-antibody ratios (DARs) of 2 and 4. Methods: The glycan group of the anti-PSMA antibody D2B was chemoenzymatically conjugated with duocarmycin or MMAE. Preservation of the immunoreactivity of the antibody on site-specific conjugation was investigated in vitro. Biodistribution and small-animal SPECT/CT imaging (18.5 ± 2.6 MBq) with 25 μg of 111In-labeled ADCs were performed on BALB/c nude mice with subcutaneous PSMA-positive LS174T-PSMA xenografts. Finally, the therapeutic efficacy of the 4 different ADCs was assessed in mice with LS174T-PSMA tumors. Results: The immunoreactivity of the anti-PSMA antibody was preserved on site-specific conjugation. Biodistribution revealed high tumor uptake of all agents. The highest tumor uptake was observed in mice administered with 111In-D2B-DAR2-MMAE, reaching 119.7 ± 37.4 percentage injected dose per gram at 3 d after injection. Tumors of mice injected with 111In-D2B, 111In-D2B-DAR2-duocarmycin, 111In-D2B-DAR4-duocarmycin, 111In-D2B-DAR2-MMAE, and 111In-D2B-DAR4-MMAE could clearly be visualized with small-animal SPECT/CT. In contrast to unconjugated D2B or vehicle, treatment with either of the MMAE-based ADCs, but not with a duocarmycin-based ADC, significantly impaired tumor growth and prolonged median survival from 13 d (phosphate-buffered saline) to 20 and 29 d for DAR2 and DAR4 ADC, respectively. Tumor-doubling time increased from 3.5 ± 0.5 d to 5.2 ± 1.8 and 9.2 ± 2.1 d after treatment with D2B-DAR2-MMAE and D2B-DAR4-MMAE, respectively. Conclusion: The site-specifically conjugated anti-PSMA ADCs D2B-DAR2-MMAE and D2B-DAR4-MMAE efficiently targeted PSMA-expressing xenografts, effectively inhibited tumor growth of PSMA-expressing tumors, and significantly prolonged survival of mice.

• Authors: Susanne Lütje, Danny Gerrits, Janneke D Molkenboer-Kuenen, Ken Herrmann, Giulio Fracasso, Marco Colombatti, Otto C Boerman, Sandra Heskamp
• Journal: Journal of nuclear medicine : official publication, Society of Nuclear Medicine (J Nucl Med) Vol. 59 Issue 3 Pg. 494-501 (03 2018) ISSN: 1535-5667 [Electronic] United States
• PMID: 29146698 (Publication Type: Journal Article)
• Copyright: © 2018 by the Society of Nuclear Medicine and Molecular Imaging.

Chemical References

• Duocarmycins
• Immunoconjugates
• Indoles
• Oligopeptides
• Pyrrolidinones
• Glutamate Carboxypeptidase II
• duocarmycin A
• monomethyl auristatin E

Topics

• Animals
• Cell Line, Tumor
• Cell Transformation, Neoplastic
• Duocarmycins
• Gene Expression Regulation, Neoplastic
• Glutamate Carboxypeptidase II (metabolism)
• Immunoconjugates (chemistry, pharmacokinetics, therapeutic use)
• Indoles (chemistry)
• Male
• Mice
• Mice, Nude
• Oligopeptides (chemistry)
• Prostatic Neoplasms (diagnostic imaging, drug therapy, metabolism, pathology)
• Pyrrolidinones (chemistry)
• Single Photon Emission Computed Tomography Computed Tomography
• Tissue Distribution