A Unique Prodrug Targeting the Prostate-Specific Membrane Antigen for the Delivery of Monomethyl Auristatin E

Monomethyl auristatin E (MMAE) is a promising treatment option for patients diagnosed with prostate cancer (PCa); however, toxicities prevent MMAE from being administered as free drug. No MMAE-based treatment is currently marketed for PCa. Herein, we describe a small-molecule-drug conjugate, CTT2274, for the selective delivery of MMAE. CTT2274 is composed of a prostate-specific membrane antigen (PSMA)-binding scaffold, a biphenyl motif, a pH-sensitive phosphoramidate linker, and MMAE payload. We demonstrate that CTT2274 shows selective binding to PSMA, which is overexpressed on PCa cells, and induces tumor cell death in vitro. In a patient-derived xenograft tumor model of PCa in mice, we show that weekly intravenous dosing of CTT2274 at 3.6 mg/kg for six weeks is superior to treatment with free MMAE at equivalent doses. Mice treated with CTT2274 experienced prolonged tumor suppression and significantly greater overall survival than mice treated with PBS. Additionally, the safety of CTT2274 compared to an equivalent dose of MMAE was assessed in healthy, non-tumor-bearing mice. Our results demonstrate that CTT2274 therapy is as efficacious as MMAE, results in superior overall survival, and has a more favorable safety profile. Together, these data indicate that CTT2274 is a candidate for clinical translation for the treatment of PCa.