Monte Rosa Therapeutics Presents Updated Clinical Data from Phase 1/2 Study of MRT-2359 in Combination with Enzalutamide in Heavily Pretreated Metastatic Castration-Resistant Prostate Cancer Patients at ASCO Genitourinary Cancers Symposium (ASCO GU)

Core Insights - Monte Rosa Therapeutics announced positive clinical data for MRT-2359 in combination with enzalutamide for mCRPC patients with AR mutations, showing a 100% PSA response rate and a 100% disease control rate among 5 patients [1][4][6] - The overall RECIST disease control rate across 15 evaluable patients was 67%, with 10 patients showing tumor size reductions [1][11] - The combination treatment was well-tolerated, with primarily Grade 1-2 adverse events and no treatment discontinuations due to adverse events [1][6] Clinical Study Details - The ongoing Phase 1/2 study evaluated MRT-2359 at doses of 0.5 mg and 0.75 mg, administered orally on a 21-days-on, 7-days-off schedule alongside enzalutamide [4][6] - As of January 30, 2026, 23 heavily pretreated patients were enrolled, with 78% having previously received a second-generation AR inhibitor and 83% having undergone taxane chemotherapy [4][6] - The study aims to confirm MRT-2359's clinical activity and position it for advancement into registrational studies [4][7] Future Plans - The company plans to initiate a new Phase 2 study in Q3 2026, targeting AR mutant patients with mCRPC, utilizing a two-stage design to assess efficacy [7][12] - The upcoming study will evaluate PSA response, RECIST response, duration of response, radiographic progression-free survival, and safety [7] About MRT-2359 - MRT-2359 is a novel molecular glue degrader targeting GSPT1, designed to disrupt translation of oncoproteins in MYC-driven cancers, including prostate cancer [8] - Preclinical models have shown robust anti-tumor activity, and the combination with enzalutamide is currently being investigated in the ongoing clinical study [8] Company Overview - Monte Rosa Therapeutics is a clinical-stage biotechnology company focused on developing selective molecular glue degrader medicines for serious diseases [9] - The company employs a unique discovery engine combining AI-guided chemistry and structural biology to design MGDs with high selectivity [9]