Monte Rosa Therapeutics Announces Compelling Clinical Activity of MRT-2359 in Combination with Enzalutamide in Heavily Pretreated Metastatic Castration-Resistant Prostate Cancer Patients with Androgen Receptor Mutations

Core Insights - Monte Rosa Therapeutics announced positive interim data from a Phase 1/2 clinical study of MRT-2359 in combination with enzalutamide for patients with metastatic castration-resistant prostate cancer (mCRPC), showing a 100% PSA response rate in patients with androgen receptor (AR) mutations [1][2][3] Study Results - The combination treatment resulted in a 100% disease control rate in AR mutant patients, with 4 out of 4 patients showing PSA responses, including 2 patients achieving PSA90 responses and 2 achieving PSA50 responses [1][3] - The overall disease control rate in the study population was 64%, with 9 out of 14 evaluable patients demonstrating stable disease or tumor size reductions [3][4] - The treatment was generally well-tolerated, with primarily Grade 1-2 adverse events reported [1][4] Future Plans - The company plans to initiate a new Phase 2 study in 2026, targeting AR mutant and AR signaling-dependent patients, to further evaluate the efficacy of MRT-2359 in combination with a second-generation AR inhibitor [1][6] - Updated data from the ongoing Phase 1/2 study is expected to be presented at the ASCO Genitourinary Cancers Symposium in February 2026 [2][5] Mechanism of Action - MRT-2359 is designed to degrade GSPT1, impacting MYC and E2F signaling pathways, suggesting a mechanism of action that may be independent of AR signaling [3][10]