Monte Rosa Therapeutics Presents Updated Clinical Data on MRT-2359 in Metastatic Prostate Cancer

Combination with enzalutamide shows promising results in heavily pretreated patients with AR mutations

Published on Feb. 24, 2026

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Monte Rosa Therapeutics announced updated positive clinical data from an ongoing Phase 1/2 study evaluating MRT-2359 in combination with enzalutamide in heavily pretreated patients with metastatic castration-resistant prostate cancer (mCRPC). The data showed a 100% PSA response rate and 100% disease control rate in patients with androgen receptor (AR) mutations, including 2 partial responses and 3 with stable disease. Across all evaluable patients, the overall RECIST disease control rate was 67%, with 10 of 15 patients showing tumor size reductions. The combination was generally well-tolerated, and Monte Rosa plans to initiate a new Phase 2 study in Q3 2026 to further evaluate MRT-2359 plus a second-generation AR inhibitor in mCRPC patients with AR mutations.

Why it matters

These results reinforce the potential of MRT-2359 in mCRPC patients with AR mutations, a population with limited therapeutic options. The high response rates and favorable safety profile observed support advancing the program into a confirmatory Phase 2 study, which could position MRT-2359 for future registrational trials.

The details

The ongoing Phase 1/2 study evaluated 0.5 mg and 0.75 mg of MRT-2359 administered orally on a 21-days-on, 7-days-off schedule in combination with the AR inhibitor enzalutamide. Of the 15 efficacy-evaluable patients, 5 of 5 with AR mutations showed PSA responses, including 2 with PSA90 responses and 3 with PSA50 responses. Two RECIST partial responses and 3 with stable disease were seen in the AR-mutant subset, resulting in a 100% disease control rate. Across all 15 evaluable patients, the overall RECIST disease control rate was 67%, and 10 of 15 patients showed tumor size reductions.

  • The data cutoff date for the analysis was January 30, 2026.
  • The poster presentation will be on February 26, 2026 at 11:30 AM PST and 5:45 PM PST.

The players

Monte Rosa Therapeutics

A clinical-stage biotechnology company developing molecular glue degrader (MGD)-based medicines.

Filip Janku, M.D., Ph.D.

Chief Medical Officer of Monte Rosa Therapeutics.

MRT-2359

An investigational, orally bioavailable, GSPT1-directed MGD discovered and developed by Monte Rosa.

Enzalutamide

An androgen receptor (AR) inhibitor used in combination with MRT-2359 in the Phase 1/2 study.

Metastatic castration-resistant prostate cancer (mCRPC)

The patient population evaluated in the Phase 1/2 study of MRT-2359 plus enzalutamide.

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What they’re saying

“These data bolster the promising results we shared in December, continuing to reinforce MRT-2359's potential in mCRPC patients with AR mutations, a population with limited therapeutic options.”

— Filip Janku, Chief Medical Officer of Monte Rosa Therapeutics (Monte Rosa Therapeutics)

What’s next

Monte Rosa plans to initiate a new, signal-confirming Phase 2 study of MRT-2359 targeting AR mutant patients in Q3 2026.

The takeaway

The positive results from the Phase 1/2 study of MRT-2359 in combination with enzalutamide in heavily pretreated mCRPC patients, particularly the high response rates in those with AR mutations, support advancing the program into a confirmatory Phase 2 trial. If successful, this could position MRT-2359 as a potential new treatment option for a patient population with limited therapeutic options.