Monte Rosa Therapeutics Inc. (NASDAQ:GLUE) shared interim data from an ongoing Phase 1/2 clinical study evaluating MRT-2359 in combination with enzalutamide in heavily pretreated patients with metastatic castration-resistant prostate cancer (mCRPC).
The Phase 1/2 study evaluated 0.5 mg and 0.75 mg of MRT-2359 administered orally on a 21-days-on, 7-day-off drug schedule in combination with Pfizer Inc. (NYSE:PFE) and Astellas Pharma Inc.’s (OTC:ALPMF) (OTC:ALPMY) Xtandi (enzalutamide).
The study population, as of the data cutoff date of December 3, included 20 individuals with advanced CRPC who were heavily pretreated.
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Trial Data
All 20 patients enrolled were evaluable for safety. The combination of MRT-2359 and enzalutamide maintained a favorable safety profile, with manageable, primarily gastrointestinal adverse events that were classified as mild or moderate.
Of the 14 evaluable patients, two RECIST partial responses (one confirmed partial response and one unconfirmed partial response) were seen in the AR mutant subset, and the disease control rate in the AR-mutant setting was 100%.
In addition, five patients with wild-type AR or positive for ARV7 transcripts had stable disease, several of which were associated with tumor size reductions, resulting in a DCR of 64% (9 of 14) in the overall population of 14 evaluable patients.
Data showed that treatment effects were durable, in particular in patients with AR mutations or naïve to AR inhibitors.
Monte Rosa plans to present updated data from the Phase 1/2 study of MRT-2359 at the ASCO Genitourinary Cancers Symposium in February.
Monte Rosa plans to initiate a Phase 2 study of MRT-2359 in combination with a second-generation AR inhibitor.
The study of up to 25 mCRPC patients is designed to efficiently assess the efficacy of MRT-2359 plus an AR inhibitor in mCRPC patients with AR mutations, with potential to expand the study into additional patient subsets.
The study will evaluate PSA response, RECIST response, duration of response, progression-free survival (PFS), radiographic progression-free survival (rPFS), and safety. The study is anticipated to start in 2026.
The Phase 1/2 study also included six patients with hormone receptor (HR)+ breast cancer. Data from this population demonstrated a favorable safety profile. However, results did not present sufficient evidence of activity to support further development in this population.
Updated Guidance for MRT-8102
Monte Rosa plans to present interim Phase 1 data on MRT-8102 in early 2026.
The ongoing Phase 1 study includes single-ascending dose/multiple-ascending dose cohorts in healthy volunteers, as well as a Part 3 cohort designed to evaluate potential early proof of concept in subjects at increased CVD risk.
The company has initiated dosing in Part 3 of the study.
Price Action: GLUE stock is up 11.43% at $18.33 at the last check on Tuesday.
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