Monte Rosa Therapeutics Inc (NASDAQ:GLUE) shares gained 3.9% in premarket trading Tuesday after the company disclosed clinical data from its Phase 1/2 study evaluating MRT-2359 in combination with enzalutamide for metastatic castration-resistant prostate cancer (mCRPC).
The company highlighted a notably strong response in the subgroup of patients carrying androgen receptor (AR) mutations. In that cohort, all 5 of 5 patients achieved a 100% prostate-specific antigen (PSA) response rate and a 100% disease control rate. Within that group, two patients registered RECIST partial responses while three had stable disease, and each of those five patients experienced reductions in the size of target lesions.
Looking at the larger evaluable population, Monte Rosa reported that 10 of 15 patients demonstrated reductions in target lesion size, yielding an overall RECIST disease control rate of 67% across all 15 evaluable patients. The study population was described as heavily pretreated: 78% of patients had prior therapy with a second-generation AR inhibitor and 83% had previously received taxane chemotherapy.
Safety findings were presented as generally manageable. The combination of MRT-2359 and enzalutamide produced mostly Grade 1-2 adverse events, with the most common events listed as fatigue, diarrhea, nausea and decreased appetite. The company said no patients discontinued therapy as a result of adverse events.
These data were presented at the 2026 ASCO GU Symposium in San Francisco on Wednesday. Monte Rosa said it plans to initiate a Phase 2 study of MRT-2359 in combination with a second-generation AR inhibitor in the third quarter of 2026. That planned Phase 2 will enroll up to 25 mCRPC patients with AR mutations and will use a two-stage design.
MRT-2359 is described by the company as an investigational, orally bioavailable molecular glue degrader targeting GSPT1. The drug’s mechanism involves disrupting translation through selective degradation of the translation termination factor GSPT1 - a protein the company says MYC-driven cancers rely on for rapid growth.
The clinical readout and the company announcement on development plans were followed by the premarket uptick in GLUE shares.
Summary of key trial facts
- AR-mutant cohort: 5 of 5 patients with 100% PSA response and 100% disease control.
- Overall evaluable population: 10 of 15 patients showed tumor size reductions; RECIST disease control rate 67%.
- Safety: Mostly Grade 1-2 adverse events; no discontinuations due to adverse events.