Monte Rosa Therapeutics announces data from Phase 1/2 study of MRT-2359

Monte Rosa Therapeutics (GLUE) announced positive 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. MRT-2359 is an investigational, orally bioavailable, GSPT1-directed MGD discovered and developed by Monte Rosa. Summary of Phase 1/2 Study Results in Metastatic CRPC Patients: 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 20 patients enrolled, 14 patients were evaluable for RECIST and were confirmed to have non-neuroendocrine mCRPC. Of the 14 evaluable patients, all of whom were assessed for AR alteration status using post hoc ctDNA analysis, 4 were confirmed to have AR mutations, and all 4 of those had PSA responses, including 2 patients with PSA90 responses. Two RECIST partial responses were seen in the AR mutant subset and the DCR in the AR-mutant setting was 100%. In addition, 5 patients with wild-type AR or positive for ARV7 transcripts had stable disease per RECIST, several of which were associated with tumor size reductions, resulting in a DCR of 64% in the overall population of 14 evaluable patients. Data showed that treatment effects were durable, in particular in patients with AR mutations or naive to AR inhibitors.