Rain Oncology Inc. announced its topline pivotal Phase 3 MANTRA data. The trial, evaluating the efficacy, safety, and tolerability of milademetan in patients with dedifferentiated (DD) liposarcoma (LPS), did not meet its primary endpoint of progression free survival (PFS) by blinded independent central review compared to the standard of care, trabectedin. The median PFS for milademetan was 3.6 months vs 2.2 months for trabectedin, with a hazard ratio of 0.89, p=0.53.

The most common treatment emergent adverse events (TEAEs) in the milademetan arm included nausea, thrombocytopenia, anemia, vomiting and neutropenia. The most common Grade 3/4 TEAEs were thrombocytopenia (39.5%), neutropenia (25.5%) and anemia (18.6%). Dose reductions in the milademetan arm were 44.2% vs 29.1% in the trabectedin arm.

Discontinuation in the milademetan arm due to AEs were 11.6% vs 19.0% for trabectedin. Based upon these topline data, Rain does not expect to pursue further development of milademetan in DD LPS. Rain hopes to present the MANTRA data in an upcoming medical conference.

Phase 3 MANTRA Topline Data Results: The median PFS was 3.6 months with milademetan versus 2.2 months for trabectedin, with a hazard ratio of 0.89 (95% CI [0.61 to 1.29]; p=0.53) based on 115 events. Most common TEAEs in the milademetan arm included nausea, thrombocytopenia, anemia, vomiting and neutropenia. The most common Grade 3/4 TEAEs in the milademetan arm were thrombocytopenia (39.5%), neutropenia (25.5%) and anemia (18.6%).

Dose reductions in the milademetan arm were 44.2% vs 29.1% in the trabectedin arm. Discontinuations in the milademetan arm due to AEs were 11.6% vs 19.0% for trabectedin. Treatment emergent SAEs in the milademetan arm were 36.0% vs 48.1% in the trabectedin arm.