Rain Oncology Inc. announced the publication of a peer-reviewed article titled, “A First-in-Human Phase I Study of Milademetan, an MDM2 Inhibitor, in Patients with Advanced Liposarcoma, Solid Tumors or Lymphomas” in the Journal of Clinical Oncology. Phase 1 clinical data in the paper highlight the activity and tolerability using intermittent dosing of milademetan across a range of tumor types including dedifferentiated liposarcoma (DD LPS), which represented the proportion of patients enrolled in the study (n=53). All liposarcoma patients enrolled in the Phase 1 trial exhibited the DD LPS subtype; Among DD LPS patients in the Phase 1 trial, median progression-free survival (mPFS) outcomes were maintained with intermittent dosing schedules (once daily [qd] on days 1-3 and 15-17 every 28 days; eg, 3/14 days) compared with extended (qd on days 1-21) /continuous (qd on days 1-28) schedules: mPFS of patients across all doses/schedules (n=53): 7.2 months; mPFS of patients with 260 mg qd 3/14 intermittent schedule (n=16): 7.4 months; mPFS of previously treated patients with 260 mg qd 3/14 intermittent schedule (n=11): 8.0 months; mPFS of treatment-naïve patients in all doses/schedules (n=17): 14.6 months.

Although all tested DD LPS patients had MDM2 gene amplification (n=22), mPFS in DD LPS patients did not differ by levels of key biomarkers including MDM2 or CDK4 copy number or by mRNA expression levels of MDM2, CDK4, or MDM4. Preliminary single-agent activity with milademetan in DD LPS prompted the ongoing, randomized Phase 3 MANTRA trial (NCT04979442), with topline data anticipated in the first quarter of 2023.