Rain Therapeutics Announces a Phase 1 Trial Update for the MDM2 Inhibitor, RAIN-32, at the 32nd EORTC-NCI-AACR Virtual Symposium

Late-breaking presentation highlights progression-free survival of 8 months and favorable safety in patients with well-differentiated/de-differentiated liposarcoma

Findings support further evaluation of RAIN-32 in liposarcoma and additional tumors leveraging a novel dosing regimen

NEWARK, Calif., Oct. 26, 2020 (GLOBE NEWSWIRE) -- Rain Therapeutics Inc., a privately-held, clinical stage biotechnology company focused on targeted therapies for patients with cancer, today announced an update on data from the Phase 1 clinical trial of RAIN-32 (milademetan), an oral MDM2 inhibitor, during a late-breaker oral presentation at the 32nd EORTC-NCI-AACR Virtual Symposium on October 25, 2020.

The presentation highlighted the enhanced safety profile of RAIN-32, enabled by its unique drug-like properties, when administered on an intermittent dosing schedule as well as prolonged progression-free survival in patients with well-differentiated/de-differentiated (WD/DD) liposarcoma (LPS).

"We are pleased to highlight these positive data," said Avanish Vellanki, co-founder and chief executive officer of Rain. "These analyses of the Phase 1 study demonstrate the opportunity for RAIN-32 to provide safe and effective MDM2 inhibition. We look forward to further evaluating RAIN-32 both in liposarcoma, as well as in other solid tumor indications characterized by MDM2 gene amplification with this dosing regimen."

The Phase 1 dose escalation and expansion study evaluated RAIN-32 across four dose schedules in patients (n=107) with liposarcoma, solid tumors or lymphomas. Key findings from the oral presentation include:

• An intermittent dose schedule of QD 3/14 x 2 of a 28-day cycle (Schedule D) allowed the highest MTD for RAIN-32 (260 mg) versus the more continuous dose schedules (Schedules A, B and C)
• RAIN-32 dosed on Schedule D at 260 mg exhibited an improved safety profile versus the more continuous dosing schedules:
  
  --  Incidence of all ≥ Gr 3 TEAEs in the 260 mg Schedule D cohort (n=20) fell to 20% versus 55% in the Schedules A, B, and C cohorts (n=78)
  
  --  Incidence of ≥ Gr 3 thrombocytopenia, neutropenia and anemia, representing the predominant dose-limiting toxicities of MDM2 inhibition, fell to 15%, 5% and 0% in Schedule D from 35%, 18% and 10% in the other schedules, respectively
  
  --  No Gr 4/5 toxicities were observed at 260 mg dose in Schedule D
• The Schedule D regimen also conferred numerically improved progression-free survival as compared to the continuous dose schedules
  
  --  In 17 patients evaluable for efficacy receiving Schedule D at doses ≤ 260 mg, median progression-free survival was 8.0 months
• The 260 mg Schedule D regimen has been identified as the dose and schedule for further studies
• Tumor shrinkage and objective responses were also observed in selected non-liposarcoma patients with MDM2 gene amplification, indicating potential for future agnostic clinical trials using biomarker selection
  
  

Rain intends to initiate subsequent clinical studies of RAIN-32 in liposarcoma and other tumors in the second half of 2021.

About RAIN-32

RAIN-32 has been evaluated in patients with various solid tumors, acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) and has received Orphan Drug Designation for the treatment of liposarcoma. RAIN-32 also has been evaluated in continuous and intermittent dose schedules that may offer a differentiated tolerability profile as compared to other MDM2 programs.

A separate clinical study for RAIN-32 is ongoing to evaluate safety and efficacy in patients with FLT3-ITD AML in combination with the FLT3 inhibitor, quizartinib. In addition, multiple investigator-sponsored studies are being conducted by MD Anderson Cancer Center (MDACC) as well as National Cancer Center Hospital (NCCH) in Tokyo, Japan.

About Rain Therapeutics Inc.

Rain Therapeutics Inc. is a privately held biotechnology company developing targeted therapies for patients with cancer. Rain's lead program is RAIN-32, a small molecule MDM2 inhibitor for patients with well-differentiated/de-differentiated liposarcoma, and other indications exhibiting MDM2 gene amplification or overexpression. RAIN-32 has completed clinical trials in certain solid tumors and hematological malignancies and has received FDA Orphan Drug Designation for patients with liposarcoma. Tarloxotinib, a hypoxia-activated pan-HER inhibitor is in clinical trials for patients with non-small cell lung cancer with HER2 activating mutations as well as a tumor-agnostic cohort for patients with NRG1, EGFR, HER2, and HER4 fusions. Rain is also developing a potential first-in-class inhibitor of RAD52 in the DNA Damage Response (DDR) pathway as a synthetic lethal strategy for tumors with BRCA1/2 mutations. For more information, visit www.rainthera.com.

Media Contact for Rain

Cait Williamson, PhD

LifeSci Communications

+1.646.751.4366

cait@lifescicomms.com