A randomized, double-blind, placebo-controlled phase Ib/II study of ralimetinib, a p38 MAPK inhibitor, plus gemcitabine (G) and carboplatin (C) versus GC for women with recurrent platinum-sensitive ovarian cancer

5537 Background: p38 mitogen-activated protein kinase (MAPK) regulates cytokine production in the tumor microenvironment and enables therapeutic resistance of cancer cells. Ralimetinib (R) is a selective small-molecule inhibitor of p38α and p38β MAPKs. Methods: Main inclusion criteria: ≥18 y; recurrent platinum-sensitive epithelial ovarian, fallopian tube, or primary peritoneal, cancer after first-line treatment. Phase (Ph)1b was to determine the recommended Ph2 dose (RP2D) of R administered 12-hourly (Q12H) on Days 1-10 (21-day cycle [Q21D]) in combination with gemcitabine (G: 1000 mg/m2 on Days 3 and 10) and carboplatin (C: AUC 4 on Day 3) for 6 cycles. In Ph2, patients (pts) were randomized double-blind, 1:1 to RP2D R+GC or placebo (P)+GC, for 6 cycles, followed by R 300 mg Q12H or P on Days 1-14, Q28D until disease progression. The stratified log-rank test compared progression-free survival (PFS; primary endpoint) between treatment groups in Ph2, at a 1-sided α level of 0.2. ClinicalTrials.gov, NCT01663857. Results: 118 pts received ≥1 dose of R or P (safety population); 8 in Ph1b and 110 in Ph2 (R+GC N = 58; P+GC N = 52). The RP2D for R in combination with GC was 200 mg Q12H. The study met its primary objective (median PFS: R+GC 10.3 mo vs P+GC 7.9 mo; HR = 0.773, 2-sided p = 0.246). The secondary objectives of median overall survival (R+GC 29.2 mo vs P+GC 25.1 mo; HR = 0.827, p = 0.469) or overall response rate (R+GC 46.6% vs P+GC 46.2%; p = 0.967) were not statistically significant, and 32.4% vs 25.0% of pts had normalized CA125 at the end of cycle 6. Most pts (safety population) experienced ≥1 Grade 3/4 treatment-emergent adverse event (TEAE: R+GC 63/66 [95.5%]; P+GC 48/52 [92.3%]). Decreased neutrophil count (60.6% vs 76.9%), platelet count (43.9% vs 38.5%), and white blood cell count, (30.3% vs 26.9%), anemia (22.7% vs 25.0%), and increased alanine aminotransferase (ALT) (19.7% vs 3.8%) were the Grade 3/4 TEAEs in ≥10% of pts in the R+GC and P+GC arms, respectively. Conclusions: Addition of ralimetinib to GC resulted in modest improvements in PFS. Grade 3/4 elevated ALT was more common in the ralimetinib arm. Clinical trial information: NCT01663857.