A randomized discontinuation phase II trial of ridaforolimus in non-small cell lung cancer (NSCLC) patients with KRAS mutations.

Abstract

7531 Background: Mutations in KRAS are present in ~25% of patients with advanced NSCLC. Preclinical data support the role of mammalian target of rapamycin (mTOR) in KRAS mediated oncogenesis. Ridaforolimus is an inhibitor of mTOR which has been shown to have efficacy in advanced endometrial cancer and soft tissue sarcoma. Everolimus, another mTOR inhibitor was previously evaluated in unselected patients with advanced NSCLC and found to have a response rate <5%. We hypothesized that by enrichment for patients with NSCLC and KRAS mutations, treatment with ridaforolimus would be associated with prolonged stable disease relative to available standard treatments for NSCLC. Methods: Patients with stage IIIB/IV non-small cell lung cancer with KRAS mutation who had received prior chemotherapy for NSCLC began treatment with oral ridaforolimus 40 mg once daily on a 5 day/week schedule. After 8 weeks, patients with >30% tumor shrinkage remained on ridaforolimus and patients with >20% tumor growth discontinued treatment. Patients with stable disease were randomized 1:1 to placebo or ridaforolimus. The primary endpoint of the study was progression-free survival (PFS) after randomization. Results: 79 patients were enrolled (40 women, median age 58 [range 28-85]). The overall response rate (CR+PR) at 8 weeks was 1/79 (1%, 95% CI 0-7%).  28 patients with stable disease at 8 weeks were randomized to ridaforolimus or placebo.  Median PFS based on investigator assessment from randomization was significantly longer with ridaforolimus (4 months) than placebo (2 months, p=0.013, HR 0.36).  Median OS from randomization was 18 months in the ridaforolimus treated arm and 5 months in the placebo treated group, (HR 0.46, p=0.09).  The most common grade ≥3 adverse events were fatigue (10%), mucositis/stomatitis (10%), pneumonia (10%), dyspnea (9%), diarrhea (6%), and hyperglycemia (6%). Conclusions: In patients with KRAS mutant NSCLC who had stable disease after 8 weeks of ridaforolimus, ridaforolimus was associated with prolonged progression-free survival.  Further evaluation of ridaforolimus in this patient population is warranted.