Combination Olaparib and Temozolomide in Relapsed Small Cell Lung Cancer

Small-cell lung cancer (SCLC) is an aggressive malignancy in which inhibitors of PARP have modest single-agent activity. We performed a phase I/II trial of combination olaparib tablets and temozolomide (OT) in patients with previously treated SCLC. We established a recommended phase II dose of olaparib 200 mg orally twice daily with temozolomide 75 mg/m2 daily, both on days 1 to 7 of a 21-day cycle, and expanded to a total of 50 patients. The confirmed overall response rate was 41.7% (20/48 evaluable); median progression-free survival was 4.2 months [95% confidence interval (CI), 2.8–5.7]; and median overall survival was 8.5 months (95% CI, 5.1–11.3). Patient-derived xenografts (PDX) from trial patients recapitulated clinical OT responses, enabling a 32-PDX coclinical trial. This revealed a correlation between low basal expression of inflammatory-response genes and cross-resistance to both OT and standard first-line chemotherapy (etoposide/platinum). These results demonstrate a promising new therapeutic strategy in SCLC and uncover a molecular signature of those tumors most likely to respond. SIGNIFICANCE: We demonstrate substantial clinical activity of combination olaparib/temozolomide in relapsed SCLC, revealing a promising new therapeutic strategy for this highly recalcitrant malignancy. Through an integrated coclinical trial in PDXs, we then identify a molecular signature predictive of response to OT, and describe the common molecular features of cross-resistant SCLC.