Durvalumab With or Without Tremelimumab in Combination With Chemoradiotherapy in Patients With Limited-Stage SCLC: Results from the Phase 1 CLOVER Study

Introduction: The phase 1 CLOVER study (NCT03509012) evaluated durvalumab with or without tremelimumab in combination with concurrent chemoradiotherapy (cCRT) in patients with advanced solid tumors; here, we report findings from the limited-stage SCLC (LS-SCLC) cohort. Methods: Patients with pathologically confirmed LS-SCLC whose disease could be encompassed within a radical radiation portal received durvalumab (arms 1 and 2) or durvalumab plus tremelimumab (arms 3 and 4) in combination with cCRT (cisplatin-etoposide and either standard radiotherapy [arms 1 and 3] or hyperfractionated radiotherapy [arms 2 and 4]). The primary end point was safety and tolerability. Preliminary efficacy and candidate biomarkers of response were assessed. Results: Overall, 33 patients were enrolled: 12 in arm 1, 12 in arm 2, six in arm 3, and three in arm 4. No patients had dose-limiting toxicity. Grade 3 or 4 adverse events occurred in 79.2% of patients from arms 1 and 2 and 88.9% from arms 3 and 4; the most common were hematologic events. In arms 1, 2, 3, and 4, objective response rate was 66.7%, 66.7%, 83.3%, and 100.0%, disease control rate was 90.9%, 100.0%, 100.0%, and 100.0% at 18 weeks and 72.7%, 83.3%, 100.0%, and 100.0% at 48 weeks, and the median progression-free survival (PFS) (95% confidence interval) was 9.2 months (5.3‒not estimable [NE]), 16.6 months (8.4–NE), not reached (16.6–NE), and 9.3 months (6.3–NE), respectively. In exploratory biomarker analyses, no difference in PFS by programmed cell death-ligand 1 expression level was observed; median PFS was numerically greater in high versus low tumor inflammation signature and CD8A expression subgroups. Conclusions: Durvalumab in combination with cCRT, with or without tremelimumab, was tolerable and active in patients with LS-SCLC.