Efficacy and Safety of Niraparib as Maintenance Treatment in Patients With Extensive-Stage SCLC After First-Line Chemotherapy: A Randomized, Double-Blind, Phase 3 Study

Introduction: ZL-2306-005 is a randomized, double-blind, multicenter phase 3 study evaluating the efficacy and safety of niraparib, a poly(adenosine diphosphate-ribose) polymerase inhibitor, as first-line maintenance therapy in Chinese patients with platinum-responsive, extensive-stage SCLC (ES-SCLC). Methods: Patients with complete response (CR) or partial response (PR) to standardized, platinum-based first-line chemotherapy were randomized 2:1 to receive niraparib or placebo (300 mg [baseline body weight > 77 kg, platelet count > 150,000/mL] or 200 mg) once daily until progression or unacceptable toxicity. Primary end points were progression-free survival (PFS) (blinded independent central review) and overall survival (sample size planned: 591 patients). Secondary end points included investigator evaluated PFS and safety. Results: ZL-2306-005 was terminated early owing to ES-SCLC treatment landscape changes (data cutoff: March 20, 2020). During July 2018-February 2020, a total of 185 of 272 patients screened were randomized (niraparib: n = 125 [CR = 1, PR = 124]; placebo: n = 60 [CR = 1, PR = 59]). Median (95% confidence interval [CI]) PFS (blinded independent central review) was 1.54 months (1.41-2.69, niraparib) and 1.36 months (1.31-1.48, placebo); hazard ratio (HR) = 0.66 (95% CI: 0.46-0.95, p = 0.0242). Median overall survival was 9.92 months (9.33-13.54, niraparib) and 11.43 months (9.53- not estimable, placebo); HR = 1.03 (95% CI: 0.62-1.73, p = 0.9052). Median investigator-evaluated PFS was 1.48 months (1.41-2.56, niraparib) and 1.41 months (1.31- 2.00, placebo); HR = 0.88 (95% CI: 0.61-1.26; p = 0.4653). Grade greater than or equal to 3 adverse events occurred in 34.4% (niraparib) and 25.0% (placebo) of patients. Conclusions: ZL-2306-005 did not reach primary end points. Nevertheless, niraparib as maintenance therapy modestly improved PFS in patients with platinum-responsive ES-SCLC, with acceptable tolerability profile and no new safety signal. (c) 2021 International Association for the Study of Lung Cancer. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4.0/).