Adding the poly (ADP-ribose) polymerase (PARP) inhibitor veliparib to platinum doublet chemotherapy modestly improved progression-free survival in a randomized, placebo-controlled, phase 2 trial of 128 patients with extensive-stage non–small cell lung cancer.
Improved progression-free survival (PFS) “did not translate into reduction in overall mortality for patients treated with veliparib. However, the improvement in the point estimate of PFS was quite modest at 6.1 months, compared with 5.5 months [in the placebo control arm],” wrote, of Emory University, Atlanta, together with his coinvestigators in the .
Preclinical studies suggest that veliparib helps potentiate standard chemotherapy of non–small cell lung cancer (NSCLC), but clinical trials have yielded mixed results for PARP inhibition in this cancer. Patients in this study had untreated, extensive-stage NSCLC and an Eastern Cooperative Oncology Group performance status of 0 or 1. They received four 3-week cycles of cisplatin-etoposide (75 mg/m2 intravenously on day 1 and 100 mg/m2 on days 1-3) plus either veliparib (100 mg orally twice per day on days 1-7) or placebo.
Grade 3 or higher lymphopenia and neutropenia were more common in the veliparib arm but did not reduce treatment delivery. After a median follow-up time of 18.5 months, overall response rate was 72% in the veliparib arm versus 66% in the control arm (P =.57). Median overall survival times were 10.3 months and 8.9 months, respectively (hazard ratio, 0.83; P = .17).
The unstratified HR for PFS favored the veliparib-doublet arm but did not reach statistical significance (0.75; P = .06). After stratifying patients by sex and serum lactate dehydrogenase levels, the HR for PFS favored veliparib-doublet chemotherapy (0.63; P = .01). However, veliparib showed a much stronger effect in the subgroup of men with abnormal lactate dehydrogenase levels (adjusted HR, 0.34; P less than .001), which violated the “proportional hazards within strata assumption” on which this model was based, rendering the overall stratified HR uninterpretable, the researchers wrote.
They added that, before pursuing a larger definitive clinical trial, they await results from the ongoing phase 2, in which patients with extensive-stage NSCLC are receiving platinum doublet therapy with carboplatin-etoposide plus either veliparib or placebo.
Funders included the Eastern Cooperative Oncology Group–American College of Radiology Imaging Network Cancer Research Group and the National Cancer Institute. Dr. Owonikoko reported ties to Novartis, Astellas Pharma, Celgene, and several other pharmaceutical companies.
SOURCE: Owonikoko TK et al. J Clin Oncol. 2018 Dec 5. .