LODESTAR: A Single-Arm Phase II Study of Rucaparib in Solid Tumors With Pathogenic Germline or Somatic Variants in Homologous Recombination Repair Genes

Abstract

Purpose: To explore poly (ADP-ribose) polymerase inhibitor utility across solid tumors and identify biomarkers that predict sensitivity.

Patients and methods: This single-arm phase II study assessed rucaparib monotherapy in patients with solid tumors and pathogenic variants (PVs) in BRCA1, BRCA2, PALB2, RAD51C, and RAD51D (cohort A) or BARD1, BRIP1, FANCA, NBN, and RAD51B (cohort B). The primary end point was overall response rate (ORR) in cohort A. Secondary end points included disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety. A scar-based homologous recombination deficiency signature (HRDsig) and platinum sensitivity status were explored post hoc.

Results: Fifty-one patients in cohort A and 12 in cohort B were evaluable for efficacy. ORR of cohort A was 18% (95% CI, 10 to 30). A significantly higher ORR was observed with HRDsig+ tumors compared with HRDsig- tumors (32%; 95% CI, 15 to 54 v 0%; 95% CI, 0 to 14; P < .01). In the entire study population, DCR was 65% (95% CI, 53 to 76), median PFS (mPFS) 5.5 months (95% CI, 3.68 to 7.82), and median OS 12.1 months (95% CI, 10.6 to inferred). PFS and hazard of death from any cause was significantly better for platinum-sensitive tumors (mPFS: 7.8 months v 3.5 months; P = .02; hazard ratio, 0.11 [95% CI, 0.02 to 0.55]). Tumor histology was not independently predictive of outcome. Tumors with PVs in cohort A genes were more likely to be HRDsig+ than tumors with PVs in cohort B genes. Analysis of a large commercial database showed that in noncanonical tumors with BRCA PVs, 30.2% were HRDsig+.

Conclusion: Rucaparib has activity in HRDsig+ solid tumors with PVs in homologous recombination repair genes, regardless of histology. Platinum sensitivity correlated with improved outcomes.

Trial registration: ClinicalTrials.gov NCT04171700.