First-in-human trial of novel oral PARP inhibitor BMN 673 in patients with solid tumors.

Abstract

2580 Background: BMN 673 is the most potent and specific inhibitor of PARP1/2 in clinical development (IC50<1nM). In tumors genetically dependent on DNA repair by homologous recombination PARP inhibition induces synthetic lethality. Methods: Pharmacokinetics (PK), pharmacodynamics (PD), safety and anti-tumor activity of BMN 673 were evaluated in a 2-stage dose-escalation study with 3-6 patients (pts)/dose level. In dose escalation (Stage 1) cycle 1 was 6 wks, with drug taken on days 1 and 8-35, for PK and PD assays, followed by daily continuous dosing in 4-wk cycles. Stage 2 (expansion at MTD) recruits pts with tumors defective in DNA repair: Ewing sarcoma, small cell lung cancer or tumors associated with BRCA mutation (mut). Results: 39 pts (33F/6M) were enrolled in 9 cohorts from 25 to 1100 µg/d that defined a MTD of 1000 µg/d. Median (range) age was 58 (19-81), PS 0 (0-1) and # of prior therapies 4 (1-13). Tumors (# with deleterious BRCA 1/2 mut) included 23 ovarian/primary peritoneal (17); 8 breast (6); 3 pancreas; 2 colon; 1 prostate (1), and 1 mullerian carcinosarcoma. 17 and 8 pts had BRCA 1 and 2 mut, respectively. Dose-limiting thrombocytopenia occurred in 1/6 and 2/5 pts at 900 and 1100 µg/d, respectively. Potentially-related adverse events in >10% of pts (# grade 1 and 2/grade 3 and 4) included fatigue (10/0); nausea (10/0); flatulence (4/0); anemia (5/2); neutropenia (4/3); thrombocytopenia (1/3); and grade 1 alopecia (10). Inhibition of PARP activity in PBMCs was observed at doses ≥ 100 µg/d. BMN 673 plasma concentrations peaked 1-2 hrs post-dose; exposure increased dose proportionally. Steady state plasma concentrations were reached by the end of the 2nd week of daily dosing; mean Cmax: 0.30 - 25.4 ng/mL and AUC0-24: 3.96 - 203 ng-hr/mL across the 25 to 1100 µg/d dose range after 28d of daily dosing. RECIST and/or CA-125 responses occurred at doses ≥ 100 µg/d in 11/17 BRCA carrier ovarian/peritoneal cancer pts. Objective responses occurred in 2/6 BRCA-carrier breast cancer pts. Conclusions: BMN 673 is well tolerated with impressive anti-tumor activity in pts with BRCA mut with a single agent recommended Phase II trial dose of 1000 µg/d due to dose-limiting thrombocytopenia. Clinical trial information: NCT01286987.