Phase I study of olaparib plus gemcitabine in patients with advanced solid tumours and comparison with gemcitabine alone in patients with locally advanced/metastatic pancreatic cancer

Background: Olaparib (Lynparza™) is an oral poly(adenosine diphosphate [ADP]-ribose) polymerase inhibitor that induces synthetic lethality in cancers with homologous recombination defects. Patients and methods: In this phase I, dose-escalation trial, patients with advanced solid tumours received olaparib (50-200 mg capsules b.i.d.) continuously or intermittently (days 1-14, per 28-day cycle) plus gemcitabine [i.v. 600-800 mg/m²; days 1, 8, 15, and 22 (cycle 1), days 1, 8, and 15 (subsequent cycles)] to establish the maximum tolerated dose. A separate dose-escalation phase evaluated olaparib in tablet formulation (100 mg o.d./b.i.d.; days 1-14) plus gemcitabine (600 mg/m²). In an expansion phase, patients with genetically unselected locally advanced or metastatic pancreatic cancer were randomised 2 : 1 to the tolerated olaparib capsule combination dose or gemcitabine alone (1000 mg/m²). Results: Sixty-six patients were treated [dose-escalation phase, n = 44 (tablet cohort, n = 12); dose-expansion phase, n = 22 (olaparib plus gemcitabine, n = 15; gemcitabine alone, n = 7)]. In the dose-escalation phase, four patients (6%) experienced dose-limiting toxicities (raised alanine aminotransferase, n = 2; neutropenia, n = 1; febrile neutropenia, n = 1). Grade ≥3 adverse events were reported in 38/47 patients (81%) treated with olaparib capsules plus gemcitabine; most common were haematological toxicities (55%). Tolerated combinations were olaparib 100 mg b.i.d. capsule (intermittently, days 1-14) plus gemcitabine 600 mg/m² and olaparib 100 mg o.d. tablet (intermittently, days 1-14) plus gemcitabine 600 mg/m². There were no differences in efficacy observed during the dose-expansion phase. Conclusions: Olaparib 100 mg b.i.d. (intermittent dosing; capsules) plus gemcitabine 600 mg/m² is tolerated in advanced solid tumour patients, with no unmanageable/unexpected toxicities. Continuous dosing of olaparib or combination with gemcitabine at doses >600 mg/m² was not considered to have an acceptable tolerability profile for further study.