Pharmacokinetic boosting of olaparib: Study protocol of a multicentre, open-label, randomised, non-inferiority trial...

Pharmacokinetic (PK) boosting is the intentional use of a drug-drug interaction to enhance systemic drug exposure. PK boosting of the anticancer drug olaparib, a CYP3A-substrate, has the potential to reduce PK variability, side effects and financial burden associated with this drug. After establishing adequate pharmacokinetic exposure with boosting in the PROACTIVE-A study, the PROACTIVE-B study is designed to evaluate non-inferiority for both efficacy and toxicity of the boosted therapy compared to the standard monotherapy of olaparib.

The PROACTIVE-B study is a nationwide, multicentre, prospective, randomized, non-inferiority trial. A total of 142 patients (128 patients with BRCA+, high-grade, FIGO III/IV ovarian cancer who receive olaparib as maintenance therapy; 14 patients with other approved indications for olaparib) who start olaparib treatment in line with the drug label will be randomized between the standard monotherapy of olaparib 300 mg twice daily (BID) and the boosted therapy of olaparib 100 mg BID with cobicistat 150 mg BID. The co-primary objectives are tolerability (dose reductions due to toxicity), and efficacy (progression-free survival at 12 months) in the ovarian cancer population. Secondary objectives include health status (EQ-5D-5L), patient satisfaction (Cancer Therapy Satisfaction Questionnaire (CTSQ)), and cost effectiveness using the institute for Medical Technology Assessment (iMTA) Productivity Cost Questionnaire (iPCQ) and iMTA Medical Consumption Questionnaire (iMCQ).

PK boosting of olaparib is a potentially valuable strategy to reduce the olaparib dose and the variability in olaparib exposure with fewer side effects. Moreover, the lower costs related to the boosted therapy contribute to a durable and accessible anticancer treatment for all patients.

The PROACTIVE study has been published at ClinicalTrials.gov under NCT05078671 on October 14, 2021 and at EudraCT under 2021-004032-28 on August 24, 2021.