Concomitant intake of abiraterone acetate and food to increase pharmacokinetic exposure: real life data from a therapeutic drug monitoring programme

Aim: Abiraterone acetate is approved for the treatment of metastatic prostate cancer. At the currently used fixed dose of 1000 mg once daily in modified fasting state, 40% of patients do not reach the efficacy threshold of a minimum plasma concentration (C_min) ≥ 8.4 ng/mL and are thereby at risk of decreased treatment efficacy. This study aims to evaluate whether pharmacokinetically (PK) guided abiraterone acetate dosing with a food intervention is feasible and results in an increased percentage of patients with concentrations above the target. Methods: Patients starting regular treatment with abiraterone acetate in modified fasting state were included. Pharmacokinetic analysis was performed 4, 8 and 12 weeks after start of treatment and every 12 weeks thereafter. In case of C_min < 8.4 ng/mL and acceptable toxicity, a PK-guided intervention was recommended. The first step was concomitant intake of abiraterone acetate with a light meal or a snack. Results: In total, 32 evaluable patients were included, of which 20 patients (63%) had a C_min < 8.4 ng/mL at a certain time point during treatment. These patients were recommended to take abiraterone acetate concomitantly with food, after which C_min increased from 6.9 ng/mL to 27 ng/mL (p < 0.001) without additional toxicities. This intervention led to adequate exposure in 28 patients (87.5%). Conclusion: Therapeutic drug monitoring of abiraterone was applied in clinical practice and proved to be feasible. Concomitant intake with food resulted in a significant increase in C_min and offers a cost-neutral opportunity to optimise exposure in patients with low C_min.