Lung cancer (Amsterdam, Netherlands), Volume 171, 25 4 2022, Pages 97-102 Pharmacokinetic boosting of osimertinib with cobicistat in patients with non-small cell lung cancer: The OSIBOOST trial. van Veelen A, Gulikers J, Hendriks LEL, Dursun S, Ippel J, Smit EF, Dingemans AC, van Geel R, Croes S

Introduction

Exposure to osimertinib, a third generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) for treatment of non-small cell lung cancer (NSCLC) and a sensitizing EGFR mutation, can be substantially below average. We evaluated whether plasma levels could be boosted by co-administration of cobicistat, a strong Cytochrome P450 3A-inhibitor.

Methods

This was a pharmacokinetic, proof-of-concept clinical trial (the OSIBOOST trial, NCT03858491). NSCLC-patients with osimertinib were eligible if their steady state osimertinib plasma trough concentration was low (≤195 ng/mL). On day 1, the area under the plasma curve (AUC0-24,ss) of osimertinib and its metabolite (AZ5104) was calculated using a limited sampling strategy (four samples). Cobicistat co-treatment (150 mg, once daily) was started on day 2. Between day 22-26, a second AUC was determined. Cobicistat dose could be escalated if the osimertinib trough concentration was still ≤ 195 ng/mL, in the absence of toxicity. Primary endpoint was the increase in osimertinib exposure, secondary endpoint was toxicity. Cobicistat could be continued during the expanded access phase, with follow-up (2-4 months) of the boosting effect.

Results

The mean baseline osimertinib trough concentration for the eleven enrolled patients was 154 ng/mL. In all patients, cobicistat addition led to an increase in osimertinib exposure. Mean increase in total AUC0-24ss (AUC osimertinib + AUC AZ5104) was 60%, (range 19%-192%). The boosting effect was consistent over time. No grade ≥ 2 toxicity was observed.

Conclusion

Pharmacokinetic boosting of osimertinib with cobicistat in patients with NSCLC is feasible without increasing toxicity, although the degree of boosting is variable.

Lung Cancer. 2022 7;171:97-102