Phase I study to assess the effect of adavosertib (AZD1775) on the pharmacokinetics of substrates of CYP1A2, CYP2C19, and CYP3A in patients with advanced solid tumors.

Purpose: Adavosertib may alter exposure to substrates of the cytochrome P450 (CYP) family of enzymes. This study assessed its effect on the pharmacokinetics of a cocktail of probe substrates for CYP3A (midazolam), CYP2C19 (omeprazole), and CYP1A2 (caffeine).

Methods: Period 1: patients with locally advanced or metastatic solid tumors received 'cocktail': caffeine 200 mg, omeprazole 20 mg, and midazolam 2 mg (single dose); period 2: after 7- to 14-day washout, patients received adavosertib 225 mg twice daily on days 1-3 (five doses), with cocktail on day 3. After cocktail alone or in combination with adavosertib administration, 24-h pharmacokinetic sampling occurred for probe substrates and their respective metabolites paraxanthine, 5-hydroxyomeprazole (5-HO), and 1'-hydroxymidazolam (1'-HM). Safety was assessed throughout.

Results: Of 33 patients (median age 60.0 years, range 41-83) receiving cocktail, 30 received adavosertib. Adavosertib co-administration increased caffeine, omeprazole, and midazolam exposure by 49%, 80%, and 55% (AUC), respectively; AUC increased by 61%, 98%, and 55%. Maximum plasma drug concentration (C) increased by 4%, 46%, and 39%. Adavosertib co-administration increased 5-HO and 1'-HM exposure by 43% and 54% (AUC) and 49% and 58% (AUC0-t), respectively; paraxanthine exposure was unchanged. Adavosertib co-administration decreased C for paraxanthine and 5-HO by 19% and 7%; C increased by 33% for 1'-HM. After receiving adavosertib, 19 (63%) patients had treatment-related adverse events (six [20%] grade ≥ 3).

Conclusion: Adavosertib (225 mg bid) is a weak inhibitor of CYP1A2, CYP2C19, and CYP3A.

Clinicaltrials: GOV: NCT03333824.