An exposure–safety analysis to support the dosage of the novel AKT inhibitor capivasertib

This study aimed to evaluate capivasertib exposure–response relationships for clinical safety events to support dosage selection.

Data from 277 patients with solid tumors participating in three phase 1 studies were analyzed. Capivasertib 80–800 mg was administered as monotherapy orally twice daily (BID) on continuous or intermittent (4 days on, 3 days off [4/3] or 2 days on, 5 days off [2/5]) schedules. Relationships between exposure related metrics (dose, weekly dose, AUC, AUC_PWD, C_max, and C_min) and probability of safety endpoints (adverse event [AE] leading to dose discontinuation, AE leading to dose modification, serious AE [SAE], AE grade ≥ 3, AE grade ≥ 1, diarrhea AE grade ≥ 2, rash AE grade ≥ 2, hyperglycemia AE grade ≥ 3 and increased blood glucose > 13.9 mmol/L) were evaluated by logistic regression.

Significant exposure–response relationships were identified for all safety endpoints evaluated, except for AE grade ≥ 1. The analysis suggested that most of the safety endpoints are driven by the total weekly exposure, whereas glucose elevations are driven by the exposure achieved within a dosing interval. The probability of experiencing an AE leading to dose discontinuation, AE leading to dose modification, SAE, AE grade ≥ 3, diarrhea or rash were lower with the 480 mg BID [4/3] schedule than with the 320 mg BID continuous schedule.

Significant exposure–response relationships were identified for safety endpoints when capivasertib was administered to patients with solid tumors suggesting that the intermittent [4/3] schedule is better tolerated than the continuous schedule due to lower total weekly exposure.