Alectinib exposure-response (ER) in ALK-inhibitor naïve ALK-positive NSCLC patients: Pooled analysis across phase III studies.

Abstract

e20575 Background: Alectinib superiority to crizotinib has been demonstrated in ALK-inhibitor naïve ALK-positive NSCLC patients (pts) in Phase III studies conducted in Japanese (J-ALEX; JapicCTI-132316) pts receiving alectinib 300 mg BID and global (ALEX; NCT02075840) and Asian (ALESIA; NCT02838420) pts receiving alectinib 600mg BID. ER analyses are undertaken to confirm the appropriate alectinib dosing regimen for the global population. Methods: A previous population PK analysis (Hsu et al, ASCO 2016) assessed PK of alectinib and major metabolite, M4, to identify factors influencing PK variability. ER analyses across the 3 Phase III studies investigated the relationship between alectinib and progression-free survival (PFS) by a Cox proportional hazards (CPH) analysis. PK simulations for alectinib 300 mg and 600 mg BID doses were conducted to determine the proportion of pts falling above and below an identified optimal PK threshold for PFS. ER for key safety events were investigated for alectinib 600 mg BID using logistic regression. Results: Alectinib PK is influenced only by body weight and not by race/ethnicity. CPH analysis demonstrated a statistically significant relationship between alectinib exposure and PFS across the 3 Phase III studies, with an improved PFS above an identified optimal PK threshold (Table). PK simulations indicate 49% and 7% of global alectinib treated patients would fall below the optimal PK threshold for 300 and 600mg BID, respectively. Alectinib 600mg BID ensures a distribution of exposures that maximize the PFS benefit while lower alectinib doses/exposures could result in reduced efficacy. Baseline tumor size (BSIZ) was shown to negatively impact PFS with larger BSIZ seen in global pts. No significant exposure-safety relationships were identified for alectinib 600mg BID. Conclusions: Alectinib 600mg BID is the most appropriate dose in the global ALK-inhibitor naïve population. Clinical trial information: NCT02075840; JapicCTI-132316; NCT02838420. [Table: see text]