P-glycoprotein and breast cancer resistance protein restrict brigatinib brain accumulation and toxicity, and, alongside CYP3A, limit its oral availability.

Brigatinib is an FDA-approved oral anaplastic lymphoma kinase (ALK) inhibitor for treatment of metastatic non-small cell lung cancer (NSCLC). Using genetically modified mouse models, we investigated the roles of the multidrug efflux transporters ABCB1 and ABCG2, and the multispecific drug-metabolizing enzyme CYP3 A in plasma pharmacokinetics and tissue distribution of brigatinib. In vitro, brigatinib was exceptionally well transported by human ABCB1 and mouse Abcg2, and efficiently by human ABCG2. Following oral brigatinib administration (10 mg/kg), brain accumulation was dramatically increased in Abcb1a/1b-/- (19.3-fold) and Abcb1a/1b;Abcg2-/-(41.8-fold), but not in single Abcg2-/- mice compared to wild-type mice. Brigatinib testis accumulation showed qualitatively similar behavior. mAbcb1a/1b and mAbcg2 together restricted systemic exposure of brigatinib: with both systems absent oral availability increased 1.9-fold. Coadministration of elacridar, an ABCB1/ABCG2 inhibitor, caused a pronounced increase (36-fold) in brain-to-plasma ratios of brigatinib, approaching the levels seen in Abcb1a/1b;Abcg2-/- mice. Unexpectedly, lethal toxicity of oral brigatinib was observed in mice with genetic knockout or pharmacological inhibition of mAbcb1a/1b and mAbcg2, indicating a pronounced protective role for these transporters. In Cyp3a-/- mice, brigatinib plasma exposure increased 1.3-fold, and was subsequently 1.8-fold reduced by transgenic overexpression of human CYP3 A4 in liver and intestine. The relative tissue distribution of brigatinib, however, remained unaltered. ABCB1 and ABCG2 thus limit brain accumulation, toxicity, and systemic exposure of brigatinib, whereas CYP3 A also markedly restricts its oral availability. Unexpected toxicities should therefore be carefully monitored when brigatinib is coadministered with ABCB1/ABCG2 inhibitors in patients. Collectively, these insights may support the clinical application of brigatinib.