Dabrafenib is a BRAF kinase inhibitor, which inhibits BRAF V600 mutation-positive cancer cell growth. It is an FDA approved drug indicated for the treatment of adult patients with unresectable or metastatic melanoma with a BRAF V600 mutation and as combination therapy since recently also for metastatic non-small cell lung cancer harboring BRAF V600E mutations . Despite improved response rates and overall survival of BRAF-V600 mutant cancer patients, resistance is rapidly acquired, resulting in a relapse of most patients within a year . This effect may be partially due to the fast metabolism of dabrafenib (with a half-life of ∼5 hours ). There are three major metabolites of dabrafenib that have been identified with potential pharmacological effects: hydroxy-dabrafenib (HDB), carboxy-dabrafenib (CDB), and desmethyl-dabrafenib (DDB), whereas HDB appears to contribute significantly to the pharmacological activity . c .