Dabrafenib is an inhibitor of some mutated forms of BRAF kinases with in vitro IC50 values of 0.65, 0.5, and 1.84 nM for BRAF V600E, BRAF V600K, and BRAF V600D enzymes, respectively. Dabrafenib also inhibits wild-type BRAF and CRAF kinases with IC50 values of 3.2 and 5.0 nM, respectively, and other kinases such as SIK1, NEK11, and LIMK1 at higher concentrations. Some mutations in the BRAF gene, including those that result in BRAF V600E, can result in constitutively activated BRAF kinases that may stimulate tumor cell growth.
Dabrafenib caused an inhibition of phosphorylated ERK. This indicates a decrease in cell proliferation. Furthermore, within 24 hours of administration, downstream mediators of the MAPK pathway were inhibited.
Dabrafenib is hepatically metabolized. The biotransformation process is primarily mediated by CYP2C8 and CYP3A4 to form hydroxy-debrafenib. This metabolite is further oxidized via CYP3A4 to form carboxy-dabrafenib and subsequently excreted in bile and urine. Carboxy-dabrafenib can also undergo decarboxylation to form desmethyl-dabrafenib, which may be reabsorbed from the gut. Desmethyl-dabrafenib is further metabolized by CYP3A4 to oxidative metabolites.
Most common adverse reactions (≥20%) for dabrafenib are hyperkeratosis, headache, pyrexia, arthralgia, papilloma, alopecia, and palmar-plantar erythrodysesthesia syndrome.
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