BRAF V600E

Class

BRAF V600E kinase inhibitor (small molecule)

Pathway

RAS-RAF-MEK-ERK (MAPK) signaling pathway

BRAF is an intracellular kinase that operates within the RAS-RAF-MEK-ERK signaling cascade (also called the MAPK pathway), which relays growth signals from cell-surface receptors to the nucleus, driving cell division and survival. In a subset of cancers, a single point mutation—valine substituted for glutamate at position 600 (V600E)—locks BRAF into a permanently active state, independent of the upstream signals that normally control it. This produces continuous, unregulated activation of the downstream MEK and ERK kinases, fueling uncontrolled tumor cell proliferation. Small-molecule inhibitors designed to selectively target the mutant V600E form of BRAF can block this constitutive signaling, slowing or halting tumor growth while sparing normal cells that rely on properly regulated BRAF activity. This mechanism is clinically relevant across several cancer types where the V600E mutation occurs, including melanoma, certain colorectal cancers, and thyroid cancers. Because tumors can develop resistance through reactivation of the same pathway at other points, BRAF V600E inhibitors are often used alongside agents that block MEK, the kinase directly downstream, to achieve more durable pathway suppression. The therapeutic rationale rests on identifying tumors that are dependent on this specific mutation, since inhibition of the mutant kinase selectively interrupts the growth signal these particular cancer cells require.