TAK‐632

KSR1 knockdown did not substantially affect ppERK responses to Type I½ RAF inhibitor (Encorafenib) in both cell types, whereas ppERK sensitivity slightly decreased for Type II RAFi (TAK-632) in MCF7 cells, aligning with simulations. The efficacy of MEKi (Cobimetinib) slightly increased in MCF7 cells following KSR1 knockdown but slightly decreased in PSN1 cells where higher MEKi concentrations were required to suppress ERK signaling, as predicted by the model. Our computational models predict, and experiments validate that in RAS-mutant cells, two conformation-specific RAF inhibitors used in combination suppress the ERK pathway more effectively than a combination of MEK and RAF inhibitors irrespective of KSR1 levels.

Accordingly, the tool compound TAK-632, which exhibits comparable biochemical and cellular potency to DAY101, was used alternatively as needed for in vitro assays.Single-agent anti-proliferative activity was observed in a melanoma BRAF fusion PDX model treated with TAK-632 ex vivo, with less sensitivity observed in models beyond melanoma harboring other BRAF fusions. Inhibition of both RAF monomers and dimers by DAY101 enables a broader indication selection strategy, beyond LGG and BRAF alterations. Ongoing translational work will highlight the potential utility of DAY101 in adult tumors harboring RAS or RAF alterations, both as a single agent and in hypothesis-driven combinations.