When combined with clinically relevant concentrations of BETi BI 894999, BI 3011441 strongly decreases in vitro proliferation and induces apoptosis in KRAS mutant cancer cells. Synergy is observed in 17 out of 44 cell lines across different indications and harboring different KRAS mutations.... In summary, we show that combining BI 3011441 with SOS1 or BET inhibitors may lead to improved responses in KRAS mutant tumors...