Erasca shares fell after the company disclosed a patient death tied to an adverse event in a previously shared dose-escalation dataset for ERAS-0015. The disclosure surfaced in investor materials and followed preliminary positive, though early, efficacy signals from pooled Phase I trials in RAS/MAPK-driven solid tumors. The drug is being developed as an oral pan-RAS molecular glue targeting KRAS G12X–mutant NSCLC and PDAC. Reported unconfirmed overall response rates ranged up to 62%–75% in KRAS G12X NSCLC cohorts and 40%–50% in second-line KRAS G12X PDAC. The company said the fatality resulted after grade 3 pneumonitis progressed to grade 5 following supportive care withdrawal at the patient’s direction, prompting investors to reassess risk even as Erasca characterized pneumonitis as a rare class effect.