Erasca shares plunged 53% after a disclosed patient death related to a grade 3 pneumonitis event in an ERAS-0015-treated individual. The company described the event in footnotes as a rare toxicity progression to grade 5 following withdrawal of supportive care at the patient’s direction. The stock move came as Erasca also shared preliminary, early dose-escalation updates from Phase I trials of the oral pan-RAS molecular glue ERAS-0015. Unconfirmed response rates in KRAS G12X NSCLC ranged up to 75% depending on line of therapy, with reported response activity also in second-line KRAS G12X PDAC. For oncology investors, the episode reinforces how clinical disclosures—even from early-stage datasets—can rapidly shift sentiment and risk perception around safety signals.