Erasca (ERAS) shares are selling off sharply Tuesday, April 28, 2026, after the company disclosed a patient death in an early-stage study of its investigational cancer drug ERAS-0015. The patient, a 66-year-old with pancreatic cancer, developed severe lung inflammation (pneumonitis) about a month after starting treatment, triggering broad concern that the safety profile could complicate dose escalation and future development. (whbl.com)

The drop follows Erasca’s April 27, 2026 release of preliminary Phase 1 dose-escalation data for ERAS-0015, a pan-RAS molecular glue being tested in RAS-mutant solid tumors. While the company characterized the dataset as positive, the newly highlighted fatal safety event is dominating investor focus and can pressure biotech valuations quickly because it raises the perceived probability of regulatory scrutiny, protocol amendments, or slower enrollment. (investors.erasca.com)

Traders are also weighing a separate overhang revealed this week: a letter received April 24, 2026 alleging ERAS-0015 infringes Revolution Medicines intellectual property and includes other claims, which could add legal risk and uncertainty around commercialization even if clinical progress continues. Against that backdrop, today’s move reflects a rapid repricing of ERAS-0015’s risk profile rather than a routine reaction to incremental trial updates. (sahmcapital.com)