The legal action centers on the development of ERAS-0015, an experimental molecular glue intended to treat RAS-mutant solid tumors. Hagens Berman, the law firm representing the class, claims Erasca improperly compared its 40-milligram dosage to the 400-milligram cohort of Revolution Medicines' competing drug, RMC-6236. Furthermore, the complaint alleges Erasca provided investors with false assurances about the strength of its patent portfolio, which it claimed was bolstered by licenses from Joyo.

The market’s confidence evaporated on April 27, 2026, when two critical disclosures surfaced. First, Erasca revealed that Revolution Medicines had challenged the validity of its intellectual property, alleging that Erasca misappropriated trade secrets. Later that day, the company reported that a patient had died following an adverse reaction to ERAS-0015. The subsequent stock drop wiped out $2.8 billion in market capitalization. Lead attorney Reed Kathrein stated the firm is investigating whether Erasca intentionally obscured the drug's safety profile and the fragility of its competitive position. Investors who purchased stock between January 14, 2025, and April 26, 2026, have until August 10, 2026, to file as lead plaintiffs.