Erasca revealed that a 66-year-old metastatic pancreatic cancer patient developed grade 3 pneumonitis about one month into ERAS-0015 treatment, leading to drug discontinuation and the patient’s death after he opted to stop supportive care. The announcement triggered a 46% plunge in the company’s share price as investors reacted to the safety setback.

Despite the fatality, ERAS-0015 demonstrated a 62% objective response rate in patients with KRAS G12X-mutated non-small cell lung cancer as second-line therapy and a 40% response rate in pancreatic cancer, surpassing the company’s goal of outperforming a competitor’s response by at least 10 percentage points in both indications.

Some analysts cautioned that the pneumonitis event may be an isolated case influenced by the patient’s pulmonary tumor burden and history of lung procedures, while others noted the selloff was driven by uncertainty around the true safety profile. Several maintained positive ratings, deeming the broader efficacy dataset too compelling to ignore despite the one-off fatality.

Erasca is defending against a lawsuit alleging improper cross-study comparisons of preclinical data, patent infringement, and trade-secret misappropriation by researchers tied to its compound. The company has rejected all claims and intends to contest the legal action while continuing clinical development.