Shares of Erasca Inc., a biotech focused on oncology, tumbled up to 55% on Tuesday after the company disclosed that a trial participant pulled out and subsequently died from severe side effects linked to its experimental therapy. The loss triggered a sharp sell‑off on the Nasdaq, wiping out roughly $200 million in market value and raising questions about the drug’s safety profile.

Erasca’s candidate, currently in Phase II, targets a rare form of breast cancer and has been the centerpiece of recent financing rounds that valued the firm at over $1 billion. Investors had banked on early efficacy signals, but the fatal outcome underscores the volatility inherent in late‑stage oncology trials, where adverse events can swiftly erode confidence.

With the stock now hovering near historic lows, Erasca may face tighter scrutiny from regulators and potential delays in upcoming study milestones. Creditors and partners will likely reassess exposure, while the episode serves as a reminder that single‑patient events can reshape valuation overnight. The market has already priced in a steep correction. Analysts now project earnings could fall sharply this year for shareholders.