Erasca Plunges 40% as Cancer Drug Trial Data Mixed

NEW YORK, April 28 —

A 62% tumor response rate is the kind of number that launches a biotech rally. A treatment-related death is the kind of detail that kills one. Erasca delivered both on the same day. After-hours traders picked the death: shares plunged roughly 40% in extended trading after the company released Phase 1 data for ERAS-0015, its experimental oncology candidate targeting RAS-driven cancers. The regular session had already carved off 10.9%, closing at $19.15.

The Data Looked Good Until It Didn't

Taken alone, the Auroras-1 Phase 1 results would have been a career highlight for most clinical-stage biotechs. Among non-small cell lung cancer patients who had previously received immunotherapy and chemotherapy, the response rate hit 75%. All 14 evaluable patients showed significant reductions in circulating tumor DNA — a biomarker that tracks how aggressively a cancer is shedding genetic material into the bloodstream. In pancreatic cancer, one of the hardest-to-treat malignancies in oncology, a 40% response rate at fourteen weeks is the kind of signal that gets a program fast-tracked.

But Phase 1 trials exist to find toxicity, and this one found it. The pneumonitis death on the 24 mg dose is exactly the kind of safety event that forces dose adjustments, protocol rewrites, and hard conversations with the FDA. Pneumonitis in oncology isn't rare. Treatment-related deaths in early-stage trials are serious enough to reframe everything around them. The efficacy numbers now look like the best-case scenario for a drug whose therapeutic window just got narrower.

A Competitor's Legal Shot Across the Bow

The clinical complication wasn't the only blow. Revolution Medicines alleged this week that ERAS-0015 may infringe its patents and incorporate misappropriated trade secrets. Revolution asked Erasca to cease manufacturing and stop making comparative statements about Revolution's competing drug. For a company whose entire valuation rests on a single clinical program, a credible IP challenge is existential risk stacked on top of clinical risk. Even if the claims go nowhere, the legal overhang gives institutional investors another reason to step aside.

The Insiders Were Already Leaving

The 90-day insider transaction record shows $1.61 million in sales against zero open-market purchases. Chief Legal Officer Ebun Garner exercised 80,000 options at $1.70 and sold the resulting shares at $16.40 on April 1, netting roughly $1.31 million. Chief Medical Officer Shannon Morris did the same a month earlier: exercise 20,000 options at $1.70, sell at $15.04 for about $301,000. Both are classic exercise-and-sell patterns on deeply in-the-money options — routine compensation management. But the optics matter. The CLO and CMO both cashed out in the weeks before a pivotal data readout. Neither bought a single share on the open market.

A $6 Billion Company With No Revenue

Erasca closed with a market capitalization of approximately $5.95 billion. It has no revenue. Trailing twelve-month free cash flow was negative $67 million, per Q4 2025 earnings filed March 12. Recent quarterly EPS has held steady at negative $0.11 to negative $0.12, roughly in line with consensus. The forward P/E of negative 35.5x is a mathematical artifact — it says only that analysts expect losses to continue. The consensus price target sat at $20 before the after-hours collapse, which means the stock was trading at the Street's fair value before it cratered. H.C. Wainwright reiterated its rating following the Phase 1 release, though the target's relevance will depend on where the stock settles.

What Changes the Story

Three questions will determine whether the after-hours selloff was an overreaction or the start of a lasting decline. First, the dose-response relationship: if the pneumonitis death is isolated to the 24 mg cohort and lower doses retain efficacy, the program survives. If it's a class effect, ERAS-0015 has a ceiling. Second, the Revolution Medicines IP dispute. Patent threats in biotech range from genuine to strategic harassment. Whether this escalates to formal litigation or dissolves into licensing negotiations will shape the legal risk for months. Third, cash. A pre-revenue company burning $67 million a year with a suddenly discounted stock price faces dilutive financing on worse terms than it imagined a week ago.

37/d126999d8k.htm">two 8-K reports on April 27 covering the data release, and a separate 8-K filed April 21 preceded the readout by a week. The next checkpoint is whatever FDA feedback emerges on dose modification and the Phase 1 expansion plan. Until then, the stock trades on sentiment — and right now sentiment reflects the worst reading of a mixed dataset.

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Basis Report does not hold positions in securities discussed. This is not investment advice.

Frequently Asked Questions

Why did Erasca stock drop 40%?

Erasca shares fell roughly 40% in after-hours trading after Phase 1 trial data for ERAS-0015 revealed a treatment-related patient death from Grade 3 pneumonitis, despite otherwise strong tumor response rates. A patent infringement allegation from Revolution Medicines deepened the selloff.

What were the ERAS-0015 clinical trial results?

The Auroras-1 Phase 1 study showed a 62% tumor response rate in previously treated non-small cell lung cancer at eight weeks, a 75% response rate among patients who received prior immunotherapy and chemotherapy, and a 40% response rate in pancreatic cancer at fourteen weeks. One patient death from pneumonitis overshadowed these results.

Is Revolution Medicines suing Erasca?

Revolution Medicines has alleged potential patent infringement and trade-secret misappropriation related to ERAS-0015 and requested that Erasca cease manufacturing. No formal litigation has been confirmed, but the legal overhang adds risk.

Did Erasca insiders sell before the data release?

Yes. The Chief Legal Officer and Chief Medical Officer collectively sold roughly $1.61 million in stock in the 90 days before the data readout, with zero open-market purchases during the same period. Both transactions involved exercising deeply in-the-money options.

Does Erasca have any revenue?

No. Erasca is a pre-revenue clinical-stage biotech with negative $67 million in trailing twelve-month free cash flow and a market cap of approximately $5.95 billion. Its valuation rests entirely on the ERAS-0015 clinical program.