New York, May 18, 2026, 19:03 (EDT)
Regeneron Pharmaceuticals shares lost 9.8% Monday. The company’s late-stage melanoma drug trial missed its main goal, putting new pressure on a pipeline that investors have seen as a key growth driver.
Regeneron Pharmaceuticals Inc. REGN closed at $629.68. Shares started at $615.93 and dropped to $610.60 at the session low, LSEG data on the company’s investor site showed. The stock trailed both the main market and other biotech names.
Why it’s key now: fianlimab was a top cancer prospect for Regeneron. The setback lands while investors keep an eye on weakening Eylea sales and hope newer treatments can help pick up the slack.
Regeneron said late Friday that the combo of fianlimab and its cancer drug cemiplimab failed to hit “statistical significance” for improving progression-free survival. That means the data didn’t meet the study’s threshold to show a clear benefit over Merck’s Keytruda. Regeneron Pharmaceuticals Inc.
The high-dose fianlimab combo posted a median progression-free survival of 11.5 months. Pembrolizumab, or Keytruda, had 6.4 months. But the p-value landed at 0.0627, over the typical 0.05 threshold set by many clinical trials, so the result isn’t considered statistically significant.
Merck’s Keytruda is still the main comparison in this study, though Regeneron has its own Phase 3 trial running—a high-dose fianlimab combo up against Bristol Myers Squibb’s Opdualag for first-line advanced melanoma. The competitive takeaway is narrow, but traders are watching.
BMO Capital Markets analyst Evan Seigerman said “Back-to-back key pipeline misses amp up the pressure,” per Reuters. Evercore’s Cory Kasimov called it the “worst-case scenario.” Reuters also said at least 10 brokerages cut price targets on the stock. Reuters
U.S. stocks mostly dipped as the Nasdaq Composite lost 0.5% and the S&P 500 edged down 0.1%. The Dow managed a 0.3% gain, according to the Associated Press. Regeneron, though, fell far more than any moves in the indexes.
Regeneron showed profit behind the falling stock. The company posted Q1 revenue of $3.6 billion, up 19% over last year. Global Dupixent net sales, reported by Sanofi, were $4.9 billion, up 33%. U.S. sales of Eylea HD and Eylea dropped 10% to $941 million, highlighting gains in immunology while eye care dragged.
Regeneron moved to grow its pipeline Monday, saying it’s partnering with private biotech Parabilis Medicines. Parabilis gets $125 million, with $50 million upfront and $75 million via equity, and could see $2.2 billion in milestones. “Cutting-edge and diversified science,” said George Yancopoulos, Regeneron’s co-chair and chief scientific officer, describing the aim. Regeneron Pharmaceuticals Inc.
The risk isn’t one-sided. The Opdualag trial might still beat expectations, and Regeneron has other cash cows outside fianlimab. On the other hand, if investors see the next 12 to 18 months as a test, there could be more trouble ahead. With Eylea still challenged and no obvious wins from the cancer pipeline, Monday’s drop may not be the end of it.
Regeneron plans to share full results from the fianlimab study at an upcoming medical conference. The Bristol Myers comparator trial is still underway. For now, the stock has shifted from having pipeline optionality to showing pipeline proof.
