Regeneron's new melanoma combo gave patients an extra 5.1 months before their cancer got worse.
The stats said that wasn't enough.
The trial tested Regeneron's new drug fianlimab paired with Libtayo, its approved cancer drug.
The combo went up against Merck's Keytruda.
Patients on the Regeneron combo went 11.5 months with no signs of the cancer growing.
Patients on Keytruda went 6.4 months.
That's a 5.1-month gap. For a deadly cancer, doctors would call that meaningful.
The problem is the math.
The p-value came in at 0.0627. That's just over the 0.05 line scientists use to call a result statistically real.
In English: the drug looked like it worked, but the data wasn't tight enough to say so with full faith.
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Regeneron shares dropped 11.8% in premarket trading.
Evercore analyst Cory Kasimov called the result "the worst-case scenario."
The reaction looked harsh next to the data. A 5.1-month gain on no-growth time could still get a drug approved.
It's just not the kind of win that makes a drug the new standard of care. That's what investors had priced in.
Libtayo is already on the market on its own. So Regeneron has a path to file the combo using just this data.
That path is slower, harder, and worth a lot less than a clean win.
Libtayo has been a steady source of growth for Regeneron, with sales topping a billion dollars in recent years. The firm has been pushing it as the spine for a broader cancer plan.
Cancer drugs are a big part of the firm's pitch to Wall Street. The Eylea eye-disease franchise pulled in nearly $6 billion in 2024.
But Eylea lost its U.S. patent shield in May 2024 and now faces cheaper biosimilar copies. New cancer wins are key to the firm's next leg of growth.
Fianlimab goes after LAG-3. That's a marker on immune cells that some cancers use to dodge an attack.
Bristol-Myers Squibb already sells a LAG-3 plus PD-1 combo called Opdualag. It owns the LAG-3 niche in melanoma.
Regeneron was trying to leapfrog it with a stronger result. A clean win would have made a flagship cancer drug.
It would have pulled share from Bristol-Myers.
A clean miss would have done the opposite. What Regeneron got is a draw.
There's no clear path to "winner."
Regeneron still has a separate Phase 3 trial in play. It pits the combo head-to-head against Opdualag.
That readout is the next big test for the firm's cancer plan.
Until then, the firm has to convince the FDA that 5.1 extra months is worth approval on its own.
Wall Street will be watching for any sign that the combo can win in a head-to-head, not just a head-to-Keytruda setup. A clean read against Opdualag would shift the story fast.
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