Regeneron Pharmaceuticals (Regeneron (REGN)) had a rough start to the week. On Friday, the company shared results from a Phase 3 trial testing its fianlimab (a LAG-3 inhibitor) combined with Libtayo (cemiplimab) in patients with advanced melanoma. The goal was to show the combo could beat Merck's (Merck (MRK)) blockbuster Keytruda (pembrolizumab). It didn't quite get there.
The trial's primary endpoint was progression-free survival (PFS), and the results were mixed. The high-dose fianlimab combo showed a median PFS of 11.5 months, which looks a lot better than Keytruda's 6.4 months. But the p-value was 0.0627, just above the typical 0.05 threshold for statistical significance. So, while the numbers are encouraging, they aren't conclusive enough to declare victory. The low-dose combo posted a median PFS of 9.6 months, with a p-value of 0.4661, which is clearly not significant.
On the safety front, no new red flags popped up, which is good. The trial enrolled 1,546 patients and tested three arms: high-dose fianlimab plus cemiplimab, low-dose fianlimab plus cemiplimab, and a control arm of placebo plus pembrolizumab or placebo plus cemiplimab.
Investors weren't thrilled. Regeneron shares fell 10.2% in premarket trading Monday to $627.01. That's part of a broader slide: the stock is down about 16.4% over the past month, while the S&P 500 has risen 4.3%. Year-to-date, Regeneron is off roughly 19%, compared to the S&P's 7.8% gain.
But Regeneron isn't sitting still. In April, the company announced a partnership with Telix Pharmaceuticals (Telix (TLX)) to develop next-generation radiopharmaceutical therapies for solid tumors. Telix brings expertise in radiopharmaceutical development and manufacturing, and the two will share commercialization costs and profits. It's a bet on precision oncology, a hot area that could pay off down the road.
For now, though, the melanoma trial is the story. The data suggest the fianlimab combo might have potential, but it needs a bigger or smarter trial to prove it. Regeneron will likely regroup and figure out next steps. Investors, meanwhile, are watching closely.
