Regeneron says study data support big bet on new blood thinners

Dive Brief:

• Regeneron Pharmaceuticals intends to advance two blood-thinning drugs into Phase 3 testing next year after mid-stage study results showed they matched or surpassed marketed medicines at preventing blood clots following knee replacement surgery.
• Regeneron’s drugs block a clotting protein, Factor XI, that’s been targeted by multiple pharmaceutical companies, some of which have candidates in large, late-stage trials. The data announced Thursday are “proof-of-concept” results that Regeneron said give it confidence to follow suit.
• Factor XI blockers have produced mixed results so far in testing, however. Even if approved, they could face commercial challenges, as the effective blood thinner Eliquis is taken orally, rather than via infusion, and generic versions could arrive in 2026.

Dive Insight:

Regeneron needs its pipeline to deliver.

The company’s biggest seller, the eye drug Eylea, could face biosimilar competition earlier than expected, complicating its plans to switch patients onto a recently approved, high-dose version that’s injected less frequently. Two blood cancer drugs it’s counting on as future revenue drivers were rejected this year by the Food and Drug Administration, delaying their market arrival and allowing rivals to further establish themselves. Company shares, which peaked in August, have fallen more than 40% since.

Positive drug development news, such as with the company’s two blood thinners, could help shift investor sentiment.

Called REGN7508 and REGN9933, the two drugs bind to different regions of Factor XI, a strategy that’s seen as a safer alternative to popular blood thinners like Eliquis. But results from other, similar drugs haven’t been clear-cut. For instance, Bayer dialed back development of its candidate, asundexian, after it failed a Phase 3 trial last year. Bristol Myers and Johnson & Johnson launched a large, late-stage clinical program for their prospect despite mixed data in earlier testing.

In one Phase 2 trial, Regeneron tested a single infusion of REGN9933 against daily use of the anticoagulant enoxaparin or Eliquis given twice daily. In the other, an infusion of REGN7508 was evaluated only against daily enoxaparin. The main goal of both studies was to show Regeneron’s drugs could prevent vein-blocking blood clots as detected by an X-ray.

According to Regeneron, a pooled analysis across both trials showed 7% of those who received REGN7508 later developed a blood clot, versus 17% of those given REGN9933, 21% among those on enoxaparin and 12% of those who took Eliquis.

People on REGN7508 had statistically fewer blood clots than people who got enoxaparin, while REGN9933 was judged to be “non-inferior,” or statistically similar, to enoxaparin, Regeneron said. The company also said REGN7508 was non-inferior to Eliquis. It didn’t provide a statistical analysis of REGN9933 versus Eliquis.

There were no major or clinically important minor bleeding events in any of the treatment groups, Regeneron said. One patient receiving enoxaparin reported a bruise.

Regeneron said the trial showed “proof of concept” for the two drugs. “We are eager to advance REGN7508 and REGN9933 into a broad Phase 3 program beginning in 2025,” Regeneron President George Yancopoulos said in a statement.

In a Thursday note to clients, RBC analyst Brian Abrahams said the small size of the studies and the lack of bleeding incidents in any patient group made it difficult to tell whether REGN7508 or REGN9933 may be safer than marketed blood thinners.

Abrahams also noted how it’s not clear which indications the company will choose for Phase 3 testing. Any trial in a setting involving people eligible for Eliquis would need to be a head-to-head study, making the risk of failure higher, he wrote.

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