A pair of Regeneron’s monoclonal antibodies have held their own against a commonly used anticoagulant in a phase 2 trial, with one of the candidates also matching Bristol Myers Squibb and Pfizer’s Eliquis.
The antibodies in question target different domains of factor XI, a protein in the blood that helps with clotting. REGN7508 targets the catalytic domain with the aim of maximizing anticoagulant activity but minimizing bleeding risk while REGN9933 focuses on the A2 domain as a potential option for patients with the highest risk of bleeding who aren’t catered to by approved anticoagulants.
The therapies were assessed in a pair of phase 2 studies conducted in the same trial centers among patients undergoing knee replacement surgery.
REGN7508 proved the most successful of the two, with a single dose of the therapy demonstrating its superiority to daily doses of the approved factor Xa-targetting anticoagulant enoxaparin, with 7% of patients on REGN7508 experiencing venous thromboembolism (VTE), a term for blood clots that form in the veins, compared to 21% of those receiving enoxaparin.
REGN7508 also showed non-inferiority to Eliquis, with patients on this approved factor Xa-targetting anticoagulant seeing a VTE rate of 12%.
In contrast, patients receiving REGN9933 in the separate trial showed a VTE rate of 17%, meaning the therapy was able to show non-inferiority to enoxaparin, but fell short of Eliquis.
The only treatment-related adverse event (AEs) in any arm was one case of minimal bleeding reported in the enoxaparin arm, Regeneron pointed out. Across both trials, AE rates were generally similar among the treatment arms, the company added.
“Our factor XI antibodies targeting the catalytic and A2 domains were rigorously evaluated alongside current standards of care and showed clear evidence of antithrombotic effect with an encouraging safety profile after a convenient single dose,” Regeneron’s president and chief scientific officer George Yancopoulos, M.D., Ph.D., said in this morning’s release.
“Together, these clinical and preclinical data, along with compelling genetic evidence, give us confidence in targeting multiple distinct domains of factor XI to potentially offer tailored therapies for patients with different bleeding risk profiles and in a variety of treatment settings,” Yancopoulos added. “We are eager to advance REGN7508 and REGN9933 into a broad phase 3 program beginning in 2025.”
Setting out the strategy behind the two anticoagulants in a presentation in August, Regeneron explained that the $20 billion atrial fibrillation market is currently dominated by direct oral anticoagulants that target factor Xa. While these are effective at reducing thrombotic events, they carry an elevated risk of bleeding, according to the pharma.
Regeneron’s aim in targeting factor XI is to provide more specific inhibition of the intrinsic coagulation pathway, the company outlined at the time.
Evercore ISI analysts said today's results meant Regeneron was ending the year “on a more favorable note” after “a forgettable 2H24.”
“The factor XI program has not been front and center for investors ... but this represents a substantial blockbuster opportunity,” the analysts wrote in a Thursday morning note. “We believe this novel anticoagulation approach could be a meaningful step forward from current standard-of-care, the widely used DOAC class (Eliquis, Xarelto etc).”
Bayer had a factor XIa inhibitor in the works in the form of asundexian, but the German company suspended a phase 3 trial late last year after the drug showed “inferior efficacy” at preventing strokes in patients with atrial fibrillation compared with Eliquis. Subsequent revelations have shown that patients receiving asundexian suffered strokes or systemic embolisms at a higher rate than those receiving Eliquis.
Meanwhile, BMS and Johnson & Johnson's milvexian failed a phase 2 trial, but the pharmas are still pursuing a phase 3.