Regeneron Pharmaceuticals, Inc. (NASDAQ:REGN) revealed data from Phase 3 trials in adults with moderate-to-severe cat or birch allergies on Monday. Both trials met their respective primary and key secondary endpoints.

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Allergen-blocking antibody treatment in Cat-allergen “Ocular Challenge” Trial

REGN1908 and REGN1909 are two fully human monoclonal antibodies (mAbs) targeting and blocking FelD1.

In the Phase 3 trial, cat-allergic participants were randomized to receive a single dose of the FelD1-blocking antibody combination therapy (REGN1908 and REGN1909, n=33) or placebo (n=31).

The primary endpoint of ocular itch and both key secondary endpoints of conjunctival redness and skin prick testing were met. Itch was reduced by 52%, conjunctival redness by 39% and skin prick reactivity by 44%.

In a post-hoc exploratory analysis of patients whose cat allergy was more specifically driven by FelD1, reductions in ocular itch and conjunctival redness were greater compared to the overall population (ocular itch reduction of 64% and conjunctival redness reduction of 49%).

The combination therapy was generally well-tolerated, with no serious treatment-related adverse events or adverse events leading to trial discontinuation reported; the trial is ongoing for further safety follow-up. Additional Phase 3 development is planned to begin in the first half of 2026.

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Allergen-blocking antibody treatment in Birch-allergen “Ocular Challenge” Trial

REGN5713 and REGN5715 are two mAbs targeting and blocking BetV1, the dominant allergenic birch pollen protein.

In the Phase 3 trial, participants were randomized to receive a single dose of the BetV1-blocking antibody combination (REGN5713 and REGN5715, n=27) or placebo (n=27).

Itch was reduced by 51%, conjunctival redness by 46% and skin prick reactivity by 44%.

The combination therapy was generally well-tolerated, with no serious adverse events or adverse events leading to trial discontinuation. Additional Phase 3 development is planned to begin by the end of the year.

The cat and birch allergy programs are part of a broader allergy pipeline, which also includes an ongoing proof-of-concept trial in adults with severe food allergy. Regeneron expects to complete enrollment by the end of the year.

REGN Price Action: Regeneron Pharmaceuticals stock is down 3.05% at $555.92 at publication on Monday.

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