Regeneron announces results of Phase 3 trials on allergen-blocking antibodies

Regeneron (REGN) announced results evaluating its nvestigational allergen-blocking antibodies in allergen-challenge Phase 3 trials in adults with moderate-to-severe cat or birch allergies. Both trials met their respective primary and key secondary endpoints. Data from the Phase 3 trials will be presented at an upcoming medical conference and will inform confirmatory Phase 3 trials. In these “ocular allergen challenge” Phase 3 trials, patients received direct ocular instillation of the allergen at day 8 following a single subcutaneous administration of the allergen-blocking antibodies. Trial endpoints assessed signs and symptoms of ocular allergy measured after instillation of allergen in the eye.a Earlier Regeneron trials evaluated “nasal allergen challenges” and “environmental exposure unit allergen challenges.” Cat allergy is one of the most common indoor allergens, affecting more than 20 million patients in the U.S. alone, often resulting in severe ocular, nasal and respiratory symptoms despite standard of care therapies. REGN1908 and REGN1909 are two fully human monoclonal antibodies targeting and blocking FelD1 – the most dominant cat allergen – which “doggedly” clings to clothes, shoes and furniture, making it challenging to avoid even in cat-free indoor environments. In the Phase 3 trial, cat-allergic participants were randomized to receive a single dose of the FelD1-blocking antibody combination therapy or placebo. The primary endpoint of ocular itch and both key secondary endpoints of conjunctival redness and skin prick testing – assessed one week after the single treatment with FelD1-blocking antibodies – were met with high degree of statistical significance in the overall population. 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. 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. The results in this “ocular challenge” trial are similar to earlier trials using “nasal allergen challenge” and “EEU allergen challenge,” which evaluated nasal and respiratory symptoms including asthma induction in those trials. In those earlier trials, statistically and clinically meaningful improvement was also seen at the earliest assessment done at 8 days following administration of REGN1908 and REGN1909, with durable benefit maintained for at least 3 months. Birch pollen is one of the most common seasonal allergens in the U.S., affecting more than 10 million people. About 35% of patients continue to experience moderate to severe symptoms despite standard of care therapy. 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 or placebo. The primary endpoint of ocular itch and both key secondary endpoints of conjunctival redness and skin prick testing – assessed one week after the single treatment with BetV1-blocking antibodies – were met with high degree of statistical significance. 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. Prior “nasal allergen challenge” and “EEU allergen challenge”b trials of REGN5713 and REGN5715 in patients with birch-induced allergic rhinitis revealed similarly rapid and profound benefit at the first assessment timepoint, with durable reduction of allergic rhinitis and conjunctivitis symptoms up to 3 months following a single subcutaneous administration of the allergen-blocking antibodies.