Regeneron Pharmaceuticals announced positive results from two separate Phase 3 allergen-challenge trials evaluating its first-in-class investigational allergen-blocking antibodies for cat and birch allergies. Both trials met their primary and key secondary endpoints with high statistical significance, demonstrating substantial reductions in allergy symptoms compared to placebo.
Cat Allergy Trial Results
The Phase 3 cat allergy trial randomized 64 participants with moderate-to-severe cat allergies to receive either a single dose of the FelD1-blocking antibody combination therapy (REGN1908 and REGN1909, n=33) or placebo (n=31). Cat allergy affects more than 20 million patients in the U.S. alone, often resulting in severe ocular, nasal and respiratory symptoms despite standard therapies.
The combination therapy targeting FelD1, the most dominant cat allergen, achieved remarkable efficacy outcomes. Ocular itch was reduced by 52% (p<0.0001), conjunctival redness by 39% (p<0.0001), and skin prick reactivity by 44% (p<0.0001) when assessed one week after treatment.
In a post-hoc exploratory analysis focusing on patients whose cat allergy was more specifically driven by FelD1 - representing the majority of the population and target patients for the confirmatory trial - the results were even more impressive. This subgroup showed ocular itch reduction of 64% and conjunctival redness reduction of 49%.
Birch Allergy Trial Demonstrates Similar Efficacy
The birch pollen allergy trial enrolled 54 participants randomized to receive either the BetV1-blocking antibody combination (REGN5713 and REGN5715, n=27) or placebo (n=27). Birch pollen affects more than 10 million people in the U.S., with approximately 35% of patients continuing to experience moderate to severe symptoms despite standard care.
The BetV1-blocking antibodies, which target the dominant allergenic birch pollen protein, achieved significant symptom reductions. Ocular itch decreased by 51% (p<0.0001), conjunctival redness by 46% (p<0.0001), and skin prick reactivity by 44% (p<0.0001) one week after a single treatment.
Novel Approach to Allergy Treatment
"Millions suffer from the debilitating effects of allergies, which can cause severe symptoms in the eyes, nose, skin and even trigger asthma," said George D. Yancopoulos, M.D., Ph.D., Board co-Chair, President and Chief Scientific Officer at Regeneron. "To try to alleviate this suffering, millions undergo allergy desensitization shots, often several times a week for several years, and often with disappointing results."
The traditional approach involves attempting to build up allergen-blocking antibodies through repeated exposure. Regeneron's strategy instead manufactures and directly provides these allergen-blocking antibodies, potentially offering "profound allergy relief – rapidly and durably after a single treatment."
Durable Benefits and Safety Profile
Both combination therapies demonstrated rapid onset of action, with significant relief observed at the earliest assessment timepoint of eight days. Previous trials using nasal allergen challenge and environmental exposure unit (EEU) allergen challenge methodologies showed that benefits were maintained for at least three months following a single subcutaneous administration.
The safety profiles were favorable across both trials. The cat allergy combination therapy was generally well-tolerated, with no serious treatment-related adverse events or adverse events leading to trial discontinuation reported. Similarly, the birch allergy treatment showed no serious adverse events or trial discontinuations.
Development Timeline and Broader Pipeline
Additional Phase 3 development for the cat allergy program is planned to begin in the first half of 2026, while birch allergy Phase 3 development is expected to start by the end of this year. The data from these trials will be presented at an upcoming medical conference and will inform the design of confirmatory Phase 3 trials.
These allergy programs represent part of Regeneron's broader allergy pipeline, which includes an ongoing proof-of-concept trial in adults with severe food allergy. This innovative approach involves ablating IgE antibody-producing cells using Regeneron's BCMAxCD3 bispecific antibody, followed by ongoing Dupixent treatment to prevent cell return. Initial results from the food allergy trial have been encouraging, with enrollment expected to complete by year-end.
Technology Platform
All four allergen-blocking antibodies were developed using Regeneron's VelocImmune technology, which utilizes a proprietary genetically-engineered mouse platform with a genetically-humanized immune system to produce optimized fully human antibodies. This platform has been used to create a substantial proportion of all original, FDA-approved fully human monoclonal antibodies, including established therapies like Dupixent, Libtayo, and Praluent.
The ocular allergen challenge trials used the Ora Conjunctival Challenge Model, with ocular itch assessed on a 0-4 point scale and conjunctival redness evaluated using a standardized hyperemia scale. These methodologies complement earlier nasal allergen challenge and EEU studies that evaluated nasal and respiratory symptoms, including asthma induction.
