Regeneron's Allergen-Blocking Antibodies Achieve Primary Endpoints in Phase III Cat and Birch Allergy Trials
Key Insights
Regeneron's first-in-class allergen-blocking monoclonal antibodies met primary endpoints in two Phase III trials, reducing ocular itch by 52% in cat allergy (search) patients and 51% in birch allergy (search) patients one week after single treatment.
The combination therapies REGN1908 (search)/REGN1909 (search) for cat allergies and REGN5713 (search)/REGN5715 for birch allergies also significantly reduced conjunctival redness and skin prick reactivity by approximately 40-46% across both studies.
Both antibody combinations were well-tolerated with no serious treatment-related adverse events or trial discontinuations, with confirmatory trials planned for birch allergy (search) by end of 2025 and cat allergy (search) in H1 2026.
Regeneron Pharmaceuticals' investigational allergen-blocking monoclonal antibodies have successfully met their primary endpoints in two Phase III trials targeting moderate-to-severe cat and birch allergies in adults, marking a significant advancement in allergy treatment approaches.
Cat Allergy Trial Results
In the cat allergen study, patients received a single dose of the combination therapy REGN1908 (search) and REGN1909 (search), which target FelD1 (search), the most dominant cat allergen protein. The primary endpoint of ocular itch reduction was achieved with a 52% improvement compared to placebo, assessed one week after treatment.
The therapy also met both key secondary endpoints, demonstrating a 39% reduction in conjunctival redness and a 44% decrease in skin prick reactivity. Notably, patients whose allergies were more specifically driven by FelD1 (search) showed enhanced responses, with ocular itch reduction reaching 64% and conjunctival redness reduction of 49%. According to Regeneron, this patient population will be the focus of confirmatory trials.
Birch Allergy Study Outcomes
The birch allergen trial evaluated the combination of REGN5713 (search) and REGN5715, two monoclonal antibodies designed to target and block BetV1, the dominant allergenic birch pollen protein. Results showed a 51% reduction in itching, 46% decrease in conjunctival redness, and 44% reduction in skin prick reactivity.
Safety Profile and Tolerability
Both combination therapies demonstrated favorable safety profiles across the trials. No serious treatment-related adverse events or adverse events leading to trial discontinuation were reported in either study, indicating good tolerability of the single-dose treatments.
Clinical Development Timeline
Regeneron has outlined its development timeline for these allergen-blocking therapies. The birch allergy (search) confirmatory trial is scheduled to begin by the end of 2025, while the confirmatory cat allergy (search) trial is planned for the first half of 2026.
Broader Allergy Pipeline
These cat and birch allergy (search) programs represent part of Regeneron's comprehensive allergy pipeline, which includes an ongoing proof-of-concept trial in adults with severe food allergy (search). The food allergy therapy involves ablating cells that produce IgE antibodies responsible for initiating allergen responses, followed by ongoing treatment with Dupixent (dupilumab) to prevent the return of these cells.
Market Considerations
Despite the positive clinical results, analysts at BMO Capital Markets noted uncertainty regarding the commercial potential of these antibody treatments in what they described as a "highly generic market" dominated by antihistamines. While acknowledging the "robust reductions" in allergy symptoms and being "broadly impressed by the strength" of the findings, BMO emphasized the need for clearer commercial strategy details.
Dr. George Yancopoulos, Regeneron's president and chief scientific officer, highlighted the significance of these results: "These recent Phase III allergen challenge trials, together with our earlier Phase II trials, provide compelling evidence that our first-in-class approach can have the potential to provide profound allergy relief – rapidly and durably after a single treatment – decreasing ocular, nasal and even asthma measures. We see significant relief at the earliest assessment timepoint, and lasting for over three months, in both our cat and birch allergy (search) programmes."