REGN1908/1909 prevented cat allergen-induced early asthmatic responses in an environmental exposure unit.

Background: The dominant allergen in cat dander, Felis domesticus allergen 1 (Fel d 1), is a persistent trigger for allergic rhinitis and asthma symptoms.

Objective: We evaluated the efficacy of Fel d 1 monoclonal antibodies (REGN1908/1909) in preventing cat allergen-induced early asthmatic responses (EARs) in cat-allergic patients with mild asthma.

Methods: Patients were randomized to single-dose REGN1908/1909 600 mg (n = 29) or placebo (n = 27). The FEV was measured for up to 4 hours in a cat allergen environmental exposure unit up to 85 days after dosing. Assessments included between-group differences in change from baseline in FEV area under the curve (AUC; 0-2 hours) and incidence of EAR (FEV reduction ≥20%).

Trial Registration: NCT03838731.

Results: Single-dose REGN1908/1909 significantly prevented reductions in FEV on days 8, 29, 57, and 85. Most REGN1908/1909 patients did not have an EAR by 4 hours (the last time point tested). In contrast, placebo-treated patients experienced a ≥20% mean FEV reduction on days 8, 29, 57, and 85 after dosing, with most experiencing an EAR within 1 hour. REGN1908/1909-treated patients tolerated 3-fold higher allergen quantities (P < .05 at all time points) versus placebo. REGN1908/1909 substantially reduced skin test reactivity to cat allergen versus placebo at all time points tested (nominal P < .001). REGN1908/1909 was generally well tolerated; no serious adverse events or deaths were reported.

Conclusion: Single-dose REGN1908/1909 significantly prevented reductions in FEV in cat-allergic patients with mild asthma on cat allergen environmental exposure unit exposure at 8 days and up to 85 days after dose.