Jonathan Corren,1 Sarbjit S Saini,2 Remi Gagnon,3 Mark H Moss,4 Gordon Sussman,5 Joshua Jacobs,6 Elizabeth Laws,7 Elinore S Chung,8 Tatiana Constant,8 Yiping Sun,8 Jennifer Maloney,8 Jennifer D Hamilton,8 Marcella Ruddy,8 Claire Q Wang,8 Meagan P OâBrien8 1Departments of Medicine and Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, CA, USA; 2Department of Internal Medicine, Division of Allergy and Clinical Immunology, Johns Hopkins Asthma and Allergy Center, Baltimore, MD, USA; 3Clinique Spécialisée en Allergie de la Capitale, Québec, QC, Canada; 4Departments of Medicine and Pediatrics, Division of Allergy, Pulmonary and Critical Care, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA; 5Department of Medicine, University of Toronto, Toronto, ON, Canada; 6Allergy and Asthma Clinical Research, Inc, Walnut Creek, CA, USA; 7Sanofi, Bridgewater, NJ, USA; 8Regeneron Pharmaceuticals, Inc, Tarrytown, NY, USACorrespondence: Meagan P OâBrienRegeneron Pharmaceuticals, Inc, 777 Old Saw Mill River Road, Tarrytown, NY, 10591, USATel +1 914 826-5271Email meagan.obrien@regeneron.comJonathan CorrenDepartments of Medicine and Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, 10833 Le Conte Ave, Los Angeles, CA, 90095, USATel +1 310 312-5050, ext 250Email jcorren@ucla.eduBackground: Subcutaneous immunotherapy (SCIT) has been proven as an effective therapy against some allergens for seasonal allergic rhinitis (SAR) patients unresponsive to intranasal corticosteroids and/or antihistamines but carries risk of systemic allergic reactions. Dupilumab blocks the shared receptor component for interleukin-4 and interleukin-13, key and central drivers of type 2 inflammation in multiple diseases.Objective: To evaluate the efficacy and safety of SCIT+dupilumab vs SCIT alone.Methods: This phase 2a, multicenter, double-blind, placebo-controlled parallel-group study conducted in 103 adults with grass pollen-induced SAR (NCT03558997) randomized patients 1:1:1:1 to SCIT, dupilumab (300 mg every 2 weeks), SCIT+dupilumab, or placebo. SCIT was administered using an 8-week cluster protocol followed by 8 weeks of maintenance injections. Primary endpoint was change from pre-treatment baseline in area under the curve (AUC) in total nasal symptom score (TNSS) 0â 1 h following nasal allergen challenge (NAC) with timothy grass extract at Week 17.Results: Although 16 weeks of treatment with SCIT+dupilumab did not significantly improve TNSS AUC (0â 1 h) following NAC at Week 17 vs SCIT (least squares mean â 56.76% vs â 52.03%), a higher proportion of SCIT+dupilumab-treated patients (61.5%) achieved SCIT maintenance dose vs SCIT (46.2%). A lower proportion of SCIT+dupilumab-treated patients (7.7%) required epinephrine rescue treatment vs SCIT (19.2%). There were significantly fewer withdrawals in the SCIT+dupilumab group than in the SCIT group (n = 2 [7.7%] vs n = 8 [30.8%]; P = 0.0216); the majority of SCIT group withdrawals were due to SCIT-related intolerability, compared with no discontinuations from the SCIT+dupilumab group.Conclusion: In SAR patients, 16 weeks of SCIT+dupilumab may improve SCIT tolerability but did not incrementally reduce post-allergen challenge nasal symptoms compared with SCIT alone.Clinical Study Number: NCT03558997.Keywords: dupilumab, seasonal allergic rhinitis, subcutaneous immunotherapy, nasal allergen responses