Efficacy and safety of a drug-free, barrier-forming nasal spray for allergic rhinitis: randomized, open-label, crossover noninferiority trial

Background Symptoms of allergic rhinitis can be reduced by nonpharmacological nasal sprays that create a barrier between allergens and the nasal mucosa. A new nasal spray (AM-301) containing the clay mineral bentonite was tested for its ability to reduce symptoms to grass pollen. Methods This open label, crossover, noninferiority trial compared the efficacy and safety of AM-301 to that of hydroxypropyl methylcellulose (HPMC; Nasaleze Allergy Blocker), an established barrier method. Adults with seasonal allergic rhinitis were exposed to Dactylis glomerata pollen, in the Fraunhofer Allergen Challenge Chamber, first without protection and then protected by HPMC or AM-301 (7 days apart). Efficacy was assessed from total nasal symptom score (TNSS), nasal secretion weight, and subjective rating. The primary endpoint was the difference, between AM-301 and HPMC, in least square mean change in TNSS over a 4-hour exposure to allergen. Results The study enrolled 36 persons, and 35 completed all study visits. The mean TNSS was 5.91 during unprotected exposure, 5.20 during protection with HPMC, and 4.82 during protection with AM-301. The difference in least square means between the two treatments was -0.39 (95% CI, -0.89 to 0.10), establishing the noninferiority of AM-301. No difference in mean weight of nasal secretions was observed between the treatments. Efficacy was rated as good or very good for AM-301 by 31% and for HPMC by 14% of subjects. 16 subjects reported adverse events with a relationship to AM-301 or HPMC; most adverse events were mild and none was serious. Conclusions AM-301 demonstrated noninferiority towards HPMC in the primary endpoint and was perceived better in subjective secondary endpoints. Both barrier-forming products had a persisting protective effect over 4 hours and were safe. Trial registration German Clinical Trial Register (DRKS00024356). EUDAMED (CIV-20-10-034870).