Long-Term Efficacy and Dose-Finding Trial of Japanese Cedar Pollen Sublingual Immunotherapy Tablet

Japanese cedar (JC) pollinosis is a common allergic rhinitis in Japan. The JC pollen sublingual immunotherapy (SLIT) tablet was developed using the highest concentration of JC pollen extract.This was a randomized, double-blind, placebo-controlled phase II/III trial to investigate the optimal dose of the JC pollen SLIT tablet and examine long-term efficacy and safety for 3 years with the selected dose, and 2-year follow-up.A total of 1042 patients with JC pollinosis (aged 5-64 years) were equally randomized into 4 groups and received daily treatment with 2,000, 5,000, or 10,000 Japanese allergy unit (JAU) or placebo. The primary end point was the total nasal symptom and medication score (TNSMS) during the peak symptom period in the first season. Key secondary end points were TNSMS for the JC pollen dispersion season and total nasal and ocular symptom and medication score for the peak symptom period and JC pollen dispersion season.For the primary end point, absolute reductions and relative mean reductions in TNSMS compared with placebo were 1.50 and 21.4%, 2.24 and 32.1%, and 2.18 and 31.2% for 2,000, 5,000, and 10,000 JAU, respectively (P < .001 in all groups). For all key secondary end points, efficacy was confirmed for all doses (P < .001 in all groups). The treatment was well tolerated. Long-term efficacy of 5,000 JAU was shown over the 3 years.The optimal dose of the JC pollen SLIT tablet was 5,000 JAU, with good efficacy and safety over a 3-year treatment period. This sustained effect was dependent on treatment duration.