Background: The clinical efficacy of Japanese cedar (JC) pollen SLIT tablets for allergic symptoms during Japanese cypress (JCY) pollen dispersal has been controversial in actual clinical settings. JC and JCY both belong to the Cupressaceae family and the major allergens of the two species have strong amino acid homology. The efficacy of JC pollen SLIT tablets against seasonal allergic rhinitis during the JC pollen and JCY pollen dispersal periods was investigated.
Methods: A post-hoc analysis was conducted in a phase II/III study (JapicCTI no. 142579). Patients with JC pollinosis (aged 5-64 years) were included (placebo n=159, 5000 JAU n=158). Patients in the active 5000 JAU treatment group was treated with JC SLIT tablet daily by self-administration for the duration of the trial. Clinical efficacy was evaluated by the total nasal symptom and medication score (TNSMS) during the peak symptom periods of each pollen season over 3 years.
Results: The daily average TNSMS in the 5000 JAU group was consistently lower than in the placebo group during both the JC and JCY pollen dispersal periods in all three seasons. The larger reduction in TNSMS in the 5000 JAU group compared with the placebo group was observed in a treatment duration-dependent manner.
Conclusions: JC SLIT tablet treatment showed sustained clinical efficacy on allergic symptoms during 3 consecutive JCY pollen seasons. Further studies are required to examine the immunological responses and extent of antibody cross-reactivity towards the homologous major allergens from different Cupressaceae family species including JC and JCY.