Timothy grass pollen therapeutic vaccine: optimal dose for subcutaneous immunotherapy.

AIMS: To establish the optimal dose of Phleum pratense subcutaneous immunotherapy (SCIT) in patients with allergic rhinoconjunctivitis with/without asthma. MATERIALS & METHODS: One hundred and fifty-one patients were randomized to receive SCIT 0.25, 0.5, 1.0, 2.0 or 4.0 skin-prick test units (SPT) or placebo. The primary end point was the variation in the concentration of Phleum pratense extract needed to produce a positive nasal provocation test from baseline (V0) to final visit (FV). RESULTS: After 17 weeks, a dose-dependent trend was apparent in the concentration of P. pratense extract needed to produce a positive nasal provocation response. Systemic adverse reactions occurred with 3.2% of administered doses. Grade III (n = 2) and IV (n = 2) events were observed only at the two highest doses. CONCLUSION: P. pratense depot SCIT showed signs of clinical and immunological efficacy by dose-dependently decreasing the allergen sensitization rate. Risk-benefit favored doses below 1.0 SPT units for confirmatory trials.