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Higher dose of SLIT-birch pollen extract confers greatest benefit for patients with allergic rhinitis

Although a range of doses of sublingual immunotherapy with birch pollen extract demonstrated activity in patients with allergic rhinitis, a 40,000 AUN/ml dose appeared optimal with regard to safety and efficacy, according to study results.

Sublingual immunotherapy (SLIT) has demonstrated potential as a treatment for patients with respiratory, IgE-mediated allergic diseases, according to study background.

Oliver Pfaar, MD, of the Center for Rhinology and Allergology Wiesbaden in Germany, and colleagues conducted a multicenter phase 2 study to assess SLIT with liquid birch pollen preparation.

The analysis included 296 adults with allergic rhinitis to one of four SLIT birch pollen doses — 3,333 AUN/ml, 10,000 AUN/ml, 20,000 AUN/ml or 40,000 AUN/ml — or placebo. Researchers assessed differences in symptom scores after a titrated nasal provocation test at baseline and after 5 months of treatment.

Pfaar and colleagues also evaluated safety, tolerability, birch pollen-specific immunoglobulin levels and peak nasal inspiratory flow.

Researchers observed improvement in symptom scores in all groups between baseline and 5 months of treatment, “with an additional stepwise improvement in the active groups compared to placebo.” The improvement was significant in the high-dose groups (P = .008 overall; P < .001 vs. placebo)

Results showed a significant linear dose-response curve suggesting the higher the dose, the better the observed improvement.

“Likewise, active treatment resulted in an increase in peak nasal inspiratory flow and serum IgG levels compared to placebo,” Pfaar and colleagues wrote.

The highest improvements were found among study participants assigned the 40,000 AUN/ml dose.

All active doses resulted in higher rates of adverse reactions than placebo; however, the adverse reactions primarily were mild and were well controlled. – by Jeff Craven

Disclosure: The researchers report no relevant financial disclosures.