In the published study, Dr. Creticos indicated that studies have shown that standard allergen immunotherapy produces a less robust improvement in ragweed seasonal symptom scores compared with AIC, with no lasting benefit unless patients are treated with three or four years of treatment. Standard allergen immunotherapy has a much less convenient schedule than AIC, requiring 14 to 27 injections before the beginning of ragweed season.
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January 2007
AIC appears to be better tolerated than standard allergen immunotherapy. No serious adverse events were associated with AIC, including serious local reactions. However, up to 20% of patients who receive standard allergen immunotherapy report systemic reactions. Standard allergen immunotherapy generally utilizes a slow buildup to minimize the risk of allergic reactions. Dr. Creticos and his co-authors wrote, “AIC may offer a safer route of allergen administration that does not sacrifice efficacy.”
The mechanisms by which AIC exerts its effects require further study, he continued, and larger Phase III studies will establish the role of AIC as a therapeutic intervention in ragweed-induced allergic disease.
Promising Results
“The most exciting thing about this study is that it is the first to demonstrate a long-term benefit from a single, brief course of allergen-specific immunotherapy; the extent of benefit during the second season was similar to that of the first. These are promising results,” said David Khan, MD, Assistant Professor of Internal Medicine in the Division of Allergy and Immunology at University of Texas Southwestern Medical School in Dallas. Dr. Khan said that Dynavax is currently sponsoring a large, 30-center, placebo-controlled study to evaluate AIC in an attempt to replicate these findings.
“The FDA typically requires placebo-controlled studies, but it would also be desirable to compare AIC directly with standard allergen immunotherapy,” Dr. Khan commented.
Dr. Khan mentioned some caveats in interpreting the results of the pilot study. The severity of allergic rhinitis in the study population was unclear, as there were no severity criteria required for participation. “The number of antihistamines and decongestants taken during the study suggest that these patients did not have severe allergies. The median number of days of antihistamine use during the second year of the study was only eight in the placebo patients for the entire ragweed season,” he noted.
Further, the magnitude of exposure to ragweed may have influenced the results. In the study, the peak pollen count during the first ragweed season was 50 to 60 grains of pollen per cubic meter in Baltimore. Dr. Khan said the peak pollen count is often 10 times higher in north Texas. In year 2, the pollen count in Baltimore was almost doubled, which is still much lower than an area such as north Texas. “The fact that the vaccine’s effects persisted in year 2, with a higher pollen count, is more encouraging,” he said.