A Phase III study conducted by Merck has revealed that its investigational allergy immunotherapy tablet (AIT) reduced the total combined score that measured nasal and eye symptoms and use of allergy medicines, compared to placebo, in Ambrosia artemisiifolia (ragweed) allergic adults with or without asthma.

AIT is a dissolvable oral tablet designed to treat the underlying cause of allergies, and is being studied to determine whether AIT may help to prevent allergy symptoms by stimulating an immune response against targeted allergens.

The multicentre double-blind randomised placebo-controlled parallel group Phase III trial enrolled 565 adults aged 18 to 50 years with ragweed-induced allergic rhinoconjunctivitis to evaluate the efficacy and safety of two doses of ragweed AIT.

In the study, patients were randomised to receive a once-daily tablet of ragweed allergen extract at a dose of 6Amb a 1-U or 12Amb a 1-U or placebo for approximately 16 weeks prior to and throughout the ragweed pollen season, for a total treatment period of 52 weeks.

The trial’s primary efficacy endpoint was total combined score, which was the sum of the daily symptom score and the daily medication score averaged over the peak ragweed pollen season.

During peak ragweed season, patients treated with ragweed AIT 12Amb a 1-U or AIT 6Amb a 1-U reported 27% and 21% reductions in total combined score, respectively, compared to placebo.

Both the doses of ragweed AIT showed 45% and 34% reductions in daily medication score, respectively, relative to placebo.

Merck Research Laboratories Respiratory & Immunology senior vice president and franchise head Rupert Vessey said patients who took AIT in the study experienced reduction in the nasal and eye symptoms caused by ragweed allergies.

In collaboration with ALK-Abello, Merck will develop AITs to treat the allergens in North America and intends to file New Drug Applications for its ragweed and grass AITs with the US Food and Drug Administration in 2013.