Grastek is an allergen extract for the treatment of grass pollen-induced allergic rhinitis with or without conjunctivitis.
The efficacy of Grastek ( Timothy Grass Pollen Allergen Extract ) was supported by two studies of approximately 24 weeks treatment duration over one grass season each in patients 5 through 65 years of age, and one 5-year grass pollen season study in patients 18 through 65 years of age. In all three randomized, double-blind, parallel-group, multi-center studies: a) patients had a history of grass pollen-induced allergic rhinitis with or without conjunctivitis, and sensitivity to grass confirmed by positive skin test or in vitro testing for pollen-specific IgE antibodies for Timothy grass; b) patients with non-grass sensitivities were included as long as the patients did not require treatment as a result of symptoms from those non-grass allergies during the grass season; c) Grastek or placebo was administered as a sublingual tablet and initiated approximately 12 weeks before the start of the grass pollen season; d) patients in both arms of the study were allowed to take symptom-relieving medications ( including systemic and topical antihistamines, and topical and oral corticosteroids ) as needed; e) efficacy was established by self-reporting of rhinoconjunctivitis daily symptom scores ( DSS ) and daily medication scores ( DMS ), the sums of which were combined into the total combined scores ( TCS ); f) daily rhinoconjunctivitis symptoms included four nasal symptoms ( runny nose, stuffy nose, sneezing and itchy nose ), and two ocular symptoms ( gritty / itchy eyes and watery eyes ).
The FDA criteria for clinically relevant efficacy of allergen immunotherapy is based on the TCS, which must have an average difference relative to placebo of less than or equal to -15%, and the upper bound of the 95% confidence interval ( CI ) must be less than or equal to -10%.
One study compared Grastek to placebo in 1,501 patients 5 through 65 years of age, of whom approximately 25% had mild, intermittent asthma and 85% were sensitized to other allergens in addition to grass.
Patients treated with Grastek had significant reduction of nasal and ocular symptoms, and reduction in use of symptom-relieving allergy medication, as measured by a decrease in the TCS for the entire grass pollen season, compared to placebo; difference for Grastek ( Timothy Grass Pollen Allergen Extract ) ( n=629 ) relative to placebo ( n=672 ) was -23% ( 95% CI: -36.0%; -13.0% ).
A second study compared Grastek to placebo in 344 patients 5 through 17 years of age, of whom 26% had mild, intermittent asthma and 89% were sensitized to other allergens in addition to grass.
Patients treated with Grastek had significant reduction of nasal and ocular symptoms, and reduction in use of symptom-relieving allergy medication, as measured by a decrease in the TCS for the entire grass pollen season, compared to placebo; difference for Grastek ( n=149 ) relative to placebo ( n=158 ) was -26% ( 95% CI: -38.2%; -10.1% ).
In one 5-year study, 634 patients 18 through 65 years of age received Grastek or placebo for three consecutive years and were then observed for two years during which they did not receive study drug.
Patients treated with Grastek had a decrease in TCS throughout the grass pollen season during the three years of active treatment. This effect was sustained during the grass pollen season in the first year after discontinuation of Grastek, but not in the second year.
TCS difference ( Grastek relative to placebo ) per year: Year 1: -34% ( 95% CI: -42.0%;-26.3% ); ( n=568 ); Year 2: -41% ( 95% CI: -51.8%;-29.5% ); ( n=316 ); Year 3: -34%; ( 95% CI: -45.5%;-21.4% ); ( n=287 ); Post Treatment Year 1: -27% ( 95% CI: -39.9%;-12.4% ); ( n=257 ). ( Xagena )
Source: Merck, 2014