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Grastek®: FDA Approves New Sublingual Immunotherapy for Allergies

By: Kevin Lin, PharmD Candidate c/o 2015

This April, the FDA approved three sublingual immunotherapies for pollen induced allergic rhinitis: Grastek® (Timothy Grass Pollen Allergen Extract), Oralair® (Grass Pollen Allergen Extract), and Ragwitek® (Short Ragweed Pollen Allergen Extract). Formulated by Merck, Grastek® is Timothy grass pollen allergen extract. It is approved for patients ages 5 through 65 and is intended to treat only Timothy grass pollen. While Timothy grass pollen is one of the most common allergens in North America, Grastek® does not cover other common grass pollens such as Bermuda grass.1 Prior to use of this medication, skin testing is done to confirm the presence of the specific allergy; a red and raised bump where the allergen extract is placed on the skin confirms sensitivity to the allergen. Another diagnostic procedure involves blood testing that detects the presence IgE antibodies against Timothy grass.2

      Immunotherapy is the only available treatment for pollen allergies that provides a long lasting benefit even if interrupted or discontinued. Immunotherapy reduces the level of antibodies to pollen in the blood, creating a less sensitive response to the allergen. Until now, immunotherapy was performed in a physician’s office, requiring patients to come back multiple times for injections for a total of 3 years.3 This new sublingual immunotherapy offers a revolutionary alternative that is both painless and convenient.

Grastek® must be initiated at least 12 weeks before grass pollen appears (typically in late spring to summer) and is taken throughout the pollen season.4 It is not indicated for immediate relief of allergic symptoms. Due to the risk of experiencing a serious allergic reaction, patients must receive the initial dose under the supervision of a physician and be observed for at least 30 minutes.5 Some of the most common adverse reactions include oral pruritus (26.7%), throat irritation (22.6%), ear pruritus (12.5%), and mouth edema. Of note, Grastek® carries the risk of anaphylaxis and as such, it is recommended that patients also be prescribed an  EpiPen while on this medicaton.5

The efficacy of Grastek® was demonstrated in 2 placebo-controlled trials. One trial involved 1501 patients ages 5 through 65, and the other 344 pediatric patients ages 5 through 17. The trials lasted approximately 24 weeks with rhinoconjuctivitis daily symptom scores (measured by nasal and ocular symptoms) and daily medication scores (measured by the need for allergy medication) as end points. Nasal symptoms included runny, stuffy and itchy nose and sneezing while ocular symptoms were described as gritty, itchy, and watery eyes. Furthermore, a third endpoint called “total combined scores” was measured. This encompassed both symptoms and need for medication. Both trials found a significant reduction in nasal and ocular symptoms as well as the use of allergy medication compared to placebo.6 In total combined scores, a reduction of 23 percent (95% CI: -36.0%; -13.0%) and 26 percent (95% CI: -38.2%; -10.1%) was found in each trial, respectively.5

Grastek® was also found to have sustained effectiveness of one year after termination of treatment. In a five year study, 634 patients ages 18 to 65 were randomized to either placebo or Grastek®. Patients received treatment for three consecutive years and were then observed for two more years with no treatment. Patients experienced a decreased total combined score after three years of active treatment and had a sustained effect for one year after discontinuation of Grastek®. However, effectiveness was not seen in the second year.5

Overall, Grastek® is found to reduce allergy symptoms as well as the need for allergy medication. It is also effective for one-year post treatment. Those who suffer from allergies from Timothy grass pollen can consider this medication for effective relief from seasonal nasal and ocular symptoms.


  1. Pollen. National Institute of Environmental Health Sciences. April 2012. http://www.niehs.nih.gov/health/topics/conditions/asthma/allergens/pollen/index.cfm. Accessed April 25, 2014.
  2. Skin Testing to Diagnose Allergies. Asthma and Allergy Foundation of America. 2005. http://www.aafa.org/display.cfm?id=8&sub=16&cont=67. Accessed April 25, 2014.
  3. Pollen Allergy. National Institute of Allergy and Infectious Diseases. January 2012. http://www.niaid.nih.gov/topics/allergicDiseases/Documents/PollenAllergyFactSheet.pdf. Accessed April 25, 2014.
  4. Pollen and Mold Counts. Asthma and Allergy Foundation of America. 2005. https://www.aafa.org/display.cfm id=9&sub=19&cont=264. Accessed April 25, 2014.
  5. Prescribing Information. Merck & Co. Inc. 2014. Accessed April 25, 2014.
  6. FDA Approves Merck’s Grastek. Merck. 2014. https://www.merckconnect.com/grastek/overview.html?hcpUser=yes. Accessed April 25, 2014.

[pubmed_related keyword1=”patients” keyword2=”allergy” keyword3=”pollen”]

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