FDA OKs Sublingual Grastek for Timothy Grass Pollen Allergy

Troy Brown, RN


April 14, 2014

The US Food and Drug Administration (FDA) has approved Timothy Grass Pollen Allergen Extract Tablet for Sublingual Use Grastek , Merck & Co, Inc) for the treatment of Timothy grass pollen-induced allergic rhinitis, with or without conjunctivitis, in individuals aged 5 to 65 years, with the understanding that autoinjected epinephrine will be available to patients at home, according to the manufacturer.

The decision follows a unanimous FDA Allergenic Products Advisory Committee vote to recommend Grastek for approval on December 12, 2013. That vote followed a discussion of data from five phase 1 studies, two phase 2 studies, six phase 3 studies, and two studies identified as phase 4 European studies.

Timothy grass is the most common allergy-provoking grass in North America. Current treatment consists of allergen avoidance and pharmacotherapies including antihistamines, leukotriene antagonists, and intranasal corticosteroids.

This is the second sublingual therapy approved by the FDA, which approved Oralair (Stallergenes, Inc) earlier this month to treat 5 different grass pollens. Grastek is the first sublingual allergy immunotherapy, though, approved for children as young as age 5, whereas Oralair is for children as young as age10. Grastek has been on the market in Europe since 2006 under the trade name Grazax.

Appealing for Use in Children

Sublingual immunotherapy has particular appeal for use in children. "[Grastek] is…approved for use in younger children, as young as 5 years of age, that many allergists, and parents, may be reluctant to treat with injections," Mark Moss, MD, director of the Allergy and Clinical Immunology fellowship program at the University of Wisconsin Hospital and Clinics in Madison, told Medscape Medical News.

Grastek dissolves in less than 10 seconds, according to a company briefing. This is important for younger children who may have trouble holding a tablet under their tongue for several minutes.

Side Effects Mainly Local

Side effects were primarily local, and included oral pruritus (26.7% MK-7243; 3.5% placebo), throat irritation (22.6% MK-7243; 2.8% placebo), ear pruritus (12.5% MK-7243; 1.1% placebo), and mouth edema (11.1% MK-7243; 0.8% placebo) in adults.

In children and adolescents, the most frequently reported side effects were oral pruritus (24.4% MK-7243; 2.1% placebo), throat irritation (21.3% MK-7243; 2.5% placebo), mouth edema (9.8% MK-7243; 0.2% placebo), and tongue pruritus (9.2% MK-7243; 0.9% placebo).

"[T]he most common [side effect] we see is oral itching…this is a common side effect of oral immunotherapy — not anaphylaxis. Other than that, it's just another way of delivering allergen to the immune system which is different than breathing them through the air," H. James Wedner, MD, chief of allergy and immunology at Washington University and Barnes-Jewish Hospital in St. Louis, Missouri, told Medscape Medical News.

Sublingual Immunotherapy May Not Cover All Allergens

Grastek only covers Timothy grass, and may be of limited use in those with multiple allergies.

"The beauty of…SCIT (standard subcutaneous immunotherapy) is that it can be tailored to the individual patient. If you use just the Grastek, you may miss an allergen or an entire group of allergens," Dr. Wedner explained.

"Timothy grass pollen is also very cross-reactive with other northern grass species but is not cross-reactive with southern grass species such as Bermuda grass," Dr. Moss said.

Grastek needs to be started 12 weeks before the grass pollen season. "For this year, that means that there may be a short window of time to begin treatment using the anticipated dosing recommendations," Dr. Moss noted.

The first dose should be administered in a healthcare setting under the supervision of a physician with experience in the diagnosis and treatment of allergic diseases. The physician should observe the patient for at least 30 minutes after receiving the first dose of Grastek to monitor for signs or symptoms of a severe systemic or a severe local allergic reaction. If the patient tolerates the first dose, the patient may take subsequent doses at home, according to the Merck statement.

Grastek includes a boxed warning that it may not be appropriate for those with severe or unstable asthma. "Grastek has not been studied in patients with severe or unstable asthma so use in patients with asthma should be extensively evaluated before this treatment is initiated," Dr. Moss said.

The product will be available in pharmacies in late April, according to the Merck statement.

Dr. Wedner and Dr. Moss have disclosed no relevant financial relationships.


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