Firazyr is an approved injection treatment for acute attacks of angioedema in patients with a genetic form of the disease, called hereditary angioedema or HAE. It may also be used to treat angioedema attacks caused by certain medications.

It was developed by Shire, which is now part of Takeda Pharmaceuticals. The active ingredient in Firazyr is icatibant.

How Firazyr works

There are three types of HAE, and all involve a deficiency or dysfunction of certain proteins in the blood. People with type 1 and 2 HAE have too little of a protein called C1 inhibitor.  This protein in insufficient amounts causes the body to make too much bradykinin.

Bradykinin is a protein involved in the swelling process. It causes blood vessels to dilate and become more permeable, which allows fluid to leak out and accumulate in tissues. Icatibant is a selective bradykinin B2 receptor antagonist, meaning that it blocks the receptors that bradykinin normally binds to so it cannot cause the painful and potentially serious swelling attacks that mark this disease.

Firazyr is an injectable form of icatibant that patients are trained to administer themselves when they feel the first symptoms of an angioedema attack. It was approved for use by adult HAE patients C1-esterase-inhibitor deficiency by the U.S. Food and Drug Administration (FDA) in 2011. The European Commission (EC) approved Firazyr for these same adult patients in 2008, and extended its use children, ages 2 and older, with HAE and C1-esterase-inhibitor deficiency in 2017.

Firazyr in clinical trials

Icatibant, the active ingredient in Firazyr, went through several Phase 3 clinical trials (NCT02584959, NCT00097695, NCT00912093, NCT00500656) to evaluate its safety and effectiveness in treating angioedema attacks in HAE patients. Results of these studies suggested that icatibant is a safe and effective treatment for acute attacks, and its ease of use was noted.

The safety, tolerability, and effectiveness of self-administered Firazyr was also evaluated in a Phase 4 and Phase 3 clinical trial (NCT01457430 and NCT00997204, respectively). Results do not appear to have been published, but a 2012 study that included trial results found self-administration of Firazyr to be safe and effective. In the Phase 4 trial, it reported a median time of 2.6 hours for a 50% reduction in symptom severity.

Icatibant also completed Phase 2 (NCT01154361) and Phase 3 (NCT01919801) clinical trials evaluating it as a treatment for angioedema attacks induced by angiotensin-converting enzyme (ACE) inhibitor medications. Results suggest that icatibant treatment is beneficial in these attacks.

A more recent and open-label (no placebo group) Phase 3 clinical trial (NCT01386658) evaluated the safety, efficacy and pharmacokinetics (how a drug is absorbed and processed in the body) of  icatibant in 32 children ages 2 to 17 with HAE and C1-esterase-inhibitor deficiency. Results, published in late 2017, showed that a single under-the-skin dose of icatibant (0.4 mg/kg; maximum 30 mg) was well-tolerated and provided “rapid” symptom relief.

An observational clinical trial (NCT01034969) is currently recruiting patients being treated with Firazyr who have HAE, ACE inhibitor-induced angioedema, non-histaminergic idiopathic angioedema, or acquired angioedema. This study will document clinical outcomes over time, with data included in a Firazyr patient registry. It opened in 2009 and expects to conclude in August 2019.


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