Three years after dismissing an application for Firazyr (icatibant) after citing the company for insufficient trial data, regulators at the FDA this morning stamped Shire's ($SHPGY) new drug for hereditary angioedema with an approval.

News of the approval was widely expected after an expert panel voted to endorse the treatment back in June. A solid majority of the panel also expressed support for letting patients inject themselves as needed when faced with a sudden attack of the rare genetic condition. Analysts estimate that peak sales could break the $100 million mark.

"Having a product like Firazyr that is portable, that you can carry with you, can be stored at room temperature and that you can self-administer at the onset of an attack is a huge advancement for these patients," Sylvie Grégoire, president of Shire HGT, told FierceBiotech.

"Firazyr provides a new option to treat acute attacks of HAE and because it can be self-administered through an injection in the abdominal area, patients can treat themselves upon recognition of an HAE attack," said Dr. Curtis Rosebraugh, director of the Office of Drug Evaluation II in the FDA's Center for Drug Evaluation and Research.

HAE is caused by low levels or the improper function of a protein called C1 inhibitor, which is involved in regulating how certain immune system and blood clotting pathways function, says the FDA. It can cause swelling all over the body, and its attack on airways can be deadly. Fewer than 30,000 people in the United States have HAE.

The FDA approval positions Shire to kick sales of Firazyr, which was given the green light in Europe three years ago, into a higher gear. Shire brought in $11 million in sales of the drug last year, up 82% from 2009. And, while not among the firm's biggest sellers, Shire expects sales of the product to grow rapidly in the years to come.