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FDA Gives Nod to Procysbi; Raptor Ascends

By Marie Powers
Staff Writer

The FDA put some lift under the wings of Raptor Pharmaceutical Corp., approving the orphan drug Procysbi (RP103, cysteamine bitartrate delayed release) on its PDUFA date in the initial indication of nephropathic cystinosis (NC). The metabolic disorder primarily affects children, causing systemic toxic cystine accumulation and leading to progressive and irreversible tissue damage and multiple organ failure. The drug was approved for individuals 6 and older, including adults.

Procysbi, which can cross the blood-brain barrier, was engineered to allow release of cysteamine bitartrate microspheres in the duodenum for optimal absorption, while simultaneously enabling administration every 12 hours. In NC patients, Procysbi may reduce cellular toxicity by continuously removing cystine from the lysosome, according to the company.

Procysbi met the primary endpoint of statistically noninferior efficacy in its pivotal Phase III trial compared to Cystagon (Mylan Inc.), an immediate-release cysteamine bitartrate that must be taken every six hours around the clock and has served as the only approved treatment for NC. Cystaran (cysteamine ophthalmic solution, Sigma-Tau Pharmaceuticals Inc.) eye drops also were approved last year but only to treat corneal cystine crystal accumulation resulting from cystinosis.

The Procysbi study involved 43 adult and pediatric patients with NC who were randomly assigned to receive Cystagon or Procysbi for three weeks before being switched to the other product for an additional three weeks. Blood testing showed Procysbi was as effective as Cystagon in controlling cystine levels. (See BioWorld Today, July 26, 2011.)

The most common side effects in patients treated with cysteamine products included nausea, abdominal pain, constipation, indigestion, headache, drowsiness and dizziness. Serious side effects can include ulcers, altered mental state, seizures, severe skin rashes and allergic reactions.

Raptor filed for Procysbi approval using the FDA's 505(b)(2) regulatory pathway.

Anticipating a quick approval, in January, HealthCare Royalty Partners II LP took a significant position in the Novato, Calif.-based biotech, providing a $50 million loan agreement to help fund commercialization of Procysbi. The deal was structured with a $25 million tranche at closing, and Raptor is set to receive an additional $25 million following FDA approval of the drug. Both tranches mature on Dec. 31, 2019, and the loan is interest-only for the first two years while Raptor ramps up Procysbi’s commercialization. (See BioWorld Today, Dec. 21, 2012.)

The drug originally had a PDUFA date of Jan. 30, 2013. The day after the HC Partners agreement was disclosed, Raptor reported that the FDA extended the PDUFA date to April 30 to provide additional time to review the new drug application.

Raptor’s shares (NASDAQ:RPTP) spiked more than 12 percent at midday, when approval was disclosed, hitting a 52-week high of $7.67.

See Wednesday's BioWorld Today for more details.