Agency says current application doesn’t include enough data for critical medical review.

Shares in Dutch firm Pharming took a bit of a battering today as FDA issued the firm and its U.S. commercialization partner Santarus with a refusal to file letter relating to a BLA for the recombinant human C1 inhibitor, Rhucin™, which is in development for the treatment of acute attacks of hereditary angioedema (HAE). FDA’s refusal to file letter indicated that the BLA was not sufficiently complete to enable a critical medical review, and by lunchtime today in Europe, shares in Pharming had taken an 18% nosedive. The firm and its partner say they plan to meet with FDA as soon as possible to discuss the issues and how best to move forward. Pharming’s recombinant human C1 inhibitor was approved in Europe in October 2010, where it is trademarked Ruconest.

The Rhucin BLA, submitted by Pharming in December 2010, included nine clinical studies involving 190 subjects. FDA’s refusal to file letter states that the submitted dossier doesn’t include data from enough subjects to support a review of the proposed 50 U/kg treatment dose. The application also lacked prospective validation of the visual analog scale used in measuring the clinical effects of Rhucin. The agency has in addition indicated that it will provide new feedback on the design of a recently started 50-patient Phase IIIb clinical trial and wants results from this study to be included in any future BLA submission for Rhucin.

Pharming initiated the new Phase IIIb study just last week and said resulting data will be used to provide additional validation of the visual analog scale used in measuring the clinical effects of Rhucin. The trial is expected to be completed in 12 to 18 months.

Rhucin/Ruconest is generated in the milk of transgenic rabbits. The product is separately undergoing development for the treatment of antibody-mediated transplant rejection and as a potential treatment for delayed graft function and ischemic reperfusion injury.

Santarus negotiated North American commercialization rights to Rhucin for the HAE indication and other potential indications back in September 2010. Pharming earned $15 million up front as part of the deal with Santarus and another $5 million on submission of the BLA. The Dutch firm is responsible for clinical development of Rhucin for HAE and HAE-related regulatory activities in the U.S. Santarus retains the responsibility for regulatory approval in Canada and Mexico. The two firms are sharing the costs of developing Rhucin for the treatment or prevention of renal transplantation rejection.

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