WRAPUP 2-U.S. FDA staff backs CSL, GTC blood clot drugs

Atryn treats hereditary antithrombin deficiency, in which irregular protein levels can cause excessive clotting. The treatment is made using a human protein produced in milk from genetically engineered goats.

While patients usually take traditional blood thinners such as warfarin, such drugs are not suitable for high-risk surgeries or giving birth, company officials have said.

In its review, the FDA said company data showed Atryn helped prevent clotting in patients and had an "acceptable" level of risks.

GTC is also developing further studies to test the drug in patients at risk for clots in non-hereditary conditions such as coronary bypass surgery, which if approved later by the FDA could also boost sales, Cox said.

To make Atryn, company scientists injected human DNA into goat cells to breed about 200 genetically modified goats at its Massachusetts facility. Females then express the human anti-clotting protein in their milk when they begin lactating after giving birth.

The drug is licensed to Ovation Pharmaceuticals Inc [OVAPH.UL] in the United States.

The other product under FDA review, Riastap, made by the company's CSL Behring unit, is intended for patients with congenital fibrinogen deficiency, which limits the blood's ability to clot.

Company research showed Riastap increased clot firmness, which was "sufficient" to support accelerated approval for drugs for serious diseases, FDA reviewers said. Accelerated approval requires further study after marketing to confirm the product provides meaningful benefits to patients.

The safety of Riastap, derived from human blood plasma, "appears to be acceptable," the FDA reviewers said. The drug is already sold in parts of Europe as Haemocomplettan P.