Ligand, Glaxo drug gets special FDA designation

Ligand Pharmaceuticals said Monday that its drug Promacta has received "breakthrough" designation by U.S. regulators for a new use in patients with a rare form of anemia.

Ligand and its partner GlaxoSmithKline already market the pill to treat chronic hepatitis C and a rare condition called chronic immune thrombocytopenic purpura, in which the body attacks its own platelets.

Now the companies are asking the FDA to approve Promacta to treat severe aplastic anemia, a rare condition in which the bone marrow fails to make enough new blood cells. Currently there are no drugs approved for patients who do not respond to existing immune system drugs. About 40 percent of patients in this group die of infection or bleeding within five years of diagnosis, according to the drugmakers.

The FDA's breakthrough drug program was authorized by Congress in 2012 with the aim of speeding up development of promising medicines. Drugmakers that get the breakthrough designation receive extra meetings and earlier communication with FDA about their applications.

Shares of LaJolla, Calif.-based Ligand Pharmaceuticals Inc. fell $3.64, or 5.9 percent, to $58.30 in afternoon trading as major market indexes slumped. Its shares are up 12 percent over the past three months.