The Food and Drug Administration on Wednesday approved a new drug from Pharmacyclics and Janssen Biotech Inc. to treat a rare and aggressive form of blood cancer.

The agency said it approved Imbruvica for patients with mantle cell lymphoma who have already received at least one previous drug therapy. The cancer typically starts in lymph nodes but has usually spread to the bone marrow and other organs by the time it is diagnosed.

The once-a-day capsule works by blocking a protein that allows the cancer to multiply and spread. Regulators approved the drug based on a study of 111 patients in which 66 percent of patients saw their cancer tumors shrink or disappear after receiving the drug. It is not yet clear whether the Imbruvica actually extends patients’ life expectancy.

Imbruvica is the second medicine approved under FDA’s breakthrough designation, which was authorized by Congress last year. The classification is designed to speed up development of promising drugs by providing companies with extra meetings and earlier communication with FDA scientists.

“The agency worked cooperatively with the companies to expedite the drug’s development, review and approval, reflecting the promise of the Breakthrough Therapy Designation program,” said Dr. Richard Pazdur, head of FDA’s office of cancer drugs, in a statement.

The new drug will be co-marketed by Sunnyvale, Calif.-based Pharmacyclics and Janssen Biotech Inc., a unit of New Brunswick, N.J.-based Johnson & Johnson.

Shares of Pharmacyclics Inc. rose $4.15, or 3.5 percent, to $123.82. Johnson & Johnson ended down 22 cents at $93.34.

(AP)