Incyte stock prices soared after the pharmaceutical company announced that U.S. federal regulators approved a drug meant to treat patients with the rare bone marrow disease myelofibrosis.

In the span of 4 minutes starting at 11:40 a.m., stock in the company based in Wilmington, Del. increased nearly 13 percent to $14.27 per share on the Nasdaq.

The drug Jakafi (pronounced JAK-ah-fye) represented two firsts in the industry: the first drug to treat myelofibrosis, a disease of the bone marrow that produces blood cells; and the first in a class of drugs known to inhibit cell signaling of Janus kinase enzymes, also known as JAKs.

The availability of Jakafi is a significant medical advancement for people living with myelofibrosis, a debilitating disease, Paul Friedman, Incyte president and CEO, said in a company release. This milestone marks a tremendous achievement for Incyte because a scientific discovery from our research laboratories has become the first JAK inhibitor to reach the market and provide a clinical benefit to patients.

Stocks gradually settled down after the initial jolt and reached $13.15 per share by 2:44 p.m., an increase of 4.4 percent.

Regulators classify Jakafi as an orphan drug since it treats the fewer than 200,000 people in the U.S. who have the rare disease.

The Food and Drug Administration, which approved twice-daily drug said the most common side effects included anemia, bruising, dizziness and headaches.

Myelofibrosis disease causes scar tissue to replace bone marrow, which causes blood to form in other organs such as the liver and spleen.

Complications from the disease include anemia, higher infection risk and organ swelling. The clinical trials showed a reduction in several symptoms 24-weeks into treatment including abdominal discomfort, pain under left ribs, night sweats, itching, bone/muscle pain and early satiety at 24 weeks compared to baseline, the FDA announcement said.