The U.S. Food and Drug Administration approved Belgian drug maker UCB Inc’s experimental drug Cimzia to treat Chron’s disease in patients who have not responded to conventional therapies.

Crohn’s disease is a chronic, inflammatory bowel disease that affects more than 1 million people worldwide. It has no cure and its cause is unknown. The disease can cause diarrhea, fever, rectal bleeding, narrowing of the intestinal tract, obstructions, abdominal pain and so on. It also can lead to abnormal connections (fistulas) leading from the intestine to the skin or internal organs.

Cimzia, an injected drug, works to reduce the signs and symptoms of Crohn’s disease, but can cause significant side effects including headache, upper respiratory infection, abdominal pain, nausea and reactions at the injection site. Moreover, the drug affects the immune system and also blocks tumor necrosis factor, which may contribute to the onset of lymphoma and other cancers.

The FDA warned that the drug comes with increased risk for “serious adverse effects, including serious infections that can lead to hospitalization or death,” the agency said, according to Reuters.

That is the reason why the drug has received approval only when conventional treatments do not work.

Cimzia’s manufacturer will be required post-marketing studies that evaluate the drug’s long-term safety, the FDA said.