An expensive drug for the treatment of myelofibrosis, a rare bone marrow cancer, will be covered by the national health insurance in South Korea starting next month.

With the coverage, patients only have to pay 170,000 won ($154) compared to 6 million won, previously, for the same amount of the drug ― one pill per day.

The Health Insurance Review & Assessment service predicts that some 450 patients with high-risk myelofibrosis will benefit from the coverage. About 700 South Koreans suffer from the disease.

The drug, named Ruxolitinib or Jakavi, is a kinase inhibitor which works by blocking certain substances ― JAK1 and JAK2 ― that are associated with myelofibrosis.

Myelofibrosis is a type of bone marrow cancer in which the marrow is replaced by fibrous scar tissue.

Symptoms include bone pain, night sweats, bruising and abdominal pain or fullness due to an enlarged spleen.

The cause of the disease is unknown, as are its risk factors. Studies show that it often develops slowly in people over age 50.

By Claire Lee (dyc@heraldcorp.com)