FILE PHOTO: Signage is seen outside of the Food and Drug Administration (FDA) headquarters in White Oak, Maryland, U.S., August 29, 2020. REUTERS/Andrew Kelly/File Photo

By Kamal Choudhury and Christy Santhosh

(Reuters) -The U.S. Food and Drug Administration on Thursday approved Kura Oncology and Japanese partner Kyowa Kirin's once-daily pill, Komzifti, to treat a rare form of blood cancer that has returned or stopped responding to treatment.

The drug is approved for acute myeloid leukemia patients with an NPM1 mutation, a genetic change found in about 30% of cases.

Acute myeloid leukemia is an aggressive cancer of the blood and bone marrow.

Kura said the drug will be available within the next few business days at a price of $48,500 for a one-month supply.

With the approval, Kura's drug now competes with Syndax Pharmaceuticals' Revuforj, which was approved for the same indication by the FDA last month.

Komzifti’s approval comes with a boxed warning for differentiation syndrome and an additional warning for QTc interval prolongation, a delay in the heart’s electrical recovery after a beat, and potential harm to unborn babies.

A boxed warning is the U.S. Food and Drug Administration’s strongest alert for serious or life-threatening risks and appears prominently on a drug’s label to warn doctors and patients.

Revuforj carries a boxed warning for QTc interval prolongation, giving Kura “a significant competitive advantage,” according to Wedbush analysts.

Kura's Chief Medical Officer Mollie Leoni said the risk of QTc prolongation with Komzifti is low, adding it is “extraordinarily unlikely” to lead to a boxed warning.

The company said it is in dialogue with the FDA about potential steps post-approval that could help refine the labeling.

Under the terms of its collaboration with Kyowa, Kura is responsible for manufacturing Komzifti and will lead commercialization in the United States, while Kyowa handles commercial strategy and development outside the U.S.

Analysts, on average, expect Komzifti to have annual sales of $1.32 billion by 2031, according to LSEG data.

(Reporting by Kamal Choudhury and Christy Santhosh in Bengaluru; Editing by Shailesh Kuber and Tasim Zahid)