(Reuters) - (This Sept. 15 story has been corrected show that momelotinib is approved for patients regardless of prior myelofibrosis therapy, not just for patients previously treated with JAK inhibitors, in paragraph 3)
British drugmaker GSK Plc said on Friday the U.S. Food and Drug Administration had approved its oral therapy to treat anemia in patients with a type of bone marrow cancer called myelofibrosis.
The approval comes after the health regulator in July delayed its decision to review additional data.
The therapy, momelotinib, has been approved for patients "regardless of prior myelofibrosis therapy", according to GSK's statement on the FDA's approval.
While GSK's therapy, branded as Ojjaara, also belongs to the same class of treatments, it additionally helps bring down the levels of a protein called hepcidin, which regulates how the body uses iron.
Myelofibrosis is associated with high levels of hepcidin and disrupts the body's production of blood cells, often causing severe anemia, or a deficiency of red blood cells. People with myelofibrosis-triggered anemia rely on periodic blood transfusions to improve their red blood cell count.
It affects less than 50,000 patients in the U.S., according to government data.
Friday's approval is based on data from a late-stage study that showed the therapy was successful in reducing disease symptoms and cut patients' dependence on blood transfusions, compared with patients who received another anemia treatment called danazol.
Morningstar analyst Damien Conover estimated the therapy would gain close to 50% of the second-line myelofibrosis market and projected annual peak sales of close to 500 million pounds ($627.45 million).
"(Momelotinib) helps drive long-term growth for GSK as the patent protection extends beyond 2033 in key markets," Conover said ahead of the approval.
In an effort to boost its cancer business, GSK added momelotinib to its pipeline through a $1.9 billion buyout of cancer drug developer Sierra Oncology last year.
GSK's oncology business, which made up 2% of its total sales in 2022, suffered trial setbacks on two cancer compounds that were touted as potential blockbusters last year.
Sierra had earlier acquired momelotinib from Gilead Sciences in 2018 for an upfront payment of $3 million, with up to $195 million in milestone payments.
($1 = 0.7969 pounds)
(Reporting by Mariam Sunny and Bhanvi Satija in Bengaluru; Editing by Devika Syamnath)