Sanofi is getting ready to file its JAK2 inhibitor for myelofibrosis on strong late-stage data for the rare, but serious blood disease.

The drug, code-named SAR302503, met its primary endpoint in both dose groups (400mg and 500mg) in a Phase III trial, assessing the proportion of patients achieving less than 35% reduction of spleen volume. Full results will be presented at an upcoming medical congress.

The French drugmaker stated that the 289-patient study was granted a Special Protocol Assessment by the US Food and Drug Administration, signifying that the trial is acceptable to support a filing. Debasish Roychowdhury, head of Sanofi Oncology, noted that submissions with other regulators are being planned.

He also pointed out that since Sanofi’s acquisition of the molecule, gained through the purchase of TargeGen, SAR302503 has moved from Phase I to the completion of Phase III in less than three years. MF is a rare, debilitating and life-threatening haematologic malignancy characterised by abnormal blood cell production and scarring, or fibrosis, in the bone marrow. The spleen and liver try to produce and store extra blood cells, which can cause these organs to become enlarged.

If approved, the drug would compete with Novartis/Incyte's Jakafi/Jakavi (ruxolitinib), which is already approved on both sides of the Atlantic. A Phase II study in patients who are either resistant or intolerant to ruxolitinib is ongoing, Sanofi noted.