Given how many infusions hemophilia patients must undergo, pharmaceutical companies have been trying to develop drugs that are taken less often but still keep bleeding in check. Sanofi and Sobi’s, for example, is meant to be administered once a week.

The partners have a stronger case for their drug, now that it’s backed by positive findings from a study of nearly 160 patients with severe hemophilia A, defined as having less than 1% the normal amount of clotting protein.

According to Sanofi and Sobi, patients who were given the drug as a once-weekly preventive treatment ended up having, on average, less than one bleeding event over the course of a year. Additionally, once-weekly dosing of the drug was significantly better at lowering annual bleeding rates than the prophylactic Factor VIII infusions that patients had received previously.

Sanofi and Sobi said they will present more detailed data from the study at an upcoming medical meeting. But in the meantime, they intend to use the results generated thus far to ask for regulatory approval.

Approval submissions will begin this year, the companies said, though in Europe, they’ll be holding off until data from an ongoing study of the drug in pediatric patients becomes available. Those results are expected in 2023.

“We believe [our drug] provides higher protection for longer duration with reduced treatment burden of once-weekly dosing, and we look forward to working with regulators to bring this therapy to patients as soon as possible,” said Dietmar Berger, Sanofi’s chief medical officer, in a statement.

Sanofi’s share price rose by more than 3% Wednesday morning, to hover around $52. Shares of Sobi, which trades on the Stockholm stock exchange, also rose, by almost 7%.

For Sanofi, an approval would further justify the company’s $11 billion acquisition of Bioverativ in 2018, which provided access to two marketed hemophilia products in Eloctate and Alprolix as well as a series of experimental programs for blood disorders. The first of those programs, an anemia therapy called Enjaymo, secured Food and Drug Administration approval last month.

Enjaymo and the newer hemophilia drug, if cleared by regulators, could also help offset challenges elsewhere in Sanofi’s rare blood disorders business. Sales of Eloctate and Alprolix, for example, have fallen due to increased competition.

Hemlibra, a hemophilia A drug developed by Roche, has been particularly impactful to Sanofi and other rivals because it can be given as infrequently as once every four weeks. In 2021, sales of Hemlibra rose 41% to just over 3 billion Swiss francs — or roughly $3.3 billion — while those of Eloctate, which also treats hemophilia A, dropped around 8%.