Anyone who’s ever undergone knee replacement understands the real and troubling risk of post-op blood clots. Many patients are told take a daily blood thinner pill long after their procedure.

But a new study finds that a one-time injection of an experimental blood thinner called abelacimab may greatly reduce the odds for these clots in recovering knee replacement patients.

The researchers compared abelacimab with another prescription blood thinner called enoxaparin (brand name Lovenox) in 412 patients undergoing knee replacement.

Compared to enoxaparin, a single injection of abelacimab reduced the risk of blood clots by 80% for up to a month after surgery, and didn’t increase the risk of bleeding — a common side effect with blood thinners.

“Patients who undergo knee replacement routinely receive anti-clotting treatment with enoxaparin or other anticoagulant medications that require daily administration,” said research team leader Jeffrey Weitz. He’s a hematologist and professor of medicine and of biochemistry and biomedical sciences at McMaster University in Hamilton, Canada. He’s also executive director of the university’s Thrombosis and Atherosclerosis Research Institute.

“With a single injection of abelacimab after surgery, we found much better protection against clots in the veins in the leg [deep vein thrombosis, or DVTs] compared with enoxaparin, one of the current standards of care,” Weitz said in a McMaster news release.

The study was funded by Massachusetts-based Anthos Therapeutics, which is developing abelacimab. The report was published July 19 in the New England Journal of Medicine and also presented at a meeting of the International Society on Thrombosis and Haemostasis.

According to the research team, abelacimab is an antibody that binds to both the inactive and activated forms of a clotting factor called factor XI, preventing its activation and activity, and halting clot formation.

One expert unconnected to the study said the drug shows some promise.

“DVT formation is a significant fear in lower-extremity orthopedic surgery. This drug could be applied not only to total joint replacement, but also to fracture treatment. I’ll look forward to further research,” said Dr. Jeffrey Schildhorn, an orthopedic surgeon at Lenox Hill Hospital in New York City.

The treatment’s convenience is also a huge plus, Schildhorn said. Patients only need the one-time injection and compliance should rise because they don’t need to remember to take a daily blood thinner pill, he added.

Still, there are unanswered questions, Schildhorn said. What if rare cases of excessive bleeding arise when abelacimab is used?

“If excess bleeding occurs in some patients, are the effects of this medication reversible? What agents are used to reverse the anticoagulant effects [that might lead to bleeding], and how much time is required for the effects to wane?” he wondered. Only further research can help answer those questions, Schildhorn said.

For their part, the research team believes that the positive findings from their trial suggest that abelacimab may help treat other cardiovascular conditions.

For example, Weitz said, the drug might be used “for prevention of stroke in patients with atrial fibrillation and for treatment of deep-vein thrombosis and pulmonary embolism — clots in the veins of the leg and clots in the lung,” and in cancer patients.

More information

The American Society of Hematology has more on blood clots.

SOURCES: Jeffrey Schildhorn MD, orthopedic surgeon, Lenox Hill Hospital, New York City; McMaster University, news release, July 19, 2021

Source: HealthDay