(HealthDay News) — Reducing factor XI levels with a second-generation antisense oligonucleotide (FXI-ASO) is effective for preventing venous thromboembolism after total knee arthroplasty, according to a study published online December 7 in the New England Journal of Medicine. The findings were released to coincide with the annual meeting of the American Society of Hematology, held from December 6–9 in San Francisco.

Harry R. Büller, MD, from the University of Amsterdam, and colleagues conducted an open-label parallel-group study involving 300 patients undergoing elective primary unilateral knee arthroplasty. Participants were randomized to receive one of two doses of FXI-ASO (200 or 300mg) or 40mg of enoxaparin once daily.

The researchers found that around the time of surgery, the mean factor XI levels were 0.38, 0.20, and 0.93 units per milliliter in the 200mg FXI-ASO, 300mg FXI-ASO, and enoxaparin groups, respectively. The primary efficacy outcome of incidence of venous thromboembolism occurred in 27% of those who received the 200mg dose of FXI-ASO, 4% of those who received the 300mg dose of FXI-ASO, and 30% of those who received enoxaparin. Compared with enoxaparin, the 200mg regimen was noninferior, and the 300mg regimen was superior (P<0.001).

“These findings support the concept that with the use of strategies targeting factor XI, thrombosis and hemostasis can be dissociated,” the authors write.

The study was funded by Isis Pharmaceuticals, the manufacturer of FXI-ASO.

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