VTE late breakers from ISTH 2021

The late-breaking clinical trials session at the ISTH 2021 Congress featured a promising new anticoagulant for the prevention of VTE and some much needed evidence for duration of anticoagulation in children.

Abelacimab after TKA

Factor XI inhibition with a single intravenous dose of abelacimab after total knee arthroplasty is effective for the prevention of postoperative VTE, according to a phase 2 study.

The study, also published in the NEJM, comprised 400 patients randomised to either 30, 75 or 150 mg of abelacimab or 40 mg of enoxaparin.

Professor Jeffrey Weitz, from McMaster University, Canada and Executive Director of the Thrombosis and Atherosclerosis Research Institute, told the Congress that the fully human IgG1 locks factor XI into an inactive form.

The study found complete factor XI inhibition at day 3 with all three doses of abelacimab but persisting to day 10 only with the two higher doses.

Rates of VTE were 22% with enoxaparin and 13% with 30 mg abelacimab, 5% with the 75mg dose and 4% with the 150 mg dose.

“The results with all three doses of abelacimab met the criteria for non-inferiority and the two higher doses of abelacimab were superior to enoxaparin with p values of 0.0006 and 0.0002 respectively,” he said.

There were no major or clinically relevant non major bleeding to day 30 with either enoxaparin or the highest dose of abelacimab, but two events with each of the lower doses of abelacimab.

Adverse events occurred in a similar proportion of patients in all four study groups (15% with all doses of abelacimab and 13% with enoxaparin).

Serious adverse events with abelacimab included a coronavirus infection and wound infection in the 30mg group, a joint infection, ileus and ovarian cyst torsion in the 75 mg group, and a wound infection in the 150 mg dose group.

There were no hypersensitivity reactions or antidrug antibodies with abelacimab infusion.

Professor Weitz said another phase 2 study of abelacimab versus rivaroxaban in patients with atrial fibrillation was currently underway.

Both studies were funded by Anthos Therapeutics.

Duration of anticoagulation in young people

Another late breaker presented at ISTH has provided new evidence regarding the duration of anticoagulation for acute provoked VTE in young patients under 21 years of age.

Professor Neil Goldenberg, associate dean for research at the John Hopkins All Children’s Hospital, told the Congress that while some guidance had come by extrapolating from adults to children, high quality data in young people was lacking.

The international Kids-DOTT RCT, which included sites in Australia, randomised 477 patients with a mean age of 8 years to either six weeks or three months duration of anticoagulation. The predominant anticoagulant was low molecular weight heparin.

About 46% of patients had lower extremity DVT +/- PE and almost a third had upper extremity DVT +/- PE.

The study found low rates of recurrent VTE ranging from 0.65% (per-protocol) to 0.97% (intention-to-treat) with the 6-week regimen compared to 1.40% to 1.91% with the 3-month regimen.

Adverse events occurred in 26% of patients in the 6-week arm and 32% in the 3-month arm.

The study concluded discontinuing anticoagulants at 6 weeks was non-inferior to continuing anticoagulation for a full three months.

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