International trials of blood thinners pause enrollment of critically ill COVID-19 patients

Three clinical trial platforms working together to test the effects of anticoagulants (blood thinners) in people with COVID-19 have paused enrollment of critically ill hospitalised patients.

 

Among critically ill COVID-19 patients requiring intensive care unit (ICU) support, full doses of anticoagulation drugs did not improve outcomes. The trials are continuing to enroll moderately ill hospitalised COVID-19 patients.
 
Three international partners have come together in an unprecedented collaboration resulting in a multiple platform randomised controlled trial. The partners include REMAP-CAP - the Randomised, Embedded, Multi-factorial Adaptive Platform Trial for Community-Acquired Pneumonia. REMAP-CAP is a nationally prioritised COVID-19 study, and as of November 2020 75% of all study participants had been recruited in the UK through the NIHR’s Clinical Research Network (CRN).
 
The other partners are Accelerating COVID-19 Therapeutic Interventions and Vaccines-4 (ACTIV-4) and Antithrombotics Inpatient and Antithrombotic Therapy to Ameliorate Complications of COVID-19 (ATTACC).
 
The three trials, which span four continents, have the common goal of assessing the benefit of full doses of blood thinners to treat moderately ill or critically ill adults hospitalised for COVID-19, compared with a lower dose often used to prevent blood clots in hospitalised patients.

As is normal for clinical trials, these trials are overseen by independent boards that routinely review the data and are composed of experts in ethics, biostatistics, clinical trials, and blood clotting disorders.

 

Informed by the deliberations of these oversight boards, all of the trial sites have paused enrollment of the most critically ill hospitalised patients with COVID-19. The researchers could not exclude potential for harm in this sub-group, and increased bleeding was noted with full-dose anticoagulation. The trials are working urgently to undertake additional analyses, which will be made available as soon as possible. It should be noted that patients who had another reason to take full-dose blood thinners were not included in the trials.
 
At the recommendation of the oversight boards, patients who do not require ICU care at the time of enrollment will continue to be enrolled in the trial. Whether the use of full-dose compared with low-dose blood thinners leads to better outcomes in hospitalised patients with less severe disease remains a very important question.