International trials of blood thinners have paused enrolment of critically ill COVID-19 patients.

Statement from the REMAP-CAP trial:

Three clinical trial platforms working together to test the effects of full doses of anticoagulants (blood thinners) in COVID-19 patients have paused enrolment for one group of patients. Among critically ill COVID-19 patients requiring intensive care unit (ICU) support, therapeutic anticoagulation drugs did not improve outcomes. Enrolment continues for moderately ill hospitalised COVID-19 patients in the trials.

We will continue to publicly share what we learn from these trial platforms as fast as possible. Professor Anthony Gordon Department of Surgery and Cancer

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 the trial sites have paused enrolment of the most critically ill hospitalised patients with COVID-19. A potential for harm in this sub-group could not be excluded 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 enrolment will continue to be enrolled in the trial. Whether the use of full-dose compared to low-dose blood thinners leads to better outcomes in hospitalised patients with less severe disease remains a very important question.

“We want to thank all the patients, clinicians, and research staff who have contributed to advancing knowledge of the best treatments for COVID-19,” said Anthony Gordon , M.D., Professor of Anaesthesia and Critical Care at Imperial College London and an NIHR Research Professor. “We will continue to publicly share what we learn from these trial platforms as fast as possible.”

COVID-19 is associated with significant inflammation and clinical and pathologic evidence of widespread blood clots. These trials were launched because clinicians have observed that many patients ill with COVID-19, including those who have died from the disease, formed blood clots throughout their bodies, even in their smallest blood vessels. This unusual clotting can cause multiple health complications, including lung failure, heart attack, and stroke.

Three international partners have come together in an unprecedented collaboration resulting in a multiple platform randomised controlled trial. The three international trials include: the Randomised, Embedded, Multi-factorial Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP) Therapeutic Anticoagulation; Accelerating COVID-19 Therapeutic Interventions and Vaccines-4 (ACTIV-4) Antithrombotics Inpatient; and Antithrombotic Therapy to Ameliorate Complications of COVID-19 (ATTACC).

The 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 to a lower dose often used to prevent blood clots in hospitalised patients. To meet the challenge of this pandemic, investigators worldwide joined forces to answer this question.

The trials are supported by multiple international funding organisations including the Canadian Institutes of Health Research (CAN), the National Institute for Health Research (UK), the National Institutes of Health (US) and the PREPARE and RECOVER consortia (EU).

In the UK this study is one of a number of COVID-19 studies that have been given urgent public health research status by the Department of Health and Social Care and is being led by investigators at Imperial College London & the Intensive Care National Audit & Research Centre (ICNARC).

See the press release of this article