Costa Rica begins clinical trials of equine plasma for coronavirus patients

Costa Rica on Monday began clinical trials of antibody-rich plasma that has been extracted from horses with the purpose of treating COVID-19 patients.

According to Román Macaya, executive president of the Costa Rican Social Security System (CCSS), four hospitalized patients received the first doses of the plasma on Monday morning. The Phase II study will comprise at least 26 patients across four public hospitals.

Ultimately, the CCSS hopes the equine plasma will prevent patients hospitalized with COVID-19 from deteriorating further. If the treatment reduces the average length of hospitalization, it would help free up Costa Rica’s limited hospital capacity.

“It’s a moment of optimism, but scientific evidence will always guide us,” Macaya said of the study.

The Clodomiro Picado Institute at the University of Costa Rica — which specializes in snake antivenoms — created the serums from the blood of horses that have been injected with non-infectious SARS-CoV-2 proteins.

The institute designed two versions of the plasma, which are being compared as part of the study. The first version is based on a single protein from the SARS-CoV-2 virus, while the other is from four different proteins.

Both serums were shown to inhibit the infectivity of SARS-CoV-2, the virus that causes COVID-19, during in vitro tests performed at the National Center for Biodefense and Infectious Diseases in the United States. In vitro refers to a study performed outside of a living organism. 

“The immune response of the horses was activated to block a ‘key,’ preventing the virus from infecting cells and replicating,” explained Alberto Alape of the Clodomiro Picado Institute, in late July.

The treatments are not a replacement for an eventual vaccine, Macaya said. The Central American Bank for Economic Integration recently approved a loan to help Costa Rica purchase an eventual vaccine.

Alfredo Sanabria-Castro is the study’s lead investigator, and each hospital with participating patients will receive additional support to monitor their progress.

Costa Rica also treats hospitalized patients with convalescent plasma created from the blood of recovered COVID-19 patients, but the equine plasma is many times stronger.

“This is not a substitute for a vaccine, [but] it’s a therapeutic strategy to use until we have a vaccine, so that we lose the fewest number of people due to COVID-19,” Macaya said.

The Clodomiro Picado Institute began exploring equine plasma to treat COVID-19 in April. In addition to the positive in vitro results at a U.S. lab, the treatment has met all regulatory guidelines for a clinical study, Macaya said.