Human antibodies produced by a herd of South Dakota dairy cattle are being tested as a potential treatment for COVID-19.
The cattle, a Holstein mix, have been genetically modified to have a partially human immune system. During a clinical trial sponsored by the National Institutes of Health, two different doses of the cow-produced antibodies are being tested in people with mild to moderate COVID-19.
SAB Biotherapeutics, the Sioux Falls biotech firm that developed the antibody-producing technology, announced late last month that the first patient in the trial already had received a dose of the antibodies, a product called SAB-185.
Eddie Sullivan, SAB’s co-founder, president and CEO, called the trial a “significant milestone” for the company.
While effective COVID vaccines now are widely available in the United States, he said, they’re not the only story. Treatments still will be needed, just as both vaccines and treatments are needed to combat influenza, another virus with a high ability to mutate.
“You need to think of it as bookends,” he said of the two strategies.
Indeed, monoclonal antibody therapies have been used throughout the pandemic. But the company’s product, Sullivan said, produces a polyclonal response, meaning the antibodies can bind to more than one site on the coronavirus. Monoclonal antibodies, as the name suggests, can bind to only one. Humans naturally fight disease through a polyclonal response.
That could be important at a time when variants of the coronavirus have begun to outmaneuver some monoclonal antibody treatments. The Food and Drug Administration last month rescinded emergency approval for one monoclonal therapy when used by itself because it had “lost potency” against some variants.
That particular therapy has been credited with helping keep some Nebraska nursing home residents with COVID-19 out of hospitals. The therapy now is recommended for use only in combination with another such treatment, according to an alert the Nebraska Department of Health and Human Services sent to health care providers. Other combination therapies also remain available.
Sullivan said the company has tested its product against variants. A recent study, published online but not reviewed by other scientists, indicates the firm’s antibodies “do not lose significant activity to many of these variants we’re seeing around the world,” he said.
The company produces the antibodies by injecting the modified cattle, which look like those found on many Midwestern farms, with a noninfectious portion of the coronavirus. The cattle produce antibodies to fight it.
Because the cows are injected over and over again, the animals build up high levels of the neutralizing antibodies, more than what are found in convalescent plasma donated by people who have recovered from COVID-19 and more than what are found in vaccinated people, Sullivan said.
Previous research by the company indicates the cow-made antibodies produced 40 times more neutralizing activity than the researchers had seen in even the highest convalescent plasma titers.
Convalescent plasma has produced mixed results during the pandemic. In March, the NIH halted a clinical trial of convalescent plasma in treating emergency room patients with mild to moderate COVID symptoms after researchers concluded it was unlikely to benefit that group.
The SAB antibodies are being added to an ongoing NIH trial that also is testing four other possible therapies in patients worldwide, run by an existing research network. A total of 220 patients, 110 at each of the two sites, will receive the product. Their results will be compared to patients who receive a placebo.
The company has been working to develop the technology behind the product for nearly two decades. Support for the development of the product now in trials came through a federal contract.