After vowing to plow on past NIH, SAB's COVID-19 drug tries to find footing in omicron era

SAB Biotherapeutics vowed to plow on through the fields with a cow-plasma-based COVID-19 treatment after the National Institutes of Health (NIH) dropped out last year. Now, the data harvest from that government-partnered study is complete and the company is pointing to secondary endpoints as signs of success.

SAB-185 was assessed in non-hospitalized people with COVID-19 at high risk for severe outcomes in a phase 3 study called ACTIV-2, which was started and completed by the NIH. Patients received either SAB-185 or Regeneron’s antibody treatment REGEN-COV—which was pulled from use in 2022 as omicron spread, rendering it ineffective.

While SAB touted in a press release Wednesday that the therapy led to sustained symptom resolution in patients with COVID-19 caused by omicron, that was not the primary endpoint of the study. On the main goal that looked at a composite of all-cause hospitalizations and deaths, the  trial was unsuccessful. SAB explained that the number of clinical events dropped significantly in late 2021. A previously conducted interim review by the data monitoring board determined that there would not be enough events to reach a conclusive result.

Now, the primary endpoint has been deemed inconclusive. A spokesperson said that the comparator treatment, REGEN-COV, stopped working, so the primary endpoint was not possible.

This is the exact issue flagged by the NIH when the agency shut down funding for the ACTIV-2 study in March last year. The NIH said that “it would not be possible to demonstrate statistically significant clinical efficacy with the existing study design” since so few enrolled patients with COVID-19 wound up at the hospital.

Ever optimistic, SAB pledged to keep working on the antibody treatment, which is derived from fully human antibodies derived from cows. The company said it could work for immunocompromised patients or to help battle future variants of the coronavirus.

On a measure of symptom resolution for COVID-19 caused by omicron, SAB said that 66% of participants taking SAB-185 reached full symptom resolution for at least four consecutive days by Day 28. In the REGEN-COV arm, 50% achieved that milestone. Patients on the SAB therapy also had a shorter time to symptom resolution by about seven days compared to the REGEN-COV patients.

SAB CEO Eddie Sullivan, Ph.D., said the data nevertheless serve as “further validation” of the company’s platform, according to the release. He separately told Fierce Biotech that conversations are ongoing with the NIH and the FDA about the future of SAB-185, including a potential emergency use authorization or full approval. 

“It shows that the DiversitAb platform can open the door to treatments that are potentially more effective and potent and which remain efficacious over longer periods of time versus monoclonal antibodies,” Sullivan said in the statement.

Sullivan and Chief Medical Officer Alexandra Kropotova, M.D., pointed to the FDA’s granting of fast-track and breakthrough-therapy designations to SAB’s anti-influenza A and B post-exposure prophylaxis treatment SAB-176 as further evidence of the platform’s potential.

Editor's note: This story was updated at 8:13 a.m. ET on April 27, 2023, with additional context from SAB.