SAB Biotherapeutic's COVID-19 antibody treatment SAB-185 is no longer following in the footsteps of AstraZeneca’s Evusheld as the National Institutes of Health has axed a sponsored phase 3 trial citing low hospitalizations.
South Dakota-based SAB said that due to declining hospitalization and death rates, the NIH decided 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.
The agency’s ACTIV-2 trial was meant to assess the efficacy of an array of outpatient COVID-19 treatments. The participants have ranged from larger pharmas, like Eli Lilly and AstraZeneca, to smaller biotechs like SAB.
According to NIH’s clinical trials database, recruitment is still ongoing. However, the only company for which enrollment has not been closed is Synairgen.
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"The good news is that infections and hospitalizations are now falling sharply in the U.S.," said SAB President and CEO Eddie Sullivan, Ph.D. "But this decrease also has had the effect of making the current ACTIV-2 phase 3 study design statistically unworkable, and the NIH has therefore decided to stop patient enrollment.”
SAB's shares fell sharply on the news, down 45% to $2.48 as of 10:40 a.m. ET on Wednesday, continuing the company's precipitous decline on Wall Street since the start of the year. The stock previously closed at $4.59.
ACTIV-2 was originally launched in August 2020 to test novel COVID therapies, the first being Eli Lilly’s monoclonal antibody treatment bamlanivimab that was ultimately authorized. The study was expanded a year ago to bring four additional therapies to the fold, including AstraZeneca’s Evusheld, which received authorization in December 2021.
Sullivan said the SAB team will review data from the ACTIV-2 trial to determine the next steps for SAB-185, which could include prophylactic or therapeutic use for high-risk populations or against future variants. He also suggested the company could develop an injectable formulation to make dosing easier.
SAB’s treatment uses the plasma of cows genetically designed to produce human antibodies. In a nonclinical study published last month, the company demonstrated that by dosing cows with different versions of the SARS-CoV-2 virus' spike protein, the immune system built more robust protection against the circulating variants.
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The company announced in January that the data safety and monitoring board of the ACTIV trial had signed off on an interim analysis of its phase 2 data, clearing the way for a move to phase 3. At the time, the company said the late-stage trial was over 50% enrolled and results were expected later in 2022.
SAB received funding for SAB-185 from the Biomedical Advanced Research and Development Authority and the Department of Defense.
In a statement, the National Institute of Allergy and Infectious Diseases said SAB's treatment arm was the only arm halted as a result of low Omicron-related hospitalizations and deaths and that the ACTIV-2 trial remains ongoing.
"Low Omicron-related hospitalizations and death rates within the SAB-185 arm led the ACTIV-2 DSMB on February 28 to recommend halting enrollment into that arm, and NIAID accepted the DSMB’s recommendation," the agency said.
Editor's note: This story was updated at 4:24 to include a statement from NIAID.