RedHill's 2nd try COVID pill staves off hospitalization in phase 2

RedHill Biopharma's daily oral antiviral, upamostat, staved off hospitalization in all 41 patients with symptomatic COVID-19 in the phase 2 portion of a small phase 2/3 study.

The patients, who were symptomatic and had not been hospitalized before treatment, were able to avoid a trip to the hospital. In the placebo arm of the phase 2, three of 20 patients required hospitalization. 

Upamostat, a once-daily oral medicine, was also safe and tolerable in the phase 2 study, meaning the antiviral met its primary endpoint, RedHill said Tuesday. The therapy, also named RHB-107, reduced new severe COVID-19 symptoms by 87.8%, the biotech said. One patient on the drug experienced severe new symptoms compared to four patients in the placebo group. 

The biotech plans to submit data and discuss nexts steps for the study with regulators. RedHill did not say which of the two doses—200 mg or 400 mg—it will carry forward into the second part of the trial. 

RELATED: RedHill BioPharma follows familiar biotech path after COVID-19 drug fails in severe patients

Shares of RedHill were trading down 8% to $2.01 apiece as of 1:18 p.m. ET on Tuesday.

RedHill tested the antiviral mainly in the U.S., with 60 of the 61 patients here and one in South Africa. The last patient was randomized Nov. 12, and 62.5% of patients had the delta variant, RedHill said. 

That means RedHill's study began before omicron became the predominant strain, and the study was not designed to specifically examine that variant. 

RedHill's medical director, Terry Plasse, M.D., tried positioning the antiviral as a "highly desirable variant-agnostic potential treatment option" given its human cell factor targeting. The company said the antiviral and its other investigational COVID-19 treatment, opaganib, are not expected to be impacted by omicron. The biopharma's claim is based on the drugs' modes of action, which target a protein in the human cell required by the virus for replication rather than directly going after the virus itself, the company said in December 2021 as the variant was rapidly spreading.

RELATED: 2021's top 10 clinical trial flops

The omicron variant has sidelined some authorized antibodies in recent months. The FDA grounded Eli Lilly's antibody cocktail of bamlanivimab and etesevimab along with Regeneron's monoclonal antibody REGEN-COV on Jan. 24. Lilly has since gained another emergency use nod for a different COVID-19 monoclonal antibody, bebtelovimab, which was shown to be effective against omicron.

As for RedHill, Plasse acknowledged the biotech's study was a "small overall sample size." The phase 2/3 study of the serine protease inhibitor, in-licensed from Heidelberg Pharma, was approved by the FDA in November 2020. 

"Given the limitations of current options for early treatment of COVID-19, we are excited to progress the development of RHB-107, subject to additional discussions with regulatory authorities," Plasse said in the company's press release. 

This is RedHill's second attempt at pushing a COVID-19 treatment to market. The biotech previously tried getting its SK2 inhibitor opaganib across the finish line but failed to show the treatment helped severely ill patients who had been hospitalized and were on supplemental oxygen. 

RELATED: AstraZeneca's COVID-19 antibody combination fails post-exposure prevention trial

That phase 2/3 test flopped in September 2021, but the company has been moving forward with the drug based on data from patients who received the med on top of Gilead's Veklury and corticosteroids. 

Based on those data, RedHill initiated submissions of opaganib data to regulators in the U.S., U.K., EU and elsewhere in the fourth quarter of 2021, the company said in February. At that time, RedHill was planning for potential emergency use and marketing authorization applications in the first half of 2022. 

Other companies have also failed in their attempts to produce an effective COVID-19 treatment. Laurent Pharmaceuticals' drug failed in September 2021 after a line of flops from CytoDyn and Novartis-partnered Mesoblast