Biotron (ASX:BIT) on Friday said its phase two trial investigating the use of the medication BIT225 to treat COVID-19 was not able to meet its trial endpoint of reducing SARS-CoV-2 nasal viral load, according to a same-day filing with the Australian bourse.

Despite the study meeting its safety and tolerability endpoints, it showed that those treated with the medication had similar viral levels after seven days to those treated with placebo, the pharmaceutical firm said in the filing.

"Demonstrating the efficacy of new drugs to treat this disease is difficult in small trials, conducted in people without high risk of progression to severe COVID, who are excluded from investigative, placebo-controlled trials," said Biotron's Managing Director Michelle Miller.

"The widespread availability of vaccination as well as immunity due to prior infection with SARS-CoV-2 contribute to challenges in demonstrating clinical efficacy in these trials," Miller added.

Biotron's shares plummeted nearly 36% in recent trade.

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