Sorrento Therapeutics Inc (NASDAQ: SRNE) has announced that it has dosed its first patients in a Phase 1 study for ST1-1558. This viral protease inhibitor is to treat COVID-19. Researchers have found that it is effective against all strains of the virus.
The COVID-19 pandemic has been a significant global issue since 2020. While the world has tried its best to combat the disease, new variants have arisen which make the task more difficult. Currently, many of the drugs and vaccines available for COVID-19 do not protect from or prevent transmission of the omicron variant.
Paxlovid is the most effective drug against COVID-19
The EUA reports a need for oral broad-spectrum antiviral drugs with little drug-drug interaction to help fight the virus. One drug that has shown efficacy in treating the disease is Pfizer Inc.’s (NYSE: PFE) Paxlovid.
However, even Paxlovid has its limitations as health care workers need to administer it with Ritonavir, a Cytochrome P450 inhibitor, to reach therapeutic levels in the blood. As a result, Paxlovid stops the liver from breaking down other drugs using this enzyme. Because of this, using Paxlovid could lead to many drug-drug interactions; thus, it should be avoided for patients taking other medications who are at risk.
Preclinical trial results for STI-1558
Fortunately, STI-1558 has shown significant activity against all strains of the virus. The drug is a Cathepsin L inhibitor and thus can prevent the virus from entering the host cell. Sorrento tested the drug on a humanised transgenic mice model and found it effective against COVID-19.
The preclinical study also showed that the drug could protect the mice from viral lung replication, weight loss, and lung pathologies. Other preclinical studies demonstrated that the drug had an oral bioavailability of about 85% in monkeys and dogs, had increased target selectivity and was stable in liver microsomes.
Sorrento also conducted repeat-dose studies in dogs and rats to test its safety and found no cause for concern. The study involved histopathology, haematology, and blood chemistry, at a dose of 300mg/kg and 2000mg/kg daily. The researchers believed that the most appropriate dose for STI-1558 would be 300mg-600mg, with no need for Ritonavir to boost its therapeutic levels.