Experts have released research that says drug repurposing is no quick fix for developing new treatments for COVID-19 with inherent dangers and pitfalls in translating drugs to treat the virus.
The potential challenges and opportunities with drug repurposing are highlighted in a paper authored by a cross-section of Australian drug discovery and translation experts, including from the pharmaceutical industry, academia, and investors.
The paper, published in Science Translational Medicine, comes as drug repurposing has been thrust into the global spotlight as a potential way to fast-track new treatments for COVID-19.
According to the study's lead author Dr Glenn Begley, who is the former global head and vice-president of haematology/oncology research at Amgen and current co-founder of Boston-based Parthenon Therapeutics, there are only a few examples of successful drug repurposing by academic groups.
Dr Begley said the regulatory process still requires a clear commercial value proposition, defined intellectual property, an established understanding of how the drug is metabolised, as well as rigorous preclinical and clinical studies to define dose and schedule in the new indication.
He cited the long road to repurposing thalidomide to treat leprosy and multiple myeloma, as one such example. Others include the repurposing of veterinary anti-worming drug moxidectin to treat river blindness and the fungicide dimethyl fumarate as a treatment for relapsing multiple sclerosis.
"Drug repurposing is seldom as trivial as taking the approved drug and performing a clinical trial in a different disease using the same dose and dosing schedule," said Dr Begley.
"It requires new preclinical safety and efficacy studies, appropriately designed phase I and 2 studies, regulatory authority oversight and typically the establishment of new IP. The failure rate, costs and time involved is similar for new drug development. It's no quick fix.
"In addition, without addressing these key issues, many of the drug-repurposing clinical programs fail to satisfy 'clinical equipoise' and are therefore unethical."
Co-author of the study and medicinal chemist, Professor Jonathan Baell from Monash University, said there was an assumption that drug repurposing was an efficient and effective way to deliver new drugs to market.
"In actual fact, this is naïve and ignores many of the realities of drug development required to achieve regulatory approval," said Professor Baell.
Professor Baell said there were more than 100 drug repurposing programs ongoing to develop new treatments for COVID-19, including anti-infective drugs like remdesivir, chloroquine, ivermectin and hydroxychloroquine.
He said without definitive randomised controlled phase 3 clinical trials to help determine their utility in different contexts, the early reports on their effectiveness were mixed.
"One major challenge with some of these repurposing efforts has been failure to correlate how the drugs move through the body or the way the body will respond to the drugs in concentrations necessary to treat COVID-19," he said.
Professor Baell said additional studies seeking to identify drugs that might be repurposed to treat COVID-19 were underway, but that many of the compounds lacked potency and would require very high, and potentially intolerable, doses to be clinically beneficial.
UniQuest executive director of commercialisation and study co-author, Dr Mark Ashton, said the group found one of the most pervasive challenges from drug repurposing was a lack of expertise to drive development and commercialisation.
"We can't expect those with undoubted expertise in basic science and clinical medicine, to also possess the required expertise to successfully navigate IP, preclinical and clinical development, and regulatory and reimbursement requirements for their potential drug candidates," said Dr Ashton.
"That's where a university technology transfer office or commercial and industry experts, and greater oversight and identification of drug repurposing opportunities, can really help."
