Even as scientists work to develop new medications, many rarely prescribed, or even forgotten, drugs are making a comeback, being used to treat illnesses they weren't originally designed for.
“It is a very easy way to explore whether something that is therapeutically beneficial in one area and for one type of patient might be useful for another type of patient," said Aris Persidis, president and co-founder of biotechnology company Biovista. "And the difference in our thinking is, 'To date, this is done by accident. Wouldn't it be great if this could be done systematically?”
Developing a brand new drug can take 10 years or more, and costs in excess of $1 billion, according Persidis, which is why Biovista is studying new uses for safe compounds that have been supplanted by newer or better formulations and are no longer prescribed. The concept is called drug repurposing.
Persidis says researchers use a huge database to identify drugs or experimental compounds developed for one illness that might be used to treat other conditions.
“There's about 90,000 drugs and drug-like compounds at any point in time in total that we have mapped against all 29,000 clinical outcomes of interest known to modern medicine," he said. "And we call this the clinical outcome, 'search space,' simply because it enables us to transverse any indication in any drug or any combination of these things as is relevant to a patient.”
Biovista has identified an anti-depressant that has proven effective against multiple sclerosis. The company is moving forward with that, and with other repurposed compounds to treat epilepsy, a deadly form of skin cancer called melanoma, and thyroid cancer.
Comeback for baby defects drug
Then there is thalidomide. Before it was banned in 1962, the anti-nausea drug was given to thousands of women early in their pregnancies. It caused horrific birth defects - as many as 20,000 babies worldwide were born with shortened arms that looked like seal flippers.
But researchers who continued to study the drug found in the 1990s that the compound caused the remission of a rare type of blood cancer called multiple myeloma. However, they also noted that the cancer eventually returned.
At New York’s Dana-Farber Cancer Institute, scientists discovered that thalidomide kills myeloma cells through a different mechanism than the one that causes birth defects. They also learned why it stops working against cancer, a discovery that could pave the way for an effective anti-cancer treatment.
"The immediate impact is we now know how these drugs work that may help in terms of their further clinical development," said researcher William Kaelin, who heads a team investigating thalidomide compounds. "Now, a number of other cancer proteins that we think of as being undruggable might be attacked. So I think hopefully we can go back to this playbook over and over.”
Kaelin is looking forward to a new era of drug development.
“I am most excited about the possibility of better thalidomides and other drugs that basically borrow from the thalidomide paradigm,” he said.
With tens of thousands of drugs waiting to be considered for repurposing, the possibilities for new, unexpected therapies are endless.