Drug Repurposing, A Pharmaceutical Revolution

Susana Fares Mazloum

Drug repurposing or drug repositioning, is a drug development strategy extensively used during the recent years within the research field, it involves predication on the reuse of existing licensed drugs that are available in the market for new medical indications, that is, the treatment of different diseases from which they were initially designed for.

This strategy has gained its own background in the research field becoming a promising one in drug discovery and in the identification of new therapeutic opportunities. It has has additionally became noticeably attractive due to the fact that conventional methods of drug development are usually a lengthy, complex, and costly process, accompanied with a high degree of ambiguity and unpredictability wether a drug will actually succeed.

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Fig.1 Drug repurpose. Credit: FutSci

The amount of money spent to develop a drug highly depends on what the expenses to conduct studies to eventually prove its safety and effectiveness, and finally to secure its regulatory approval. All in all, recent evaluation from the Tufts Center for the Study of Drug Development, puts the cost of bringing a medicine from trials, final development and to pharmacy shelves at $2.7 billion approximately, it’s also emphasized that it may range from $10 million to $2 billion, depending on what exactly the drug developed is for. But what really raises the cost is the fact that 90% of medicines that go through the process of human trials will not reach the market in the long run because the trial results will demonstrate to be unsafe or ineffective.

 

Time is also an important setback in the drug development challenge, it can take at least ten years for a new drug to complete the process from its early discovery to the marketplace, and it can raise to 20 years. Sometimes clinical trials alone can take six to seven years on average.

According to Donald R. Kirsch, the author of the Drug Hunters, there can be times that the researchers start developing one specific drug but end up with something different, in his book he says, “I’ve learned that the only sure thing in the drug hunting business is that you almost never end up with the exact drug you started stalking. The vast majority of my colleagues, all educated at top-flight research universities and working at posh laboratories festooned with high-tech gear, have spent their entire careers groping through the labyrinth of bio-active molecules without ever finding a new compound that safely and effectively improves human health” he adds, “only about 5 percent of a scientist’s ideas for a drug discovery project get funded by management. Of these, only 2 percent end up producing an FDA-approved medicine. That means a drug hunting scientist can only expect to make a difference about one tenth of 1 percent of the time. Finding new drugs is so challenging, in fact, that it has led to a crisis in the pharmaceutical industry. Big Pharma companies are becoming increasingly frustrated with the massive research expenditures necessary to come up with new drugs—an average of about $1.5 billion and fourteen years for each FDA-approved drug—and the exasperating fact that the vast majority of their endeavors don’t produce a usable drug”.

Recent instances of successful repurposed drug include, all-trans retinoic acid (ATRA), a popular marketed chemical compound found in medications that treat severe acne. ATRA when combined with traditional chemotherapy demonstrated to induce complete remission in 90% of patients with acute promyelocytic leukemia, additionally, decreasing the chance of relapse among leukemia patients in remission. During the 1950s, Methrotrexate was developed as a chemotherapy drug. Now, at a low dose, it has become a standard care for patients suffering from auto-immune diseases such as rheumatoid arthritis. Researchers have since turbinated the drug’s alternative mechanisms through studies on juvenile idiopathic arthritis.

Moreover, Rapamycin was originally developed as a transplant anti-rejection drug that it was later found to be an effective treatment for the pediatric blood disease Autoimmune Lymphoproliferative Syndrome (ALPS) due to its immunosuppressant properties. ALPS patients usually spent an average 5-10 days in the hospital monthly during childhood, and statistics showed that many were not living beyond their teens. Research shows that children from a study at the Children’s Hospital of Philadelphia that have been on this treatment since 2006, are thriving. Due to the success of this repurposed drug the average annual cost of treatment for an ALPS patient on Rapamycin has gone from $100K per year to under $5K per year.

A recent research from the Neglected Disease Research Center in Brazil, detected that the potassium-sparing diuretic compound spironolactone, had potent antischistosomal effects on Schistosoma mansoni in vitro and in vivo in a murine model of schistosomiasis. According to statistics, 230 million people worldwide are affected by this parasitic disease.

Drug repurposing can eliminate the expensive process of discovering a completely new compound, another important advantage of repurposing is that reseahers are working with compounds they aleady know. Usually, there is a vast of information, studies and research of FDA already approved drug. Researchers can promptly have information about the side effects of the repurposed drug, its effect on different age groups, its target, life span and where it acts in the body. All of these advantages can significantly reduce the time and money spent on identifying novel treatments, and running clinical trials.