Repurposing Medications: Reimagining Treatment Options

Last month around the Chinese New Year holiday, a prominent Chinese scientist from Guangzhou Medical University made an announcement that stirred controversy both domestically and internationally while also highlighting a route to combat ailments that global academia and pharmaceutical industries have been attracted to for years. The scientist revealed that his team had been injecting patients with a malaria-causing parasite in order to cure a range of cancers – with two patients seeming to have no cancer cells remaining at the site of tumor and five additional patients having no disease progression out of ten total patients receiving this malarial therapy for at least a year. Although this type of treatment has been attempted in the past in an attempt to combat HIV in the 1990s, the Centers for Disease Control (CDC) and other health governing bodies determined that there was insufficient pre-clinical data to justify human trials during this time period. The controversy revolving around this announcement encompasses the aforementioned determination by CDC, the release of trial results before being published in a peer-reviewed journal, and, most importantly, the possibility of creating a malaria public health emergency for a country due to eradicate the communicable disease by 2020. Although the scientist who underwent this study clearly abdicated internationally conferred health principles, this avenue of repurposing – repositioning, re-profiling, re-tasking, etc – medications and therapy is becoming more appealing to those invested in novel treatment options for both established and emerging diseases.

Throughout the development lifecycle of new chemical entity (NCE), the process for regulatory approval could span over ten to fifteen years with an associated cost of over 2 billion dollars. This has led to an average of only 20 to 30 NCEs being approved by the Food & Drug Administration (FDA) each year. However, through repurposing medications, the development span can be cut to five to eight years at approximately 60% of the total NCE cost – in addition to higher approval rates from regulatory agencies. This repurposing process, as shown by the statistics, is enormously appealing for pharmaceutical companies/investors, but also provides targeted therapy for patient’s disease states at a theoretically lower price than an NCE. Even for rare genetic diseases, repurposing has become common due to only 400 medications being on the market to treat over 7000 genetic conditions. Repurposing is accomplished through the theory of translational research which takes a look at basic scientific discoveries and determining how a medication can be made to match this discovery – for example, examining the molecular pathway of diabetes and then matching it with a chemical entity that has an effect within the pathway like glucagon-like peptide 1 (GLP-1). The known chemical entities are commonly stored in giant databases within academia and the industry. Through big-data analytics, advanced modeling, and high throughput screening techniques, these chemical entities can then be extracted from the databases and determined if it has a possible role in a certain molecular pathway.

This method of establishing novel treatment options ought to be utilized more frequently and effectively, though there are medications over the years that have undergone this type of approval. The following are examples of already approved medications and others undergoing clinical trials:

Approved Repurposed Medications:

  1. Thalidomide, which was originally developed as a racemic mixture of enantiomers for the treatment of morning sickness but found to be teratogenic due to the effect of the (S)-isomer, was later successfully developed by Celgene as a single (R)-isomer product for the treatment of leprosy and multiple myeloma.
  2. Viagra (Pfizer’s sildenafil) was a drug that initially failed as an angina treatment in clinical studies; however, during these trials, its effect on erectile dysfunction was noted and then later approved for this indication.
  3. Celebrex, commonly used in osteoarthritis, works by inhibiting COX-2 receptors. Recently it has been shown that for patients that previously had colon cancer, taking this agent can reduce the risk of additional polyp formation without negative gastrointestinal effects associated with existing treatments.
  4. All-trans retinoic acid (ATRA), which is an acne medication, when combined with traditional chemotherapy, results in complete remission of acute promyelocytic leukemia in 90% of treated patients.
  5. Tamoxifen, a hormone therapy medication, treats metastatic breast cancers, or those that have spread to other parts of the body, in both women and men, and it was originally approved in 1977. Thirty years later, researchers discovered that it also helps people with bipolar disorder by blocking the enzyme PKC, which goes into overdrive during the manic phase of the disorder.
  6. Raloxifene was initially developed to treat osteoporosis, but has since been shown to reduce the risk of invasive breast cancer in postmenopausal women in 2007.
  7. Zidovudine (AZT) was initially developed to treat various types of cancer, but was determined to be ineffective. However, it was repurposed into the first approved HIV/AIDs medications in 1987 and has had a tremendous impact on the progression of the autoimmune disorder.

Repurposed Medications Undergoing Clinical Trials:

  1. The lipid soluble simvastatin is currently undergoing a trial in the UK to assess the efficacy of reducing the progression of Parkinson’s disease. The statin drug class is thought to prevent this ailment through its pleiotropic effects including reducing inflammation, reducing oxidative stress, reducing the formation of sticky bundles of alpha-synuclein, and increasing the production of neurotrophic factors. The results are expected to be released in 2020.
  2. Purdue University received a grant from the National Institutes of Health (NIH) to discover the effectiveness of Ebselen, a chemical entity, against methicillin-resistant Staphylococcus aureus (MRSA), and auranofin, which is FDA-approved for the treatment of unresponsive rheumatoid arthritis, against Clostridium difficile.
  3. Metformin, a first line agent for many diabetics, has been shown to reduce the risk of breast cancer in diabetes patients and is being investigated as a treatment for cancer in many different clinical trials

Although this is certainly not an exhaustible list of the impacts repurposing has had on healthcare, the majority of this repurposing stems from serendipitous observations rather than targeted interventions. Through these unanticipated occurrences, a range of disease states can now be more effectively treated ranging from communicable diseases like HIV/AIDS to mental health ailments including bipolar disorder and Parkinson’s disease to non-communicable diseases. As the rising cost of healthcare continues to devastate humanity and lead to health inequalities, heads of governments, pharmaceutical industries, academia, and nonprofits need to commit themselves into investing their time and resources into this repurposing method. The targeted repurposing interventions are more vital and should be devoted to in order to expand options for health disorders rather than the unexpected observed effects. The financial and health outcomes will lead to novel treatment options accessible to a majority of the world which will allow health care professionals to properly accompany their patients through their disease state.

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