Repurposing FDA approved drugs for cancer therapy

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Rachel Cherney

*This article does not take the place of professional medical advice. Consult with your doctor*

One of the most limiting aspects of drug development is the time it takes to design, optimize, and implement new drugs, which in turn limits patient treatment and survival. Unfortunately, for patients suffering from cancer, time is often the greatest adversary. Therefore, it may be more beneficial for these patients to repurpose FDA approved drugs for cancer therapy rather than creating new ones via the lengthy drug development pipeline. Drug development, from discovery to FDA approval, takes around 10 years, whereas finding additional uses for already approved drugs could shorten that timeline dramatically.

Recently, a group from the United Kingdom at Sheffield University found they could repurpose an already approved arthritis drug, methotrexate, to treat blood cancers that produce too many blood cells (called myeloproliferative neoplasms; MNPs) such as polycythemia vera, primary myelofibrosis and essential thrombocythemia. Methotrexate works by inhibiting the JAK/STAT pathways, which regulate the cells’ responses to signals that promote growth and immune system activity. JAK/STAT inhibition causes tumor cells to grow more slowly, thereby reducing their cancerous effects.

Several years ago, the Sheffield group performed a screen to identify molecules that regulate JAK/STAT signalling. Methotrexate was one of the molecules identified1 to suppress JAK/STAT signalling. Though this study, the scientists realized that the suppressive effects of methotrexate occurred at concentrations normally prescribed to patients, and postulated that methotrexate could be used to treat conditions other than arthritis.

To test their new hypothesis, the Sheffield group used mouse models of human blood cancers2. They did this by putting a human JAK2 gene mutation that causes cancer into the mouse. Once the mice developed symptoms of MNPs, they were treated with methotrexate. Cancerous symptoms were reduced, along with high blood cell counts that are seen in MNPs.

Lastly, the Sheffield group moved to retrospective observations, where they looked at patients with blood cancers who were given  methotrexate for reasons other than cancer3. They identified three cases in which the start of methotrexate reduced cancerous symptoms, as seen in mice. In each of these cases, once methotrexate treatment ended, the cancerous symptoms returned.

By repurposing methotrexate, scientists have found a safe, effective, and low-cost alternative therapy for those suffering from certain blood cancers. How many other already approved drugs could function in similar ways?

Edited by Alex Woodell

Works Discussed:

  1. Thomas S, Fisher KH, Snowden JA, Danson SJ, Brown S, Zeidler MP. Methotrexate Is a JAK/STAT Pathway Inhibitor. PLoS One. 2015 Jul 1;10(7):e0130078. doi: 10.1371/journal.pone.0130078. PMID: 26131691; PMCID: PMC4489434.
  2. Chinnaiya K, Lawson MA, Thomas S, Haider MT, Down J, Chantry AD, Hughes D, Green A, Sayers JR, Snowden JA, Zeidler MP. Low-dose methotrexate in myeloproliferative neoplasm models. Haematologica. 2017 Sep;102(9):e336-e339. doi: 10.3324/haematol.2017.165738. Epub 2017 May 26. PMID: 28550185; PMCID: PMC5685234.
  3. Francis, S. , Thomas, S. , Luben, R. , Sousos, N. , Mead, A. , Snowden, J. A. and Zeidler, M. P. (2019), Low‐dose methotrexate: potential clinical impact on haematological and constitutional symptoms in myeloproliferative neoplasms. Br J Haematol. doi:10.1111/bjh.16193

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