A model of sustainable drug development: recycling old drugs to turn them into long term anti-cancer targeted therapies
Drug repositioning consists in using old drugs for new indications. The theoretical and pragmatic advantages to testing already established drugs for a potential effect on cancer cells are clear. The side-effects are known and have already been well documented. Phase I are not mandatory so that, those drugs can immediately enter phase II studies to test their efficacy for cancer treatment. One of the main efforts of drug repositioning relies in identifying the right new therapeutic areas to prospectively test for a given drug. Some examples are available in the field of cancer with drugs such as celecoxib, valproic acid, statins, or more recently propranolol or nifurtimox. Interestingly these agents display new mechanisms of action that can be found in expensive new developed agents !
Traditionally, anticancer treatments were based on the use of anticancer agents administered at their Maximal Tolerated Dose (MTD) given every 3 weeks. Recently, the concept of metronomic scheduling proposed that low frequent dose of anticancer agents could be an alternative strategy to spaced-out MTD. This kind of scheduled has been largely adopted for the so called targeted therapy and is being increasingly used with old anticancer drugs such as etoposide, cyclophosphamide or anti-tubulin agents. Metronomic scheduling makes it possible for almost any drug given on a daily basis (usually orally) to turn into an anticancer agent.
Repositioned drugs because of their well know and well established low toxicities, their low cost and their new mechanism of action allows low income countries to innovate to built the treatments their people with cancer need at low cost.