Lydie Meheus

Repurposing drugs in oncology (ReDO)—cimetidine as an anti-cancer agent

Cimetidine, the first H2 receptor antagonist in widespread clinical use, has anti-cancer properties that have been elucidated in a broad range of pre-clinical and clinical studies for a number of different cancer types. These data are summarised and discussed in relation to a number of distinct mechanisms of action. Based on the evidence presented, it is proposed that cimetidine would synergise with a range of other drugs, including existing chemotherapeutics, and that further exploration of the potential of cimetidine as an anti-cancer therapeutic is warranted. Furthermore, there is compelling evidence that cimetidine administration during the peri-operative period may provide a survival benefit in some cancers. A number of possible combinations with other drugs are discussed in the supplementary material accompanying this paper.

The Repurposing Drugs in Oncology (ReDO) Project

The Repurposing Drugs in Oncology (ReDO) Project seeks to repurpose well-known and well-characterised non-cancer drugs for new uses in oncology. The rationale for this project is presented, examining current issues in oncological drug development, challenges for health systems, and existing and future patient needs. In addition to discussing the advantages of repurposing, the paper also outlines some of the characteristics used in the selection of drug candidates by this project. Challenges in moving candidate drugs into clinical trial and subsequent practice are also discussed.

Repurposing Drugs in Oncology (ReDO)—itraconazole as an anti-cancer agent

Mebendazole, a well-known anti-helminthic drug in wide clinical use, has anti-cancer properties that have been elucidated in a broad range of pre-clinical studies across a number of different cancer types. Significantly, there are also two case reports of anti-cancer activity in humans. The data are summarised and discussed in relation to suggested mechanisms of action. Based on the evidence presented, it is proposed that mebendazole would synergise with a range of other drugs, including existing chemotherapeutics, and that further exploration of the potential of mebendazole as an anti-cancer therapeutic is warranted. A number of possible combinations with other drugs are discussed in the Appendix.

Repurposing Drugs in Oncology (ReDO)—clarithromycin as an anti-cancer agent

Clarithromycin (CAM) is a well-known macrolide antibiotic available as a generic drug. CAM is traditionally used for many types of bacterial infections, treatment of Lyme disease and eradication of gastric infection with Helicobacter pylori. Extensive preclinical and clinical data demonstrate a potential role for CAM to treat various tumours in combination with conventional treatment. The mechanisms of action underlying the anti-tumour activity of CAM are multiple and include prolonged reduction of pro-inflammatory cytokines, autophagy inhibition, and anti-angiogenesis. Here, we present an overview of the current preclinical (in vitro and in vivo) and clinical evidence supporting the role of CAM in cancer. Overall these findings justify further research with CAM in many tumour types, with multiple myeloma, lymphoma, chronic myeloid leukaemia (CML), and lung cancer having the highest level of evidence. Finally, a series of proposals are being made to further investigate the use of CAM in clinical trials which offer the greatest prospect of clinical benefit to patients.

Repurposing drugs in your medicine cabinet: untapped opportunities for cancer therapy?

Many forms of cancer lack efficacious treatments, despite continuing advances in our understanding of molecular biology, and the development of precisely targeted agents that exploit relevant drivers and pathways of malignancy. To date the effectiveness of most tumor cell-focused molecularly targeted agents, in terms of event free and overall survival appears to be modest [1]. What is more, these new drugs come with a high price tag as companies seek to recoup development costs and to generate a return on investment (in part a consequence of a high attrition rate in oncological drug development, high regulatory burdens and expensive clinical trial costs) [2]. In the developing economies of the world, where cancer incidence is rising, the problems of unmet patient need is exacerbated by these high costs, putting many cancer treatments out of reach of patients and imposing strains on local health systems [3]. An alternative approach to seeking new drug treatments for cancer is not to start with molecular targets in mind, but to assess those drugs – approved for any indication – in our existing armamentarium which show some evidence of anticancer activity. This is the field of drug repurposing in oncology and there is now an increasing interest in the use of non-cancer drugs as anticancer therapeutics. There are two main advantages of repurposing. Firstly, by starting with well-known and well-characterized drugs we can draw on existing and detailed knowledge of pharmacodynamics, pharmacokinetics, bioavailability, toxicities, established protocols and dosing. This body of knowledge is far in excess of what can be gained in early phase clinical trials of new agents, particularly for first in class drugs. This is not to say that repurposed drugs do not need Phase I trials, since they may be used for cancer in schedules and combinations that differ from their accepted use, but it does represent a considerable short-circuiting of the preclinical phase of the drug d evelopment life cycle [4]. Secondly, many of the candidate drugs for repurposing are available at low cost; indeed many are available as generics. This is in stark contrast to the very high costs associated with the newest agents emerging from current pharmaceutical pipelines.

Repurposing Drugs in Oncology (ReDO)-diclofenac as an anti-cancer agent.

Diclofenac (DCF) is a well-known and widely used non-steroidal anti-inflammatory drug (NSAID), with a range of actions which are of interest in an oncological context. While there has long been an interest in the use of NSAIDs in chemoprevention, there is now emerging evidence that such drugs may have activity in a treatment setting. DCF, which is a potent inhibitor of COX-2 and prostaglandin E2 synthesis, displays a range of effects on the immune system, the angiogenic cascade, chemo- and radio-sensitivity and tumour metabolism. Both pre-clinical and clinical evidence of these effects, in multiple cancer types, is assessed and summarised and relevant mechanisms of action outlined. Based on this evidence the case is made for further clinical investigation of the anticancer effects of DCF, particularly in combination with other agents - with a range of possible multi-drug and multi-modality combinations outlined in the supplementary materials accompanying the main paper.

Repurposing Drugs in Oncology (ReDO)—Propranolol as an anti-cancer agent

Propranolol (PRO) is a well-known and widely used non-selective beta-adrenergic receptor antagonist (beta-blocker), with a range of actions which are of interest in an oncological context. PRO displays effects on cellular proliferation and invasion, on the immune system, on the angiogenic cascade, and on tumour cell sensitivity to existing treatments. Both pre-clinical and clinical evidence of these effects, in multiple cancer types, is assessed and summarised and relevant mechanisms of action outlined. In particular there is evidence that PRO is effective at multiple points in the metastatic cascade, particularly in the context of the post-surgical wound response. Based on this evidence the case is made for further clinical investigation of the anticancer effects of PRO, particularly in combination with other agents. A number of trials are on-going, in different treatment settings for various cancers.

Repurposing Drugs in Oncology (ReDO)-nitroglycerin as an anti-cancer agent.

Nitroglycerin (NTG), a drug that has been in clinical use for more than a century, has a range of actions which make it of particular interest in an oncological setting. It is generally accepted that the main mechanism of action of NTG is via the production of nitric oxide (NO), which improves cardiac oxygenation via multiple mechanisms including improved blood flow (vasodilation), decreased platelet aggregation, increased erythrocyte O2 release and decreased mitochondrial utilization of oxygen. Its vasoactive properties mean that it has the potential to exploit more fully the enhanced permeability and retention effect in delivering anti-cancer drugs to tumour tissues. Moreover NTG can reduce HIF-1α levels in hypoxic tumour tissues and this may have anti-angiogenic, pro-apoptotic and anti-efflux effects. Additionally NTG may enhance anti-tumour immunity. Pre-clinical and clinical data on these anti-cancer properties of NTG are summarised and discussed. While there is evidence of a positive action as a monotherapy in prostate cancer, there are mixed results in NSCLC where initially positive results have yet to be fully replicated. Based on the evidence presented, a case is made that further exploration of the clinical benefits that may accrue to cancer patients is warranted. Additionally, it is proposed that NTG may synergise with a number of other drugs, including other repurposed drugs, and these are discussed in the supplementary material appended to this paper.

Repurposing Drugs in Oncology: Next Steps

The repurposing of existing non-cancer drugs is a potential source of new treatment options for cancer patients with high unmet medical needs. While scientific research is progressing rapidly in the field of drug repurposing, the implementation of drug repurposing still faces important financial and regulatory hurdles that should be addressed to optimise clinical adoption.

Repurposing non-cancer Drugs in Oncology — How many drugs are out there?

Background Drug repurposing can speed up access to new therapeutic options for cancer patients. With more than 2000 drugs approved worldwide and 6 relevant targets per drug on average, the potential is quantitatively important. In this paper, we have attempted to quantify the number of non-cancer drugs supported by either preclinical or clinical cancer data. Methods A PubMed search was performed to identify non-cancer drugs which could be repurposed in one or more cancer types. Drugs needed at least one peer-reviewed article showing an anticancer effect in vitro, in vivo or in humans. Results A total of 235 eligible non-cancer drugs were identified (Table 1). Main charateirstics of the drugs are summarized in Table 2. 67 (29%) are on the WHO list of essential medicines and 176 (75%) are off-patent. 133 (57%) had human data in cancer patient(s). Four were listed in clinical guidelines, namely thalidomide, all-trans retinoic acid, zoledronic acid and non-steroidal anti-inflammatory drugs (NSAID). Several drugs have shown a survival benefit in randomized trials such as cimetidine (colorectal cancer), progesterone (breast cancer) or itraconazole (lung cancer). Several other drugs induced responses in rare tumours, like clarithromycin, timolol or propranolol. Conclusion We have found that the number of off-patent repurposing opportunities is large and increasing. Joint non-commercial clinical development (academics, governments, charities) may bring new therapeutic options to patients at low cost, especially in indications for which the industry has no incentive to invest in.