Diclofenac is generic nonsteroidal anti-inflammatory (NSAID) that has been used to treat pain associated with inflammatory disorders since it was launched as Voltaren by Ciba-Geigy, now part of Novartis, in 1973.
The drug is also recommended for the treatment of cancer pain by the World Health Organisation (WHO).
But diclofenac could play a bigger role in cancer treatment according to new research by scientists from the Anticancer Fund in Belgium and US organisation GlobalCures under the Repurposing Drugs in Oncology (ReDO) collaboration.
ReDO project researcher Pan Pantziarka told us that, in addition to demonstrating anticancer properties in various preclinical studies, diclofenac has been linked to improved disease-free and overall survival in a range of cancers.
“There are also interesting data showing that diclofenac was effective in a number of rare soft tissue cancers, including desmoid and inflammatory myofibroblastic tumours, with multiple cases reported in the literature but no clinical trials to confirm these positive results” Pantziarka said.
He added that: “These positive effects in cancer are related to multiple mechanisms of action, including anti-angiogenic effects, immune-related activity and acting as a treatment-sensitiser.
“Some of these effects are generic to the class of NSAIDSs, particularly with respect to COX-2 inhibition, but some of these effects are specific to diclofenac.”
Repurposing road block
One aim of the ReDO project is to identify generic drugs with the potential to treat new diseases. The idea is to help the drug industry overcome its reluctance to pay for the clinical development of products that already face competition.
Such work is necessary according to Pantziarka who told us “the incentives issue is a major road-block to drug repurposing. However, the momentum in favour of drug repurposing is increasing all the time.
“Work such as ours at the ReDO project is making high-quality information more easily available to clinical investigators and driving interest from patient groups. The potential cost savings are particularly attractive in low and middle income countries, and also in rare disease patient populations.
Whether these efforts can convince drugmakers to trial generc drugs for new indications remains to be seen.
One expert at a major CRO told us "these may be worthwhile trials but they struggle to get funded commercially because no one is likely to derive a commercial benefit."
But some progress is being made according to Pantziarka.
“We already have some examples were off-patent drugs with good evidence of anticancer activities are being reformulated to increase bioavailability or tweaked to improve efficacy, thereby also securing IP protection and the incentive to fund clinical trials.
“This is not the only solution to the issue but one that we may see increasingly in the future.”
ReDO project scientists are also trying to lead by example. The organisation is funding clinical trials of a drug called ketorolac – another painkiller related to diclofenac – in the treatment of pre-operative breast cancer.