Drug repurposing is an encouraging approach to discover innovative, effective treatment for diseases while being less risky, faster, and less expensive than traditional approaches to new drug discovery.
Statistics suggest that up to 15% of given indications for drugs on the WHO’s Essential Drugs List were follow-on indications.
A major drawback to the development of repurposed drugs is insufficient exclusivity. Normally 505(b)(2) regulatory pathway is used to file these products. And only three years exclusivity (until it is an orphan use) is granted, which can be extended by another 6 months if paediatric studies are done. Therefore, development of repurposed drugs hinges on the availability of adequate patent protection.
However, when it comes to patent protection, most of the time potential medical uses have already been reported in the literature or are already being exploited in the clinical practice as off-label, non-registered uses. Even if such uses have still not been backed by controlled clinical trials, the information is already in the public domain.
Otherwise also new indications are recognized long after patent protection has been obtained on the original indication and often, so long after, that the patent has expired. This effectively makes the development process around second indications riskier, as the diminished patent exclusivity reduces the innovator’s opportunity to recoup their R&D spend and secure returns on investment.
Therefore, it is important to explore the possibility of obtaining patents on seemingly minor improvements or innovations that are not obvious considering the prior art. One should review the new clinical data carefully for unexpected or unpredictable results. In addition to new strength, new dose, new formulation, new route of administration, improved toxicity profile, new combination showing synergistic/unexpected results or new patient population, one should also explore narrower aspects like titration dose, food affect, plasma levels, pharmacokinetic profile, drug-device combination and drug-packaging combination, etc.
Narrower set of claims, emphasizing the unpredictability aspect and comparative data from the clinical trials may help overcome the novelty & obviousness objections and provide the valuable patent protection.