Drug Repurposing, the emerging trend resulting from increasing cost of new drug discovery, researches, trails and generic competition. In this article we will have a review about the potential of drug repurposing and the associated Patentability aspect. We will discuss the type of claims related to drug repurposing and their eligibility for Patent Grant in India.

5Introduction:

Drug repurposing (also known as drug repositioning, re-profiling, re-tasking or therapeutic switching) is the application of known drugs and compounds to treat new indications (i.e., new diseases).

A significant advantage of drug repositioning over traditional drug development is that since the repositioned drug has already passed a significant number of toxicity and other tests, its safety is known and the risk of failure for reasons of adverse toxicology are reduced. More than 90% of drugs fail during development, and this is the most significant reason for the high costs of pharmaceutical R&D. In addition, repurposed drugs can bypass much of the early cost and time needed to bring a drug to market. It significantly reduces the transition of bench research work to treatment at bedside. On the other hand, drug repositioning faces some challenges itself since the intellectual property issues surrounding the original drug may be complex and from a commercial point of view it may not always make sense to take such a drug to market.

Drug repositioning has been growing in importance in the last few years as an increasing number of drug development and pharmaceutical companies see their drug pipelines drying up and realize that many previously promising technologies have failed to deliver 'as advertised'. Computational approaches based on virtual screening of comprehensive libraries of approved and other human use compounds against large numbers of protein targets simultaneously have been developed to enhance the efficiency and success rates of drug repositioning, particularly in terms of high-throughput shotgun repurposing.

One notable example of drug repurposing is taking the partial mu-opioid receptor against buprenorphine - which has been prescribed for control of moderate pain for decades in low dosages in the form of Temgesic 200mcg sublingual tablets, Buprenex 300mcg/mL ampoules - and marketing a high-dosage formulation (Subutex 2 mg and 8 mg) for the interruption and maintenance of heroin and other opioid addictions, which it has proven very beneficial for, with over 200,000 people in the United States alone on buprenorphine maintenance.

Some of the reasons for this are that the drug has a ceiling effect - higher doses do not cause further activation of opioid receptors - and a very long half-life in >2 mg dosages. It also has an extremely high binding affinity for opioid receptors, which keeps the drug from being displaced by opioids like Dilaudid, heroin, morphine, and oxycodone, with the result that a user maintained on it cannot get high no matter what dosage taken of most opioids. The only opioids that may be able to break through the buprenorphine blockade (which are required in an acute care setting if a buprenorphine patient requires pain relief, as no standard opioids are strong enough) - drugs with similar or higher binding affinities to buprenorphine itself - are the fentanil-class opioids, and the Bentley-series opioids (cf. etorphine, dihydroetorphine), which are rarely primary drugs of abuse and not often found on the streets. Buprenorphine itself is a modified Bentley-series opioid.

Swiss type claim:

A Swiss type claim is by and large used to claim a new use of a known substance. It is normally used in the form: "Use of compound X in the manufacture of a medicament for the treatment of disorder Y." Swiss type claims can be for medicaments as well as non-medicaments.

In India claims relating to the second use of a known substance have been barred from patentability. Section 3 of the Indian Patents Act, states what are not inventions within the meaning of the Indian Patent Act.

Before the amendment of 2005, clause (d) of Section 3 of the Patents Act, 1970 read as: "the mere discovery of any new property or new use for a known substance or of the mere use of a known process, machine or apparatus unless such known process results in a new product or employs at least one new reactant"

However, in 2005, clause (d) of Section 3 of the Patents Act, 1970, has been amended and now reads as: "the mere discovery of a new form of a known substance which does not result in the enhancement of the known efficacy of that substance or the mere discovery of any new property or new use for a known substance or of the mere use of a known process, machine or apparatus unless such known process results in a new product or employs at least one new reactant"

Explanation: "Salts, esters, ethers, polymorphs, metabolites, pure form, particle size, isomers, mixtures of isomers, complexes, combinations, and other derivatives of known substance shall be considered to be the same substance, unless they differ significantly in properties with regard to efficacy.

Section 3(d) of the Indian Patents Act restricts grant of patent for "incremental innovations", in many drugs unless it provides significant therapeutic advantages to existing molecules.

There have been questions on existence of section 3(d) and the defining of term efficacy in that section, how is enhanced efficacy defined in the section. The dispute relates to India's IPR regime, which prevents patenting of known drugs, and linking the marketing approval of drugs with their patent status, among other issues.

Its Interpretation is something like this:

Mere discovery of a new form of a known substance which does not result in the enhancement of the known efficacy of that substance is not patentable. Which means different forms of a known substance must differ significantly in the properties with regards to efficacy.

The examiner makes comparison with regard to properties or enhancement of efficacy between the known substance and the new form of known substance. In case the new form is further converted into another new form, the comparison is made between the already existing form and another new form but not between the base compound and another new form.

The efficacy need not be quantified in terms of numerical value to determine whether the product is efficacious because it is not possible to have a standard numerical value for efficacy for all products including pharmaceutical products.

In regard to 'efficacy' in pharmaceutical products, the Madras High Court observed: "going by the meaning for the word "efficacy" and "therapeutic" ... ..., what the patent applicant is expected to show is, how effective the new discovery made would be in healing a disease/ having a good effect on the body? In other words, the patent applicant is definitely aware as to what is the "therapeutic effect" of the drug for which he had already got a patent and what is the difference between the therapeutic effect of the patented drug and the drug in respect of which patent is asked for."

"Due to the advanced technology in all fields of science, it is possible to show by giving necessary comparative details based on such science that the discovery of a new form of a known substance had resulted in the enhancement of the known efficacy of the original substance and the derivatives so derived will not be the same substance, since the properties of the derivatives differ significantly with regard to efficacy." (Novartis AG v. Union of India W.P. 24760/06)

Mere discovery of new property of a known substance:

A mere discovery of a new property of known substance is not considered patentable. For instance, the paracetamol has antipyretic property. Further discovery of new property of paracetamol as analgesic can not be patented. Similarly, ethyl alcohol is used as solvent but further discovery of its new property as anti knocking, thereby making it usable as fuel, can not be considered patentable.

Mere discovery of any new use of known substance:

A mere discovery of new property of known substance is not considered patentable. For instance, new use of Aspirin for treatment of the cardiovascular disease, which was earlier used for analgesic purpose, is not patentable. However, a new and alternative process for preparing Aspirin is patentable. Similarly, the new use of methyl alcohol as antifreeze in automobiles. The use of methanol as a solvent is known in the prior art. A new use has been claimed in this claim as antifreeze which is not allowable. Further, a new use of Chloroquine for Sarcoidosis (a fungal disease) and for Infectious mononucleosis (a viral disease) and for Diabetic neuritis (inflammation of nerves) is not patentable.

Mere use of a known process is not patentable unless such known process results in a new product or employs at least one new reactant. Similarly mere use of known apparatus or machine for another purpose is also not considered patentable.

The term 'significant' cannot be used while interpreting the section because it is vague (the term varies with regard to the application) Therefore, in order for a new drug (in respect of which a patent is asked for) to have greater efficacy when compared to a known drug, the new drug must not be bio-equivalent to the patented drug i.e. the new drug must lie outside the defined range of bio-equivalency when compared to the existing drug.

The reason why Big Pharma dislikes Section 3(d) is that it makes it difficult to get patent rights for new (physical) forms or admixtures of previously known new chemical entities (NCEs) unless these seemingly trivial changes bring 'significant improvement in the efficacy' of the product in question. If vigorously implemented, 3(d) can thwart stockpiling of separate 20-year patents for multiple attributes of a single product. It is not that the Indian patent office haven't granted patents for deserving incremental inventions that are of real therapeutic value to the patient-consumer.

Novelty:

Considering the novelty aspect in Drug Repurposing, it is important to consider that prior public use of the invention is novelty destroying. Therefore in case the known substance has been administered as a medicament earlier, it is unlikely that its new therapeutic use would be patentable unless the prior use did not result in the same chemical effect within the body. It can be said that the use of a known medicament in the manufacture of a medicament for a different therapeutic indication may not be patentable. A new form of a known substance may however be patentable in case there is enhancement of efficacy.

Treatment of new indication:

It is important to consider clause (i) of Section 3 of Patents Act, 1970, here while discussing Swiss type claims.

Section 3 (i) says any process for the medicinal, surgical, curative, prophylactic [diagnostic, therapeutic] or other treatment of human beings or any process for a similar treatment of animals to render them free of disease or to increase their economic value or that of their products.

Accordingly Section 3 (i) prevents the patenting of the process for the medical treatment of human beings or animals. One needs to consider the claims accordingly differentiating between the use of a substance in the preparation of a medicine for the treatment of a disease and the process for treating a disease using a substance.

It is important to consider factors like "New therapeutic use for a known substance", "New form of a known substance" and "Efficacy of the new form of the known substance", while drafting of claims.

In India, any claim pertaining to method of treatment of a disease is not patentable.

Footnote

5 https://en.wikipedia.org/wiki/Drug_repositioning  

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.