New use of known substance always remain out of the purview of patent protection perhaps for the very reason that the discovery of new property of a known substance is not inventive enough to qualify for patentability standards. Primary requirement which is fundamental to patentability is novelty. The root of this concept is 'made available to public'. This is really important when judges are faced with granting of an injunction restraining the defendant from what he was doing before the grant of the patent. The golden thread that weaves all the patent jurisprudence is that a patent cannot take control or take away which is already in public domain. A patentee cannot take away public's right to do what they were doing before the grant of a patent. Does it mean every prior user must understand or potentially know every patent that is granted? It seems to be to taxing for public to know every nuance of millions of patent granted every year. This becomes more complicated particularly in drug patents when life of the original patent can be extended by securing other patents like compositions, new polymorphs /formulations/doses, and new therapeutic uses and so on. In particular the patents for second medical use raised many issues in various patent jurisdictions. There exists an uncertainty how the original patentee establishes a case for infringement of a second medical use patent. It may take some more time for the generic manufacturers to climb the wall of second use patent before they would be able to launch the generic product after expiry of the patent term. The use claims drafting silently entered the patent system where normal kind of claims for product and methods suffers from stiff novelty and inventive step objections.

Second Use of a Substance

New medical use /new medical indications or second use of a substance is nothing more than a set instruction to a physician that such substance can be prescribed for combating other medical conditions. The novelty in this case rest in the new use of the known substance. It is invariably argued that such inventions are very valuable technically and commercially if one look objectively at their inventive contribution to the state of art. This also raises the issue of extent of disclosure and coverage. If one sift through many cases relating to second use disputes one would find that it is difficult to reconcile with the well-established concepts of loss of novelty by reason of 'inevitable results' or use being inherent in the prior art or such property is inherent in the known substance. Whatever may be the difficulties in the use claims, the use claims have found their entry in the patent system of various jurisdictions. The concept of use claim has gained significance following the acceptance of product claims for drugs and chemicals. The inherent difference in extent and coverage of mechanical products from chemical and drugs products has called upon the judges to interpret the product claims of the drugs and chemicals not in the traditional manner. These products are normally constructed in terms of their chemical structure or composition or its constituents. Though the chemical structure so defined can primarily predicts its use in general but its exact technical advantage can only be known when the product is actually put to use. The technical advantage in other words depends on the environment in which the product is used. The question which baffled the patent jurisprudence and that remained unresolved was, can the absolute protection the product patent confer, justify the basis for denying the patent for technical advantage associated with second use of the product?

Need for use claims

It is known that the product claimed by a patent especially chemicals and pharmaceuticals when first prepared can be protected by a product claim. In case such products produces new and surprising technical affect the same can be protected if such steps are associated with particular method steps. However, if a patented product reveals new and surprising properties the benefits of such research does not find recognition in the patent law for the reason that mere discovery of the new property of known substance is specially excluded from patentability by the patents statutes. Can the benefit such research be protected by the way of use claims? A claim drafted in the form such as "compound X, for use as active therapeutic substance". Such claim do not specify the specific therapeutic use, however, novelty of such claimed subject matter stems from the disclosed first therapeutic use of the compound. Does that mean further therapeutic uses of the same compound would be regarded as novel? It may pass the test of novelty but such claims would not be allowable for the simple reason that such a defined used would involve a method of treatment of human or animal body by therapy. It does not mean that further use of a known product cannot find patent protection. If the use claim is drafted differently as "use of a substance or composition (product X) for the manufacture of medicament for a specific therapeutic indication" then the chances of its acceptance in various jurisdiction is possible. The legal basis for accepting such use claims resides in new use, or purpose of such use, reflecting the newly found technical effect in form of a therapeutic activity. No doubt one may say that such claim in fact defines a "mere new use". Need for such claims were first recognised by EPO in Art 54(5) which allows the patentability of a known substance or compound for use in medical or veterinary treatment provided that such use is not comprised in the state of the art. The new Article 54(5) EPC eliminates any legal uncertainty on the patentability of further medical uses. It unambiguously permits purpose—related product protection for each further new medical use of a substance or composition already known as a medicine.

Second use of medicines

The first classic example of medicine which found its second use was aspirin the well-known out off the shelf drug for relieving head ache which was later found to be useful as Anticoagulant/Anti stroke/anti-ischemic drug. There are dozens of instances of existing medicines being developed for new uses. For instance, Sildenafil citrate primarily used for Heart and vascular disease later marketed as drug for Erectile dysfunction. Similarly, Finasteride meant for treatment of prostate disorders was also found to be effective in the treatment of androgenetic alopecia. Thalidomide found second use to relive morning sickness in pregnant women but it's first use was for respiratory infections. Further, it was found to be useful in the treatment of leprosy and for cancer. Other known drug for second use are Daclizumab [transplant rejection] now used in treating certain types of multiple sclerosis; Aclasta [osteoporosis] ; Zometa [bone cancer] ; Ravatio [pulmonary Hypertension]. List of few more drugs with second used approved by USFDA in year 2016.

Type of second use claims

A. Purpose-limited process claims : Swiss type claims.

These claims take the form "Use of X for the manufacture of medicament for the treatment of Y", i.e. they are purpose-limited process claims. Such claima are also known as swiss type claims and have found acceptance with Article 54(4) of EPC. But such claims are not patentable in India under section 3(i) as they are being treated as method of treatment of human body.

B. Purpose-limited product claims

This type of use claims take normally the forms "X for use in the treatment of Y" and are construed as purpose-limited product claims. These claims are formatted in accordance with Article 54(5) EPC .These claims take normally the form "X for use in the treatment of Y" and are construed as purpose-limited product claims. Thus, the categories of such claims are different from swiss type of claims [purpose limited - process claims]. In EPO such claims find acceptance in view of the fact that even though both set of claims define the same compound and the same therapeutic use but the swiss type claims comprise in addition the manufacture of a medicament while the purpose limited product claims do no seek manufacture of a medicament. These types of claims are also objected in India in view section 3 (d) which clearly exclude new use of known substance from patentability.

Double patenting : Second use

This basic purpose for denying the patent to new use is to avoid grant of double patent to the same substance. While for the determination of whether or not the prohibition of double patenting applies in connection with claims drafted as use claims the IPO practice is not so clear. At times it unambiguously permits purpose—related product protection for composition already of already known drugs if these combinations are found to be synergist or produce some surprising results. That proves that there is no manifest objective reason to deny the legitimate interest of the applicant in pursuing new use claims drafted in purpose limited product claims. Therefore, obtaining protection different from - albeit partially overlapping - with that of the originally known or already patented product is possible in some cases even in Indian context.

Principles laid down to examine new use cases

The protection of the second use /new use /further use claims in principle hinge upon what is "made available to the public" through the state of art. The true interpretation of such claim depends on what is accessible to the skilled person through the prior art. The overall result would be, it may be difficult to interpret or it may be subject to different interpretations. In the cases where composition of known substances is claimed the applicant is expected to substantiate it with existence of synergistic results or unexpected /surprising results. Indian patent office practice varies from Controller to Controller. For example the patent 256057 was granted for administering to a patient Calcitonin (anti osteoporosis) followed by Glucocorticoid (anti-inflammatory) for a "Pharmaceutical composition comprising a calcitonin and a pharmaceutically acceptable carrier". This patent was allowed after the applicant amended the claims to a synergistic composition of Calicitonin and Glucorticoid where the two components come into contact with each other only in human body. Even the method claim for preparing the composition by bringing the two compounds into contact with each other at a locus was allowed. But in similar case where composition of combination claim such as " A composition for use in long-term treatment of fibromyalgia and its symptoms in a patient suffering from fibromyalgia comprising milnacipran, or a pharmaceutically acceptable salt thereof, and a second active compound administered adjunctively with the milnacipran " was denied for the reason that applicant failed disclose or substantiate through examples the synergistic effect claimed in the reply arguments.[ Cypress Bioscience, Inc. application 3183/DELNP/2008]. It was refused under section 3(e). It seems that one of the principal reasons for refusal of second case was the non-disclosure of the synergistic effect in the specification. However, it does give a hope to patent a new uses for existing medicines provided that they are claimed as synergistic combinations supported by the disclosure of data in the specification.


One must understand that bring a new molecule costs not less than 1Bn and it is required to build the market for such molecule from scratch. It is not only expensive but also time consuming process. However developing and bringing to market a new use for a known medicine is less expensive. But it is still as expensive and time-consuming process as to find the new use of the old molecule. It known that Phase 3 clinical to show that the medicine is safe and efficacious for the new use would also cost hundreds of millions of dollars and take considerable time. In view of this there is a need to encourage the development of existing drugs for new uses. No doubt the law makers are aware either directly or by way of a IPO practice that law must be amended to give some sort of protection to new uses through second medical use patents with proper riders to check the misuse like double patenting. Final question that would keep hammering the Indian patent system will be whether second medical use patents are the right solution to provide sufficient incentives to the originators? Till then the new use patents seekers would keep on trying to climb the cliff of novelty to obtain a favourable patent for the second use through synergistic effect route acceptable to Indian patent office.

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.