Diabetes drug ruling attempts to provide clarity amid pharma enforcement struggle

In another uphill battle on the enforcement of genus and species patents in India’s pharmaceutical space, the Delhi High Court has vacated interim injunctions that were granted in favour of Boehringer Ingelheim Pharma against six Indian companies (Vee, Excel Drugs, Alkem, Micro Labs, Natco and Mankind Pharma) concerning linagliptin, a diabetes drug. This decision is the latest in a slew of struggles that pharmaceutical and chemical companies are facing when it comes to patent enforcement.


The plaintiff filed six suits against various Indian pharma companies, seeking permanent injunctions to prevent them from infringing its Indian species patent “8-(3 AMINOPIPERIDIN–1–YL)-XANTHINE COMPOUNDS” (IN243301). The defendants were allegedly manufacturing and selling an infringing product that contained linagliptin – a substance used to treat diabetes. The infringing product was covered in the suit patent, which is due to expire on 18 August 2023. The plaintiff also owns a genus patent (227719), which recites a Markush formula, the elements of which are also covered in the species patent.

The defendants contended that linagliptin was claimed in the genus patent, which expiredin February 2022. They pointed out that linagliptin is also one of the alternatives in Claims 1 and 3 of this earlier patent. Further, using the plaintiff’s response to the first examination report, the defendant asserted that the plaintiff admitted before the Indian Patent Office (IPO) that linagliptin was one of the 371 examples that form the basis of the different elements covered in the genus patent’s claimed Markush formula. Thus, the genus patent covered and protected linagliptin. The defendants also claimed that the plaintiff was attempting to extend its monopoly over linagliptin through the suit patent, resulting in double patenting and evergreening. Ultimately, the defendants claimed that the species patent’s validity was questionable and no injunction should be granted.

However, by comparing Claim 1 of the genus patent and Claim 1 of the species patent, the plaintiff argued that linagliptin specifically is neither disclosed nor claimed in the genus patent. Rather, it was merely covered by the Markush structure in the genus patent.

The court’s decision

The court decided to vacate the interim injunctions, which had been granted earlier to the plaintiff.

Patent validity

On the issue of whether the courts must assume validity in cases of old patents and where no opposition/revocation petitions have been filed, the court – after perusing the relevant provisions in patent law and existing jurisprudence – concluded that there is no merit in this argument. It opined that Section 13(4) of the Patents Act, which deals with the granting of patents, does not distinguish between old and new patents and therefore, granting a patent is not prima facie evidence of its validity. The court observed that parties can challenge validity:

  • when an grant application is moved forward;
  • after its publication or its grant;
  • by seeking revocation; or
  • by way of a counterclaim in an infringement suit.

A credible challenge?

On the crucial issue of whether the defendants offered a credible challenge to the suit patent, the court examined the existing jurisprudence concerning genus and species patents.

Comparing the chemical structure of the compounds in Claim 1 of both patents, the court observed that a substantial part of the structure of the suit patent’s claimed compound was similar to that of the genus patent. The court referenced the Delhi High Court’s division bench’s decision concerning AstraZeneca’s dapagliflozin patent from 2021, from which it deduced that once a patentee claims infringement of an earlier genus patent concerning a product, the said product should be the subject matter of the earlier genus patent. Only one patent can be granted for one inventive concept, and a patentee cannot claim infringement of two patents for the same concept. The court further observed that while Indian law permits the grant of a Markush patent, if one of the combinations within it includes the product in question, it would form part of the earlier patent’s inventive concept and cannot be claimed again as inventive in a new one.

The court further referred to the statement of working that was filed at the IPO, which showed that all the pharmaceutical products that the two patents claimed to work on in India were exactly the same. Therefore, in the court’s opinion, it was evident that both the species and genus patents were directed towards the same invention – this is impermissible under Section 10 of the Patents Act, as it only allows for one invention per application.

The words ‘covered’ and ‘encompassed’ essentially mean the same thing in the eyes of the court; the plaintiffs relied on semantics to make an artificial distinction between the words ‘claimed’, ‘covered’, ‘encompassed’ and ‘disclosed’. The court also held that when the product is specifically covered in a patent’s claims, whether specific disclosure was made or not is irrelevant. In this regard, the court concluded that linagliptin was disclosed, claimed and covered under both the genus and suit patents, which is not allowed under patent law.

The court also found that the plaintiff’s stance was inconsistent. Up until the genus patent expired, the plaintiff had sought injunctive relief claiming that linagliptin was covered in both the genus and species patents. After it expired, the plaintiff asserted that linagliptin was only covered in the species patent. The court was of the opinion that, based on the admissions and pleadings made by the plaintiff itself, linagliptin was disclosed, claimed and covered in both patents. In light of this, the court was of the prima facie opinion that the suit species patent was vulnerable to revocation on the ground of prior claiming in terms of Section 64(1)(a) of the act. It further concluded that by filing multiple patent claims for the same invention, the plaintiff was attempting to evergreen the invention and re-monopolise the suit patent, which is impermissible under the provisions of Section 3(d).

On the issue of balance of convenience, the court ruled in favour of the defendants, noting that monetary damages can be calculated in the present case and it also factored in the public interest element. The drug is a diabetes drug, which is a widely prevalent disease in India. The court also considered the price of the drug sold by the defendants, which was much cheaper than the plaintiff’s drug that was only being imported into the country.

An uphill battle

The present judgment is the latest in a line of struggles that pharmaceutical and chemical companies have faced in India when trying to enforce a compound that is covered in a genus patent and a subsequent species patent under the country’s prevailing patent law. Appeals have been filed on the matter and the patent community is awaiting more concrete findings on these issues.

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