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Delhi High Court grants permanent injunction in case of Sitagliptin

By Sanuj Das

Nearly three years after Merck (patentee) initiated an infringement action over its patented diabetics drug sitagliptin (Indian Patent 209816, sold under the brand names Januvia and Janumet), the Delhi High Court recently permanently restrained the defendant from the business of Sitagliptin.


Order of Delhi High Court Single judge (First instance)

In April 2013, the patentee approached the Delhi High Court seeking a permanent injunction against the respondent for infringement of its patent for sitagliptin. Patentee alleged that respondent’s product SPM infringed its patent for sitagliptin as the patent claims covered the active ingredient sitagliptin and any of its salts, including its various stereo isomeric forms. In addition to filing a counterclaim challenging the validity of the sitagliptin patent under Section 64 of the Patents Act 1970, the defendant argued that patentee was guilty of suppression and had failed to disclose that a separate patent application (5948/DELNP/2005) had been filed for a dihydrogenphosphate salt of sitagliptin, but subsequently abandoned.

The single judge vide his order dated April 5, 2013 held that on account of patentee's failure to explain satisfactorily its admission in the patent application for a dihydrogenphosphate salt of sitagliptin, Patentee could not be granted an interim injunction.

Order of Delhi High Court Division Bench

The patentee appealed the single judge's order to the Division Bench. It argued that its non-disclosure of other applications for phosphate salts of sitagliptin in India and elsewhere was a minor detail and should not have influenced the decision as to whether Respondent had infringed its sitagliptin patent or been the basis for refusing an interim injunction. On the other hand, the respondent had argued that SPM was qualitatively different from sitagliptin per se, such that it had enhanced pharmaceutical qualities, and therefore the manufacture and sale of SPM did not violate the patent for sitagliptin. Further, the respondent had relied on a patent for SPM granted in the United States to assert its enhanced pharmaceutical qualities.

While dealing with the grounds for revocation asserted by the respondent, the Division Bench highlighted its limitations in addressing technical matters in an interim hearing and examined the three grounds for granting an interim injunction (i.e., a prima facie case, the balance of convenience and irreparable harm or injury).

The bench held that the following issues had to be considered in the case at hand:
  • Public interest – The bench observed that the price difference between the commercial products sold by the respondent and the patentee was not high. Hence allowing the respondent to sell the drug would not necessarily result in lowering of the price so as to increase access. The bench also held that it must be mindful of the need to enforce the act, particularly where a strong case of infringement is established. 
  • Price - An infringer who is allowed to operate during a trial may lower the price of the product since it has no R&D expenses to recoup but it does not apply to the patentee. Moreover, even assuming that the patentee can survive the financial setback during the trial, prices may not recover.
  • Challenge to validity of patent - The bench observed that the respondent had released the drug without initiating revocation proceedings under the act, which would have obviated the need for an interim arrangement. Although the bench cautioned that the respondent’s right to question the validity of the patent in an infringement was unaffected, it held that the manner of challenge was a relevant factor against it at the interim stage.
  • The combination of the three primary factors (a prima facie case, the balance of convenience and irreparable harm or injury) – The bench held that the patentee had established a prima facie case of infringement. Further, there existed an interim arrangement which secured the interests of both parties and maintained the public interest, and also ensured that the possibility of irreparable harm to the patentee was removed.
In light of this, the bench set aside the order of the single judge dismissing the application for grant of an interim injunction and granted the same in favour of patentee along with certain directions.

Before Supreme Court

On appeal by the defendant, the Supreme Court upheld the interim protection granted by the Division Bench of the Delhi High Court restricting the defendant from manufacturing and selling unfinished formulations of Sitagliptin and gave directions to complete the trial before the Single Judge within a stipulated time-frame.

Final Judgment by the Single Judge of the Delhi High Court

The Court observed that the onus to prove that the invention in the suit patent was obvious to a person skilled in the art, rested on the defendant and it had failed to prove the same. The Court said that mere comparison of chemical structure or picking up parts of chemical structures of different patents and clubbing them, is not sufficient to prove that the invention is not novel or obvious. Further, the defendant witness in this case is said to have followed a methodology referred to as ‘hindsight analysis’ which is a prohibited methodology in patent law.

While answering the issue of infringement, two things that the court observed to be relevant were that, one Sitagliptin is the molecule with the therapeutic utility; whereas Sitagliptin Phosphate Monohydrate has advantage over the Sitagliptin Free Base, in that it has got better physical and chemical characteristics so as to make it in tablet forms. The court placed heavy reliance on the testimony of the Plaintiff’s witness, being an independent witness, to rule that “suit patent provides compounds that inhibit the activity of DPP-IV along with compositions, articles of manufacture and processes for making the compounds”. The plaintiff’s witness also stated in his cross-examination that Sitagliptin Phosphate Monohydrate is generically disclosed in the suit patent though not specifically. It was clarified to the court that DPP-IV inhibition was on account of Sitagliptin alone and it was irrelevant as to the form in which it was being administered, the same being done to merely enhance the availability of the drug in the body to facilitate further absorption and faster action.

On the issue of lack of sufficient disclosure and broad claiming, the court in this case observed that the disclosure in the suit patent is not for a lay person but is addressed to a person of ordinary skill in the art. Further, since the defendant itself has been successful in making Sitagliptin Phosphate Monohydrate, it cannot claim that the patent in question is too wide and broad.

On the question of revocation on account of non-compliance with Section 8, the court observed that the provisions under Section 64 of the Patents Act make it clear that it is not mandatory for the court to revoke the patent merely because any of the grounds mentioned in Section 64(1) are made out. It is the discretion of the court to revoke or not to revoke in the given facts and circumstances of a case. The word “may” used in Section 64(1) of the Act makes it clear that it is the discretion of the Court to revoke the patent under this provision if any of the ground(s) stipulated therein are disclosed or made out and “may” cannot be read as “shall” as contended by the defendant.

With respect to the arguments made about “public interest”, the court noted that Sitagliptin is not the only inhibitor for treatment of type II diabetes in the market and there are several other inhibitors, including the one manufactured and marketed by the respondent, called “Teneligliptin”.
The present judgment is one of its kind judgment where the trial has been concluded within a period of three years. It remains to be seen what would be its implications in the pharmaceutical sector and what outcome it will have on the interface of patents & pharma.

[The author is a Junior Associate, IPR Practice, Lakshmikumaran & Sridharan, New Delhi]
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