After a two-year fight, Merck (MSD) finally won an injunction restraining Glenmark’s generic versions of its diabetes drug. The Delhi High Court’s detailed analysis found a prima facie case of infringement — despite Markush-claim and Section 8 objections.
The facts
Merck Sharp & Dohme (MSD) imports and sells its patented (IN 209816) diabetes drug under “Januvia” and “Janumet” — the active ingredient Sitagliptin, which lowers blood sugar in Type 2 Diabetes (T2DM) patients. Glenmark launched “Zita” and “Zitamet” for the same condition. MSD alleged infringement; a single judge refused an injunction, holding MSD hadn’t made out a case. MSD appealed.
The arguments
MSD:
- Glenmark lacked freedom to operate given MSD’s US compound patent;
- Glenmark’s Sitagliptin Phosphate Monohydrate (SPM) is covered by Claim 19 and 13 other claims, and can’t be made without manufacturing Sitagliptin itself;
- Section 48 gives MSD the exclusive right to exclude others from making/using/selling products within the claims; and
- the patent protected Sitagliptin “with pharmaceutically acceptable salts thereof.”
Glenmark:
- MSD didn’t reveal title and failed to disclose corresponding applications (two abandoned) — and the abandoned application was the one covering SPM, so using SPM isn’t infringement;
- the patent is invalid under Section 64(1) — obvious, not useful, lacking industrial applicability, insufficiently described, Section 8 non-compliance, and overbroad claims.
The ruling
The court examined whether the invention related to the Sitagliptin free base or the salt, and whether SPM was sufficiently disclosed. It observed that SPM wasn’t specifically disclosed (only a generic reference as a pharmaceutically acceptable salt) — but that didn’t disentitle MSD to interim relief. The abandoned applications were not of great importance here. On the Markush claim (broad/ambiguous), the court found it overgenerous but not a bar to an injunction. And Section 8 non-compliance was prima facie insufficient for revocation under Section 64(1)(m).
On the detailed analysis, the court found a prima facie case of infringement, granted an injunction against Glenmark (reversing the single judge), while permitting Glenmark to sell products already in the market.
The takeaways
- A salt made from the patented molecule can infringe — SPM couldn’t be made without Sitagliptin.
- Generic disclosure can still support interim relief — SPM’s lack of specific disclosure didn’t defeat MSD.
- Markush breadth isn’t an automatic bar — an overgenerous claim didn’t block the injunction.
- Section 8 non-compliance ≠ automatic revocation — consistent with the discretionary reading of Section 64(1)(m).
Frequently asked questions
Can a generic drug infringe a patent on the base molecule? Yes — the court found Glenmark’s salt (SPM) couldn’t be manufactured without the patented Sitagliptin molecule, supporting a prima facie case of infringement.
Did the abandoned corresponding applications defeat MSD? No — the court held the abandoned applications were not of great importance to the case and didn’t disentitle MSD to interim relief.
Do overbroad (Markush) claims bar an injunction? Not automatically — the court found the claim overgenerous but still granted the injunction.
Does Section 8 non-compliance automatically revoke a patent? No — it was held prima facie insufficient for revocation under Section 64(1)(m), which is discretionary.
Legislation referred to
- The Patents Act, 1970