In a recent, very intensely contested litigation between Merck Sharp and Glenmark Pharmaceuticals Ltd., the Hon'ble Delhi High Court delivered a much awaited judgement. In the suit Merck contended infringement of its Anti-diabetic drug Sitagliptin [protected by Indian Patent No. 209816 (IN'816); marketed under trade names - Januvia and Janumet or (Istavel or Istamet of Merck's Licensee-Sun Pharma] by Glenmark. Whereas Glenmark contended that its product on Sitagliptin, which is Sitagliptin phosphate monohydrate (marketed under trade names Zita and Zitamet) did not infringe Merck's patent IN'816 considering the said patent only covered the basic free form Sitagliptin i.e. Sitagliptin hydrochloride and not Sitagliptin phosphate monohydrate. Glenmark also contended that Merck had abandoned its Indian Application No. 5948/DELNP/2005 pertaining to Sitagliptin Phosphate Monohydrate which attributed to the fact that both molecules namely Sitagliptin Phosphate monohydrate and Sitagliptin Hydrochloride were separate molecules.
The Hon'ble Delhi High Court was of the opinion that Merck's patent IN'816 generically covered Sitagliptin Phosphate monohydrate. To arrive at its opinion, the Hon'ble High Court relied on the facts that (a) the free base Sitagliptin Form was the active biological ingredient having therapeutic efficacy as DPP-IV inhibitor and; (b) the monohydrate phosphate salt of Sitagliptin (contested by Glenmark) only had improved chemical and physical properties for delivering Sitagliptin to the body, wherein its therapeutic efficacy was due to the free base Sitagliptin whereas phosphate had no role to play in the therapeutic efficacy.
Moreover the Hon'ble Delhi High Court also opined that in the Sitagliptin Phosphate monohydrate salt, the Sitagliptin existed in Sitagliptin –H+ form and phosphate as an anion form along with water molecule; and that in a tablet form of 128.5 mg Sitagliptin Phosphate Monohydrate, 100 mg was the Sitagliptin free base which in fact is the biologically active moiety responsible for therapeutic efficacy. The Hon'ble Court in this matter relied on the Judgement by the Hon'ble Supreme Court of India in Novartis AG vs. Union of India &Ors. (2013 (54) PTC 1), wherein it was held that, that therapeutic efficacy cannot be attributed to more beneficial flow properties; better thermodynamic stability and lower hygroscopicity as these properties do not contribute to therapeutic efficacy. Thus in view of the aforesaid the Hon'ble court held that use of Sitagliptin free base by Glenmark in its product Sitagliptin Phosphate Monohydrate amounts to infringement of Merck's patent IN'816.
This judgement may be regarded by pharmaceutical experts in various perspectives, as some may consider it to be pro-innovators. Whatever may be the opinion of the experts, but the essentials of this judgement lies in looking at the innovations, patents and Indian patent law in a more structured manner so as to ensure that legitimate protection to innovations can be given within the ambit of Patent Law.
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