Delhi HC: Markush Genus Claims Can Defeat Novelty of a Species Even Without Specific Disclosure

Intra Cellular Therapies holds the genus patent IN 451581, a Markush claim covering a broad family of psychiatric-drug compounds. It later filed a separate application, titled simply "Organic Compounds," covering deuterated versions of that same family -- where select hydrogen atoms are swapped for the heavier, stable isotope deuterium, a common medicinal-chemistry move used to improve pharmacokinetics without changing a molecule's core activity. The Patent Office rejected the deuterated application on three grounds: lack of novelty, lack of inventive step, and non-patentability under Section 3(d). The Delhi High Court upheld the rejection, but only reached two of the three grounds.

On novelty, the applicant's own position was that a Markush claim discloses only the broadest representation of a compound family, not every individual species buried inside it -- so the deuterated species should count as new. The Court disagreed, holding that where a compound falls within the coverage of an existing genus claim, specific disclosure of that exact species is immaterial to defeating novelty. That is a consequential reading for anyone drafting or defending genus patents in this space: it treats claim coverage itself as sufficient disclosure, even though the genus patent's text never called out the deuterated variants by name.

On Section 3(d), the applicant submitted in vivo data showing the deuterated compound left more intact drug in the bloodstream than the non-deuterated version. The Court accepted the bioavailability improvement as real, but held that bioavailability alone does not establish enhanced therapeutic efficacy, the actual bar Section 3(d) sets for new forms of a known substance. Better pharmacokinetics without evidence the drug treats the underlying disease more effectively wasn't enough.