Delhi HC Dismisses Roche Appeal, Allows Natco to Continue Selling Generic Risdiplam for Spinal Muscular Atrophy

Risdiplam is admittedly manufactured and marketed by the appellants in various countries, including India, under the brand name EVRYSDI Risdiplam is an oral prescription medicine used for the treatment of Spinal Muscular Atrophy.

Roche, which manufactures Risdiplam under the brand name Evrysdi, alleged that Natco’s generic version infringed its subsisting Indian Patent IN 334397, valid until May 11, 2035. The company sought an interim injunction under Order XXXIX Rules 1 and 2 of the CPC, restraining Natco from selling the drug.

Roche contended that Risdiplam, though related to compounds described in its earlier genus patent, represented a distinct and novel invention deserving independent protection. It argued that the drug was not merely “covered” by the broad Markush formula of the genus patent but was a specific compound not disclosed or enabled therein.

The company submitted that the Single Judge had erred in equating “coverage” with “disclosure” and in holding the compound “obvious” without any concrete teaching or motivation to make such structural modification.

Roche emphasized that the substitution of a nitrogen atom (-N) for a carbon-hydrogen (-CH) group in the molecule involved a non-obvious inventive step and that the difference conferred significant therapeutic efficacy, making Risdiplam a new chemical entity under the law.

Natco, on the other hand, invoked Section 107(1) of the Patents Act to defend itself, arguing that Risdiplam was already covered and obvious from Roche’s earlier genus patent WO 2013/119916 / US 9586955, which disclosed a large set of similar compounds for treating Spinal Muscular Atrophy (SMA).

Natco maintained that the only structural difference between Risdiplam and Compound 809 of the genus patent was the replacement of a -CH radical with a nitrogen atom (-N), a well-known and predictable modification in medicinal chemistry based on Grimm’s Hydride Displacement Law.

It pointed out that four inventors were common to both the genus and species patents, showing that the later patent was a mere routine optimization aimed at extending exclusivity rather than a genuine innovation. The company therefore contended that the suit patent lacked an inventive step and was vulnerable to revocation under Section 64(1)(f).

The Division Bench agreed with the Single Judge’s view that Risdiplam was prima facie obvious to a person skilled in the art, particularly because the same inventors were involved in both patents.

“Something which is ‘obvious’ to a person skilled in the art would be ‘more obvious’ to the inventor of the genus patent, who would be ‘in the know’ of things,” the Bench observed.

The judges further held that allowing minor molecular substitutions to extend patent protection would amount to evergreening, contrary to the public interest in ensuring access to essential medicines.

The court stated, “

"By no means can an inventor be permitted, by making changes to an invented pharmaceutical preparation… to keep the invention out of the public domain beyond the period of life of the patent.”

While the Bench expressed reservations about whether Risdiplam lacked novelty under Section 64(1)(e), it found “no reason to interfere” with the Single Judge’s conclusion that the compound was obvious under Section 64(1)(f). The Bench reiterated that under the Wander Ltd. v Antox India Pvt Ltd principle, appellate courts should not interfere with discretionary orders unless the lower court’s findings are arbitrary or perverse. The Division Bench held;

“We do not deem this to be a fit case for interference with the impugned judgment of the learned Single Judge. The appeal is, accordingly, dismissed.”

With this, the Delhi High Court effectively upheld Natco Pharma’s right to continue manufacturing and marketing its generic version of Risdiplam pending the outcome of the main suit.

To view the official order, click the link below: