Introduction:

A Recurrent Problem in Pharma Patent Law

The intersection of genus and species patents remains one of the most difficult and contested frontiers in pharmaceutical patent jurisprudence. A genus patent typically claims a broad class of compounds often represented by a Markush formula while a species patent claims a narrower, specific compound within that class. The legal conflict arises when a patentee seeks to secure a new monopoly over a species that arguably falls within the earlier genus.

Indian patent law, particularly under the Patents Act, 1970, has consistently resisted efforts at "evergreening" the practice of securing serial patents for marginal modifications of known substances. Section 3(d), introduced after the TRIPS amendments, explicitly excludes patenting of new forms of known substances unless they result in "enhanced efficacy." However, even beyond Section 3(d), courts have deployed doctrines such as anticipation, obviousness, prior claiming, and public interest to deny undue extensions of exclusivity.

The Delhi High Court's Division Bench (DB) judgment in Roche Products (India) Pvt. Ltd. v. Natco Pharma Ltd. concerning the drug Risdiplam used for treating Spinal Muscular Atrophy (SMA) is the latest and perhaps most significant addition to this evolving line of decisions. The court refused an interim injunction sought by Roche, holding that the species patent for Risdiplam was prima facie obvious in light of an earlier genus patent.

This article examines the facts, legal reasoning, and implications of the Risdiplam decision, situating it within the broader trajectory of Indian genus-species jurisprudence from Novartis to AstraZeneca and Dapagliflozin (Dapa). It argues that while Risdiplam strengthens the anti-evergreening position and advances access to medicines, it also raises conceptual tensions around the notion of inventive step and the new "person in the know" standard.

The Background: Roche's Risdiplam Patent Battle

Roche holds Indian Patent No. IN 334397, claiming the specific compound Risdiplam, used to treat SMA a rare, life-threatening neurodegenerative disorder. The patent expires in 2035. Roche also owns an earlier international (PCT) genus patent--WO 2013/119916 (WO'916) covering a broad class of similar compounds with potential activity against SMA.

Indian generic manufacturer Natco Pharma sought to launch a generic version of Risdiplam. Roche filed an infringement suit in the Delhi High Court, seeking an interim injunction to restrain Natco's market entry.

In March 2025, Justice Pratibha Singh (Single Judge) refused the injunction. She held that Natco had raised a credible challenge to the validity of Roche's species patent, noting that the genus patent WO'916 already disclosed compounds so structurally close to Risdiplam that the latter lacked an inventive step. The decision also relied heavily on the "person in the know" concept articulated in AstraZeneca AB v. Intas Pharmaceuticals and the Dapagliflozin (Dapa) Division Bench ruling.

Roche appealed. A Division Bench comprising Justice C. Hari Shankar and Justice Ajay Digpaul upheld the Single Judge's refusal of interim relief on 9 October 2025. The DB found that the species patent was prima facie vulnerable under Section 64(1)(f) of the Patents Act (lack of inventive step) and that the balance of convenience and public interest favored Natco.

As a result, Natco was allowed to continue marketing generic Risdiplam in India a major relief for patients, given that the generic version costs over 90% less than the branded product.

The Central Legal Issues

A striking feature of Risdiplam is its reliance on the "person in the know" yardstick for assessing inventive step when both the genus and species patents share the same inventors.

Ordinarily, inventive step is judged from the standpoint of a "person skilled in the art", a hypothetical construct representing an average expert in the relevant field. In Risdiplam, however, the court reasoned that where the same inventors file both the genus and species patents, the question becomes: would those inventors, knowing what they already disclosed in the genus, have found it obvious to arrive at the species?

This "internalization" of the inventive-step analysis effectively collapses the objective test into a subjective one. As Dr. Praharsh Tandon observed in his SpicyIP commentary , this approach "turns the inventor into the yardstick" which, while logical in genus/species overlap cases, risks hindsight bias and may depart from statutory interpretation under Section 2(1)(ja).

The Division Bench justified this shift by invoking precedent: AstraZeneca AB v. Intas and Dapagliflozin DB had both used this framework to prevent patentees from re-patenting compounds already within their earlier disclosures.

However, the DB in Risdiplam did not hold that this standard applies universally it limited the test to "circumstances where the same inventors are behind both the genus and the species patents." Whether this becomes a binding general rule remains open for higher judicial scrutiny.

Coverage versus Disclosure

The Risdiplam dispute also revisited the classic tension between "coverage" and "disclosure".

A genus patent covers a large chemical space but may not disclose every individual compound within it in an enabling way. Indian law (as seen in Novartis v. Union of India, 2013 ) has warned against a "vast gap between coverage and disclosure."

In Risdiplam, Roche argued that while the genus patent WO'916 covered Risdiplam, it did not disclose it. The Division Bench disagreed, noting that the genus patent's "Compound 809" and its analogs were so structurally similar to Risdiplam that a skilled medicinal chemist could easily arrive at it through routine substitution specifically, a C-H to N bioisosteric substitution.

Thus, even if not literally disclosed, the species was implicitly disclosed or rendered obvious by the genus. The DB therefore found a strong prima facie case of lack of inventive step.

This reasoning aligns with a growing trend in Indian jurisprudence to collapse the distinction between coverage and disclosure when the structural or functional proximity is too close. Earlier decisions in AstraZeneca and Boehringer Ingelheim v. MSN Labs (Linagliptin case, 2022) follow a similar logic.

Prior Claiming and Double Patenting

The judgment also hinted at concerns of prior claiming where the genus patent effectively claims the same invention as the species patent, making the latter invalid under Section 64(1)(a).

Although the Division Bench did not explicitly rule on prior claiming, it acknowledged that Roche's overlapping patents with similar inventors and subject matter created "prima facie uncertainty" over distinct inventive subject matter. This echoes the Linagliptin case, where the Delhi High Court held that a later species patent cannot stand if the earlier genus already "claims" the same subject matter.

Public Interest and Anti-Evergreening

Perhaps the most striking part of the Risdiplam ruling lies in its invocation of public interest. The Division Bench stated:

"In the case of drugs and pharmaceutical products, the principle acquires a superadded and predominant element of public interest. If patents relating to essential and life-saving drugs are permitted to be evergreened, the drug may forever remain outside the public domain, resulting in calamitous public harm."

This observation underscores the constitutional and social policy dimension of India's patent jurisprudence, anchored in access to affordable medicines, as affirmed in Novartis (2013) .

By refusing interim relief, the court ensured continuing access to a life-saving drug at affordable prices. Reports suggest that the generic version by Natco costs less than 10 lakh per year, compared to the imported version's price exceeding 7 crores, a difference with life-or-death consequences for many Indian families.

The decision, therefore, represents not only a doctrinal but also a moral reaffirmation of India's commitment to balancing innovation with public health imperatives

Implications and Emerging Trends

1. Doctrinal Consolidation

The Risdiplam judgment cements a doctrinal consolidation across Indian case law:

o A species patent will rarely survive if the same inventors already claimed a genus covering that species.

o Courts are willing to infer implicit disclosure or obviousness even in the absence of explicit examples.

o Public interest can decisively tip the injunction balance, especially for life-saving drugs.

2. Evolving Standard of Inventive Step

The "person in the know" approach effectively raises the bar for inventors seeking follow-up patents on their own research. This may deter strategic filings but risks conflating legitimate incremental innovation with evergreening. Critics argue that it creates a quasi-subjective test inconsistent with Section 2(1)(ja), which envisions an objective skilled person.

A future Supreme Court ruling will likely determine whether this test becomes a settled standard or remains confined to overlapping-inventor cases.

3. Policy Implications

For innovators, Risdiplam underscores the need for robust data demonstrating unexpected advantages such as superior efficacy, bioavailability, or stability to justify a new patent. Companies may also need to structure their R&D and inventorship teams more carefully to avoid internal overlap that could trigger the "person in the know" inference.

For generic firms, the ruling reaffirms the viability of defensive strategies based on prior art, genus disclosure, and public interest arguments.

For policymakers, it may prompt reconsideration of whether explicit statutory guidance on overlapping patent families and selection inventions is needed to ensure both innovation and accessibility.

VI. A Broader Reflection: Law, Innovation, and Access

The Risdiplam decision encapsulates the Indian judiciary's balancing act between two imperatives:

• Preventing unjustified extensions of monopoly that hinder affordable access to essential medicines.

Unlike in some Western jurisdictions, Indian courts have embedded public interest directly into patent enforcement, treating access as an integral part of the patent ecosystem--not a post-grant policy issue. The Risdiplam DB's explicit warning against evergreening "life-saving drugs" continues this normative stance.

• At the same time, the decision raises methodological questions: Can courts coherently apply both objective and subjective standards for inventive step? Could the "person in the know" doctrine lead to inconsistent results? And might it discourage legitimate refinement research by pharma innovators?

These questions await clarification in future cases, perhaps when the Risdiplam matter proceeds to a full trial or reaches the Supreme Court.

VII. Conclusion

The Risdiplam Division Bench judgment is a watershed in India's genus-species jurisprudence. It reaffirms a strong anti-evergreening ethos, embeds public interest firmly within the patent framework, and extends the "person in the know" standard as a tool against repetitive, intra-inventor filings.

While its immediate effect is to make Risdiplam more accessible to SMA patients, its doctrinal implications extend far beyond one drug. Together with Novartis, AstraZeneca, and Dapagliflozin, the decision outlines an increasingly coherent Indian model one that prizes disclosure, transparency, and social welfare as much as inventive ingenuity.

Whether this model finds equilibrium between innovation and access will depend on how courts and policymakers refine the delicate boundary between coverage and disclosure, invention and evergreening, and ultimately, property and public good.

Author :- Sanskriti Sharma, in case of any query, contact us at Global Patent Filing or write back us via email at support@globalpatentfiling.com.