The Infringer’s Burden in Process Patent Suits in India

Summary:

Indian patent law contains a unique provision that shifts the burden of proof onto the accused / infringer in process patent suits. But this applies only if certain conditions are met. The Delhi High Court clarifies what those are, and when the law kicks in .

Introduction

Enforcing a process patent is one of the most complex areas of patent litigation, as the allegedly infringing act would be concealed in the defendant’s manufacturing operations. In such matters, proving the infringement becomes particularly challenging. Section 104A of the Patents Act, 1970 (the ‘Act’) comes in useful here, as it departs from the general rule that the burden of proof rests with the party asserting infringement.

Recently, the Delhi High Court in F. Hoffmann-La Roche AG & Anr. v. Zydus Lifesciences Ltd. (Delhi High Court, decision dated 22 July 2025, CS(COMM) 159/2024) has clarified the scope, applicability, and limitations of S. 104A, which this note discusses.

Factual Background

Hoffmann-La Roche (“Roche”) filed a suit against Zydus Lifesciences (“Zydus”) alleging infringement of Pertuzumab, a monoclonal antibody (MAb) marketed under the name Perjeta, used for the treatment of early stage-breast cancer and metastatic cancer. Specifically, Roche alleged infringements of its Indian patents IN268632 and IN 464646, covering a pharmaceutical formulation comprising HER2 antibody, and the process for making Pertuzumab and its variants, respectively.

In February 2024, the Court directed Zydus to submit  in a sealed envelope, the process used to develop the formulation for which it had sought drug approval/licensing. A confidentiality club was duly formed, and Zydus submitted the information in a sealed envelope in March 2024.

After many appeals and counter-appeals, the case returned to the Delhi High Court, where Roche pressed its application seeking disclosure of Zydus’ manufacturing process to members of the confidentiality club.

Scope and interpretation of Section 104A

The Court was essentially required to determine the scope and interpretation of S. 104A. This provision reverses the burden of proof in process patent infringement suits. Here, if the plaintiff is able to prove that the defendant’s product is identical to the product obtained by the patented process, the court may require the defendant to prove that the process used by them is different from the patented process. In doing so, the court may also be mindful of the defendant’s manufacturing or commercial secrets, and direct appropriately.

The Court cited two decisions, i.e., Natural Remedies Pvt. Ltd. v. Indian Herbs Research and Supply Co. Ltd. (2011 SCC OnLine Kar 4561); and Bristol-Myers Squibb Holdings Ireland v. Mylan Laboratories Limited (2014 SCC OnLine Hyd 1511), which outline key principles applicable to S. 104A:

1. Only when the plaintiff proves that the two products in question are identical, the Court may direct the defendant to disclose its process to show it is different from the patented process.
2. The two products being identical is a sine qua non for 104A to apply. Mere similarity between the two products would not suffice.
3. While directing disclosure of process, the Court is expected to protect the trade and commercial secrets of the defendant.
4. Where the products are found to be identical and the defendant nonetheless refuses to furnish the particulars of its process, the Court may draw adverse inference and invoke 104A.

Thus, S. 104A shifts the burden of proof in process patent infringement cases to the defendant, since only the defendant knows the manufacturing process. However, this applies only if the plaintiff first shows that the defendant’s product is identical to that obtained from the patented process.

Interim Applicability

The first question before the Court was whether S. 104A could be invoked before trial, particularly when the plaintiff sought disclosure of the defendant’s process at the interim stage. Roche attempted to argue that S. 104A could only be invoked during final arguments, not at an interim stage. However, the defendant said the plaintiff had not demonstrated that the products were identical, as statutorily required. The Court held that if disclosure was sought at an interim stage, the plaintiff must discharge the initial burden under S. 104A.

Special vs General Laws

Closely related to the first question was whether the plaintiff could bypass statutory safeguards contained in S. 104A by invoking broader discovery provisions under the Commercial Courts Act, 2015 (“CC Act”), and the Civil Procedure Code (“CPC”).

Here, Roche sought discovery of Zydus’s manufacturing process under Order XI Rules 1(7), 1(12) and 5 of the CPC as amended by the CC Act, arguing that it was within the defendant’s special knowledge and necessary to establish infringement, and that the defendant would be caused no prejudice by disclosing this information to the confidentiality club.

Zydus argued that the Patents Act is a self-contained code, and its requirements, including Section 104A, cannot be overridden by the CPC.

Following precedent on this account, the Court held that the Patents Act is a specialized legislation dealing with patent-related matters, whereas the CC Act is a general legislation dealing with all commercial disputes. As the provisions of a special statute would always prevail over those of general law, S. 104A would prevail over the discovery provisions under the CPC.

Are Biologics Exempted?

Roche also tried to argue that, biologic drugs, by their very nature, cannot be identical to each other, and S. 104A would not apply to this category of drugs.

Disagreeing with this line of argument, the Court noted that while the Guidelines on Similar Biologics, 2016 (‘Biosimilar Guidelines’), allow ‘similar’ biological as being sufficient for regulatory approval, the legal burden under S. 104A requires proving identity in substance and composition; this cannot be diluted in biologic cases merely because absolute replication is scientifically difficult. Moreover, the term ‘identical’ in S. 104A reflects conscious legislative intent, and to impute a lower threshold would amount to diluting the requirement.

Adequacy of Plaintiff’s Proof

Roche contended that Zydus’s product is identical to their product as Zydus had cited Roche’s product as a ‘reference biologic’ in its application for drug approval/licensing. Thus, it argued that the biosimilar (Zydus’s “Sigrima”) could be considered identical to the reference biologic (Roche’s “Perjeta”).

To address this issue, the Court turned to the Biosimilar Guidelines, which defines key terms as follows:

•  ‘Reference Biologic’: “A Reference Biologic is used as a comparator for comparability studies with the Similar Biologic in order to show Similarity in terms of safety, efficacy and quality”
• ‘Similar Biologic’: “A Similar Biologic product is that which is similar in terms of quality, safety and efficacy to an approved Reference Biologic product based on comparability.”

According to the Court, drug approval does not hinge on the similar biologic being identical to the reference biologic. Instead, it must have a similar active ingredient, the same dosage form, strength, and route of administration, as well as ensure comparable quality in terms of identity, purity, and potency. Moreover, any manufacturing process may be used, provided it ensures product safety, efficacy, and quality. The Court concluded that Zydus’s application for drug approval before the drug regulatory authority would not fulfil the ‘identical’ requirement under S. 104A; it also does not establish that Zydus has used the Roche’s patented process.

Finally, the Court held that the plaintiff had failed to fulfil the mandatory requirements of S. 104A, and refused to direct the defendant to disclose its manufacturing process.

Conclusion

The decision in Hoffmann v. Zydus reaffirms the limited but significant role of S. 104A, which, being a special law, overrides general discovery norms. The shifting of burden of proof does not happen automatically, but requires certain preliminary conditions to be met before it can apply, i.e., plaintiff must prove identity of product, and inability to ascertain the defendant’s process.

More importantly, the Court’s strict reading of “identical” product might impact biologic patent enforcement in fundamental ways. The Court highlighted that regulatory standards for “similar biologic” (safety, efficacy, quality) cannot be conflated with the patent law standard of “identical product.” In the circumstances, innovator companies may find it challenging to prove identity between biologics and biosimilars, given inherent molecular variability. At the same time, biosimilar manufacturers benefit from a stronger shield against forced disclosure of trade secrets.