Delhi High Court Dismisses Appeal Against Refusal Of Smelling Disease Patent

Soon after dismissal of an appeal against the rejection of a patent application on a diagnostic method in the 'Natera Inc' case [2025:DHC:8937], the Delhi High Court once again got an opportunity to relook at the reach of Section 3(i) of the Indian Patent Act, 1970. This time, the patent application rejected by the Patent Office in question was 201617022947, for a "Cancer Detection Method Using Sense of Smell of Nematode" filed by Hirotsu Bio Science Inc.

In the case of Hirotsu Bio Science Inc. vs Assistant Controller of Patents and Designs [C.A.(COMM.IPD-PAT) 45/2023] decided on January 17, 2026, the Delhi High Court referred to its earlier decisions, viz. Natera Inc. and Anr [where it was noted that Section 3(i) of the Act does not make any distinction between in vivo or in vitro processes] and The Chinese University of Hong Kong 4863/CHENP/ 2012 [where it was noted that Section 3(i) of the Act extends both to in vitro and in vivo diagnosis]. The Court found that, in both cases, the High Court had clearly interpreted Section 3(i) of the Act to prohibit both in vivo and in vitro processes, without differentiating between the two.

Appellant's Arguments

The appellant submitted that in the present invention, the inventor utilised the behaviour of an identified nematodes that exhibit a chemotaxis to an odorant, such as approaching or escaping from it. By using such a behaviour of the nematodes as an indicator in the present invention, the reactions of nematodes to the smells of cancers will be examined. The appellant argued that amended Claim 5 was directed to a method for identifying olfactory receptors in nematodes and that this method is used for deciding which nematodes to use in the cancer detection method, and thus, is not related to the diagnostic method.

The appellant also relied on the Chinese University of Hong Kong case [Paragraph Nos. 51 and 52] to argue that the assessment to be undertaken by the Controller should have been whether the test was inherently, and per se, capable of identifying the disease, disorder or condition for treatment of the person. According to the appellant, the claimed invention related to detection, i.e., identifying cancer-specific odour responses in biological samples outside the human body. It did not amount to a diagnosis, which requires medical correlation, interpretation, and clinical judgment.

The claimed method for detecting cancer, which was characterised by breeding nematodes in the presence of a subject-derived bio-related substance or a processed product thereof, and then detecting cancer, for example, using the chemotaxis of the nematodes, based on their olfaction, as an indicator. According to the appellant, the inventive feature of the invention lay in the detection process, which utilised the olfactory responses of nematodes to biological samples to identify the presence or risk of cancer in vitro. The appellant argued that since the claim language explicitly restricted the scope to "in vitro" conditions and no step involves diagnosis, treatment, or medical decision-making on a human or animal body, the claimed invention fell entirely outside the exclusions under Section 3(i) of the Act.

Respondent's Reply

The respondent Controller relied on Paragraph No. 30 of the decision in The Chinese University of Hong Kong case and submitted that the expression "diagnostic" under Section 3(i) of the Act extends both to in vitro and in vivo diagnosis. The respondent also relied on the decision in Natera Inc. & Anr., which states that the manner in which a diagnosis is performed under the "diagnostic process" is important in determining patentability.

In the present case, the claimed invention was for a method for detecting and characterising cancer type in human subjects, which is not allowed under Section 3(i) of the Act. According to the respondent Controller, the claimed method was clearly a diagnostic method, and it involved all the essential steps of a diagnostic method, viz.

1. the examination phase involving the collection of data
2. comparison of these data with standard values
3. the finding of any significant deviation, i.e., a symptom, during the comparison, and
4. the attribution of the deviation to a particular clinical picture, i.e., the deductive medical decision phase.

Court's Analysis and Findings

From reading the complete specification, the Court found that the subject matter of the invention was to detect cancer by using the chemotaxis of nematodes based on the olfaction or the response of olfactory neurons. To be more precise, the present inventor had found that cancer could be detected using the chemotaxis of nematodes based on the olfaction thereof or the response of olfactory neurons.

According to the Court, contrary to the submission of the appellant, Paragraph No. 79 of the Natera case clearly notes that Section 3(i) of the Act does not make any distinction between in vivo or in vitro processes. Both the Chinese University of Hong Kong and Natera cases have clearly interpreted that Section 3(i) of the Act prohibits both in vivo and in vitro processes. Therefore, Section 3(i) of the Act does not differentiate between the in vivo and in vitro processes.

Additionally, the Court found that the Complete Specification showed that the screening claimed in amended Claim 1 yielded highly accurate cancer identification. According to the Court, based on the repetition of the analysis to be performed on the specimen, the outcome/result was highly accurate. In the Complete Specification, it was disclosed that the cancer diagnosis system could detect early cancer, including stage 0 or 1, with high accuracy.

The appellant admitted that the invention related to a method of detecting cancer involving steps such as collecting data, comparing the data with standard values, and drawing a conclusion based on the results. The Court concluded that the claimed method could detect cancer, including early-stage cancer, with a high rate of accuracy. The claimed method, according to the Court, led to the detection of cancer. Therefore, the claims are not allowable under Section 3(i) of the Act.

The Court relied on Paras 100 and 101 of the decision in Sequenom Inc. & Anr., wherein the Court held that since the extremely accurate test had 98.6% sensitivity and 99.8% specificity, it led to conformity. In this case, the Court also emphasised that when the language of Section 3(i) of the Act uses the word "diagnostic", it includes both positive and negative diagnoses. The Court observed that an application cannot be held patentable merely because the test does not confirm the presence of a particular medical condition. The Court noted that while there can be no doubt that the subject invention could be a useful invention, the mere fact that it is an in vitro method would by itself be insufficient to make the invention patentable, so long as the purpose of the process is to diagnose a medical condition.

Court's Decision

The Court upheld the order of refusal of patent and noted that the respondent Controller had rightly noted the steps involved in the Subject Application while providing reasons for the claimed method being a diagnostic method. Therefore, the appeal was dismissed.

Conclusion

The Court in this case reaffirmed that Section 3(i) of the Patent Act, 1970, does not distinguish between in vitro or in vivo diagnostic methods for the detection of a disease. The Court relied on the ruling of the 'Sequenom case' to emphasise that when the language of Section 3(i) of the Act uses the word diagnostic, it would include both positive and negative diagnoses. According to the Court, since there was a tangible result achieved by the test, it would defeat the purpose of Section 3(i) if a patent were granted. The Court further noted that the argument of the in vitro diagnostics method would by itself be insufficient to make the invention patentable, so long as the purpose of the process is to diagnose a medical condition. Therefore, the decisive factor which may lead to the refusal of a patent would be that the purpose of the process is to diagnose a medical condition.

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