The Indian Patent Office has revoked the Patent No. 281489 (Application No. 201641013830) subsequent to a post-grant opposition by Symed Labs. The patent was revoked for lacking obviousness/inventive step, not being a patentable invention under section 3(d) and failure to disclose requisite information under section 8 of the Patents Act. The patent was granted on 20 March, 2017 and the post grant opposition was filed on 5 March, 2018. The patent relates to Linezolid, an antibiotic primarily used against pneumonia, skin related infections and importantly drug-resistant tuberculosis. Notably, an earlier patent over the same drug expired on 1 January, 2012. Interestingly, the drug features in the list of drugs for which the National Pharmaceutical Pricing Authority (NPPA) has fixed the ceiling price. A review challenging the fixation by Abbott Healthcare was rejected by the Department of Pharmaceuticals in October 2024.
Symed Labs, the opponent in this case, has previously litigated against patents related to Linezolid. And Symed’s infringement claim against Glenmark back in 2013 for the same was hotly debated on the blog. (Read a three part post by Rupali here, here, here and another post on the same issue here. A response to Rupali’s post by Arun C Mohan here)
Post-Grant Opposition Timeline
Since the filing of the post-grant opposition in March 2018, there had been several rounds of back and forth between the patent office, patentee and the opponent, before a hearing could take place in June 2024. This included filing additional evidence and a writ petition by the patentee before the Madras HC for the constitution of a fresh opposition board in 2023. The patentee had also amended its claims during the opposition proceedings and urged that the application under Form 13 (for amendment of claims) be disposed of so as to be certain of the final set of allowed claims for the hearing. But the patent office had insisted on completion of the opposition proceedings first.
Post-Grant Opposition Grounds and Analysis
The post-grant opposition order by the patent office revoking the patent seems to be a well-reasoned and straightforward decision. Let us look into each of the grounds closely and the analysis of the decision on the same.
- Section 25(2)(b): Anticipation by Prior Publication
The opponent had argued that the claims in the patent were anticipated by prior publication. Allegedly, prior patent applications (5865/CHE/2013 – Abandoned, 444/CHE/2014 – Refused, 2498/CHE/2014 – Abandoned) by the same patentee existed with the same claims. The opponent had gone on to compare the claims in both the current patent in question and the prior claims. The patentee had refuted the arguments by stating that the intermediate used to prepare Linezolid in the present patent application was different from the other prior applications. This was further substantiated by the lack of disclosure of using inorganic bases such as sodium hydride in the preparation of Linezolid in the earlier applications.
The patent office held that though the use of sodium hydride as the base is disclosed in the cited documents but the documents “do not exemplify any specific embodiment which discloses the reaction … and also the conditions and reaction parameters for such use.” Therefore anticipation by prior publication was held to be not a valid ground of opposition.
- Section 25(2)(c): Anticipation by Prior Claiming
The argument under this ground seemed a slightly confused attempt by the opponent. Section 25(2)(c) reads as follows:
To my understanding, this ground pertains to claims made in a document published on or after the priority date of the claim of the patentee and filed in pursuance of a patent application for which the priority date is earlier than that of the patentee’s claim. However, the documents cited by the opponent were both published before the priority date of the patentee’s claims. These are the same documents as presented in support of its ground under section 25(2)(b). The patent office’s decision therefore made a straightforward decision that the documents cited by the opponent did not satisfy the requirements for the aforesaid ground.
- Section 25(2)(e): Obviousness and Lack of Inventive Step
The opponent had alleged that the current patent merely involved a “workshop improvement” and has involved mere mosaicing of multiple prior art documents. The opponent had relied on patent no. 449110 (PROCESS FOR THE PREPARATION OF OXAZOLIDINONE DERIVATIVES by Benova Labs) and patent no. 213062 (NOVEL INTERMEDIATES FOR LINEZOLID AND RELATED COMPOUNDS by the opponent Symed). The opponents argued that the prior art documents discloses the use of safe, easy to handle and less expensive inorganic bases (in addition to the organic bases). Also additionally arguing that there was no technical advantage disclosed by the patentee compared to the prior art documents and did not involve any inventive step therein.
The patentee had contended that the prior documents did not disclose that the reaction in question in presence of inorganic base like metal hydride (sodium hydride) can be completed in less span of time for example if the reaction is carried in presence of Sodium hydride as a base. Further arguing that the features of the current patent such as very ‘less impurities profile, reduction in time for the completion of process and reduction in cost when using inorganic bases such as metal hydrides’ cannot be anticipated from the disclosure of prior documents.
The patent office after a detailed analysis had concluded that the prior art documents do have a disclosure of using sodium or potassium bases combination with lithium salt can be used for forming the lithium cation and the base in situ for the similar process. The prior documents also disclosed the use of safe, easy to handle and less expensive inorganic bases (in addition to the organic bases). Therefore concluding that the cited disclosures sufficiently taught the use of inorganic bases for the claimed process in the current patent in question. Also stating that the use of alkali metal hydrides like sodium hydride, and others as reagents is an obvious selection from the disclosure of the prior art documents and that the technical advancement cannot be solely attributed to the sodium hydride reagent, as claimed by the patentee.
- Section 25(2)(f): Not an Invention
The opponent had claimed that under Section 3(d) of the patents act, the claimed process in the patent is a “known process” and does not either result in the formation of a new product. The opponent had reiterated the use of sodium hydride as being already known in the view of prior art documents. Further arguing that the use of aforesaid reagent was not considered safe at industrial level and that the patentee had shown no evidence that the use of sodium hydride resulted in better yield or purity.
The patentee argued that their patented process has advantage with respect to reduction in time and providing good yield and high purity. Refuting the arguments on the use of the reagent at industrial level, the patentee had argued that the cited document did not teach the same. Additionally, the same reagent had been used in commercial processes.
The patent office did not state detailed reasons or analysis but merely stated that based upon the prior art documents cited by the patentee, the patent process was a known process and therefore objections under section 25(2)(f) r/w section 3(d) were valid.
- Section 25(2)(h)
Under section 8 of the Patents Act, the patentee is mandated to disclose foreign applications. The patent office had noted that till the time of hearing the patentee has not taken any steps to disclose the same. Further adding that the disclosure under Form 18A cannot be equated with the disclosure under Form 3 for foreign application disclosures. Therefore, holding this ground to be maintainable.
Conclusion
The decision seems to have taken into consideration all the arguments raised by the opponent and the patentee, arriving at the revocation conclusion. It is surprising to see that the patent office in its assessment of the patent application missed out on assessing the procedural requirements such as required disclosures under section 8. Since admittedly the aforesaid disclosure was not made under form 3 as mandated under the act, this raises some questions on the level of scrutiny made by the patent office. On similar lines, the analysis by the patent office on the grounds of obviousness as well as under section 3(d), which seem to be pretty straightforward courtesy of key prior art documents produced by the opponent, ought to have been scrutinised closely at the stage of the patent grant itself. In critical pharmaceutical patent applications especially, safeguards under 3(d) should be subjected to higher standards and careful examination.