Calcutta High Court Sets Aside Patent Office Order Rejecting TopoTarget's Cancer Drug Patent Application

A Single Judge Bench of Justice Ravi Krishan Kapur, in a judgment dated January 30, 2026, allowed TopoTarget's appeal and quashed an order dated November 29, 2019, passed by the Deputy Controller of Patents and Designs, Kolkata.

The impugned order had rejected the patent application on multiple grounds including insufficiency of disclosure, lack of inventive step, obviousness, and non-patentability under Section 3(d) of the Act.

Disagreeing with the patent office findings, the Court observed that, “In discharging its statutory functions, the Examiner was only to make a Report to the Controller. An examiner is not entitled to participate or make submissions during the hearings of the proceedings. In such circumstances, the Controller was obliged to apply his mind independently to the objections and submissions made and adjudicate the matter and not merely endorse the Examiner's opinion.”

The patent application relates to a pharmaceutical composition comprising a known substance histone deacetylase (HDAC) inhibitor, PXD101, as the active ingredient, along with arginine or meglumine as an inactive ingredient. According to the applicant, the composition achieved enhanced solubility and stability of the drug in both concentrated and diluted liquid forms.

The Deputy Controller rejected the application by relying on multiple prior art documents, including documents not cited in the First Examination Report and concluded that the invention lacked novelty and inventive step and was non-patentable under Section 3(d).

Challenging the rejection, TopoTarget argued that the Controller failed to consider the invention as a whole, misconstrued the claimed composition as a salt of a known substance and merely endorsed the Examiner's conclusions without applying independent reasoning.

The Patent Office, on the other hand, defended the rejection, arguing that the claimed invention was disclosed in prior art and failed to demonstrate any technical advancement or therapeutic efficacy.

After examining the material on record, the Court noted that PXD-101 was admittedly a known substance and TopoTarget claimed inventive step in identifying specific inactive ingredients i.e., arginine and meglumine, as in-situ salt formers however, this aspect was not examined in the impugned order.

The Court held that none of the cited prior art documents disclosed or suggested the claimed combination capable of achieving both enhanced solubility and formulation stability.

“The impugned order although mentions the prior arts, however fails to show how are they more effective than the claimed invention,” the Court said.

On the applicability of Section 3(d), the Court clarified that the provision applies to new forms of a single known substance whereas the present invention was directed towards a multi-component pharmaceutical composition, placing it outside the scope of said provision.

The Court observed, “Section 3(d) is only applicable when the invention is a new form of a single known substance and is put to the test of “therapeutic efficacy”. Section 3(d) is also applicable to combinations involving derivatives of a known substance whether alone or with the known substance itself. A combination of two separate active drugs cannot be treated as derivatives of each other and therefore do not fall within the scope of section 3(d) of the Act.”

The Court also found that the findings on insufficiency of disclosure under Section 10(4) were unsupported by reasons and internally contradictory.

Accordingly, the Court set aside the rejection order and remanded the matter to a different Controller for fresh consideration, clarifying that it had expressed no opinion on the merits of the patent claims.

For Appellant: Advocates Subhatosh Majumder, Paritosh Sinha, K. K. Pandey, Mitul Dasgupta, Sonia Nandy, Teesham Das and Mallika Bothra

For Respondent: Advocates Swatarup Banerjee and Shankharit Chakraborty