Valganciclovir Patent revoked after Post-Grant Opposition

August 10, 2015

Facts of the case

  • Valganciclovir, manufactured by Hoffman- La Roche, is an anti-retroviral drug used for the treatment of active cytomegalovirus retinitis (CMV) infection.
  • Roche was granted patent (207232) entitled “2- (2-AMINO-1,6-DIHYDRO-6-OXO-PURIN-9-YL)METHOXY-1,3-PROPANEDIOL DERIVATIVE’ on July 27, 1995 covering L- Valinate Ester of Gancyclovir and all acceptable salts in oral form with increased bioavailability.
  • In May 2010, Controller had revoked the patent on grounds that it was obvious and did not satisfy the requirements of Section 3(d) of the Patents Act, 1970 in response to the oppositions filed by the Indian Network of Positive People (INP), the Tamil Nadu Network of Positive People (TNNP), the Delhi Network of Positive People (DNP) and generic companies. The details of the Post-grant opposition can be found on our website.
  • Roche challenged the decision by filing an appeal with the Intellectual Property Appellate Board (IPAB). INP and TNNP also filed an appeal against the some of the Controller’s findings. Both appeals came up for hearing on January 30, 2014.
  • The IPAB then set aside the Patent Controller’s decision to revoke the patent relating to valganciclovir on technical grounds and remanded it to the Controller for re-consideration.
  • The controller revoked the Indian Patent No. 207232 pertaining to Valganciclovir in the order dated July 01, 2015.

The Controller’s order

i) Experts’ opinion

The patentability of the drug was the issue in the Controller’s order. The Controller noted that the three main aspects of determining patentability were disclosure, relevant prior art and judgments available at the time of deciding the case. The issue before the Controller was whether expert evidence was prior art publications or disclosures. The Controller held that the view of the expert is only a personal opinion on the given subject matter, but it is never a conclusion arrived after continuous research work in the specific area.

Therefore, expert evidence is not a prior art document to be relied upon for deciding a case, but it may be considered for understanding the prior art documents,

ii) Prior arts cited- EP 0375329 (EP’329)

Acyclovir and Gancyclvovir are similar in structure and function targeting similar diseases (anti-viral). It is known that acyclovir is poorly absorbed and large doses are required to increase its bioavailability. If Acyclovir is esterised, its bioavailability is increased when administered orally. EP’329 mentions several amino acids which can be used to result in the L-valinate ester of Acyclovir called Valacyclovir. Adding Hydrochloride to acyclovir yields L-valinate ester of Acyclovir called Valacyclvoir (sold as Valtrex, an anti Herpes drug by GSK).

  • L-Valinate ester of Gancyclvovir in the intra-venous form is already in the market against anti-viral diseases (mainly HIV infections).
  • In order to increase the bioavailability a person skilled in the art would have been motivated to come up with an oral form of the compound by following the step of esterization of Gancyclvovir resulting in the L-valinate ester of Gancyclovir (namely Valgancyclovir) and later, a combination with hydrochloric acid to result in Valgancyclovir Hydrochloride (sold as Valcyte by Roche).
  • iii) Bioavailability

    The next issue to be discussed is whether the improvement of oral bioavailability constitutes enhancement of the known efficacy of that substance. The Controller ruled that while bioavailability is one of the factors affecting efficacy, it cannot be directly equated to efficacy. The Controller ruled that the present patent was a ‘mere use of a known process’ which was not patentable under S. 3(d) of Indian Patents Act.

    As a result, for all these reasons, the Controller revoked the patent granted to Valganciclovir.

    The Controller’s order can be found on the below link:

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