A patent attack on three fronts
The Indian patent system has been known for its strict prosecution of patents in the pharmaceutical sector ever since the product patent regime came into force in 2005. Furthermore, several opportunities are provided to third parties to challenge patent applications and make use of multiple pre-grant oppositions, while post-grant attacks are the norm for important pharma product patents.
The most recent example is that of a pneumococcal conjugate vaccine (PCV), Prevnar, which we discuss here.
Prevnar 13 patent
Pneumococcal vaccines are based on capsular polysaccharide, which is poorly antigenic in children below two years of age, which is when there is the highest risk of mortality due to invasive pneumococcal disease (IPD). PCVs such as Prevnar 13, have been developed to overcome this problem.
The conjugation with a carrier protein helps enhance the immune response, and achieve other positive effects. However, conjugation with a carrier protein raises other issues, such as antigen-induced immune suppression which limit the number of serotypes that can be added to a vaccine composition.
Prevnar helps prevent infections caused by the 13 most common strains of Streptococcus pneumoniae. Pfizer’s subsidiary, Wyeth, filed a Patent Cooperation Treaty (PCT) patent application in 2006 covering Prevnar which was later nationalised in various countries including India. The claims of the patent application related to a 13-valent immunogenic composition for use as a vaccine, comprising polysaccharide-protein conjugates derived from 13 S. pneumoniae serotypes (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F and 23F), each serotype being conjugated to a diphtheria toxoid variant carrier protein called CRM197.
The patent application for Prevnar has been challenged in countries such as South Korea, the US, Japan, China, etc. Its patent in Europe was revoked by the European Patent Office in 2014, and the decision is under appeal. The Indian case has seen much action before the Indian Patent Office (IPO).
