Earlier this year, the Patent Review Board of China’s State Intellectual Property Office (SIPO) rejected Gilead Sciences’ claims regarding their Viread patent covering the compounds of the fumerate of Bis (POC) PMPA which is an active ingredient in treating HIV, AIDS and Hepatitis B, known under the trade name ‘Viread’.

The Board declared all claims invalid. Claim 1 was found to lack inventive step over the combined teachings of two prior art documents. Part of claim 1 was directed at the fumerate of Bis (POC) PMPA which according to the description, has unexpected physical and chemical properties when compared to its free base. Some of the Bis (POC) PMPA properties were disclosed in one piece of prior art. Another disclosed a number of acids, including fumeric acid, for forming salts of a compound similar to the Bis(POC)PMPA. The Board concluded that those skilled in the art would be motivated to improve the stability of the free base by trying different salts based on the common understanding that salts of the free base usually retain their pharmacological activity.

The Board also concluded that experimental data comparing only the chemical stability of citrate and fumerate is not sufficient to show that fumerate is considerably better than all other salts.

Before the Board issued its decision, some commentators speculated that China would issue a compulsory license for Viread. After the invalidation, some commentators surmised that the Government wished to establish a favorable position in order to negotiate lower prices for drugs.

In view of Pfizer’s success in appealing the Viagra case, Gilead may decide to bring the case to the People’s Court. A spokesperson for Gilead said: “We are currently reviewing the notice from the Chinese Patent Review Board and evaluating our options. The notice from the [Review Board] refers to one of the patents covering TDF. There is an additional patent covering the compound that is not affected by this ruling.”