In yet another blow to the multinational drug companies in patent cases in India, the Chennai Patent Office has revoked Pfizer's patent on Detrol, a drug used to manage overactive bladder symptoms. The patent on the drug was challenged by Ranbaxy Laboratories.

In his order dated November 27, 2013, Assistant Controller of  Patents & Designs, Chennai, Dr SP Subramaniyan said that the invention claimed in the revoked patent by Pfizer was found to be 'prior claimed' by another patent of Pfizer on the same drug. Pfizer had two patents on Detrol, the first patent (211539) was filed in August 1999, and the second (229260) three months later in November 1999.

Though the second patent has been revoked by the patent office, Pfizer's first patent on Detrol is still valid.

In his order, Dr Subramaniyan further said that the invention claimed in the now revoked patent was also found to be obvious, and not involving any technical advancement compared to existing knowledge.

“Therefore, person skilled in the art would have been motivated to prepare controlled release bead for tolterodine with the teachings of preceding prior art together with common general knowledge in the art at that time of filling the application without undue experimentation. Further, the study carried out by the patentee on 'effect of sealcoat thickness' do not possess any inventive merit. It is common general knowledge in the art when thickness of layer increases, release rate of the drug or permeability of water decreases. Workable range of sealcoat layer neither suggested nor described in the complete specification. Therefore, present patent do not involve any technical advancement as compare to the existing knowledge. The inventive features as claimed by the Counsel for the patentee are obvious to the person known in the art. Thus claims of the claimed invention are not inventive and opposition filed 25(2)e of the Act is allowed.”

“In view of the discussion in the preceding paragraphs, considering the relevant submissions made by the parties and all the circumstances of the case, the post-grant opposition filed by the opponent under section 25(2) (c) and 25(2) (e) of the Act is accordingly accepted and revoking the patent u/s 25(4) of the Act without any order as to costs,” the order further said.

Earlier, Pfizer Health AB had filed a patent application for an invention “A controlled release bead and method of producing the same” and patent was granted after substantial examination and disposing of pregnant opposition. Then Ranbaxy Laboratories filed a post-grant opposition u/s 25(2) of the Patent Act within the prescribed time limit. Ranbaxy challenged the grant of patent under section 25(2)b, 25(2)c, 25(2) and 25(2)e of the Patent Act.