The turf war between Big Pharma and generic companies, which was largely restricted to exorbitantly priced drugs for cancer and HIV, is now spilling over to chronic and lifestyle problems. In yet another instance of a drug MNC losing monopoly, the Chennai Patent Office, an opposition filed by Ranbaxy, has revoked Pfizer’s patent on a drug used in urinary incontinence, which is expected to bring down its price substantially.

Significantly, the revocation of the patent may challenge Pfizer’s claims of monopoly on the Detrol formulation, experts say. The patent office recently revoked Pfizer claims on patent exclusivity for a formulation of its best-selling drug Detrol, used to manage overactive bladder symptoms.

The patent office said the invention claimed in the revoked patent was found to be "prior claimed" by another patent of Pfizer on the same drug. The invention claimed in the revoked patent was also found to be obvious, and not involving any technical advancement compared to existing knowledge, legal sources say. Simply put, the invention claimed in the patent is same to the formulation on which Pfizer has monopoly rights, weakening the basic premise of the first patent.

Pfizer had two patents on Detrol, the first patent (211539) was filed in August 1999, and the second (229260) three months later in November.

Though Pfizer’s first patent on Detrol is still valid, experts say that it is now under threat, as the second one has been revoked.

"In case the second patent (229260) on the extended release formulation of Detrol was not revoked, Pfizer would have had almost an additional three months of monopoly up to November 2019 instead of August 2019, when the first patent (211539) on the said formulation is supposed to expire. Generic companies are likely to use this additional three months time. Moreover, since the second patent has been revoked for being ‘prior claimed’, that is by the invention already claimed in the first one, it implies that the first patent is prone to attack on grounds of obviousness and lack of inventive step, and hence may be an inspiration for other players to attack the first patent," said Sanchita Ganguli, patent attorney at S Majumdar, the firm which represented Ranbaxy.

Ranbaxy declined to comment on its future strategy regarding opposing the first patent, now that the second has been revoked. Pfizer’s first patent on the drug is on weak ground and now prone to attack, experts say. Earlier, Ranbaxy had opposed the first patent on Detrol, and lost the case.

A spokesperson from Pfizer said the company is "reviewing the decision and considering its options".