New Delhi, Sept. 7: India has denied US pharma major Pfizer's new patent application for its rheumatoid arthritis drug, tofacitinib, as it does not enhance the efficacy of the existing drug.

Pfizer had sought a patent that covers an important chemical formulation of the active compound in the medicine. The Indian patent office said the company would have to establish that the compound for which it was seeking the patent was therapeutically more effective than the active compound.

"After having considered the submissions of the applicant, it is hereby ordered that the invention disclosed and claimed in the application is not considered as an invention under the provisions of the act," Bharat N.S, assistant controller of patents and designs, said in an order.

Pfizer is reviewing its options for further action, a company spokesperson said.

The patent office had earlier rejected Pfizer's application for the same drug in 2011. The Intellectual Property Appellate Board later asked the patent authority to reconsider the decision after an appeal by Pfizer.

"I do not admit that the claimed compound has enhanced efficacy over the base compound and hence not patentable under Section 3(d) of Patents Act. I therefore, hereby refuse this application," Bharat added in his order.

Quoting a Supreme Court judgment, the order said the applicant would have to establish the therapeutic enhanced efficacy of the claimed compound over the base compound.

Patents have become a thorny issue among global drug makers looking to expand in India's fast-growing healthcare market. Companies such as Pfizer, Bayer and Roche have in recent years struggled to retain exclusivity on drugs in India, blaming domestic patent laws for favouring the local industry.

India has said its patent policy is designed to ensure affordable medicines in a country where less than 15 per cent of the population has health insurance.