India has revoked a patent on German pharmaceutical company Boehringer Ingelheim's lung drug Spiriva and ruled in favor of domestic drugmaker Cipla Ltd , in the latest setback for a multinational drugmaker operating in India. Cipla, India's fourth-largest drugmaker by sales, filed an opposition to Boehringer's patent on Spiriva in 2013, claiming the drug was "obvious" and did not constitute an invention under India's patent laws. Spiriva is a respiratory drug used in the treatment of chronic obstructive pulmonary disease. India's patent office ordered the revocation in a decision posted on its website on Thursday. A spokeswoman at Boehringer's India office said the company will be "evaluating carefully the basis for the recent decision once the detailed reasons thereof are available." A Cipla spokesman declined to comment. The move adds to the woes of Western drugmakers who covet a large share of India's fast-growing $15 billion pharmaceuticals market, and have expressed frustration over a series of drug patent-related decisions taken by the government to improve affordability. India is working on revamping its intellectual property rights policy, but has maintained its patent rules are compliant with international patent protection law. (Reuters)