The recent legal reverses suffered by multinational majors Novartis [Get Quote] and Roche over patents for cancer medicine could be the tip of a huge iceberg.

A city-based policy research group has found that multinational drug firms have filed over 350 patent applications for drugs used in cancer treatment.

An analysis of pharma patent applications pending with the patent office by the group, which did not wish to be identified, has put the number of cancer drug patent applications at 413. Of these, 358 came from top multinationals like Novartis, Aventis [Get Quote], Bristol Myers Squibb, Pfizer [Get Quote], Boehringer, Roche and Abbot.

The rush for patents on cancer medicine can be explained by the potential of the Rs 1,200 crore (Rs 12 billion) Indian market.

With nearly 2.5 million patients, cancer is one of the ten leading causes of death in India. Data sources from the National Cancer Registry Programme show that over 700,000 new cases and 300,000 deaths occur annually due to cancer.

However, not all 413 applications will pass muster with the patent office, a patent expert warned. India does not give patents on drugs patented elsewhere before 1995.

The patent expert said only two drugs in the list of applicantions were granted patent in the United States after 1995. Most applications, people involved in the research said, are for derivatives or minor modifications of medicines that are not eligible for patents.

"Our analysis shows that most of these applications do not qualify for patents in India. Therefore, the patent examiners need to be very careful while scrutinising them," the researcher who leads the study said.

The concerns of the researchers gain more significance in the backdrop of the Delhi High Court's interim order allowing Cipla to market its anti-cancer drug, Erlontib, though Roche was granted a patent on it. Tarceva is the first and only cancer medicine to get a product patent (the patent that denies the entry of low-cost copycat versions of the medicine) in India.

The other cancer medicine, Glivec, from Novartis, was denied a patent in the country because the patent office felt that the medicine was an improvement of a known substance and hence non-patentable.

Novartis has appealed against the patent denial to the Intellectual Property Appellate Board (IPAB). The high-profile patent war has been considered a test case in pre-grant opposition of patent applications.