Novartis is hoping to convince doctors to switch patients to Tasigna to shield its sales once Glivec, one of its best-selling medicines, loses patent exclusivity in 2015.

The latest data, which are being presented at the American Society of Hematology's (ASH) annual meeting, examined the benefits of Tasigna in patients with Philadelphia chromosome-positive chronic myeloid leukemia.

Two-year data from the ENESTcmr trial showed patients who still had evidence of residual disease after long-term treatment with Glivec achieved undetectable levels of the disease after switching to Tasigna.

More than twice as many patients treated with Tasigna continued to show undetectable levels of the disease compared with Glivec, according to the data. Novartis said the results were statistically significant.

Meanwhile, four-year data from the ENESTnd trial showed more than three times as many patients being treated with Tasigna as a frontline therapy experienced a reduction in the level of disease versus Glivec, marketed as Gleevec in the United States.

Novartis plans to start a clinical trial in early 2013 to test whether some patients may be able to stop treatment after achieving a sustained response to therapy.

Other data also presented at ASH showed that Novartis' drug Jakavi - which gained EU approval in August - significantly reduced the disease burden in patients with myelofibrosis, a rare blood cancer with limited treatment options.

Follow up data from a late-stage study showed that nearly half of patients treated with Jakavi achieved a reduction of at least 35 percent in spleen volume, Novartis said.

(Reporting by Caroline Copley; Editing by David Holmes and Tim Dobbyn)

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