Swiss drugmaker Novartis AG (NVS) said Monday an intermediate stage study showed that its experimental drug Tasigna achieved impressive results in the treatment of blood cancer patients who no longer responded to treatment with its drug Gleevec.
The study showed that 74% of patients in the chronic phase of chronic myeloid leukemia, or CML, a blood cancer, achieved normal white blood cell counts after six months of treatment. Of 279 patients treated, the defective chromosome that causes the disease was significantly reduced in more than half, and was completely eliminated in about a third of these patients.
All these patients had developed resistance to Gleevec, the standard of care for the condition, or didn't tolerate Gleevec.
The study was presented at the American Society of Hematology, or ASH, meeting in Orlando, Florida.
Gleevec, launched five years ago and one of the first of what are known as targeted cancer drugs is Novartis' second-best selling drug with sales of $2.17 billion in 2005. Targeted cancer drugs work by killing cancer cells specifically, or by hindering their proliferation, while traditional chemotherapy often kills deranged and healthy cells alike, leading to troublesome side effects.
Tasigna, known generically as nilotinib, and Gleevec, known generically as imatinib, both work by telling a specific gene to stop producing excessive white blood cells. Tasigna was designed to also work in cases when this gene had mutated. Such mutations can cause resistance to the Gleevec treatment. CML patients usually go through three phases: chronic phase, accelerated phase and blast phase.
In 52% of patients in the chronic phase of CML, the Ph+ chromosome - the genetic abnormality that characterizes most cases of this form of leukemia - was significantly reduced, while in 34% it was undetectable after treatment with Tasigna, Novartis said.
Patients in a more advanced phase of CML also responded to the Tasigna therapy.
Of the 64 patients in the accelerated phase, 59% achieved a normalization of their white blood cell counts, and in 36% the Ph+ chromosome was reduced or eliminated after eight months of treatment.
The study researchers concluded that Tasigna was generally well tolerated. Specifically, the investigators said that the compound wasn't associated with many of the side effects seen with Gleevec, such as fluid retention and superficial edema.
Novartis, based in Basel, Switzerland has recently submitted Tasigna for U.S. and European Union regulatory approval, on the basis of this study. When considering cancer drugs, the regulators sometimes accept earlier phase II studies rather than larger phase III trials that it typically requires most companies to submit with drug-approval applications.
James Shannon, head of drug development at Novartis, said recently that he expects global peak sales of Gleevec and Tasigna combined to exceed $3.5 billion.
David Epstein, who heads Novartis' oncology business told an agency that the company plans to start a trial that directly compares Tasigna to Gleevec in the first half of 2007. Should Tasigna turn out to be more effective, as well as safer, in this trial, it could eventually replace Gleevec as the standard of care for this form of leukemia.
However, both Gleevec and Tasigna will also be competing with Sprycel, or dasatinib, a drug developed by Bristol-Myers Squibb Co. (BMY), which has been launched in both Europe and the U.S. this year.
Tasigna and Sprycel have never been tested against each other, which makes it difficult to compare them, but data so far suggest that the Novartis drug has less unwanted side effects, analysts say.
"Tasigna appears to be at least as effective as Sprycel, but with fewer side effects," said Karl-Heinz Koch, analyst in Zurich at private bank Vontobel, who has a buy rating on Novartis.
Bristol-Myers also presented data at the ASH conference, that are directly comparing Sprycel to a high dose of Gleevec, when given to patients who no longer responded to the standard Gleevec those.
After 15 months of treatment, the defective chromosome that causes CML was significantly reduced in 53% of patients who were given Sprycel, compared to 33% of patients who took the high dose of Gleevec.
"This study may help answer important questions about treating resistant chronic-phase CML patients and suggests that physicians should consider treatment with Sprycel in patients resistant to lower doses of Gleevec," said Neil Shah, an assistant professor at the division of hematology and oncology of the University of California, in a statement.
Still, given that these patients had already developed resistance to the standard dose of Gleevec, it shouldn't come as a huge surprise that Sprycel was shown to work better for these patients, Vontobel's Koch added.
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