Tasigna and Sprycel Outshine Gleevec

Oncologists have begun trading in what had become a miracle pill for patients with chronic myeloid leukemia for more potent, newer-generation drugs that appear to work even better as first-line treatment for CML. 

MELISSA WEBER
PUBLISHED: 1:00 AM, TUE SEPTEMBER 7, 2010
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Oncologists have begun trading in what had become a miracle pill for patients with chronic myeloid leukemia for more potent, newer-generation drugs that appear to work even better as first-line treatment for CML.

That doesn’t mean, though, that if you currently take Gleevec (imatinib) you should switch drugs, say oncologists interviewed for this article. However, the new drugs may replace Gleevec in newly diagnosed patients.

Giving Tasigna (nilotinib) or Sprycel (dasatinib) to previously untreated CML patients resulted in faster, better responses compared with Gleevec, according to research presented at the American Society of Clinical Oncology annual meeting in early June and published that same month in The New England Journal of Medicine. Two weeks after the meeting, the Food and Drug Administration approved Tasigna as a first-line treatment for CML. The agency will decide by October whether to approve Sprycel as an upfront option.

 “I think that either [Sprycel] or [Tasigna] are better drugs than [Gleevec]. But you’re going from a great drug to a greater drug, so the margin of benefit is fairly small,” says Jerald Radich, MD, a leukemia specialist at Fred Hutchinson Cancer Research Center in Seattle. Tasigna and Sprycel are already approved to treat CML patients whose cancer progressed or who could not tolerate Gleevec.

For 10 years, Gleevec has been the closest thing to a cure for CML. Touted as a breakthrough, the drug has lived up to the hype. Deaths from CML dropped from 10 to 20 percent a year to 1 percent, says Hagop Kantarjian, MD, chair of the department of leukemia at M.D. Anderson Cancer Center in Houston.

In the Tasigna study, 80 percent of 282 newly diagnosed patients on Tasigna saw cancer cells completely disappear from the bone marrow after one year of therapy compared with 65 percent of 283 patients on Gleevec. Achieving this response, called a complete cytogenetic response, within a year of starting treatment is associated with better long-term survival. Tasigna beat Gleevec—in fact, had double the effectiveness of Gleevec—in eradicating the expression of the fusion gene called bcr-abl, which results from the translocation of chromosomes 9 and 22 and that defines and drives CML. For the Tasigna group, 44 percent achieved this so-called major molecular response compared with 22 percent in the Gleevec group. For newly diagnosed patients in the Sprycel study, 77 percent of 259 patients on Sprycel achieved a complete cytogenetic response compared with 66 percent of 260 patients on Gleevec after one year. The rate of major molecular response was also tipped in Sprycel’s favor: 46 percent versus 28 percent.

It’s almost an embarrassment of riches to be having conversations about how whether one drug is more wonderful than the last. 

Considering the generally slow progression of CML, it will take another three to five years to see each drug’s effect on survival, says Kantarjian, who served as lead investigator on the Sprycel study and co-investigator on the Tasigna study. With Gleevec, almost 90 percent of patients are alive after 10 years.

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