Top cancer researchers unconvinced by Xyotax trials so far
Seattle Times business reporter
ORLANDO, Fla. — Dr. Corey Langer zipped through his presentation about Xyotax, and there was no roar of applause at the end, and no public follow-up questions.
At the world's biggest showcase for cancer therapy, the meeting of the American Society of Clinical Oncology, hundreds of physicians and stock analysts listened to Langer talk about how a drug from Seattle-based Cell Therapeutics performed for terminal lung-cancer patients.
When it was over, some walked out quietly shaking their heads, seemingly let down by the results. The gist of the story was already known from reports earlier this spring: All three clinical trials of Xyotax failed to show it could extend patients' lives better than standard chemotherapy. But this was the first time researchers had detailed the results for other cancer specialists.
In a cavernous conventional hall, Langer, of Fox Chase Cancer Center in Philadelphia, said the 400-patient Xyotax trial called Stellar 3 found "there was no significant difference" in patient survival. Patients lived a median time of 7.8 months on Xyotax and carboplatin, a chemotherapy drug, versus 7.9 months for patients on the conventional chemo combination of paclitaxel and carboplatin.
Xyotax, a molecule made of a polymer that binds to paclitaxel, is supposed to be more stable and less toxic in the blood than straight paclitaxel. But in the Stellar 3 trial, there were some worse side effects: slightly more cases of severe peripheral nerve damage and white blood-cell damage in the patients receiving Xyotax.
Those patients did have less hair loss and fewer heart problems, though, and they spent less time getting infusions — an average of 48 minutes versus nearly four hours.
Langer said he's encouraged by another Xyotax trial, Stellar 4, which studied the drug as a single agent, at a lower dose. He said the side effects were significantly better in that setting.
Earlier this month, after unveiling initial Stellar 4 results, Cell Therapeutics said it would pursue Food and Drug Administration (FDA) approval for Xyotax based on its milder side effects and its ability to improve quality of life, rather than any claim of improving patient survival.
Langer said there are "disparate opinions" among his peers about whether the better side effects will be enough for Xyotax to win FDA approval.
Cell Therapeutics Chief Executive James Bianco sounded upbeat after the presentation, saying the Stellar 4 trial "will get this drug approved." He ascribed some of the side effects in Stellar 3 to the carboplatin used in tandem with Xyotax.
Full results on Stellar 4 are expected to be presented in July at the World Conference on Lung Cancer in Barcelona, Spain.
Other local companies also presented data at the conference.
• Seattle-based Dendreon got a mixed response for Provenge, its treatment for prostate cancer. Lead investigator Dr. Eric Small of the University of California, San Francisco elaborated on previously announced findings of a 127-patient study that showed terminal patients on Provenge lived a median time of 25.9 months, compared to 21.4 months on placebo. Side effects were mild: fever and chills that lasted one or two days.
Skeptics wondered, after initial results came out in February, whether the Provenge patients were healthier to start, or possibly got some extra chemotherapy that skewed the results.
But after reviewing patient records over the last several months, Small said Provenge patients actually got less chemotherapy than those on placebo, and all had similar prognoses at the start.
In a discussion after Dendreon's presentation, Dr. Skip Trump of Roswell Park Medical Center in Buffalo, N.Y., said he still isn't convinced the survival edge is real, because the trial was small.
"Small trials are exploratory, and as we are exploring, we need to be careful about drawing conclusions," Trump said.
• Seattle Genetics displayed midstage results of its SGN-30 antibody treatment for Hodgkin's disease. It studied 15 patients at a low dose, and seven patients at a higher dose, finding the drug well-tolerated at both levels. Six patients at the lower dose had their disease stabilize for a median of 4.8 months, while nine saw their disease progress. One patient experienced damage to white blood cells.
The drug also showed an effect in another cancer, anaplastic large-cell lymphoma. One of six patients had a complete response, one had a partial response, and one saw the disease stabilize.
• ZymoGenetics released summary data on IL-21 in an early-stage study of six patients with renal-cell cancer and metastatic melanoma. The Seattle company said it saw no serious side effects at two different doses. It said one patient with renal-cell cancer had a partial response on the drug, and two with metastatic melanoma had stable disease.
• Sonus Pharmaceuticals outlined a study of 36 cancer patients who took either its reformulated version of paclitaxel, or the conventional paclitaxel at the same dose. The company found that its version gave patients an average of 67 percent more of the drug in the blood.
Neile Grayson, Sonus' vice president of corporate development, said the finding will enable the company to use a lower dose that it believes will allow better tolerated and more frequent dosing than conventional paclitaxel. The company is planning to do a pivotal study with as many as 800 patients.
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