NEW YORK (Reuters) - SuperGen Inc. on Wednesday said its drug for a group of blood disorders slowed progression to leukemia or death in a key study, but shares tumbled on confusion over whether the positive results were statistically significant.
SuperGen shares fell 29 percent to $9.10 in after-hours trading on the Inet electronic brokerage, from their close of $12.80 on Nasdaq.
The Dublin, California-based company said it will seek U.S. approval of the medicine, Dacogen, in the third quarter, based on data from the Phase III trial of 170 patients with the group of blood disorders called Myelodysplastic Syndromes.
An estimated 20,000 to 30,000 new cases of the syndromes are diagnosed in the United States each year and the life expectancy of patients typically ranges between 6 months and 5 years, SuperGen said.
Patients with the condition are very prone to developing acute myelogenous leukemia, the most common form of leukemia in adults.
The company said 89 patients in the trial got Dacogen injections in addition to supportive care such as antibiotics, growth factors and/or blood transfusions. The remaining 81 patients received supportive care only.
The average patient taking Dacogen progressed to acute myelogenous leukemia or death in 338 days, compared with 263 days in patients who did not take the medicine. The difference in progression times, the primary focus or “endpoint” of the trial, was statistically significant based upon a statistical means of analyzing trial data called the Wilcoxon test.
CONFUSION OVER TRIAL RESULTS
But the difference was well below statistical significance based upon another analysis method called the log-rank test.
“Company officials were not able to adequately clear up confusion about whether the trial met its primary endpoint and that’s why SuperGen shares came down,” said Elemer Piros, a biotech analyst at Rodman & Renshaw Inc.
Piros said U.S. regulators will likely approve Dacogen because 22 percent of patients taking it saw their levels of red and white blood cells and blood platelets temporarily return to normal or closer to normal, in contrast to no such improvements for any patients who did not take the drug.
“But even those patients whose blood profiles returned to normal eventually relapsed and died,” said EKN Inc. analyst Robert LeBoyer, who gave the drug no more than a 50 percent chance of being approved because of the drug’s limited benefit and the study’s “inconclusive” data.
The mortality rate for patients taking Dacogen was 12 percent, compared with 9 percent not taking the drug, but SuperGen said the difference was not statistically significant.
SuperGen said patients receiving Dacogen suffered a greater incidence of severe adverse events such as leukopenia, an abnormal decrease in the number of white blood cells, and of febrile neutropenia, an abnormally low number of important immune system cells called neutrophils.
“These are the kinds of side effects you expect for (cancer) drugs, so I’m not overly worried about the safety of Dacogen,” Piros said.
Currently there are no treatments for Myelodysplastic Syndromes, although Pharmion Corp. in December asked U.S. regulators to approve its similar medicine for the syndromes, called Vidaza. (Additional reporting by Toni Clarke and Bill Berkrot).
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