The documents released on Monday posted that U. S. drug reviewers criticized effectiveness data from Cell Therapeutics Inc for an experimental lymphoma drug and revealed that the medicine posed significant side effects.

A Food and Drug Administration advisory panel review of the drug, originally scheduled for Wednesday, was postponed due to weather.

Seattle-based Cell Therapeutics is seeking permission to sell pixantrone with the label Pixuvri for treating non-Hodgkin's lymphoma that has stopped responding to other treatments.

Although pixantrone fulfilled its primary endpoint, suggesting that 25 percent of patients medicated with the anthracycline drug experienced a complete response vs. 5.7 percent of those given comparator agents, it's possible the panel will ask for additional data.

The company's study involved testing 140 patients whose cancer worsened after at least two chemotherapy regimens, FDA staff claimed, which was even less than 50% of 320 originally planned.

The company revealed that it had initiated a decision to conduct a full analysis of the trial instead of an earlier planned interim analysis, based partly on FDA guidance that a primary endpoint analysis could be acceptable for a new drug application if it succeeded in demonstrating statistical significance between treatment arms.