Cell Therapeutics, Inc announced that it has submitted a formal appeal to the Office of New Drugs in the US Food and Drug Administration's Centre for Drug Evaluation and Research regarding the agency's decision from earlier this year on the pixantrone New Drug Application (NDA) to treat relapsed/refractory aggressive Non-Hodgkin's Lymphoma (NHL). CTI had requested accelerated approval of its pixantrone NDA for a patient group for which there are no drugs currently approved in this clinical setting.

The Office of Oncology Drug Products issued a Complete Response Letter to CTI related to this NDA stating, in part, that CTI's prior clinical trial, PIX301, did not demonstrate efficacy, and that CTI should conduct an additional clinical trial prior to approval. Although CTI is preparing to initiate its PIX306 trial, which would serve as either a post-approval confirmatory trial or a second registration trial for approval, CTI has filed an appeal under the FDA's formal dispute resolution process asking the Office of New Drugs to conclude that PIX301 demonstrated efficacy.

“We believe the FDA diverged from accepted statistical principles and practices when the FDA applied a more stringent statistical significance level in concluding that the PIX301 primary analysis required an adjustment for type 1 error as if an interim analysis had been conducted. This was not the case in the PIX301 trial where only a single final analysis was undertaken,” said Richard Kay, PhD, Statistical Consultant, RK Statistics Ltd., Honorary Visiting Professor, School of Pharmacy, Cardiff University. “We believe the results of the PIX301 clinical trial should be analyzed with the appropriate threshold that is standard for trials of this type in which only one efficacy analysis was conducted.”

FDA regulations provide a formal dispute resolution process to obtain review of any FDA decision, including a decision not to approve an NDA, by raising the matter with the supervisor of the FDA office that made the decision. The formal dispute resolution process exists to encourage open, prompt discussion of scientific (including, medical) disputes and procedural (including, administrative) disputes that arise during the drug development, new drug review, and post-marketing oversight processes of the FDA.

Based on the guidance documents available from the FDA, CTI expects an FDA decision on the appeal in the first quarter of 2011. CTI continues to prepare for the initiation of an additional pixantrone clinical study in the US that would serve as either a post-approval confirmatory study or as a second registration study for approval in the U.S. This trial, referred to as PIX306, was submitted for a Special Protocol Assessment (SPA) review by the FDA.

Pixantrone is a novel aza-anthracenedione that has distinct structural and physio-chemical properties that make its anti-tumour activity unique in this class of agents. Similar to anthracyclines, pixantrone inhibits Topo-isomerase II but unlike anthracyclines--rather than intercalation with DNA--pixantrone alkylates DNA--forming stable DNA adducts, with particular specificity for CpG rich, hyper-methylated sites. These structural differences resulted in significantly enhanced anti-lymphoma activity compared to doxorubicin in preclinical models.

In addition, the structural motifs on anthracycline-like agents that are responsible for the generation of oxygen free radicals and the formation of toxic drug-metal complexes have also been modified in pixantrone to prevent the binding of iron and perpetuation of superoxide production--both of which are the putative mechanism for anthracycline induced acute cardiotoxicity. These novel pharmacologic differences may allow re-introduction of anthracycline like potency in the treatment of relapsed/refractory aggressive lymphoma without unacceptable rates of cardiotoxicity.

Headquartered in Seattle, CTI is a biopharmaceutical company committed to developing an integrated portfolio of oncology products aimed at making cancer more treatable.