Cell Therapeutics is to appeal the US regulator's decision to turn down its New Drug Application for pixatrone to treat patients with relapsed/refractory aggressive non-Hodgkin's lymphoma.

In April, the US Food and Drug Administration issued a complete response letter to the company saying it should conduct an additional clinical trial on Pixuvri (pixatrone). The letter followed a review by the agency's Oncologic Drugs Advisory Committee meeting in March which voted 9-0 against recommending approval.

However, Cell Therapeutics is now preparing to file an appeal under the FDA's Formal Dispute Resolution process as "there are no approved or effective therapies for patients with relapsed or refractory aggressive NHL beyond second relapse". As such, it says the PIX 301 study "was the first and only randomised trial in this patient group to demonstrate significant improvement in clinically relevant endpoints".

Cell Therapeutics quoted Stanley Marks, chief medical officer for the University of Pittsburgh Cancer Centers, as saying that PIX 301 produced "robust clinically meaningful results including improvement in response rate and progression free survival that could have a significant impact on treating the disease in this setting". The firm's CMO, Jack Singer, added that "after discussions with a number of leading US and international lymphoma experts and leading biostatisticians...we felt encouraged to appeal the initial decision".

He believes the data should be reviewed "in the context of a trial that achieved statistically and clinically meaningful primary and secondary endpoints in this end stage patient population for whom there are no approved or effective agents". Dr Singer concluded by saying "we are committed to conducting a confirmatory trial in this patient population but continue to strongly believe that the PIX 301 data met the requirements for accelerated approval with sufficient scientific rigour".

Cell Therapeutics expects the FDA decision on the appeal in the fourth quarter and noted that it hopes to file a Marketing Authorisation Application for pixantrone in Europe before the end of this year.