Allos Therapeutics, Inc. has reached on an agreement with the US Food and Drug Administration (FDA) under the Special Protocol Assessment process (SPA) on the design of a pivotal phase 2 trial of the company's novel, next generation antifolate PDX (pralatrexate) in patients with relapsed or refractory peripheral T-cell lymphoma (PTCL).

The SPA process allows for FDA evaluation of a clinical trial protocol intended to form the primary basis of an efficacy claim in support of a new drug application, and provides a binding agreement that the study design, including trial size, clinical endpoints and data analyses are acceptable to the FDA.

"We're pleased to have reached agreement with the FDA on the design of this important clinical trial as it provides a well defined pathway for pursuit of marketing approval of PDX," said Paul L. Berns, President and CEO. "We expect to move forward as planned with the initiation of enrolment in this trial by the end of the third quarter", he added.

The phase 2, non-randomized, open-label trial will look to, establish the safety and efficacy of PDX with concurrent vitamin B12, and folic acid supplementation in patients with relapsed or refractory PTCL.

Patients will receive PDX at 30 mg/m2 once every week for six weeks followed by one week of rest per cycle of treatment. The company currently plans to enrol 100 evaluable patients at approximately 35 leading cancer centres in the US, Canada and Europe. The study protocol includes interim assessments of safety and response. Owen A. O'Connor, Head of the Laboratory of Experimental Therapeutics for Lymphoproliferative Malignancies, Lymphoma and Development Chemotherapy Services, Memorial Sloan-Kettering Cancer Centre, will serve as the international study chair.

Interim results from a phase 1/2 study of PDX in patients with relapsed or refractory non-Hodgkin's lymphoma (NHL) and Hodgkin's disease, which is currently on-going at Memorial Sloan-Kettering Cancer Centre, demonstrated preliminary evidence of activity in patients with various subtypes of aggressive and chemotherapy resistant T-cell lymphoma. As reported at the 2005 American Society of Hematology Annual Meeting, four of seven evaluable patients with T-cell lymphoma achieved a complete response following treatment with PDX, despite having failed multiple prior therapies. The addition of vitamins to the treatment regimen appeared to successfully mitigate the previously established dose limiting toxicity of stomatitis.

"To date pralatrexate has achieved a high complete response rate that has proven very durable among PTCL patients with a historically very poor prognosis," said Dr. O'Connor. "These results suggest that pralatrexate may offer a new therapeutic option for patients with PTCL a disease desperately in need of new effective treatments."