Analysis of Long-Term Response Population From BEXXAR Clinical Trials Presented at ASCO
Saturday May 31, 2:00 pm ET
Data Reported With up to Nine Years of Follow-up
CHICAGO, May 31 /PRNewswire-FirstCall/ -- According to data presented today at the 39th annual meeting of the American Society of Clinical Oncology (ASCO, Abstract #2316), a high proportion of patients with advanced low-grade or transformed low-grade non-Hodgkin's lymphoma (NHL) who achieved long-term, durable responses to BEXXAR® (tositumomab and iodine I 131 tositumomab) therapy had complete responses and many of these patients remain in remission five or more years after treatment (median 59.1 months, range 47.2-NR). BEXXAR therapy, being co-developed by Corixa Corporation (Nasdaq: CRXA - News) and GlaxoSmithKline (NYSE: GSK - News), is an investigational radioimmunotherapy in the final stages of regulatory review by the U.S. Food and Drug Administration (FDA).
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Analyzing data from 250 patients enrolled in five clinical trials of BEXXAR therapy, investigators determined that 30.4 percent (76 of 250) of patients had achieved a long-term, durable response, defined as time to disease progression of one year or more after treatment. These patients were followed for a median of three and a half years (44.6 months), with a range extending up to nearly nine years (15.5 months to 107.3 months). Within this long-term response population, the complete response (CR) rate was 76 percent (58/76). The median durations of overall response and of complete response both approached five years; 58.4 months (range 36.5-NR) and 59.1 months (range 47.2-NR), respectively. The median time to progression or death was 60.1 months.
"The ability of BEXXAR therapy to produce remissions lasting five or more years in patients with advanced, treatment-resistant non-Hodgkin's lymphoma is very encouraging," said Andrew D. Zelenetz, MD, PhD, Chief, Lymphoma Service, Memorial Sloan Kettering Cancer Center, and an author of the study. "We've now been following some durable responders since the early 1990s and can say with some confidence that patients whose disease does not progress for at least a year after BEXXAR therapy have a good chance of staying in response for several more years."
Patients in the long-term response population had a median of three treatment regimens (range 1-8) prior to receiving BEXXAR therapy and had multiple poor prognostic characteristics including Stage III/IV disease (88 percent), no response to prior therapy (62 percent), bulky disease >5 cm (49 percent), bone marrow involvement (41 percent), and transformed histology (20 percent). Similar durations of response were observed in patients regardless of their response to prior therapy, suggesting that the durable responses in the long-term response population did not simply represent favorable patient characteristics.
BEXXAR Regulatory Status
As previously announced, the FDA informed Corixa in early May 2003 that it was extending its review of the BEXXAR therapy application by up to three months. The three-month extension provides additional time to further refine post marketing commitments and package insert language and to ensure that they are consistent with an updated safety database requested by the FDA and submitted by Corixa in early April 2003. The updated safety database now contains safety information on 995 treated patients with up to 9.5 years of follow up. Although it can take action at any time, the new Prescription Drug User Fee Act (PDUFA) goal date for the FDA to complete its review of BEXXAR therapy is August 1, 2003.
BEXXAR Therapy
Corixa, in collaboration with GlaxoSmithKline, is seeking approval of BEXXAR therapy as a single course of treatment for patients with CD20 positive, follicular, non-Hodgkin's lymphoma (NHL), with and without transformation, whose disease is refractory to rituximab and has relapsed following chemotherapy.
BEXXAR is a dual-action therapy that pairs the tumor-targeting ability of a cytotoxic (cancer killing) monoclonal antibody (tositumomab) and the therapeutic potential of radiation (iodine 131) administered as a patient- specific dose. Iodine 131 has a well-established safety profile in the treatment of thyroid disease and tositumomab has anti-tumor activity of its own. Combined, these agents form a radiolabeled monoclonal antibody (iodine I 131 tositumomab) that binds to the target antigen CD20 found on NHL cells, thereby initiating an immune response against the cancer and delivering a dose of radiation directly to tumor cells. BEXXAR therapy is the only NHL therapy that is specifically dosed based on an individual's drug clearance rate, allowing the delivery of a pre-determined amount of radiation to each individual patient.<snip> |
