By Lisa Seachrist
As Coulter Pharmaceutical Inc. nears filing a biologics license application (BLA) for its lead cancer therapy, Bexxar, the company reported long-term, follow-up data bolstering its safety claims.
South San Francisco-based Coulter presented data on 432 non-Hodgkin¿s lymphoma (NHL) patients who¿ve received Bexxar indicating that for the 42 percent of patients whose NHL has relapsed, treatment with Bexxar doesn¿t preclude any other treatment modalities. The news quells some fears that the drug may in fact make it impossible to receive other forms of cancer therapy including chemotherapy, radiation and antibody treatment.
¿What we¿ve found is that for patients who¿ve received Bexxar and relapsed, treatment with Bexxar doesn¿t preclude you from receiving chemotherapy or any other treatment,¿ said Robert Stagg, senior director of clinical research at Coulter.
Stagg said some people were concerned that Bexxar, because its primary toxicity is to the bone marrow, would so weaken patients that they couldn¿t survive further treatment that also causes bone marrow toxicity, such as chemotherapy. However, the company presented data at the International Conference on Malignant Lymphoma in Lugano, Switzerland, on almost every patient who has been treated with Bexxar to date showing patients who have relapsed after treatment with Bexxar can subsequently be treated with other therapies and even retreated with Bexxar.
Kevin Tang, an analyst with Deutsche Banc Alex. Brown in New York, said in a research report: ¿We believe the data demonstrating that Bexxar-treated patients can successfully receive bone marrow transplants is the strongest evidence that Bexxar doesn¿t irreversibly damage the bone marrow, as some naysayers have suggested, and that the total body exposure to radiation in Bexxar therapy falls well below any cumulative threshold level.¿
The fact that patients could be successfully retreated with Bexxar or with Idec Pharmaceuticals Inc.¿s approved therapy, Rituxan another antibody aimed at the CD20 antige ¿ indicates that the immune responses that patients may develop to Bexxar aren¿t significant enough to make subsequent antibody therapy ineffective.
¿We think the data coming out of the meeting is quite good,¿ Peter Ginsberg, senior research analyst with US Bancorp Piper Jaffray in Minneapolis, told BioWorld Today. ¿First of all, the sheer size of the database is impressive and backs up the company¿s pivotal trial, which only includes 60 patients. And it shows that patients may receive other therapies.¿
Coulter received fast-track designation for Bexxar in December. The company has several portions of the BLA ready for a rolling admission. However, the agency hasn¿t requested those packets be sent. The BLA will be ready for a normal submission by the end of this month. The company will be requesting a label encompassing treatment in relapsed or refractory NHL.
¿Bexxar is one of the most promising cancer drugs in development today,¿ Ginsberg said. ¿I¿m very confident Bexxar will receive approval.¿
NHL is a B cell-specific cancer that is the sixth leading cause of death among cancer patients in the U.S. and has the second fastest-growing mortality rate. In addition, the incidence of NHL is on the rise. NHL is an insidious disease in which patients experience remission periods that tend to shorten with each round of therapy.
Bexxar is an antibody specific to the CD20 antigen on B cells that is conjugated to radioactive iodine 131. The CD20 antigen is found only on B cells, including NHL cells and normal B cells. By targeting the B cell, Coulter hopes to deliver a much greater concentration of deadly radiation to tumor cells compared to normal tissues.
Patients treated with Bexxar receive an initial intravenous infusion of Bexxar to determine the appropriate dose, and a week later a therapeutic dose is delivered. Conventional chemotherapy treatments are given repeatedly over several months.
The 432 patients accounted for in the database presented in Switzerland had all been heavily treated with other regimens before being treated with Bexxar. Of those patients, 58 percent remain free of disease progression. The 42 percent of patients who relapsed after Bexxar treatment subsequently received a variety of therapies: 20 patients were retreated with Bexxar, 101 patients received single-agent or combination chemotherapy, 41 patients received Rituxan, and 15 patients underwent bone marrow transplantation.
Patients experienced no unexpected safety issues with subsequent therapies that could be attributed to having been treated with Bexxar. For patients undergoing bone marrow transplantation, the time for the new marrow to ¿take¿ was 14 days, which is comparable to patients who¿ve never received Bexxar.
Coulter¿s stock (NASDAQ: CLTR) closed at $20.875 a share Monday, down $1.187.