Undaunted by an FDA advisory committee's recommendations not topermit expansion of Leukine to all leukemia patients, ImmunexCorp., of Seattle, is pressing ahead with plans to obtain FDAapproval to market Leukine for use in surgical prophylaxis, neonatalsepsis and peripheral blood cell stimulation.
Investors, however, took note of the Biological Response ModifiersAdvisory Committee's vote not to recommend label expansion forLeukine, a white blood cell growth stimulant. Immunex stock(NASDAQ:IMNX) fell 13.6 percent Tuesday to close at $13.50 ashare. News of the panel's decision came after the market closed onMonday night.
Immunex CEO Edward Fritzky told BioWorld that his company "willinvest strongly in these new uses. We have already filed anapplication for peripheral blood cell stimulation and a liquid form ofLeukine. Now in Phase III clinical trials are use of Leukine forsurgical prophylaxis and neonatal sepsis. Immunex is also exploringthe use of Leukine in the treatment of infections associated withAIDS and tumor vaccines. If these indications are approved we willbe able to expand into significantly larger markets."
Immunex senior vice president for pharmaceutical development,Peggy Phillips, said the company plans to meet immediately withFDA staff to discuss future action on approving labeling to expanduse of Leukine into general chemotherapy.
The FDA's advisory committee did approve Immunex's petition toexpand the labeling for Leukine for two indications: followinginduction chemotherapy in acute myelogenous leukemia the mostcommon form of acute leukemia and for allogeneic bone marrowtransplant patients. But the panel voted against recommending thatLeukine's labeling be amended for broader use followingchemotherapy.
Panel members voted 4-to-10 not to recommend that Leukine bemarketed for use following other chemotherapy regimens. Immunexwas heartened by the limited show of support among the panelmembers which they interpreted as criticism of FDA setting differentstudy end points after initial ground rules were established, saidImmunex spokeswoman Robin Shapiro. "We thought the end pointwas a decrease in neutropenia," she said.
FDA officials expressed concern to the advisory committee aboutsignificantly higher adverse events associated with Leukine whenused in a broader application following chemotherapy. Karen Weiss,from the FDA's Center for Biologics Evaluation and Research(CBER), found that two clinical trials showed significantly higherrates of infection, deaths and thrombocytopenia with Leukine use.
CBER staffer Kevin Conlon told the panel that in one clinical trialthere was a "significant worsening in patients taking Leukinecompared to the controls, with a 16 percent mortality rate amongpatients in the Leukine arm and only 6 percent in the control arm."
Conlon said one of the clinical trials which involved patients withadvanced breast cancer patients taking Leukine required significantlymore blood transfusions.
FDA officials also were concerned that while Leukine decreasedneutropenia, there have been little or no concomitant benefits in therelated endpoints of febrile neutropenia, infection, hospitalization orantibiotic usage.
If the FDA approves the committee's action, a secondary market of6,000 autologous bone marrow transplant patients and 6,000allogeneic bone marrow transplant patients will be available toImmunex. If the panel had approved the additional indication forbroader use, an additional 25,000 patients would have becomeeligible for this therapy.
The label expansion would have allowed Leukine to compete withAmgen Inc.'s Neupogen _ a product that earned Amgen more than$600 million in 1994. Leukine was first approved by the FDA in1991 for use following autologous bone marrow transplantation. n
-- Michele L. Robinson Washington Editor
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