Enzon Inc. and its marketing partner Rhone-Poulenc Rorer Inc.announced on Tuesday that Oncaspar (pegaspargase) hasreceived FDA approval for the treatment of acutelymphoblastic leukemia (ALL) in patients who have developedhypersensitivity to native forms of L-asparaginase. Theoncology agent is indicated only when multi-agentchemotherapy is judged to be inappropriate.
The product has a potential market in what Enzon hasestimated are more than three-quarters of ALL patients thatdevelop hypersensitivity to native L-asparaginase. In contrast,the company reported that 20% of patients treated withOncaspar have exhibited hypersensitivity reactions. The drugrequires only one dose every other week, the companies noted,less than that required in standard L-asparaginase therapy.
Oncaspar is Enzon's second approved product. Its first, Adagen-ADA, is indicated for severe combined immunodeficiencydisease. The Piscataway, N.J., company said its most recent FDAapproval makes it one of only six biotech companies with twoor more products on the market in the U.S.
Rhone-Poulenc Rorer obtained marketing rights to Oncaspar inDecember, giving Enzon $6 million and a 50 percent share ofsales profits. Enzon (NASDAQ:ENZN) will manufacture the drug.
Oncaspar is contraindicated in patients with pancreatitis or ahistory of pancreatitis, and in patients who have had previousanaphylactic reactions to the agent, the companies said. Inaddition, Oncaspar should be administered with caution topatients on concurrent anticoagulant therapy.
The agent is based on Enzon's "pegnology" drug-deliverytechnology. Strands of a polymer polyethylene glycol (PEG) areattached to native L-asparaginase to make the agent. Thecompany says this method helps "disguise" the enzyme andreduce its recognition by the immune system, loweringimmunogenic potential and extending the circulating half-life.
Enzon filed a product license application for Oncaspar inJanuary 1991. The drug has been "approvable" since December.
Enzon's stock closed at $5.50 per share on Tuesday, up 63cents. Rhone-Poulence Rorer's stock (NYSE:RPR) closedunchanged at $35.88 per share.
-- Karl A. Thiel Associate Editor
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