Biogen Idec is asking physicians to prescribe the lyophilized powder formulation of its multiple sclerosis agent Avonex to help prevent a shortage of the liquid prefilled syringe formulation.

"Biogen Idec may experience shortages in supply of the liquid formulation of Avonex in prefilled syringes," an April 29 "Dear Health Care Professional" letter states.

"We encourage you to prescribe lyophilized Avonex for your new patients instead of prefilled syringes until this situation is resolved."

The company is ramping up production of its lyophilized powder version "to assure that we meet patients' needs."

The prefilled syringe formulation of Avonex (interferon beta-1a) was approved by FDA in May 2003. Biogen Idec said the liquid formulation represents the majority of Avonex sales and will eventually replace the powder.

The powder must be reconstituted for use as an intramuscular injection. To assist patients, the company is providing free preparation and administration training for the formulation.

Avonex labeling states it is "intended for use under the guidance and supervision of a physician."

"Patients may self-inject only if their physician determines that it is appropriate and with medical follow-up, as necessary, after proper training in intramuscular injection technique."

The letter explains that the "possible short supply" of Avonex is due to "some prefilled syringes containing more than expected levels of aggregates."

Biogen Idec is performing additional evaluations on manufactured lots of the prefilled syringes to test for aggregates.

However, "until the manufacturing issue is fully resolved, some liquid Avonex syringes released for distribution may contain increased levels of aggregates," the letter states.

The letter cautions that, "in theory, the presence of increased aggregate levels could lead to increased immunogenicity and increased production of antibodies," which has the potential to cause allergic reactions such as anaphylaxis, dyspnea, orolingual edema, skin rash and/or urticaria.

In the Warnings section, Avonex labeling describes anaphylaxis as a "rare complication."

Biogen Idec disclosed the manufacturing issues with the Avonex liquid formulation in a year-end conference call in March. The company described the problem as a "technical issue" with the fill-finish process (¹ Also see "Biogen Addressing Avonex Liquid Formulation Manufacturing Problems" - Pink Sheet, 3 March, 2004.).

- Steele Thomas

Biogen Idec Advises Use Of Avonex Powder Formulation To Prevent Shortage

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