We extend sincere congratulations to Dr Jacobs and colleagues for the successful conclusion of their study of recombinant interferon p l a (rIFN-pla) in patients with multiple sclerosis (MS). The impressive results showed that 6 million international units of rIFN-Pla applied once weekly via the intramuscular route was safe and effective in patients with relapsing-remitting MS.
For all its merits, we are compelled to point out an error in the article [ l ] . Dr Jacobs' designation of the study material as Avonex is incorrect and misleading. The only IFNp l a used in this study was not as stated in the study, ie, the substance with the trade name Avonex, produced by Biogen Inc, in Cambridge, Massachusetts, but the Chinese hamster ovary-derived rIFN-P 1 a developed and produced by Bioferon Biochemische Substanzen GmbH (Bioferon) in Laupheim, Germany. Today all product rights of the clinically tested product are held by Dr Rentschler Biotechnologie GmhH (Rentschler), which is continuing the development of its proprietaiy rIFN-f3 l a product.
According to a public statement by an FDA official, the marketed Biogen product Avonex is only "comparable" with [2] but not identical to thc Bioferon product used in the trial by Dr Jacobs. The FDA obviously dccided that the clinical data derived from the use of Bioferon's product supports licensure of Biogen's product. However, according to our knowledge, an identity or comparability between the two molecules in terms of safety and efficacy in MS has not been proved in a pivotal trial.