Transkaryotic Therapies, Inc. (TKT), a biopharmaceutical company, announced that Aventis Pharmaceuticals Inc. has returned rights to Dynepo (epoetin delta) to TKT for all indications in Europe and all other territories outside the United States. Dynepo is a fully human erythropoietin product developed using TKT's patented gene activation technology and is approved for the treatment of anemia associated with kidney disease in the European Union.

According to a media release from TKT, the company is in the process of establishing contract manufacturing outside the United States in order to bring Dynepo to patients in a manner consistent with applicable court orders and regulatory requirements.

Under the revised agreement, TKT will pay Aventis a scaled royalty on Dynepo sales. Aventis will retain rights to commercialize Dynepo in the United States under essentially the same terms as the original agreement and has obtained an option on certain TKT gene therapy technology for one year.

Additionally, TKT is no longer obligated to reimburse Aventis from future royalties for legal expenses incurred to date from the Dynepo patent infringement actions with Amgen in the United States and Kirin-Amgen in the United Kingdom. TKT is responsible for any future litigation expenses in Europe and half the future expenses in the United States.

Clinical testing involving approximately 1,400 dialysis and pre-dialysis patients supported marketing approval of Dynepo in the European Union as a treatment for anemia related to kidney disease. As described in the European Public Assessment Report, treatment with Dynepo was comparable to epoetin alfa and was effective in raising hemogloblin and hematocrit levels. In patients treated with Dynepo, there have been no reported cases of pure red cell aplasia, a condition in which the bone marrow fails to produce vital red blood cells and a safety concern with other marketed erythropoietin products derived from Chinese hamster ovary (CHO) cells.