HMR Seldane marketing future under discussion at FDA; withdrawal would preclude terfenadine generics.

HOECHST MARION ROUSSEL SELDANE MARKETING FUTURE UNDER DISCUSSION AT FDA because of continuing safety concerns and the availability of a related, alternative product. FDA is considering whether Hoechst should remove Seldane (terfenadine) from the market in light of the recent approval of the company's Allegra (fexofenadine), which lacks the cardiovascular side effects of the parent compound.

FDA's consideration is being hastened by an imminent approval decision for a generic terfenadine product. If the agency were to remove the innovator product from the market for safety reasons, the generic could not be marketed.

Ivax' terfenadine ANDA approval path was cleared by a summary judgment in which the court ruled the generic version would not infringe Hoechst's patent for active metabolites of terfenadine. Ivax' terfenadine received tentative ANDA approval in January ("The Pink Sheet" Nov. 18, T&G-12).

At the time of the Allegra launch, Hoechst said that it had no plans to discontinue the marketing of Seldane. The company, however, said it would move promotional resources from Seldane to Allegra in the recognition that many current Seldane users will switch to Allegra. Allegra was approved as a new chemical entity receiving five years of marketing exclusivity ("The Pink Sheet" Aug. 26, T&G-2).

Seldane labeling was revised in July 1992 to include a boxed warning on QT interval prolongation and ventricular arrythmias, especially in combination with some antibiotic and antifungal products, after FDA received reports of the serious cardiovascular events including death with the product. Similar warnings about drug interactions were added to labeling for Janssen's antihistamine product Hismanal (astemizole) in October 1992.