Merck Serono and partner Zymogenetics say they have started a mid-stage trial to evaluate the safety and efficacy of their investigational compound atacicept in patients with systemic lupus erythematosus.

The Phase II/III study is being conducted under a special protocol assessment agreement with the US Food and Drug Administration will involve some 500 patients with SLE. A second Phase II/III trial in lupus nephritis, a severe form of SLE in which the kidneys are affected, was initiated in December 2007.

Merck Serono noted that the two studies are intended to form part of a potential registration package to support worldwide applications for marketing authorisation. "Atacicept has the potential to alter the course of SLE, a complex and devastating disease," said Anton Hoos, the firm's head of global development.

The companies are also developing atacicept, a recombinant fusion protein formerly called TACI-Ig, as a potential treatment for other autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, as well as B-cell malignancies.