Merck KGaA has pulled Phase II clinical trials of atacicept for the treatment of multiple sclerosis, according to development partner ZymoGenetics, weeks after the compound failed to impress in a rheumatoid arthritis study.

Zymogenetics says that the German firm’s Merck Serono unit has discontinued the trial based on a recommendation from an independent data monitoring panel. The latter observed an increase in disease activity in patients receiving atacicept compared to those administered placebo.

The development path for atacicept, a recombinant fusion protein formerly called TACI-Ig, is not going too smoothly. Earlier this month, ZymoGenetics said preliminary results from a Phase II trial of the drug as a possible treatment for rheumatoid arthritis did not meet the pre-specified level of disease-control activity.

As such, that data did not support moving the compound directly into Phase III. Further exploratory analyses are underway and no final decision has been made by Merck Serono regarding RA as a potential indication for atacicept. However, Zymogenetics said the studies confirmed the biological effect of atacicept on immunoglobulin and autoantibody production and no new safety signals were observed.

The compound is also still being studied as a treatment for systemic lupus erythematosus, as well as RA.