Ablynx NV said its drug vobarilizumab failed to meet the main goal in a phase 2 study for treating the disease known as lupus.

In the trial, dubbed Steady, patients failed to respond to various doses of the drug after 24 weeks. The trial enrolled 312 patients suffering from moderate to severe active seropositive systemic lupus erythematosus.

Lupus is an autoimmune disease in which the immune system mistakenly attacks healthy tissue in different parts of the body, resulting in pain and swelling.

Sanofi is acquiring Ablynx in a €3.9 billion deal, looking to bulk up on therapies for rare diseases.