30 After administration of Tregalizumab, downmodulation of CD4 expression levels can be determined in vitro and in vivo, representing a marker for the antibody activity.31, 32 In the latest phase IIb trial (TREAT 2b, T-cell Regulating Arthritis Trial 2b, ClinicalTrials.gov Identifier: NCT01999192 and EudraCT No. 2013-000114-38) conducted with patients suffering from RA, the primary end point was not achieved. The gene discussed is CD4; the disease is rheumatoid arthritis.