Assessing responsiveness of rheumatoid arthritis patients to biological treatment

An in vitro diagnostic method for assessing the responsiveness of a synthetic disease-modifying antirheumatic drug (sDMARD) treated RA patient to biological synthetic disease-modifying antirheumatic drug therapy (bDMARD therapy), wherein the patient is in need of a switch or modification of the sDMARD therapy and is before or in an initial phase of a bDMARD therapy, wherein the initial phase of the bDMARD therapy is no longer than 8 weeks, said method comprising the steps of

• providing a biological sample of said sDMARD treated RA patient, said sample comprising CD3+ T-lymphocytes from said patient,
• obtaining one or more multidrug transporter activity value(s) by measuring transport activity of MDR1 (ABCB1) in the CD3+ T-lymphocytes of said sDMARD treated RA patient, before or in the initial phase of the bDMARD therapy, by using one or more detectable, fluorescent substrate(s) of MDR1,
• said substrate(s) being taken up by CD3+ T-lymphocytes once contacted with them in a biological sample,
• comparing the one or more transporter activity value(s) with one or more pre-determined threshold transporter activity level(s),
• wherein each pre-determined threshold transporter activity level is a threshold value for said one or more multidrug transporter activity value(s) and has been determined using the same one or more detectable, fluorescent substrate(s) of MDR1 by,
• measuring or quantifying transport activity of MDR1 in the CD3+ T-lymphocytes in
• a reference patient group known to be responder to the bDMARD therapy and
• a reference patient group known to be non-responder to the bDMARD therapy, by using said substrate(s), and
• the transport activity values measured in the responder and non-responder patient groups are analysed to find a threshold level which differentiates between responder transport activity values and non-responder transport activity values,
• considering said RA patient as a non-responder to the bDMARD therapy and therefore suitable/eligible for another sDMARD therapy, or an alternative therapy, when the level of said one or more multidrug transporter activity value(s) measured is above said pre-determined threshold transporter activity level, and
• considering said RA patient as a responder to and therefore suitable for carrying out or continuing the bDMARD therapy when the level of each multidrug transporter activity value is not higher than said pre-determined threshold transporter activity level.