Oral cladribine treatment and idiosyncratic drug-induced liver injury in multiple sclerosis.

Background: Oral cladribine (OC) is approved for the treatment of highly active relapsing multiple sclerosis. Postmarketing safety assessments have reported rare, but occasionally severe cases of liver injury in temporal association with OC, with pathophysiologic mechanisms still unknown. In the only detailed case report on this topic, idiosyncratic drug-induced liver injury (iDILI) during OC treatment was well characterised for the first time, but occurred in the context of prior high-dose steroid exposure. Although high-dose steroids are known to induce iDILI in patients with multiple sclerosis with a delay of up to 12 weeks, OC was assumed to be the culprit agent for observed liver injury and the role of steroid exposure was not further investigated. Case: Herein, we describe a case of a 35-year-old women treated with high-dose oral prednisolone during the first treatment cycle OC and subsequently developed iDILI. A causality assessment of the role of prednisolone and OC was performed using the updated Roussel Uclaf Causality Assessment Method which also included a negative re-exposure test for OC during the second OC treatment cycle 1 year later. Conclusion: Our observations suggest that prednisolone or interactions between prednisolone and OC are more likely to foster development of iDILI rather than OC treatment itself.