MEK-inhibitors in treatment of Langerhans cell histiocytosis

Abstract

Background. There are increasing data of targeted therapy efficacy of different types of Langerhans cell histiocytosis (LCH) with inhibitors of BRAF-specific serin-threonine kinase (BRAF-inhibitors) in cases with BRAF V600E mutation published last years. At the same time there are no published data of use of inhibitors of MAPK/ERK pathway (MEK-inhibitors) in pediatric patients with BRAF-negative forms of LCH.Purpose of the study is to evaluate efficacy and safety of MEK-inhibitor (cobimetinib) in eight pediatric BRAF V600E-negative refractory LCH patients.Materials and methods. The study included 8 children with various forms of LCH. All patients received therapy according to the LCH-IV protocol and were diagnosed with progression of LCH during or after termination of the treatment. The response to the therapy was assessed in accordance with the international scale Response Evaluation Criteria in Solid Tumors (RECIST v.1.1). The assessment of the toxicity was performed in accordance with the international scale of Common Terminology Criteria for Adverse Events (CTCAE v.5.0).Results. Complete response was not achieved in any patient. Partial response was established in 5 cases. One patient was diagnosed with disease progression in three months after termination of the therapy. The incidence of adverse events was high.Conclusion. Cobimetinib therapy is effective in BRAF V600E-negative refractory pediatric LCH patients. The response to the treatment can be delayed. All cases of the toxicity were dose depended and successfully resolved after dose correction. Further research is needed to define duration of treatment and optimal dosage.