Which of the following drugs is used for the treatment of refractory histiocytosis :

Treatment of LCH : 1. Single system disease  : The clinical course of single system disease is usually benign with a high chance of spontaneous remission. Therefore, treatment should be minimal and should be directed at arresting the progression of a bone lesion that could result in permanent damage before it resolve spontaneously. Curettage or less often low dose local radiotherapy may accomplish this. 2. Multisystem disease : It should be treated with systemic multiagent chemotherapy. Any one, of following two should be included in regimen :  i) Etoposide   ​ii) Vinblastin For unresponsive disease following therapies are available : i) Cyclosporine / antithymocyte globulin. ii) Imatinib. iii) 2-chlorodeoxyadenosine (Cladribine). iv) Stem cell transplantation.