The primary end point is to document the number of doses required by each of the two dose schedule to produce a response, achieve a nadir absolute lymphocyte count of 200 cmm. Secondary endpoints are short term safety of ATG-Fresenius, change in absolute neutrophil count from the baseline in both arms, change in platelet count from the baseline, change in absolute reticulocyte count, Number of blood units required till 8 weeks and 26 weeks, Number of platelet doses required till 8 weeks and 26 weeks, relapse, response rates at 6 and 12 months, clonal evolution to PNH, myelodysplasia or acute leukaemia. Long-course CsA will be assessed separately for its efficacy in reducing late events of relapse and evolution by comparison to historical control data.