This is an open label, multiple cohorts, dose escalation Phase Ib study, in which up to 3 doses of VLX103 will be assessed for safety, pharmacodynamics and pharmacokinetics in well defined moderate ASH patients cohorts receiving increasing doses of VLX103. The overall study design is characteristic for early phase, first in patient clinical evaluation of safety and pharmacodynamics, especially when prudent dose escalation is recommended. A maximum of 18 moderate ASH patients will be enrolled and treated in at least 4 clinical sites throughout the US. The open label nature of the study design will allow to efficiently monitor the safety of VLX103 throughout the trial, and taking rapid decisions about dosing adjustments (dose reduction or discontinuation within each dosing cohort, for each patient).