The primary endpoint is the proportion of HD participants who collect ≥5*10^6 CD34+ cells/kg with this mobilization regimen. The secondary endpoints include the safety of this mobilization regimen, the proportion of participants who collect ≥2*10^6 CD34+ cells/kg, the change in CD34+ cells circulating in the peripheral blood after a dose of plerixafor, and the number of days of apheresis required to obtain ≥5*10^6 CD34+ cells/kg. In addition, success of the transplantation will be evaluated by measuring the time to engraftment of PMNs and PLTs. Participants will be followed for 12 months to assess transplant durability.