• Evaluate the efficacy of CD26/DPP-IV inhibition in increasing the proportion of adult patients with hematological malignancies engrafting by day +30 following transplantation of UCB by 30 percent. [ Time Frame: Transplant (Day 0) through Day +100 ] [ Designated as safety issue: No ]
  

• Define the median times to neutrophil and platelet engraftment [ Time Frame: Day 0 through Day +100 ] [ Designated as safety issue: No ]
  
• Describe rate of engraftment failure by day +100 [ Time Frame: Day 0 through Day +100 ] [ Designated as safety issue: No ]
  
• Describe the incidence of grade 3 and 4 non-hematological toxicity [ Time Frame: Day 0 through Day +100 ] [ Designated as safety issue: Yes ]
  

Drug: Sitagliptin
600 mg/day PO starting on Day -1 for a total of 4 doses

Umbilical cord blood (UCB) is increasingly used as a source of stem cells for patients with blood cancers who need an allogeneic stem cell transplant (a transplant with stem cells from another person) but who have no suitably matched donors. The advantages of UCB are that (1) it is associated with less risk of transmitting an infection from a donor, (2) it can be more safely given even if not completely matched compared to bone marrow or blood stem cells, and (3) it is much more quickly available than unrelated donor bone marrow or blood stem cells.

While more commonly used for transplantation in children, UCB is increasingly being used in adults. However, because they are larger than children, the relatively smaller stem cell dose in UCB is major limitation for transplantation in adults, and engraftment can be delayed. This study is investigating whether the drug sitagliptin can be used to increase and speed up engraftment in adults receiving UCB transplantation, overcoming the limitation of small stem cell doses associated with umbilical cord blood.

Sitagliptin is a drug given in tablet form that has been recently approved by the Food and Drug Administration (FDA) for the treatment of certain patients with diabetes mellitus (a disease that results in high blood sugar).

Sitagliptin has been given to both normal healthy volunteers and diabetic patients and has been found to be safe and well-tolerated. The drug improves control of blood sugar in diabetics by inhibiting an enzyme called "CD26/DPP-IV." Recent studies at Indiana University (and other centers) have shown that this same enzyme plays an important role in the way transplanted stem cells find their way to the bone marrow and engraft.

Transplant studies in mice have found that inhibiting CD26/DPP-IV significantly increases the engraftment of stem cells. Based on these studies, it is believed that drugs that inhibit CD26/DPP-IV, such as sitagliptin, may also increase engraftment in patients who receive clinical stem cell transplants.