HIgh Dose Thymoglobulin Instead of Cyclosporine With a Low Dose of Thymoglobulin for GVHD Prophylaxis

The purpose of this study is to find out whether compared to our standard low dose ATG with CSA, the high dose ATG with low-dose CSA minimizes the chances of relapse and chronic GVHD, without increasing the chances of other transplant complications.

There are a number of complications of allogeneic hematopoietic cell transplantation.

The main complications are:

* Relapse (leukemia or leukemia-like disease returning). This usually leads to death.
* Acute graft-versus-host disease (GVHD). This may lead to death.
* Chronic GVHD. This may lead to poor quality of life long-term.

This study is being done to minimize the chances of patients getting relapse and chronic GVHD, without increasing the chances of getting acute GVHD.

At this time, the standard of care approach to treat this condition would be with:

* Low dose thymoglobulin (ATG), given on Day -2, -1 and 0.
* Cyclosporin (CSA), given from Day -1 through to Day 84.
* Methotrexate, given on Days 1, 3, 6 and 11

CSA reduces the chances of getting acute GVHD, but it does not reduce the chances of getting chronic GVHD and increases the chances of getting relapse. ATG reduces both acute and chronic GVHD, and does not increase relapse.

In this study, high dose ATG will be given on days -4, -3, -2, -1 and 0 (instead of only on days -2, -1 and 0), CSA will be given only from day 21 through 84 (instead of from day -1 through 84), and the routine dose of methotrexate (unchanged) will be given. We think that this may lead to better outcomes.

Patients will be followed per standard practice of the Alberta Blood and Marrow Transplant Program for the development of acute and chronic GVHD, and for relapse.

Patients will also be asked to complete a quality of life questionnaire 2 years after the transplant to assess how their treatment and illness affects their quality of life.

Eligibility Criteria:
Inclusion Criteria:

1. First allogeneic HCT, performed for a hematologic malignancy, using filgrastim-mobilized peripheral blood stem cells (PBSC).
2. Conditioning with fludarabine 50 mg/m2 daily on day -6 to -2, busulfan approximately 3.2 mg/kg daily on day -5 to -2 with PK adjustment (target AUC of 3750 uM\*min/L) and total body irradiation (TBI) 2 Gy x 2 given typically on day -1 and/or day 0 (before graft infusion), ie, our standard myeloablative conditioning.79 Dose and schedule adjustments per Investigator discretion are permitted.
3. Planned GVHD prophylaxis with our standard of low-dose ATG (4.5 mg/kg) + MTX + high-dose CSA.
4. HLA matched sibling donor, or ≥7/8 HLA allele-matched unrelated donor (maximum 1 allele mismatch at HLA-A, B, C, or DRB1).
5. Age \>17 years.

Exclusion Criteria:

1. Nonmyeloablative conditioning.
2. Cord blood or marrow graft.
3. Myelofibrosis being the primary indication for HCT.
4. Previous autologous or allogeneic HCT.
5. Total Bilirubin \>1.5-fold above upper normal limit (UNL), ALT \>2.0-fold above UNL, or alkaline phosphatase \>2.5-fold above UNL.
6. HIV positive by a serologic test that includes detection of both antibody and antigen)
7. Increased risk of tuberculosis, defined as patient requiring an anti-tuberculosis drug peritransplant. All patients with a history of tuberculosis (active or latent) or contact with a person with active tuberculosis will be evaluated by an infectious disease specialist to determine whether treatment or prophylaxis of tuberculosis with an anti-tuberculosis drug peritransplant is needed. The infectious disease specialist will order tests (eg, Mantoux tuberculin skin test or interferon gamma release test) as needed to arrive at the decision on whether an anti-tuberculosis drug peritransplant is needed.
8. High risk of cytomegalovirus (CMV) disease or recurrent CMViremia based on donor negative AND recipient positive CMV serostatus.2 If recipient serostatus was determined since the presentation of his/her hematologic malignancy more than once and the results are discrepant, the determination performed \>4 weeks after a transfusion of platelets or plasma (or before transfusions of platelets or plasma were initiated) is considered valid. If unclear, the CMV serostatus determination will be at the discretion of the treating Investigator
9. High risk of PTLD based on donor positive AND recipient negative Epstein-Barr virus (EBV) serostatus (EBNA1 or VCA IgG)80
10. Hypersensitivity to rabbit blood protein, Thymoglobulin or a Thymoglobulin excipient.
11. Severe obesity, defined as body mass index ≥40 kg/m2.81 The reason is that obese patients are at risk of achieving a high ATG area under the time vs concentration curve (AUC).82 This could lead to substantial toxicity (e.g., death due to an infection) when using the studied high dose (10 mg/kg) of ATG.
12. Contraindication to methotrexate:

    1. Hypersensitivity to methotrexate or to any ingredient in the formulation or component of the container.
    2. Females of childbearing potential who are pregnant, breastfeeding or unwilling to use adequate contraception from the time of enrolment until at least day 100 posttransplant.