A Safety and Tolerability Study of CDX-301 With or Without Plerixafor for Stem Cell Mobilization in Matched Related Allogeneic Donor/Recipient Sibling Transplant Pairs

Inclusion Criteria:

Donors:

* Read, understood and provided written informed consent and willing to comply with all study requirements and procedures
* 6 out of 6 HLA-matched sibling
* Negative test for human immunodeficiency virus (HIV), hepatitis B, and hepatitis C
* Both male and female patients of childbearing potential enrolled in this trial must use adequate birth control measures
* Subjects should be in generally good health and without significant medical conditions, based upon pre-study medical history, physical examination, electrocardiogram (ECG), chest X- ray, and laboratory tests
* Meets all criteria to serve as a mobilized blood cell donor in accordance with all applicable individual Transplant Center criteria

Recipient:

* Read, understood and provided written informed consent and willing to comply with all study requirements and procedures
* 6 out of 6 HLA-matched sibling
* Both male and female patients of childbearing potential enrolled in this trial must use adequate birth control measures

Diagnosis of one of following:

* Acute Myelogenous Leukemia (AML) in 1st remission or beyond
* Acute Lymphoblastic Leukemia (ALL) in 1st remission or beyond
* Chronic Myelogenous Leukemia (CML)
* Chronic Lymphoblastic Leukemia (CLL), relapsing after at least one prior regimen
* Myelodysplastic Syndrome (MDS), either intermediate 1,2, or high risk by IPI Scoring System or transfusion dependent
* Non-Hodgkins Lymphoma (NHL) or Hodgkins Disease (HD) in 2nd or greater complete remission, partial remission, or in relapse
* Meets all criteria to serve as a transplant recipient in accordance with all applicable individual Transplant Center criteria

Exclusion Criteria:

Donors:

* Unwilling or unable to give informed consent, or unable to comply with the protocol including required follow-up and testing
* Prior treatment with any rhuFlt3L product
* Any vaccination within 4 weeks prior to CDX-301 dosing
* Donation of blood within 8 weeks, or donation of plasma within 2 weeks prior to CDX-301 dosing
* Any experimental treatment within 4 weeks prior to CDX-301 dosing
* Use of systemic immunosuppressive agents (excluding topical steroids) within 12 months prior to CDX-301 dosing.
* History of first degree relatives with primary or secondary immunodeficiency to include type 1 diabetes, multiple sclerosis, rheumatoid arthritis, scleroderma or psoriasis
* History of tuberculosis infection
* Herpes zoster within 3 months prior to starting study drug
* Pregnant or nursing

Recipient:

* Unwilling or unable to give informed consent, or unable to comply with the protocol including required follow-up and testing
* Prior allogeneic transplant
* More than one prior autologous transplant
* Prior treatment with any rhuFlt3L product
* Any vaccination within 4 weeks prior to transplant
* Uncontrolled infection at the time of the transplant conditioning regimen
* Pregnant or nursing
* Any condition, which, in the opinion of the clinical investigator, would interfere with the evaluation of the study outcome