Patients must be ≥ 12 months and ≤ 50 years of age at the time of study enrollment.

Patients with histologically confirmed solid tumors with an estimated poor long term survival.

Performance Level: Karnofsky ≥ 50% for patients > 16 years of age and Lansky ≥ 60 for patients ≤16 years of age.

Patients must be post RIC haploidentical BMT.

Patients must have fully recovered from the acute toxic effects of prior BMT.

Concomitant radiation therapy can be administered in the setting of this trial.

Subjects must consent to allow for a baseline tumor biopsy. If a biopsy is not feasible, then archival tumor material must be made available. Tumor biopsies to be taken (if a subject's tumor is thought to be reasonably safe and easy to biopsy) at baseline (any time prior to the first dose after eligibility is met) and at Cycle 2 (4-6 cores per time point) or when lesions are visualized on physical examination or imaging studies in the case of no identifiable masses at cycle 2. Additional optional biopsies may be obtained later in the course of study treatment. The proposed investigation is considered a non-significant risk (NSR). A significant risk procedure is generally considered to be one for which the procedure-associated absolute risk of mortality or major morbidity, in the patient's clinical setting and at the institution completing the procedure, is 2% or higher. Diagnostic Tissue Samples Tissue, fluid, or blood may be collected from standard of care procedures used to treat or diagnose immune related toxicities/GVHD.

Organ Function Requirements:

I. Adequate Hematologic Parameters:

1. For patients with solid tumors without known bone marrow involvement:

   • Peripheral absolute neutrophil count (ANC) ≥ 500/mm3
   • Platelet count ≥ 50,000/mm3

2. Patients with known bone marrow metastatic disease will be eligible for study without the above criteria. They may receive transfusions provided they are not known to be refractory to red cell or platelet transfusions. These patients will not be evaluable for hematologic toxicity.

II. Adequate Renal Function Defined as:

1. Creatinine clearance or radioisotope Glomerular filtration rate (GFR) ≥ 70ml/min/1.73 m2 or

2. A serum creatinine based on age/gender as follows:

   • Age 1 to <2 years, Male: 0.6 and Female: 0.6
   • Age 2 to <6 years, Male: 0.8 and Female: 0.8
   • Age 6 to <10 years, Male: 1 and Female:1
   • Age 10 to <13 years, Male: 1.2 and Female 1.2
   • Age 13 to <16 years, Male: 1.5 and Female 1.4
   • Age ≥ 16 years, Male: 1.7 and Female 1.4

III. Adequate Liver Function Defined as:

1. Bilirubin (sum of conjugated + unconjugated) ≤1.5 x upper limit of normal (ULN) for age
2. Serum glutamic pyruvic transaminase (SGPT) (ALT) ≤110 U/L. For the purpose of this study, the ULN for SGPT is 45 U/L.

Patients must have been registered on protocol J12106 "A Phase II Trial of Reduced Intensity Conditioning and HLA-matched or Partially HLA-mismatched (HLA-haploidentical) Related Donor Bone Marrow Transplant for High-risk Solid Tumors" before enrolling on this study.Patient may be screened prior to Day +120 but first dose of study drug must be given on or after Day +120.