Allogeneic stem cell transplantation is allowed provided the patient is >= year from transplant at time of registration, is not on immunosuppressive therapy to treat/prevent graft-versus-host disease, has no evidence of active graft versus host disease, and no evidence of active infection Prior allogeneic stem cell transplantation with active graft-versus-host-disease. Autologous hematologic stem cell transplant within months of study entry; allogeneic hematologic stem cell transplant within months; grade II, or greater, active graft-versus-host disease Patients with a history of allogeneic stem cell transplantation are eligible for study participation provided the transplant was > days prior to the first dose of treatment on study; patients must be off of immunosuppressive therapies for at least weeks prior to the first dose of treatment on study without signs or symptoms of graft versus host disease other than grade skin involvement Patients, who relapsed months after bone marrow transplant and have no evidence of active graft versus host disease and are off systemic immunosuppressant medications for at least months and have received hypomethylating agents (HMA) therapy before or after transplant and meet other eligibility criteria of progression after at least months of DNMTi therapy, are eligible to be enrolled in this clinical trial Patients who have undergone allogeneic stem cell transplant > months, without active graft-versus-host-disease, and not on immunosuppression for prevention of graft-versus-host disease are eligible Patients who have underwent autologous or allogeneic stem cell transplant =< weeks prior to cycle day or have active graft-versus-host disease are excluded Prior allogeneic stem cell transplantation with active graft-versus-host- disease Stem cell transplant recipients must have no evidence of active graft-versus-host disease Prior allogeneic stem cell transplant within months of study drug administration and no requirement for graft versus host therapy. At least months from stem cell transplant with no active graft versus host disease Has received a prior allogeneic hematopoietic stem cell transplant within the past years, requires immunosuppression, or has evidence of active graft-versus-host-disease Received an allogeneic stem cell transplant in the past year (if over year post allogeneic transplant, must not have active chronic graft versus host disease [cGVHD]) Allogeneic stem cell transplant within the last months, or active graft-versus-host disease following allogeneic transplant or autologous stem cell transplant within the last months before the date of the first dose of study drug administration. Stem cell transplant recipients must have no evidence of and not receive treatment for graft-versus-host disease Subjects are not a candidate, or have failed allogeneic stem cell transplantation. Subjects who underwent allo-transplant in the past are eligible under following conditions: transplant was > year prior to enrolment, and no evidence of active graft-versus-host disease (GVHD) Previous allogeneic bone marrow transplant are restricted, unless there is no evidence of acute or chronic graft versus host disease. Has had an allogeneic stem cell transplant with current active graft-versus-host-disease. Patients having undergone prior allogeneic stem cell transplant within months or having active graft versus host disease If patient has undergone prior allogeneic stem cell transplant, they must be greater than days post transplant and have =< grade graft-versus-host disease Patients must have relapsed after first line chemotherapy; may have relapsed after autologous or allogeneic stem cell transplant, or have primary refractory disease; no upper limit for number of prior therapies; if status post allogeneic stem cell transplant, no active graft versus host disease Patients having undergone prior allogeneic stem cell transplantation within months or having active graft versus host disease. Less than months since received hematopoietic stem cell transplantation, autologous or allogeneic and/or have clinically significant graft versus-host disease requiring treatment at the time of screening and/or patient having a history of severe graft versus-host disease; Patient had an allogeneic stem cell transplant within months before first dose of PRLX or has evidence of graft versus host disease. Prior allogeneic stem cell transplant within months of study drug administration and no requirement for graft versus host therapy. Stem cell transplant recipients must have no evidence of active graft-versus-host disease and should not be receiving treatment for it Allogeneic stem cell transplant less than months prior to initiation of study treatment and who have not discontinued immunosuppressive treatment for at least four weeks prior to initiation of study treatment and who are currently dependent on such treatment; patients may also not have active graft versus (v.) host disease Prior hematopoietic stem cell transplant within months of enrollment. If the subject had an allogenic transplant there must be no apparent signs of graft versus host disease and subjects must have discontinued all immunosuppressive therapies for at least weeks Is within the first days of having undergone an allogeneic stem cell transplant; otherwise, patients who have received an allogeneic stem cell transplant are allowed as long as they have no evidence of active graft versus host disease (GVHD) or are on immunosuppressive therapy Unless approved by the medical monitor, may not have received an allogeneic hematopoietic stem cell transplant within months before treatment, or have active graft-versus-host-disease following allogeneic transplant Allogeneic stem cell transplant within the last months, or active-graft-versus-host disease following allogeneic transplant, or subjects currently on immunosuppressive therapy following allogeneic transplant Allogeneic stem cell transplant within the last months, or active graft versus host disease following allogeneic transplant, or autologous stem cell transplant within the last months. Post-autologous stem cell transplant (ASCT) or not a candidate for ASCT; prior allogeneic stem cell transplant is allowed if patient is off all immunosuppressives and has no evidence of active graft-versus-host disease (GVHD) Subjects with a history of allogeneic stem cell transplant are eligible for study participation provided the following eligibility criteria are met: transplant was > days prior to study enrolment; subject has not taken immunosuppressive medications for at least month; no signs or symptoms of graft versus host disease other than Grade skin involvement; no active infection. Received allogeneic hematopoietic stem cell transplant within the last months, or has active graft versus host disease (GVHD) following allogeneic transplant, or currently receiving immunosuppressive therapy following allogeneic transplant Allogeneic stem cell transplant within the previous months, or active graft versus host disease following allogeneic transplant. Patients who have had allogeneic hematopoietic stem cell transplant (HSCT) are not eligible if they meet any of the following: \r\n* transplant is within months from cycle , day (CD) \r\n* Has clinically significant graft-versus-host disease requiring treatment\r\n* Has >= grade persistent non-hematological toxicity related to the transplant Autologous hematologic stem cell transplant within months of study entry; allogeneic hematologic stem cell transplant within months; post allogeneic (allo) patients must not have active graft versus-host disease and be off all immune suppression (other than steroids, as above) Patients who have had a previous allogeneic transplant within months and have evidence of clinically significant graft versus host disease Patients who have received allogenic stem cell transplantation < months prior to entering the study or show evidence of active graft-versus-host disease that requires immunosuppressive therapy Participants who have had prior allogeneic stem cell transplantation with evidence of active graft-versus-host disease requiring immunosuppressive therapy Patients who have undergone allogeneic stem cell transplant within months, without active graft-versus-host-disease, and not on immunosuppression for prevention of graft-versus-host disease are eligible Patients who have undergone prior allogeneic transplant are excluded only if they remain on any immunosuppression or have signs or symptoms of clinical graft-versus-host disease Subjects who have undergone stem cell transplant who are undergoing treatment or prophylaxis for Graft versus host disease Patients who have had prior allogeneic stem cell transplantation and show evidence of active graft-versus-host disease that requires immunosuppressive therapy Autologous or allogeneic stem cell transplant within months prior to enrolment [NOTE: subjects with evidence of active graph versus host disease are excluded]. Subject may not have had hematopoietic stem cell transplant (HSCT) meeting any of the following: \r\n* Is within months of transplant from cycle day (CD) \r\n* Has clinically significant graft-versus-host disease requiring treatment\r\n* Has >= grade persistent non-hematological toxicity related to the transplant \r\n* Donor lymphocyte infusion (DLI) is not permitted < days prior to study registration Active graft versus host disease (after allogeneic stem cell transplantation) at CD. Phase II: Received an autologous or allogeneic stem cell transplant at the Hospital of the University of Pennsylvania and experienced a sentinel event of either ) disease relapse, ) severe (grade III or IV) graft-versus-host disease, or ) unplanned hospital admission with length of stay greater than hours Active graft versus host disease (after allogeneic stem cell transplantation) at CD. Patients who have undergone prior allogeneic transplantation are eligible provided they do not have significant active graft versus host disease and that their transplant day is > months from their first dose of chemotherapy Previously received an allogeneic stem cell transplant and the occurrence of one or more of the following: received the transplant within months prior to study day ;received immunosuppressive therapy within the last months prior to study day ;having signs or symptoms of acute or chronic graft-versus-host disease.