Pilot and Feasibility Trial of Plerixafor for Hematopoietic Stem Cell (HSC) Mobilization in Patients With Sickle Cell Disease Pilot and Feasibility Trial of Plerixafor for Hematopoietic Stem Cell (HSC) Mobilization in Patients With Sickle Cell Disease
Condition: Sickle Cell Disease Without Crisis
MeSH terms: Anemia, Sickle Cell
Study type: Interventional
Phase: Phase 1

Summary: 
      Sickle cell disease (SCD) is one of the most common genetic diseases in the world. In North
      America, an estimated 2600 babies are born with SCD each year1, and approximately 70,000 to
      100,000 individuals of all ages are affected in the United States2. The clinical
      manifestations of SCD include acute events, such as recurrent debilitating painful crises, as
      well as life-threatening pulmonary, cardiovascular, renal, and neurologic complications. The
      only established curative treatment for SCD patients is allogeneic hematopoietic stem cell
      transplant (HSCT). Unfortunately, access to this intervention is limited by availability of
      suitable matched donors, and HSCT is associated with significant morbidity and mortality. For
      patients who cannot undergo HSCT, treatment of SCD has been limited to one FDA-approved
      medication, hydroxyurea, and supportive symptomatic care. After decades with very few novel
      therapeutic options for SCD patients, autologous cell-based genetic therapies, including
      lentiviral-based gene therapy as well as gene editing, now offer the possibility of
      innovative curative approaches for patients lacking a matched donor for hematopoietic stem
      cell transplantation.

      Gene therapy for sickle cell disease is increasingly promising, and there are currently open
      clinical trials at several centers that employ a gene addition strategy.

      Options for autologous HSC collection include bone marrow harvest or peripheral blood HSC
      mobilization. Bone marrow (BM) harvest is an invasive procedure requiring anesthesia, which
      is associated with sickle cell-related morbidities, and may not achieve goal CD34+ cell dose,
      necessitating repeated procedures scheduled over multiple months. In most gene therapy
      trials, HSCs are obtained through peripheral collection after mobilization with granulocyte
      colony-stimulating factor (G-CSF) followed by peripheral blood (PB) apheresis. However, this
      approach is contraindicated in SCD because G-CSF has been reported to cause severe adverse
      effects in sickle cell patients. Even with doses sometimes smaller than standard, G-CSF has
      been shown to result in vaso-occlusive crises, severe acute chest syndrome, and in one
      report, massive splenomegaly and death. Alternative options for mobilization are needed.

      Plerixafor has been compared to G-CSF in a sickle cell mouse model, and results showed
      effective mobilization of HSC subsets, without neutrophil or endothelial activation, and with
      lower total WBC and neutrophil counts compared to G-CSF-treated mice. Plerixafor use has not
      yet been documented in sickle cell patients. One other trial is currently open to test
      plerixafor in SCD patients (NCT02193191) but no results have yet been reported. Based on
      pre-clinical data, the mechanism of action of plerixafor, as well strategies the investigator
      will employ to mitigate risk, the investigator anticipates that it will be well-tolerated in
      the SCD patient population.
    

Detailed description: 
      This is a non-randomized pilot safety and feasibility single-center study which will treat
      subjects with SCD with plerixafor, followed by collection of peripheral HSPCs by apheresis.
      Accrual is a sample of up to 6 patients, with at least three patients treated with a
      plerixafor dose of 180 mcg/kg, and potential for escalation to a dose of 240 mcg/kg according
      to safety and tolerability of the lower dose. Three patients will be treated at the lower
      dose of 180 mcg/kg. If none of these patients experience a dose limiting toxicity (DLT), the
      next three patients will be treated with the higher dose of 240 mcg/kg. If one or more of the
      patients treated at 240 mcg/kg has a DLT, then 180 mcg/kg will be selected as the safe dose
      level. If no patients at the 240 mcg/kg have a DLT, then 240 mcg/kg will be selected as the
      safe dose level.

      Within 30 days prior to plerixafor administration, subject will undergo laboratory testing,
      history, and physical exam. In order to retain the possibility for the subject to use his/her
      autologous cells for a future therapeutic indication, infectious disease testing and
      suitability for autologous transplant will be assessed per autologous transplant routine
      procedure.

      If the subject is taking hydroxyurea, the medication will be stopped 14 days prior to the
      planned apheresis.

      Between Days -7 and -2 prior to apheresis, the subject will undergo an exchange transfusion.
      This transfusion will be timed in accordance with the patient's existing chronic transfusion
      regimen. An exchange transfusion will be performed with post-transfusion hemoglobin
      electrophoresis confirming a %HbS of </= 30%.

      After the exchange transfusion a bone marrow aspirate will be performed under local
      anesthesia or conscious sedation. The reason for performing the pre-plerixafor bone marrow is
      that in addition to our primary objective of assessing safety and feasibility of plerixafor
      in SCD patients, the investigator also aim to increase knowledge of HSPCs and their bone
      marrow niche in SCD patients - this will be relevant for better understanding basic disease
      pathophysiology, but also for the possible future use of BM HSPCs (obtained in basal
      conditions or after plerixafor administration) for gene therapy or gene editing therapies. It
      will be important to compare these phenotypic features in BM-derived cells versus
      plerixafor-derived cells. Additionally however, in order to also understand whether the HSPCs
      from SCD patients differ substantially from healthy donors, having a pre-plerixafor baseline
      sample of HSPCs from the same SCD subjects will provide important biological information as
      well.

      On Day -1, the subject will be admitted to the Hematology service at Boston Children's
      Hospital. Confirmation of available, compatible units of packed red blood cells will be
      confirmed prior to administration of plerixafor (for use in case of an unexpected acute
      clinical need for transfusion). Labs will be drawn, including CBC, differential, hemoglobin
      electrophoresis, type and screen, and peripheral CD34+ cell count. The subject will receive a
      single dose of subcutaneous plerixafor.

      On Day 0, prior to apheresis, labs will be drawn, including CBC, differential, and peripheral
      CD34+ count. Starting 6 hours after plerixafor dose, apheresis will be performed to collect
      3-5x blood volumes. If the subject does not already have central venous access, access for
      apheresis will be obtained peripherally using 2 large bore 16g needles, and blood will be
      processed in the cell separator. Blood within the instrument will receive acid citrate
      dextrose formula A (ACD-A) (3%) at a rate of 1 mL/min/L of total blood volume, which is the
      standard apheresis dose. 2 grams of calcium gluconate is infused over the course of the
      procedure to prevent hypocalcemia associated with citrate administration. A CBC is drawn at
      the end of the procedure. Vital signs are monitored every 15 minutes while on the instrument.
      A second bone marrow aspirate will be performed before apheresis. The subject will remain
      admitted to the Hematology service overnight.

      If excess cellular material is collected, a portion of the collected apheresis product (a
      minimum of 1 x 106 and a maximum of 3 x 106 unmanipulated CD34+ cells/kg) will be stored in
      clinically compliant conditions for any possible future use for the patient.

      On Day + 1 after apheresis, labs will be drawn again including CBC, differential, and
      peripheral CD34+ count. The subject will be discharged from the Hematology service unless the
      subject does not meet standard clinical discharge criteria. On Day + 2 after apheresis, the
      study team will communicate with the subject via phone to inquire about any symptoms
      experienced. On Days +3, +7, +14, the subject will return for outpatient visit and labs.
    

Intervention name(s): Plerixafor
Intervention type(s): Drug
Intervention description(s): Dose escalation of Plerixafor for Hematopoietic stem cell mobilization in patients with Sickle Cell Disease
Intervention MeSH terms: Plerixafor
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Plerixafor