Plerixafor: what we still have to learn

Plerixafor, a hematopoietic stem cell mobilizer, is indicated in combination with G-CSF to mobilize hematopoietic stem cells to the peripheral blood for collection and subsequent autologous transplantation in patients with non-Hodgkin’s lymphoma and multiple myeloma. Current evidence suggests that the addition of plerixafor with chemotherapy plus G-CSF is safe and effective in the large majority of the patients with low blood CD34⁺ cell count after mobilization and/or poor yield after the first collection. Nevertheless, there are several questions strongly debated, and in this paper, we would like to identify areas of possible future use and development of the drug.     

Plerixafor for mobilization of blood stem cells in autologous transplantation: an update

Introduction: About 99% of all autologous transplants are now performed with blood stem cells. G-CSF alone or combined with chemotherapy have been used to mobilize CD34⁺ cells. Plerixafor is a novel drug used for mobilization purposes.

Areas covered: We have evaluated recent data in regard to plerixafor use in predicted or proven poor mobilizers. In addition, we have looked for preemptive strategies to optimize the use of this expensive drug. Also cost-efficacy issues and effects of plerixafor on graft composition and post-transplant outcomes will be discussed.

Expert opinion: Plerixafor added to G-CSF is superior than G-CSF alone for mobilization of CD34⁺ cells. This combination is also efficient in patients who have failed a previous mobilization attempt with other methods or in patients with risk factors for poor mobilization. Addition of plerixafor to G-CSF or chemotherapy plus G-CSF mobilization in patients who appear to mobilize poorly is under active investigation and algorithms for a preemptive use of this expensive agent have been proposed. Grafts collected after plerixafor appear to contain more lymphoid cells than the grafts collected without it. Whether this affects post-transplant outcomes such as immune reconstitution and risk of relapse needs to be evaluated.     

The efficacy of residual plerixafor for second-day stem cell mobilization in multiple myeloma patients

BackgroundGranulocyte colony-stimulating factor (G-CSF) plus plerixafor has been shown to improve the efficacy of peripheral blood stem cell (PBSC) mobilization, however, due to its high price, the use of plerixafor is limited in China. The purpose of this study was to assess the efficacy of residual plerixafor for second-day stem cell mobilization in multiple myeloma (MM) patients.Materials and methodsIn this single-center retrospective study, 69 MM patients received G-CSF + plerixafor to mobilize PBSCs, which were collected from 28 patients only for one day and 41 patients for two days. Some of the patients received residual plerixafor, and PBSCs were collected on the second day. The data on the characteristics, different doses of plerixafor and efficacy of PBSC mobilization were collected and analyzed.ResultsAfter 1 or 2 apheresis procedures, 85.5% of patients collected more than 2 × 10⁶ cells/kg PBSCs. There was no statistically significant difference in the success rate of CD34 + PBSC mobilization with the different doses of plerixafor on the first day, but the higher residual plerixafor dose resulted in better success rates on the second day (P＜0.001). Among the patients who collected PBSCs for two days, the level of the CD34 + cell yield of 24 patients (58.5%) changed better, which was significantly correlated with the dose of residual plerixafor on the second day (P = 0.001).DiscussionThese results suggested that the administration of residual plerixafor to mobilize stem cells on the second day is an economical, efficient and clinically feasible method.     

A comparison of chemo-free strategy with G-CSF plus plerixafor on demand versus intermediate-dose cyclophosphamide and G-CSF as PBSC mobilization in newly diagnosed multiple myeloma patients: An Italian explorative cost Analysis

BackgroundUpfront single or tandem ASCT still represents an integral part of treatment for patients with multiple myeloma. The combination of intermediate dose (ID) - cyclophosphamide plus G-CSF, has been considered the standard method as mobilization regimen. No prospective randomized clinical trials have compared efficacy and costs using ID - cyclophosphamide against a chemo-free mobilization strategy with G-CSF and plerixafor on demand.MethodsA prospective single arm of 20 patients enrolled in three Italian Centers mobilized with G-CSF plus plerixafor on demand was compared with a retrospective historical control arm of 30 patients mobilized with ID - cyclophosphamide (4 g/sqm) and G-CSF. Costs of the prospective arm was compared with the ones of the retrospective control arm with the aim to collect ≥4 × 10⁶/kg CD34 + . The exploratory cost analysis was performed using microcosting specific inputs of G-CSF plus plerixafor on demand versus ID - cyclophosphamide + G-CSF considering pre-apheresis, peri-apheresis and post-apheresis session.ResultsMobilization with ID - cyclophosphamide and G-CSF resulted in a significantly higher CD34+ peak mean on day 1 yield (119 CD34+ μL vs 67.3; p = 0.06) and in total average CD34+ yield (mean collection 10.6 × 10⁶/kg vs 5.8 × 10⁶/kg; p = 0.004) compared to patients mobilized with G-CSF and plerixafor. There was no significant differences (p = 0.36) in the two groups of patients collecting ≥ 4 million CD34+/Kg with ID - cyclophosphamide and G-CSF (93.3 %) vs G-CSF and plerixafor (90.0 %). None of the patients undergoing G-CSF and plerixafor mobilization had febrile neutropenia compared with 7 patients who received ID - cyclophosphamide and G-CSF (0% vs 23 %, p = 0.03) who had a median of 5 days hospitalization (range 4–6). All patients proceeded to ASCT with a mean of 3.6 CD34+/kg infused for G-CSF and plerixafor arm and 4.4 CD34+/kg for the ID - cyclophosphamide + GCSF group (p = 0.37) with a median time to ANC and PLT engraftment not different in the two groups. Total costs of a mobilizing strategy using a combination of G-CSF and plerixafor on demand was 12.690 euros compared to 16.088 euros with ID - cyclophosphamide and G-CSF (p = 0.07); in particular, mobilization cost components were significantly lower for G-CSF and plerixafor vs G-CSF and ID - cyclophosphamide for hospital stay (3080 euros vs 9653 euros; p < 0.001) whereas for mobilizing agent, there was a significative difference with 5470 euros for G-CSF and plerixafor use due to the cost of plerixafor compared with 1140 euros for ID - cyclophosphamide and G-CSF treatment (P = 0.001).ConclusionsOur data demonstrate that in patients with multiple myeloma eligible for ASCT, a chemo-free mobilization with G-CSF and plerixafor on demand is associated with efficacy in PBSC collection and optimal safety profile with similar average costs when compared to a chemo-mobilization with ID - cyclophosphamide. A prospective randomized multicenter study could address which is the most cost-effective strategy for this setting of patients.Clinical Trial RegistryEudract Number EudraCT 2013−004690-27.     

Plerixafor combined with G-CSF for stem cell mobilization in children qualified for autologous transplantation- single center experience

Failure of autologous peripheral blood CD34⁺ stem cells collection can adversely affect the treatment modality for patients with hematological and nonhematological malignant diseases where high dose chemotherapy followed by hematopoietic stem cell transplantation has become part of their treatment. Plerixafor in conjunction with G-CSF is approved for clinical use as a mobilization agent. The clinical efficacy of Plerixafor in CD34⁺ cells collection was analyzed in our institution. A total of 13 patients aged 1–15,5 years received Plerixafor in combination with G-CSF: 7 with neuroblastoma, 2 with Ewing’s sarcoma and single patients with Hodgkin’s lymphoma, germ cell tumor, retinoblastoma and Wilms tumor. Twelve patients (923%) achieved CD34+ cell counts of ≥ 20 × 10⁶/L after 1–7 doses of Plerixafor. The average 9,9 - fold increase in number of CD34⁺ cells were achieved following the first dose and 429 - fold after second dose of plerixafor. Among the 13 patients, 12 yielded the minimum required cell collection of 2 × 10⁶/kg within an average of 2 doses of Plerixafor. The mean number of apheresis days was 1.75. The median total number of collected CD34⁺ cells was 982 × 10⁶/kg. Plerixafor enables rapid and effective mobilization, and collection of sufficient number of CD34⁺ cells.     

Pre-emptive plerixafor injection increases blood neutrophil, lymphocyte and monocyte counts in addition to CD34+ counts in patients with non-Hodgkin lymphoma mobilizing poorly with chemotherapy plus G-CSF: potential implications for apheresis and graft composition

BackgroundCXCR4 receptor antagonist plerixafor is used to mobilize hematopoietic stem cells. No detailed data regarding the effects of plerixafor on other blood cell components have been published but may be of importance in regard to graft composition collected after plerixafor injection.Patients and methodsThe study included thirty-nine patients with non-Hodgkin lymphoma (NHL) mobilized with chemotherapy plus G-CSF. Plerixafor was given pre-emptively in twenty patients due to poor mobilization or low collection yield. Nineteen NHL patients served as controls. We evaluated CD34⁺ counts and WBC counts and differential from the morning of the first plerixafor injection and 8 h after the plerixafor injection. From the control patients the corresponding values were evaluated on the morning of the first apheresis and 24 h before it.ResultsThe first plerixafor dose increased CD34⁺ counts and number of leukocytes, neutrophils, lymphocytes, eosinophils and monocytes. Leukocyte, neutrophil, lymphocyte, monocyte and eosinophil counts were higher after plerixafor injection compared to the control group at the time of the first apheresis. Minimal graft (?2 × 10⁶/kg CD34⁺ cells) was collected in 85% of plerixafor treated patients, with a single apheresis in 45% of the patients.DiscussionPlerixafor significantly increases B-CD34⁺ cell counts on the next morning making effective blood stem cell collection possible in the majority of the patients mobilizing poorly. It also influences other blood cell components but impact of this observation in regard to graft content and post-transplant course needs to be assessed in further studies.     

The effective use of plerixafor as a real-time rescue strategy for patients poorly mobilizing autologous CD34(+) cells

Plerixafor enhances CD34⁺ cell mobilization, however, its optimal use is unknown. We hypothesized that plerixafor could “rescue” patients in the midst of mobilization when factors indicated a poor CD34⁺ yield. Of 295 consecutive autologous peripheral blood mobilization attempts at our center, 39 (13%) used plerixafor as rescue strategy due to a CD34⁺ cell concentration <10/μl (median 5.95/μl, n = 30), low CD34⁺ cell yield from prior apheresis day (median 1.06 × 10⁶ CD34⁺ cells/kg, n = 7), or other (n = 2). Patients received a median of one plerixafor dose (range: 1–4). Thirty‐four (87%) collected =2 × 10 ⁶ CD34⁺ cells/kg and 26 (67%) collected =4 × 10 ⁶ CD34⁺ cells/kg. Median collections for lymphoma (n = 24) and myeloma (n = 15) patients were 4.1 × 10⁶ and 8.3 × 10⁶ CD34/kg, respectively. A single dose of plerixafor was associated with an increase in the mean peripheral blood CD34⁺ concentration of 17.2 cells/μl (P < 0.001) and mean increased CD34⁺ cell yield following a single apheresis of 5.11 × 10⁶/kg (P < 0.03). A real‐time rescue use of plerixafor is feasible and may allow targeted use of this agent. J. Clin. Apheresis, 2012. © 2012 Wiley Periodicals, Inc.     

Kinetics of PBPC mobilization by cyclophosphamide, as compared with that by epirubicin/paclitaxel followed by G-CSF support: implications for optimal timing of PBPC harvest

BACKGROUND: Limited information is available on the mobilization kinetics of autologous PBPCs after induction with various chemotherapy regimens. With PBPC mobilization in patients with breast cancer used as a model for chemotherapy-induced PBPC recruitment, the kinetics of progenitor cells mobilized either with cyclophosphamide (CY) or epirubicin/paclitaxel (EPI-TAX) followed by the administration of G-CSF was compared. STUDY DESIGN AND METHODS: The study included a total of 86 patients with breast cancer (stage II-IV) receiving either CY (n = 39) or EPI-TAX (n = 47), both followed by G-CSF support. The progenitor cell content in peripheral blood and apheresis components was monitored by flow cytometric enumeration of CD34+ cells. PBPC collection was started when the threshold of >20 x 10(6) CD34+ cells per L of peripheral blood was reached. RESULTS: The PBPC collection was begun a median of 9 days after the administration of EPI-TAX followed by G-CSF support, as compared to a median of 13 days after mobilization with CY plus G-CSF. After treatment with CY, the total numbers of PBPCs peaked on Day 1 of apheresis, and they rapidly declined thereafter. In contrast, treatment with EPI-TAX followed by G-CSF administration led to a steady mobilization of CD34+ cells during leukapheresis. The difference in the mobilization patterns with CY and EPI-TAX resulted in a greater yield of CD34+ cells per L of processed blood volume. Compared to EPI-TAX, mobilization with CY required the overall processing of 30 percent less whole-blood volume to reach the target yield of > or = 10 x 10(6) CD34+ cells per kg of body weight. After a median of three apheresis procedures, however, both CY+G-CSF and EPI-TAX+G-CSF were equally effective in obtaining this target yield. CONCLUSION: These results imply that specific PBPC mobilization as part of a given chemotherapy regimen should be taken into consideration before the planning of a PBPC harvest.     

Peripheral blood progenitor cell collection without close monitoring of peripheral blood CD34+ cells: A feasible strategy for multiple myeloma or pre-treated Non-Hodgkin’s Lymphoma patients mobilized with low-dose cyclophosphamide plus G-CSF

BackgroundDaily monitoring of peripheral blood CD34+ cells may not be necessary for all patients with hematologic malignancies for adequate peripheral blood progenitor cells (PBPC) mobilization and harvesting. We therefore designed a regimen for PBPC mobilization in patients with multiple myeloma or pre-treated Non-Hodgkin’s lymphoma based on a combination of low-dose cyclophosphamide (Cy) plus granulocyte colony-stimulating factor (G-CSF) without daily monitoring of peripheral blood CD34+ cells.Study design and methodsA prospective study was performed on patients with multiple myeloma (n = 22) or pre-treated Non-Hodgkin’s lymphoma (n = 17) whose PBPC were harvested according to the following regimen: 1.5 g/m² Cy at day 1, 12 μg/kg/day G-CSF from day +7 to +11 avoiding daily monitoring of peripheral blood CD34+ cells and two consecutive leukapheresis at days +12 and +13. The optimum threshold of 2 × 10⁶ CD34+ cells per kg was established.ResultsThe proportion of patients with higher CD34+ cell yield after two leukapheresis was similar: multiple myeloma (16/22–72.7%) and Non-Hodgkin’s lymphoma (12/17–70.6%). Exposure to radiotherapy and greater than two prior chemotherapy regimens were significantly associated with lower yield in multiple myeloma (p = 0.002) and Non-Hodgkin’s lymphoma patients (p = 0.002), respectively.ConclusionOur data suggested that adequate yields of CD34+ cells may be achieved in multiple myeloma or pre-treated Non-Hodgkin’s lymphoma mobilized with low-dose Cy plus G-CSF regardless of the daily monitoring of peripheral blood CD34+ cells.     

Selection of the mobilization regimen in lymphoma patients: A retrospective cohort study

Background and objectivesConsolidation with autologous stem cell transplantation (ASCT) is recommended for patients with recurrent or refractory lymphoma after salvage chemotherapy. Stem cells which will be used in ASCT are provided by mobilization using granulocyte colony stimulation factor (G-CSF) or chemotherapy plus G-CSF. The aim of this study was to compare the effect of various mobilization regimens on the clinical parameters of lymphoma patients.Materials and methodsMobilization interventions of lymphoma patients were analysed retrospectively. The patients were divided into 3 groups according to the mobilization method implemented to collect stem cells before ASCT, (Group 1: Salvage chemotherapy plus G-CSF, Group 2: Cyclophosphamide plus G-CSF, Group 3: G-CSF alone).ResultsAnalysis of CD34⁺ cell counts of the 3 groups revealed a significant difference (p < 0.001). Although the number of CD34⁺ cells collected were different, the neutrophil and platelet engraftment of the 3 groups were similar (p > 0.05). Furthermore, the results were similar in the separate analysis of NHL and HL patients. While the mobilization success rate in group 1 was 97.8 %, it was 90.2 % in group 3. This difference showed a certain trend towards statistical significance (p = 0.074). Patients who received DHAP plus G-CSF had a higher CD34⁺ count, while neutrophil engraftment was shorter than with ESHAP plus G-CSF (p < 0.05).ConclusionAlthough the success rate of mobilization and number of CD34⁺ cell collected were higher in the salvage chemotherapy plus G-CSF than G-CSF alone, G-CSF alone group provided similar neutrophil and thrombocyte engraftment in most lymphoma patients.     

An updated single center experience with plerixafor and granulocyte colony-stimulating factor for stem cell mobilization in light chain amyloidosis

The use of granulocyte-colony stimulating factor (G-CSF) with or without chemotherapy to mobilize hematopoietic progenitor cells (HPCs) can result in significant morbidity in light chain (AL) amyloidosis patients. Plerixafor, a strong inducer and mobilizer of HPCs, can be used as an adjunct to G-CSF to improve mobilization efficiency. We describe the outcomes for combined G-CSF/plerixafor mobilized patients with AL amyloidosis. We reviewed data of 53 consecutive AL amyloidosis patients who underwent combined G-CSF/plerixafor HPC mobilization between May 2011 and October 2017 at our institution. We evaluated patients for HPC collection efficiency, perimobilization toxicity and postautologous hematopoietic cell transplantation (autoHCT) outcomes. Median CD34⁺ cell collection was 12.4 × 10⁶ cells/kg (range 2.5 × 10⁶ to 34.1 × 10⁶ cells/kg) and 45 (85%) patients had collections of ≥5.0 × 10⁶ CD34⁺ cells/kg. There were no mobilization failures or perimobilization mortality. During mobilization, 37 (70%) patients had weight gain (median 1.3 kg, range 0.1-4) but none >10% body weight, 5 (10%) patients had diarrhea, and one patient each had hypotension and cardiac arrhythmia. Among the 31 patients analyzed for CD34 collection efficiency (CE), the median CD34 CE was 47% (range 36-62). At 5 years follow-up 82% and 84% of patients were progression-free and alive, respectively. Our results suggest that G-CSF/plerixafor mobilization is safe, well tolerated, and effective in AL amyloidosis.     

Preemptive use of plerixafor in difficult-to-mobilize patients: an emerging concept

Mobilized peripheral blood (PB) is the preferred source of stem cells (PBSCs) for autologous stem cell transplantation (ASCT). The use of cytokines, alone or in combination with chemotherapy (chemomobilization), is currently the most common strategy applied to collect PBSCs. However, a significant proportion of patients with lymphoid malignancies fail to mobilize enough PBSCs to proceed to ASCT. Plerixafor has been recently introduced for clinical use to enhance PBSC mobilization and has been shown to be more effective than granulocyte-colony-stimulating factor (G-CSF) alone in patients with multiple myeloma or non-Hodgkin's lymphoma. There is limited experience on combining plerixafor with chemotherapy plus G-CSF in patients who mobilize poorly. This review attempts to summarize the published experience on the preemptive use of plerixafor after chemomobilization or G-CSF mobilization to enhance stem cell collection and to prevent mobilization failure. Current evidence suggests that addition of plerixafor is safe and effective in the large majority of the patients with low blood CD34+ cell counts after mobilization and/or poor yield after the first collection(s). Circulating CD34+ cell counts can be increased by severalfold with plerixafor and the majority of the patients considered difficult to mobilize can be successfully collected. Although more studies are needed to evaluate proper patient selection and optimal timing for the addition of plerixafor after chemotherapy, its mechanism of action inducing the rapid release of CD34+ cells from the marrow to the PB makes this molecule suitable for its "preemptive" use in patients who are difficult to mobilize.     

An algorithm for utilizing peripheral blood CD34 count as a predictor of the need for plerixafor in autologous stem cell mobilization—cost‐effectiveness analysis

Certain patients who receive granulocyte colony‐stimulating factor (GCSF) for autologous hematopoietic stem cell (AHSC) collection fail to mobilize well enough to proceed with transplant. When plerixafor is used with GCSF, the likelihood of achieving the CD34⁺ stem cell target in fewer collections is higher; plerixafor use in all patients is unlikely to be cost‐effective. This study retrospectively evaluated the effectiveness of utilizing a peripheral blood CD34⁺ stem cell count (PBCD34) ≤8/µL on day 4 of GCSF‐based AHSC mobilization as a threshold for plerixafor administration, and compared the efficacy of collection and cost analysis using historical controls. All patients in the study cohort reached their CD34⁺ targets in ≤3 collections. Significantly more patients who received plerixafor + GCSF versus GCSF alone reached their CD34⁺ target in one collection (P = 0.045); however, there were no significant differences in the number of collections or in cumulative product yields. The historical cohort had 10.3% mobilization failures; the number of collections per patient needed to reach the target was significantly higher in the historical cohort versus study cohort (P = 0.001) as was the number of patients requiring more than one collection to reach their target (P = 0.023). However, the average cost per patient was also significantly higher in the study cohort (P = 0.025). Further refinement of the algorithm may reduce the difference in cost between the two mobilization strategies. J. Clin. Apheresis 28:293–300, 2013. © 2013 Wiley Periodicals, Inc.     

Cytokines and vascular cell adhesion molecule-1 in the blood of patients undergoing HPC mobilization

BACKGROUND: The mechanism of HPC mobilization in humans is unclear. In this study, the relationship between PBPC mobilization and blood levels of G-CSF, endogenous cytokines (IL-8, SCF, thrombopoietin [TPO]), and the vascular cell adhesion molecule-1 (VCAM-1) was analyzed in patients with malignancy who were undergoing a PBPC mobilization regimen. STUDY DESIGN AND METHODS: Fifty-four patients with multiple myeloma (MM) and 29 with breast cancer (BC) underwent a mobilization regimen combining conventional chemotherapy and G-CSF up to the last day of PBPC collection. The CD34+ cell count was determined on each day when leukapheresis was scheduled. Venous blood samples (n = 117) were drawn before apheresis for CD34+ cell count (flow cytometry) and cytokine (G-CSF, IL-8, SCF, TPO) and VCAM-1 measurements (ELISA). RESULTS: In multiple regression analysis, SCF was a significant determinant of CD34+ cell levels in BC patients (R = 0.50, p = 0.03) and of VCAM-1 levels in MM patients (R = 0.32, p = 0.02). SCF was negatively correlated with CD34+ cell count in patients with BC. SCF and VCAM-1 blood levels were correlated in MM and BC patients. CONCLUSION: SCF and VCAM-1 could play a role in PBPC mobilization in patients and could be useful measures by which to study patients undergoing a mobilization regimen.     

A specific time course for mobilization of peripheral blood CD34+ cells after plerixafor injection in very poor mobilizer patients: impact on the timing of the apheresis procedure

BACKGROUND: This report describes the specific kinetics of the peripheral blood (PB) CD34+ cell concentration in a selected group of very poor stem cell mobilizer patients treated with granulocyte–colony‐stimulating factor (G‐CSF) and plerixafor and determines the kinetics' impact on apheresis. STUDY DESIGN AND METHODS: All patients had previously experienced at least two failures of mobilization (without use of plerixafor). The present salvage therapy consisted in the administration of 10 µg/kg/day G‐CSF for 5 days added to a dose of plerixafor administered at between 5 a.m. and 6 a.m. on Day 5. The PB CD34+ cell counts were tested every 3 hours thereafter. Apheresis was initiated as soon as the PB CD34+ cell count reached 10 × 10⁶/L. RESULTS: A PB CD34+ cell count higher than 10 × 10⁶/L was observed as soon as 3 hours after plerixafor administration in 10 of the 11 patients who reached this threshold at some point in the monitoring process. Interestingly, all patients presented an early decrease in the PB CD34+ cell count 8 to 12 hours after plerixafor administration (below 10 × 10⁶/L for seven patients). CONCLUSION: Had such patients been tested for PB CD34+ cell mobilization according to conventional criteria (i.e., 11 hr after plerixafor administration), apheresis would not have been performed at the optimal timing. For very poor stem cell mobilizer patients, early monitoring of PB CD34+ cell count may be required for the optimal initiation of apheresis.     

Management of mobilization failure in 2017

In contemporary clinical practice, almost all allogeneic transplantations and autologous transplantations now capitalize on peripheral blood stem cells (PBSCs) as opposed to bone marrow (BM) for the source of stem cells. In this context, granulocyte colony-stimulating factor (G-CSF) plays a pivotal role as the most frequently applied frontline agent for stem cell mobilization. For patients classified as high-risk, chemotherapy based mobilization regimens can be preferred as a first choice and it is notable that this also used for remobilization. Mobilization failure occurs at a rate of 10%–40% with traditional strategies and it typically leads to low-efficiency practices, resource wastage, and delayed in treatment intervention. Notably, however, several factors can impact the effectiveness of CD34⁺ progenitor cell mobilization, including patient age and medical history (prior chemotherapy or radiotherapy, disease and marrow infiltration at the time of mobilization). In recent years, main (yet largely ineffective) approach was to increase G-CSF dose and add SCF, but novel and promising pathways have been opened up by the synergistic impact of a reversible inhibitor of CXCR4, plerixafor, with G-CSF. The literature shows to its favorable results in upfront and failed mobilizers, and it is necessary to use plerixafor (or equivalent agents) to optimize HSC harvest in poor mobilizers. Different CXCR4 inhibitors, growth hormone, VLA4 inhibitors, and parathormone, have been cited as new agents for mobilization failure in recent years. In view of the above considerations, the purpose of this paper is to examine the mobilization of PBSC while focusing specifically on poor mobilizers.     

The composition of leukapheresis products impacts on the hematopoietic recovery after autologous transplantation independently of the mobilization regimen

BACKGROUND: Effects of mobilization regimen on the composition of leukapheresis products (LPs) and on hematopoietic reconstitution after autologous peripheral blood progenitor cell transplantation (PBPCT) are not well known. STUDY DESIGN AND METHODS: The effects of three different mobilization regimens--stem cell factor (SCF) plus granulocyte colony stimulating factor (G-CSF) plus cyclophosphamide (CCP), G-CSF alone, and G-CSF plus CCP--on the composition of LPs from patients with nonhematologic PBPC malignancies compared to LPs from G-CSF-mobilized healthy donors and normal marrow (BM) samples were analyzed. The impact of LP composition on both short- and long-term engraftment after autologous PBPCT was also evaluated. RESULTS: The most effective regimen for mobilization of CD34+ hematopoietic progenitor cells (HPCs) into peripheral blood was SCF, G-CSF, and CCP, providing the highest numbers of all CD34+ HPCs subsets analyzed. Patients mobilized with SCF plus G-CSF plus CCP showed the highest numbers of neutrophils and monocytes, whereas the highest numbers of lymphocytes and NK cells were observed in LPs from G-CSF-mobilized patients. The overall number of CD34+ HPCs was the strongest factor for predicting recovery of platelets, whereas the number of myelomonocytic-committed CD34+ precursors was the most powerful independent prognostic factor for WBC and neutrophil recovery. The overall number of CD4+ T cells returned showed an independent prognostic value for predicting the occurrence of infections, during the first year after transplant. CONCLUSIONS: The use of different mobilization regimens modifies the overall number of CD34+ HPCs obtained during leukapheresis procedures, and also affects both the absolute and the relative composition of the LPs in different CD34+ and CD34- cell subsets.     

The collection and evaluation of peripheral blood progenitor cells sufficient for repetitive cycles of high-dose chemotherapy support

BACKGROUND: The development of an optimized peripheral blood progenitor cell (PBPC) harvest protocol to provide support for repetitive chemotherapy cycles is described. STUDY DESIGN AND METHODS: PBPCs mobilized by cyclophosphamide plus granulocyte-colony-stimulating factor (G-CSF) were studied in 163 leukapheresis harvests from 26 lymphoma patients. Harvested cells were transfused with two chemotherapy cycles and with an autologous bone marrow transplant. Progenitor cell content was examined in the context of hematopoietic engraftment. RESULTS: Mobilization allowed the harvest of large numbers of PBPCs. Peak harvests tended to occur after the recovering white cell count exceeded 10 × 10(9) per L. CD34+ lymphomononuclear cell (MNC) and colony-forming units-granulocyte-macrophage (CFU-GM) counts correlated poorly, but both measures peaked within 24 hours of each other in 21 of 26 patients, which demonstrated PBPC mobilization. Engraftment of platelets (> 50×10(9)/L) and granulocytes (> 500×10(6)/L) was achieved in a median of 20.5 and 16 days, respectively. A minimum number of progenitors necessary to ensure engraftment could be derived. CONCLUSION: Cyclophosphamide and G-CSF allowed the harvest of sufficient PBPCs to support multiple rounds of chemotherapy. Harvest should commence when the recovery white cell count exceeds 10×10(9) per L. PBPC harvest CD34+MNC counts are as useful as CFU-GM results in the assessment of PBPC content, and they may allow harvest protocols to be tailored to individual patients.     

Who should be really considered as a poor mobilizer in the plerixafor era?

Patients with a number of peripheral CD34+ cells ≥20/μL have recently been defined in the literature as "poor mobilizers". We retrospectively reviewed medical records from a total of 248 patients affected by hematological malignancies or solid tumors undergoing peripheral blood stem cell collection following chemotherapy plus G-CSF. On the basis of the CD34+ cell peak in peripheral blood following mobilization therapy, patients were defined as good mobilizers (group A, CD34+ cells ≥20/μL), relative poor mobilizers (group B, CD34+ cells <20 and ≥8/μL) and absolute poor mobilizers (group C, CD34+ cells <8/μL). One hundred and seventy-seven (71%) patients resulted good mobilizers, 35 (14%) patients relative poor mobilizers and 36 (15%) patients absolute poor mobilizers. Target of stem cell collection was ≥2.0×10(6) CD34+cells/kg for each transplantation procedure. All patients in group A, 20 patients in group B (57%) and 1 patient in group C (2.7%) were able to collect ≥2.0×10(6) CD34+cells/kg. The multivariate analysis confirmed that more than three lines of previous chemotherapy and a previous autologous PBSC transplantation negatively affect mobilization of CD34+ cells in peripheral blood. Our data suggest that a number of CD34+ cells ≥20/μL does not always result in a failed stem cell collection and in fact in our patient series more than 70% of the patients defined as poor mobilizers have indeed collected the minimum number of 2.0×10(6) CD34+cells/kg required for a successful transplantation. The use of new agent such as CXCR4 antagonist plerixafor might further improve mobilization efficacy in such patients.     

Addition of plerixafor to G-CSF in poor mobilizing healthy related donors overcame mobilization failure: An observational case series on behalf of the Grupo Español de Trasplante Hematopoyético (GETH)

Plerixafor (Mozobil, Sanofi) is approved for using in patients with lymphoma and multiple myeloma when steady-state mobilization strategies fail. Although off-label use of plerixafor in healthy related donors (HRD) is known, limited data are available and no recommendations exist to guide its use in this setting. With the aim of collecting data from HRDs who received plerixafor in our country, we designed an observational case series study within the Spanish Group of Hematopoietic Transplant and Cell Therapy (GETH). Plerixafor was administered subcutaneously to 30 HRDs at a median dose of 0.24 mg/Kg (interquartile range (IQR): 0.23?0.25) because mobilization failure after using mobilization with G-CSF (mobilization failure was defined as collection of <4.0 × 10⁶ CD34+ cells/Kg recipient). All HRDs received G-CSF at a median dose of 11 μg/Kg/day (IQR: 10–12) for 4–5 days. Leukocytapheresis after G-CSF mobilization was performed in 23 (77 %) HRDs collecting a median of 1.6 × 10⁶ CD34+ cells/Kg recipient weight (IQR: 0.9–2.5). Addition of plerixafor allowed the collection of a higher median number of CD34 cells (4.98 × 10⁶ CD34+ cells/Kg recipient weight (IQR: 3.5–5.8)) when compared with the collection of CD34+ cells with G-CSF alone (p < 0.01). The final median total number of CD34+ cells collected was 6.1 × 10⁶/Kg recipient weight (IQR: 4.8–7.3). Mild adverse events related with plerixafor administration were reported in 8 (27 %) donors. In conclusion, addition of plerixafor after G-CSF mobilization failure in HRDs allowed collecting higher number of CD34+ cells in comparison with steady-state mobilization.