Impact of plerixafor use in the mobilization of blood grafts for autologous hematopoietic cell transplantation

Plerixafor (PLER), a reversible antagonist of the CXC chemokine receptor type 4, has been in clinical use for mobilization of blood grafts for autologous hematopoietic cell transplantation (AHCT) for about 15 years. Initially PLER was investigated in placebo-controlled trials with the granulocyte colony-stimulating factor (G-CSF) filgrastim. It has also been used in combination with chemotherapy plus G-CSF in patients who had failed a previous mobilization attempt or appeared to mobilize poorly with current mobilization (preemptive use). This review summarizes what is known regarding addition of PLER to standard mobilization regimens. PLER increases mobilization of CD34+ cells, decreases the number of apheresis sessions needed to achieve collection targets and increases the proportion of patients who can proceed to AHCT. It appears also to increase the amount of various lymphocyte subsets in the grafts collected. In general, hematologic recovery after AHCT has been comparable to patients mobilized without PLER, although slower platelet recovery has been observed in some studies of patients who mobilize poorly. In phase III studies, long-term outcome has been comparable to patients mobilized without PLER. This also appears to be the case in patients receiving plerixafor for poor or suboptimal mobilization of CD34+ cells. In practice, PLER is safe and has not been shown to increase tumor cell mobilization.

Loss of CD34+ Cells and Effect of the Number of Viable Cryopreserved CD34+ Cells in the Infused Blood Grafts on Hematologic Recovery, Progression-Free Survival and Overall Survival in NHL Patients After Autologous Stem Cell Transplantation

PATIENTS

This post-hoc study aimed to find out factors affecting graft viable CD34+ cell loss during processing and cryopreservation in 129 non-Hodgkin lymphoma (NHL) patients receiving autologous stem cell transplantation (auto-SCT) and the impact of a low (< 2.0 × 106/kg, group A) and a decent number (≥ 2 × 106/kg, group B) of viable CD34+ cells infused on the hematologic recovery, progression-free survival (PFS) and overall survival (OS) after auto-SCT.

RESULTS

The median loss of viable CD34+ cells during cryopreservation was higher in group A (47% vs. 19%, p < .001). A higher yield of CD34+ cells at the first apheresis in group B (p = .002) was linked with greater loss of viable graft CD34+ cells after cryopreservation. Filgrastim (FIL) use for mobilization seemed to associate with higher viable CD34+ cell loss compared to pegfilgrastim (PEG) or lipegfilgrastim (LIPEG) in both groups (in group A FIL 66 vs. PEG 35%, p = .006; in group B FIL 37 vs. PEG 15 vs. LIPEG 13%, p < .001). Hematologic recovery after auto-SCT was faster in group B. Neither viable CD34+ cell loss during storage nor viable CD34+ cell number < 2.0 × 106/kg infused affected on PFS or OS.

CONCLUSIONS

G-CSF type used in mobilization and mobilization capacity were found to correlate with viable CD34+ cell loss during processing and storage. Most importantly, low infused viable CD34+ cell count did not seem to impact on PFS or OS.

Mobilization Strategies in Myeloma Patients Intended for Autologous Hematopoietic Cell Transplantation

Background

Multiple myeloma is currently the leading indication for autologous hematopoietic cell transplantation (AHCT). A prerequisite for AHCT is mobilization and collection of adequate blood graft to support high-dose therapy. Current mobilization strategies include granulocyte colony-stimulating factor (G-CSF) alone or in combination with chemotherapy most commonly cyclophosphamide (CY). More recently, plerixafor has become into agenda especially in patients who mobilize poorly. In the selection of a mobilization method, several factors should be considered.

Summary

Preplanned collection target is important as G-CSF plus plerixafor is more effective in the mobilization of CD34+ cells than G-CSF alone. On the other hand, CY plus G-CSF is superior to G-CSF only mobilization. Previous therapy and age of the patients are important considerations as G-CSF alone may not be effective enough in patients with risk factors for poor mobilization. These factors include extensive lenalidomide exposure, irradiation to bone marrow-bearing sites, higher age, or a previous mobilization failure. Also, local preferences and experiences as well as the number of apheresis needed are important issues as well as cost-effectiveness considerations. Mobilization method used may have implication for cellular composition of collected grafts, which might have an impact on posttransplant events such as hematologic and immune recovery in addition to also potential long-term outcomes.

Key Message

Currently, G-CSF alone and preemptive plerixafor if needed might be considered as a standard mobilization strategy in MM patients intended for AHCT.

CD34+ Cell Mobilization, Autograft Cellular Composition and Outcome in Mantle Cell Lymphoma Patients

Backgound

Autologous stem cell transplantation (ASCT) is a standard treatment in transplant-eligible mantle cell lymphoma (MCL) patients after first-line chemoimmunotherapy.

Study Design and Methods

This prospective multicenter study evaluated the impact of CD34+ cell mobilization and graft cellular composition analyzed by flow cytometry on hematologic recovery and outcome in 42 MCL patients.

Results

During CD34+ cell mobilization, a higher blood CD34+ cell count (>30 × 106/L) was associated with improved overall survival (median not reached [NR] vs. 57 months, p = 0.04). The use of plerixafor did not impact outcome. Higher number of viable cryopreserved graft CD34+ cells (>3.0 × 106/kg) was associated with faster platelet (median 11 vs. 15 days, p = 0.03) and neutrophil (median 9 vs. 10 days, p = 0.02) recovery posttransplant. Very low graft CD3+CD8+ cell count (≤10 × 106/kg) correlated with worse progression-free survival (PFS) (HR 4.136, 95% CI 1.547-11.059, p = 0.005). On the other hand, higher absolute lymphocyte count >2.5 × 109/L at 30 days after ASCT (ALC-30) was linked with better PFS (median NR vs. 99 months, p = 0.045) and overall survival (median NR in either group, p = 0.05).

Conclusions

Better mobilization capacity and higher graft CD3+CD8+ cell count had a positive prognostic impact in this study, in addition to earlier lymphocyte recovery (ALC-30>2.5 × 106/L). These results need to be validated in another study with a larger patient cohort.

Impact of the number of cryopreserved CD34+ cells in the infused blood grafts on hematologic recovery and survival in myeloma patients after autologous stem cell transplantation: Experience from the GOA study

BACKGROUND

Prospective data on the impact of CD34⁺ cell loss during cryopreservation and the amount of cryopreserved CD34⁺ cells infused after high-dose therapy on hematologic recovery and post-transplant outcome in multiple myeloma (MM) are scarce.

PATIENTS AND METHODS

This post-hoc study aimed to investigate factors associating with CD34⁺ cell loss during cryopreservation and the effects of the infusion of a very low number (<1.0 × 10⁶ /kg, group A), low number (1-1.9 × 10⁶ /kg, group B), and optimal number (≥2 × 10⁶ /kg, group C) of thawed viable CD34⁺ cells on hematologic recovery, progression free survival, and overall survival after autologous stem cell transplantation among 127 patients with MM.

RESULTS

In group C, pegfilgrastim use (P = 0.001), plerixafor use (P = 0.039), and older age ≥ 60 years (P = 0.026) were associated with less loss of CD34⁺ cells during cryopreservation. Better mobilization efficacy correlated with greater CD34⁺ cell loss in group B (P = 0.013 and P = 0.001) and in group C (P < 0.001 and P < 0.001). Early platelet engraftment was slowest in group A (20 d vs 12 d in group B vs 11 d in group C, P = 0.003). The infused viable CD34⁺ cell count <1.0 × 10⁶ /kg seemed not to have influence on PFS (P = 0.322) or OS (P = 0.378) in MM patients.

CONCLUSIONS

Cryopreservation impacts significantly on the CD34⁺ cell loss. A very low number of graft viable CD34⁺ cells did not affect PFS or OS.

Blood Graft and Outcome After Autologous Stem Cell Transplantation in Patients With Primary Central Nervous System Lymphoma

Background

Autologous stem cell transplantation (auto-SCT) is a treatment option for patients with primary central nervous system lymphoma (PCNSL).

Methods

In this prospective multicenter study, the effects of blood graft cellular content on hematologic recovery and outcome were analyzed in 17 PCNSL patients receiving auto-SCT upfront.

Results

The infused viable CD34⁺ cell count > 1.7 × 10⁶/kg correlated with more rapid platelet engraftment (10 vs. 31 days, P = 0.027) and with early neutrophil recovery (day + 15) (5.4 vs. 1.6 × 10⁹/L, P = 0.047). A higher number of total collected CD34⁺ cells > 3.3 × 10⁶/kg infused predicted worse 5-year progression-free survival (PFS) (33% vs. 100%, P = 0.028). In addition, CD3⁺CD8⁺ T cells > 78 × 10⁶/kg in the infused graft impacted negatively on the 5-year PFS (0% vs. 88%, P = 0.016).

Conclusion

The cellular composition of infused graft seems to impact on the hematologic recovery and PFS post-transplant. Further studies are needed to verify the optimal autograft cellular content in PCNSL.

Autograft cellular composition and outcome in myeloma patients: Results of the prospective multicenter GOA study

BACKGROUND

Autologous stem cell transplantation (auto-SCT) is a widely used treatment option in multiple myeloma (MM) patients. The optimal graft cellular composition is not known.

STUDY DESIGN AND METHODS

Autograft cellular composition was analyzed after freezing by flow cytometry in 127 MM patients participating in a prospective multicenter study. The impact of graft cellular composition on hematologic recovery and outcome after auto-SCT was evaluated.

RESULTS

A higher graft CD34⁺ cell content predicted faster platelet recovery after auto-SCT in both the short and long term. In patients with standard-risk cytogenetics, a higher graft CD34⁺ count (>2.5 × 10⁶ /kg) was linked with shorter progression-free survival (PFS; 28 vs. 46 months, p = 0.04), but there was no difference in overall survival (OS) (p = 0.53). In a multivariate model, a higher graft CD34⁺ CD133⁺ CD38^- (>0.065 × 10⁶ /kg, p = 0.009) and NK cell count (>2.5 × 10⁶ /kg, p = 0.026), lenalidomide maintenance and standard-risk cytogenetics predicted better PFS. In contrast, a higher CD34⁺ count (>2.5 × 10⁶ /kg, p = 0.015) predicted worse PFS. A very low CD3⁺ cell count (≤20 × 10⁶ /kg, p = 0.001) in the infused graft and high-risk cytogenetics remained predictive of worse OS.

CONCLUSIONS

Autograft cellular composition may impact outcome in MM patients after auto-SCT. More studies are needed to define optimal graft composition.

Mobilization characteristics, blood graft composition, and outcome in diffuse large B-cell lymphoma after autologous stem cell transplantation: Results from the prospective multicenter GOA study

BACKGROUND

Diffuse large B-cell lymphoma (DLBCL) is a common indication for autologous stem cell transplantation (auto-SCT).

STUDY DESIGN AND METHODS

This prospective noninterventional study aimed to evaluate the impact of mobilization characteristics and graft cellular content on hematologic recovery and outcome after auto-SCT among 68 patients with DLBCL.

RESULTS

Better mobilization capacity as manifested by blood CD34⁺ cell count >32 × 10⁶ /L and CD34⁺ cell yield of the first apheresis >2.75 × 10⁶ /kg correlated with faster neutrophil (P = .005 and P = .017) and platelet (P = .002 and P < .001) recovery. A higher number of infused CD34⁺ cells (> 2.65 × 10⁶ /kg) was associated with better 5-year overall survival (OS; 95% vs 67%, P = .012). The graft CD34⁺ CD133⁺ CD38^- cell count >0.07 × 10⁶ /kg was predictive of better 5-year OS (87% vs 63%; P = .008) and higher graft CD3⁺ cell count (>23.1 × 10⁶ /kg) correlated also with better 5-year OS (80% vs 40%, P = .008). In multivariate analysis only disease status of CR I at auto-SCT was associated with better progression-free survival (P = .014) and OS (P = .039).

CONCLUSION

The mobilization capacity of CD34⁺ cells impacted on early hematologic recovery in patients with DLBCL after auto-SCT. Higher graft CD34⁺ cell count and both CD34⁺ CD133⁺ CD38^- and CD3⁺ cells were also associated with better OS. The effect of optimal graft cellular composition on outcome in DLBCL should be evaluated in a randomized study.

CD34+ cell mobilization, blood graft composition, and posttransplant recovery in myeloma patients compared to non-Hodgkin's lymphoma patients: results of the prospective multicenter GOA study

BACKGROUND

Autologous stem cell transplantation is an established treatment option for patients with multiple myeloma (MM) or non-Hodgkin's lymphoma (NHL).

STUDY DESIGN AND METHODS

In this prospective multicenter study, 147 patients with MM were compared with 136 patients with NHL regarding the mobilization and apheresis of blood CD34+ cells, cellular composition of infused blood grafts, posttransplant recovery, and outcome.

RESULTS

Multiple myeloma patients mobilized CD34+ cells more effectively (6.3 × 10⁶ /kg vs. 3.9 × 10⁶ /kg, p = 0.001). The proportion of poor mobilizers (peak blood CD34+ cell count <20 × 10⁶ /L) was higher in NHL patients (15% vs. 3%, p < 0.001). Plerixafor was added to rescue the mobilization failure in 17 MM patients (12%) and in 35 NHL patients (26%; p = 0.002). The infused grafts contained more natural killer (NK) and CD19+ cells in MM patients. Blood platelet and NK-cell counts were higher in MM patients posttransplant. Early treatment-related mortality was low in both groups, but NHL patients had a higher late (>100 days) nonrelapse mortality (NRM; 6% vs. 0%, p = 0.003).

CONCLUSIONS

Non-Hodgkin's lymphoma and MM patients differ in terms of mobilization of CD34+ cells, graft cellular composition, and posttransplant recovery. Thus, the optimal graft characteristics may also be different.

Importance of early immune recovery after autologous hematopoietic cell transplantation in lymphoma patients

Lymphomas constitute the second most common indication for autologous hematopoietic cell transplantation (AHCT). Graft infusion is followed by a rapid hematological recovery and slower immune recovery. The number of natural killer cells and CD3⁺ T lymphocytes achieve normal counts usually within a month, whereas the recovery of CD3⁺CD4⁺ T lymphocytes is much slower. Early immune recovery is usually defined as the absolute lymphocyte count (ALC) ≥0.5 × 10⁹/L, which has been associated with improved progression-free and even overall survival. Several factors have been associated with early immune recovery, including higher infused lymphocyte and CD34⁺ cell doses, both of which are affected by the choice of mobilization. This review summarizes the clinical importance of early immune recovery for long-term success of AHCT in lymphomas. Factors known to affect early immune recovery are discussed and suggestions made how to improve mobilization and collection processes to optimize immune recovery and post-transplant outcomes.

Comparison of filgrastim, pegfilgrastim, and lipegfilgrastim added to chemotherapy for mobilization of CD34+ cells in non-Hodgkin lymphoma patients

BACKGROUND

Data are limited on the long-acting granulocyte-colony stimulating factors (G-CSFs) pegfilgrastim (PEG) and lipegfilgrastim (LIPEG) compared with filgrastim (FIL) regarding the mobilization efficiency of CD34⁺ cells, graft cellular composition, and engraftment.

STUDY DESIGN AND METHODS

In this prospective nonrandomized study, 36 patients with non-Hodgkin lymphoma received FIL, 67 received PEG, and 16 patients received LIPEG as a cytokine after chemotherapy. We analyzed the mobilization and collection of CD34⁺ cells, cellular composition of blood grafts, and hematologic recovery after auto-SCT according to the type of G-CSF used.

RESULTS

Patients in the LIPEG group had fewer apheresis sessions (1 vs. 2, p = 0.021 for FIL and p = 0.111 for PEG) as well as higher median blood CD34⁺ cell counts at the start of the first apheresis (LIPEG 74 × 10⁶ /L vs. FIL 31 × 10⁶ /L, p = 0.084 or PEG 27 × 10⁶ /L, p = 0.021) and CD34⁺ yields of the first apheresis (FIL 5.1 × 10⁶ /kg vs. FIL 2.3 × 10⁶ /kg, p = 0.105 or PEG 1.8 × 10⁶ /kg, p = 0.012). Also, the costs associated with G-CSF mobilization and apheresis were lower in the LIPEG group. The graft composition was comparable except for the higher infused CD34⁺ cell counts in the LIPEG group. The engraftment kinetics were significantly slower in the FIL group.

CONCLUSION

LIPEG appears to be more efficient compared with PEG after chemotherapy to mobilize CD34⁺ cells for auto-SCT demonstrated as fewer sessions of aphereses needed as well as 2.8-fold CD34⁺ cell yields on the first apheresis day. Early hematologic recovery was more rapid in the LIPEG group. Thus further studies on LIPEG in the mobilization setting are warranted.

Blood graft composition and post-transplant recovery in myeloma patients mobilized with plerixafor: a prospective multicenter study

The composition of autologous blood grafts after cryopreservation, post-transplant hematological recovery up to 1 year and immune recovery up to 6 months as well as outcome was analyzed in 87 patients with multiple myeloma (MM). The patients receiving added plerixafor due to poor mobilization (11%) were compared to those mobilized with G-CSF or cyclophosphamide (CY) plus G-CSF. The use of plerixafor was found to significantly affect the graft composition as there was a significantly higher proportion of the more primitive CD34⁺ cells, higher number of T and B lymphocytes as well as NK cells in the grafts of patients who received also plerixafor. The hematological recovery after auto-SCT was comparable between the groups. The recovery of CD3⁺CD4⁺ T cells was faster in plerixafor mobilized patients at 1 and 3 months post-transplant. There were no significant differences in progression-free (PFS) or overall survival (OS) according to the plerixafor use.

Preemptive plerixafor injection added to pegfilgrastim after chemotherapy in non-Hodgkin lymphoma patients mobilizing poorly

Filgrastim is usually combined with chemotherapy to mobilize hematopoietic progenitor cells in non-Hodgkin lymphoma (NHL) patients. Limited information is available on the efficacy of a preemptive plerixafor (PLER) injection in poor mobilizers after chemotherapy and pegfilgrastim. In this prospective study, 72 patients with NHL received chemotherapy plus pegfilgrastim, and 25 hard-to-mobilize patients received also PLER. The usefulness and efficacy of our previously developed algorithm for PLER use in pegfilgrastim-containing mobilization regimen were evaluated as well as the graft cellular composition, hematological recovery, and outcome after autologous stem cell transplantation (auto-SCT) according to the PLER use. A median 3.4-fold increase in blood CD34⁺ cell counts was achieved after the first PLER dose. The minimum collection target was achieved in the first mobilization attempt in 66/72 patients (92%) and 68 patients (94%) proceeded to auto-SCT. An algorithm for PLER use was fulfilled in 76% of the poor mobilizers. Absolute numbers of T-lymphocytes and NK cells were significantly higher in the PLER group, whereas the number of CD34⁺ cells collected was significantly lower. Early neutrophil engraftment was slower in the PLER group, otherwise hematological recovery was comparable within 12 months from auto-SCT. No difference was observed in survival according to the PLER use. Chemotherapy plus pegfilgrastim combined with preemptive PLER injection is an effective and convenient approach to minimize collection failures in NHL patients intended for auto-SCT. A significant effect of PLER on the graft cellular composition was observed, but no difference in outcome after auto-SCT was detected.

Impact of lenalidomide-based induction therapy on the mobilization of CD34+ cells, blood graft cellular composition, and post-transplant recovery in myeloma patients: a prospective multicenter study

BACKGROUND

Lenalidomide is an immunomodulatory drug that is also currently used in transplant-eligible patients with multiple myeloma. Previous studies have suggested a negative impact of lenalidomide on the mobilization of CD34⁺ cells. No data are available regarding the more detailed composition of blood grafts after lenalidomide.

STUDY DESIGN AND METHODS

In a multicenter, prospective study, we analyzed the mobilization of CD34⁺ cells, graft cellular composition, and post-transplant hematologic recovery in 26 patients with multiple myeloma after lenalidomide-based induction and in 34 lenalidomide-naive controls with multiple myeloma. All patients were mobilized with low-dose cyclophosphamide plus granulocyte-colony-stimulating factor. The cellular composition of the grafts was analyzed from thawed, cryopreserved samples with flow cytometry. Graft function was evaluated by engraftment data and by complete blood counts until 12 months after the graft infusion.

RESULTS

Patients in the lenalidomide arm had lower median peak CD34⁺ counts and approximately 40% lower CD34⁺ cell yields from the first apheresis session, but these differences were not significant. The median total number of CD34⁺ cells collected was comparable (6.4 vs. 7.5 × 10⁶ /kg). The number of apheresis sessions was higher in the lenalidomide group (2 vs. 1; p = 0.039). The blood graft composition was comparable between the groups. Hematologic recovery within 12 months post-transplant did not differ between the groups.

CONCLUSION

Lenalidomide-based induction seems to have an impact on the number of aphereses performed, but not on the total yields of the CD34⁺ cells in the graft. Neither cellular composition of the grafts nor post-transplant recovery was affected by the limited pre-transplant exposure to lenalidomide.

Blood graft cellular composition and posttransplant outcomes in myeloma patients mobilized with or without low-dose cyclophosphamide: a randomized comparison

BACKGROUND

Autologous stem cell transplantation is a standard treatment in multiple myeloma (MM). Blood grafts are usually collected after mobilization with granulocyte-colony-stimulating factor (G-CSF) alone or in a combination with cyclophosphamide (CY). There is limited knowledge of the possible effects of different mobilization regimens on blood graft characteristics and posttransplant outcomes.

STUDY DESIGN AND METHODS

Thirty-eight patients with MM were included in this study. The patients were randomly assigned at registration to mobilization with either low-dose CY plus G-CSF (Arm A) or G-CSF alone (Arm B) and received three cycles of lenalidomide, bortetzomib, and dexamethasone induction. Flow cytometry analysis of lymphocyte subsets in the blood grafts after cryopreservation was performed. Hematologic and immune recovery were evaluated up to 12 months posttransplant.

RESULTS

The blood grafts in Arm A contained significantly more CD34+ cells but in Arm B there was a greater proportion of CD34+CD38- cells and higher numbers of T and B lymphocytes as well as natural killer (NK) cells. The engraftment was comparable but lymphocyte count at 15 days posttransplant was higher in Arm B (0.8 × 10(9) /L vs. 0.5 × 10(9) /L, p = 0.033). At 3 and 6 months posttransplant the total number of NK cells was also higher in G-CSF-mobilized patients. There was no difference in progression-free survival between the study arms.

CONCLUSION

CY plus G-GSF yields more CD34+ cells but seems to diminish lymphocyte and NK cell counts in the grafts and hampers immune recovery after transplantation. Thus G-CSF alone might be a preferred mobilization method due to more rapid immune recovery posttransplant.

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.

CD34+ cell subclasses and lymphocyte subsets in blood grafts collected after various mobilization methods in myeloma patients

BACKGROUND

Cyclophosphamide (CY) combined with granulocyte-colony-stimulating factor (G-CSF) is commonly used to mobilize stem cells in multiple myeloma (MM). Plerixafor may also be used with G-CSF in patients who mobilize poorly or it may be added to chemomobilization to boost mobilization. Limited data are available on graft content collected after various mobilization methods.

STUDY DESIGN AND METHODS

Blood grafts collected from 21 MM patients were retrospectively analyzed. We analyzed CD34+ subclasses and lymphocyte subsets from cryopreserved grafts collected on the next morning after plerixafor injection in nine MM patients mobilized with G-CSF with (n = 5) or without preceding CY (n = 4). As controls we had the first collections from 12 MM patients mobilized with low-dose CY with G-CSF.

RESULTS

The proportion of the most primitive stem cells (CD34+CD133+CD38-) from all CD34+ cells in the graft was higher in the plerixafor-treated patients but there was no significant difference in the total number of these cells. The numbers of CD19+ B lymphocytes and natural killer cells were higher in patients collected after G-CSF plus plerixafor when compared to the patients mobilized with CY plus G-CSF. Early engraftment after high-dose melphalan was comparable between the groups.

CONCLUSION

Plerixafor appears to have effects on blood stem cell graft composition in myeloma patients. A higher number of grafts should be evaluated in regard to cellular content and longer follow-up of the patients is needed to evaluate the potential clinical impact of graft content.

Kinetics of blood CD34(+) cells after chemotherapy plus G-CSF in poor mobilizers: implications for pre-emptive plerixafor use

Mobilization and collection of stem cells is difficult in a proportion of patients intended for autologous stem cell transplantation (ASCT). We have evaluated mobilization kinetics of blood CD34(+) cells (B-CD34(+)) to form basis for algorithm to facilitate rational pre-emptive plerixafor use. Altogether 390 chemomobilized patients were included.Forty-three patients (11%) did not reach BCD34+count ≥10×10(6)/l. Mobilization kinetics differed according to the mobilization capacity observed. Among those who were very poor or inadequate mobilizers (peak BCD34(+)count ≤5×10(6)/l and 6–10×10(6)/l, respectively), BCD34+counts rarely rose after white blood cells (WBC) >5–10×10(9)/l, whereas in many standard mobilizers a later rise in CD34(+) counts could be observed. Four algorithms based on WBC and CD34(+) counts were constructed. According to this patient series, algorithm II (WBC >5×109/l and BCD34+≤10×10(6)/l) and algorithm IV (WBC >10×10(9)/l andB-CD34(+) ≤10×10(9)/l) were the most applicable. For algorithm II the sensitivity was 0.97 and specificity 1.00, respectively, to identify patients for plerixafor use provided that all patients with B-CD34+ maximum ≤10×10(6)/l would have needed plerixafor.This simple model needs a prospective validation.

Blood graft composition after plerixafor injection in patients with NHL

BACKGROUND

Plerixafor is used to mobilize CD34(+) hematopoietic stem cells from bone marrow to circulation. Limited data are available in regard to graft cellular content collected after plerixafor.

OBJECTIVES

The aim of this study was to assess effects of plerixafor added to chemomobilization on graft CD34(+) cell subclasses, lymphocyte subsets, engraftment, and post-transplant course in non-Hodgkin lymphoma (NHL) patients.

METHODS

Thirty-four patients with NHL were included. All patients received chemotherapy plus G-CSF to mobilize stem cells. Nineteen patients received plerixafor pre-emptively owing to poor mobilization or poor collection yields. The rest of the patients constituted the control group. Flow cytometric analyzes were performed from cryopreserved graft samples. Also, data on post-transplant engraftment and outcome were collected.

RESULTS

The proportion of primitive stem cells (CD34(+)  CD133(+)  CD38(-) ) was significantly higher after the plerixafor injection when compared to the first collection in the control group. The amount of T cells (CD3(+) ), helper (CD3(+)  CD4(+) ) T subsets, and suppressor (CD3(+)  CD8(+) ) T subsets in the graft was all significantly higher in the plerixafor group. Also, the amount of NK cells (CD3(-)  CD16/56(+) ) was higher. Engraftment after high-dose therapy was comparable between the groups, but leukocyte and platelet count at 6 months were higher in patients receiving plerixafor-mobilized grafts.

CONCLUSION

Plerixafor, when used pre-emptively in addition to chemomobilization, seems to mobilize more primitive CD34(+) stem cells, T lymphocytes, and NK cells. Whether these differences are associated with immune reconstitution, long-term engraftment, or patient outcomes needs to be evaluated in larger patient groups with longer follow-up.