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

Retrospective comparison between COBE SPECTRA and SPECTRA OPTIA apheresis systems for hematopoietic progenitor cells collection for autologous and allogeneic transplantation in a single center

INTRODUCTION

COBE SPECTRA [COBE] (Terumo, BCT Lakewood CO) apheresis system has been the most used device for hematopoietic progenitor cells (HPC) collection. Recently, it has been replaced by the SPECTRA OPTIA [OPTIA] (Terumo, BCT Lakewood CO) apheresis system. The aim of our study is to compare both methods for HPC collection.

MATERIAL AND METHODS

We retrospectively compared 302 HPC collection apheresis procedures (115 allogeneic donors and 187 autologous). The study cohort was divided according to the apheresis system used to analyze the differences between COBE and OPTIA, specifically efficacy of apheresis procedure and product characteristics.

RESULTS

OPTIA collections result in a higher CD34⁺ collection efficiency in both groups (autologous 45.3% vs 41%, P < .006; allogeneic 54.9% vs 45%, P < .0001). The total of CD34⁺ cells ×10⁶ /kg recipient collected in the product were comparable in both groups (autologous 2.9 in OPTIA group vs 2.8 in COBE group, P = .344; allogeneic 6.2 in OPTIA group vs 5.8 in COBE group, P = .186). The percentage of platelet loss in autologous donors was significantly lower (35.7% vs 40.8%, P < .01). Regarding quality of the product, we observed a significantly lower hematocrit in products collected with OPTIA in both groups (1.8% vs 4%, P < .0001) as well as significantly lower amount of leukocytes (median 153.4 vs 237.2 × 10⁹ /L in autologous, P < .0001; 239.5 vs 340.2 × 10⁹ /L in allogeneic P < .0001).

CONCLUSION

Both apheresis systems are comparable in collection of hematopoietic progenitor cells, with significantly higher collection efficiency with the OPTIA system. Collection products obtained with OPTIA contain significantly lower hematocrit and leukocytes.

Autologous Stem Cell Mobilization and Collection

Peripheral blood stem cell collection is an effective approach to obtain a hematopoietic graft for stem cell transplantation. Developing hematopoietic stem/progenitor cell (HSPC) mobilization methods and collection algorithms have improved efficiency, clinical outcomes, and cost effectiveness. Differences in mobilization mechanisms may change the HSPC content harvested and result in different engraftment kinetics and complications. Patient-specific factors can affect mobilization. Incorporating these factors in collection algorithms and improving assays for evaluating mobilization further extend the ability to obtain sufficient HSPCs for hematopoietic repopulation. Technological advance and innovations in leukapheresis have improved collection efficiency and reduced adverse effects.

Mobilization of hematopoietic progenitor cells for autologous transportation: consensus recommendations

Selected patients with certain hematological malignancies and solid tumors have the potential to achieve long-term survival with autologous hematopoietic progenitor cell transplant. The collection of these cells in peripheral blood avoids multiple bone marrow aspirations, results in faster engraftment and allows treatment of patients with infection, fibrosis, or bone marrow hypocellularity. However, for the procedure to be successful, it is essential to mobilize a sufficient number of progenitor cells from the bone marrow into the blood circulation. Therefore, a group of Brazilian experts met in order to develop recommendations for mobilization strategies adapted to the reality of the Brazilian national health system, which could help minimize the risk of failure, reduce toxicity and improve the allocation of financial resources.

Panobinostat for the treatment of acute myelogenous leukemia

INTRODUCTION

Therapeutic strategies in patients with acute myeloid leukemia (AML) have not changed significantly over the last decades. Appropriate strategies are ultimately driven by the assessment of patients' fitness to define suitability for intensive induction chemotherapy, which produces high initial remission rates but, increased likelihood of relapse. Old/unfit AML patients still represent an urgent and unmet therapeutic need. Epigenetic deregulation represents a strategic characteristic of AML pathophysiology whereby aberrant gene transcription provides an advantage to leukemic cell survival. Efforts to re-establish impaired epigenetic regulation include hypomethylating agents and histone deacetylase inhibitors (HDACi).

AREAS COVERED

The review discusses the underlying mechanisms leading to disruption of lysine acetyltransferases (KAT or HAT)/deacetylase (KDAC or HDAC) balance and the rationale for using the HDACi panobinostat (LBH-589) in AML.

EXPERT OPINION

Although panobinostat has produced significant results in myeloma, its efficacy remains limited in AML. Panobinostat exerts pleiotropic activity and lack of specificity, which likely contributes to its inadequate safety in elderly AML patients. Phase I-II trials, utilizing panobinostat associated with well-known chemotherapeutic agents are ongoing and combinations with other druggable targets may likely be evaluated in future trials. The clinical use of this HDACi in AML the near future does not appearing promising.

Autologous Stem Cell Mobilization in the Age of Plerixafor

BACKGROUND

Autologous stem cell transplantation remains important in the treatment of myeloma and relapsed lymphoma. Plerixafor has been shown to significantly enhance stem cell mobilization but is very expensive.

PATIENTS AND METHODS

We evaluated plerixafor use in the 3-year period after its approval in December 2008.

RESULTS

A total of 277 patients with myeloma and lymphoma had stem cell mobilization; 97.5% were successfully mobilized, including 41.5% who received plerixafor. Plerixafor was generally used for rescue after suboptimal granulocyte-colony stimulating factor (G-CSF) mobilization ("just in time") or for remobilization after an unsuccessful attempt with chemotherapy plus G-CSF. In addition, 10% of patients received planned G-CSF plus plerixafor because of high risk factors for inadequate collection. Rescue plerixafor was more effective in patients with myeloma than lymphoma as after 1 dose of plerixafor; 85% versus 55% collected a minimum number of stem cells (2 × 10E6 CD34 cells/kg) for 1 transplant and 51% versus 15% collected > 5 × 10E6 CD34 cells/kg. After transplantation, there were no significant differences in engraftment as a consequence of plerixafor use. Among all patients, there were less platelet transfusions in patients provided ≥ 3.5 × 10E6 CD34(+) cells/kg.

CONCLUSION

With the judicious use of plerixafor, nearly all patients can collect enough stem cells to proceed to transplantation. Further studies, including hematologic tolerance to posttransplantation therapy, are required to determine the cost-effectiveness of using plerixafor to convert adequate to more optimal mobilizers.

BMP2 Regulation of CXCL12 Cellular, Temporal, and Spatial Expression is Essential During Fracture Repair

The cellular and humoral responses that orchestrate fracture healing are still elusive. Here we report that bone morphogenic protein 2 (BMP2)-dependent fracture healing occurs through a tight control of chemokine C-X-C motif-ligand-12 (CXCL12) cellular, spatial, and temporal expression. We found that the fracture repair process elicited an early site-specific response of CXCL12(+)-BMP2(+) endosteal cells and osteocytes that was not present in unfractured bones and gradually decreased as healing progressed. Absence of a full complement of BMP2 in mesenchyme osteoprogenitors (BMP2(cKO/+)) prevented healing and led to a dysregulated temporal and cellular upregulation of CXCL12 expression associated with a deranged angiogenic response. Healing was rescued when BMP2(cKO/+) mice were systemically treated with AMD3100, an antagonist of CXCR4 and agonist for CXCR7 both receptors for CXCL12. We further found that mesenchymal stromal cells (MSCs), capable of delivering BMP2 at the endosteal site, restored fracture healing when transplanted into BMP2(cKO/+) mice by rectifying the CXCL12 expression pattern. Our in vitro studies showed that in isolated endosteal cells, BMP2, while inducing osteoblastic differentiation, stimulated expression of pericyte markers that was coupled with a decrease in CXCL12. Furthermore, in isolated BMP2(cKO/cKO) endosteal cells, high expression levels of CXCL12 inhibited osteoblastic differentiation that was restored by AMD3100 treatment or coculture with BMP2-expressing MSCs that led to an upregulation of pericyte markers while decreasing platelet endothelial cell adhesion molecule (PECAM). Taken together, our studies show that following fracture, a CXCL12(+)-BMP2(+) perivascular cell population is recruited along the endosteum, then a timely increase of BMP2 leads to downregulation of CXCL12 that is essential to determine the fate of the CXCL12(+)-BMP2(+) to osteogenesis while departing their supportive role to angiogenesis. Our findings have far-reaching implications for understanding mechanisms regulating the selective recruitment of distinct cells into the repairing niches and the development of novel pharmacological (by targeting BMP2/CXCL12) and cellular (MSCs, endosteal cells) interventions to promote fracture healing.

The hematopoietic system in the context of regenerative medicine

Hematopoietic stem cells (HSC) represent the prototype stem cell within the body. Since their discovery, HSC have been the focus of intensive research, and have proven invaluable clinically to restore hematopoiesis following inadvertent radiation exposure and following radio/chemotherapy to eliminate hematologic tumors. While they were originally discovered in the bone marrow, HSC can also be isolated from umbilical cord blood and can be "mobilized" peripheral blood, making them readily available in relatively large quantities. While their ability to repopulate the entire hematopoietic system would already guarantee HSC a valuable place in regenerative medicine, the finding that hematopoietic chimerism can induce immunological tolerance to solid organs and correct autoimmune diseases has dramatically broadened their clinical utility. The demonstration that these cells, through a variety of mechanisms, can also promote repair/regeneration of non-hematopoietic tissues as diverse as liver, heart, and brain has further increased their clinical value. The goal of this review is to provide the reader with a brief glimpse into the remarkable potential HSC possess, and to highlight their tremendous value as therapeutics in regenerative medicine.

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.