Potentially modifiable predictors of cell collection efficiencies and product characteristics of allogeneic hematopoietic progenitor cell collections

Evaluation of blood cell count using an automatic hematology analyzer to optimize collection of peripheral blood progenitor cells by leukapheresis

BACKGROUND

Autologous stem cell transplantation is a treatment modality for several diseases. Prediction of successful mobilization may be useful to optimize hematopoietic stem cell collection.

STUDY DESIGN AND METHODS

This was a retrospective study with data from transplantation candidates between September 2015 and December 2021 being analyzed. The medical record of each patient was reviewed to mine mobilization information. The laboratory data analyzed were CD34+ cell enumeration and pre-collection peripheral blood cell count. The primary outcome, good mobilization, was defined as a CD34+ cell count ≥20/μL.

RESULTS

This study included 807 patients. Increased patient weight, low mean corpuscular volume, high nucleated red blood cells, peripheral blood mononuclear cell and immature granulocyte counts were significantly associated with good mobilization. In addition, patients diagnosed with multiple myeloma were two times more likely to be good mobilizers than patients with lymphoma. The model was applied to a validation set to identify patients who underwent apheresis (CD34+ cell count ≥10 µL), resulting in a sensitivity of 69 %, a specificity of 95 %, positive predictive value of 98 %, and a negative predictive value of 50 %.

CONCLUSION

Success in mobilization was greater in patients who underwent the first mobilization cycle and who had a diagnosis of multiple myeloma. Furthermore, higher body weight, and nucleated red blood cells, immature granulocytes and mononuclear cell counts, as well as low mean corpuscular volumes, were associated with successful mobilization.

Apheresis collection of mononuclear cells for chimeric-antigen receptor therapies

Collections of lymphocytes to be genetically modified to treat hematologic malignancies have seen a dramatic increase over the last few years as commercial products have been approved. Reports of new products in development that can possibly treat solid organ malignancies represent a massive change in the field. Apheresis is at the center of the collection of cells for the manufacture of these chimeric-antigen receptor therapy products. The expansion of these collections represents one of the areas of apheresis procedures growth. This review will summarize concepts important to this type of collection and variables that need to be optimized to obtain desired cell yields while increasing patients' safety.

Use of subgroup-specific hematopoietic stem cell collection efficiencies to improve truncation calculations for large-volume leukapheresis procedures

PURPOSE

A critical component of optimizing peripheral blood (PB) hematopoietic stem cell (HSC) collections is accurately determining the processed blood volume required to collect the targeted number of HSCs. Fundamental to most truncation equations employed to determine this volume is the procedure's estimated collection efficiency (CE), which is typically applied uniformly across all HSC collections. Few studies have explored the utility of using different CEs in subpopulations of donors that have substantially different CEs than the institutional average.

METHODS

Initial procedures from 343 autologous and 179 allogeneic HSC collections performed from 2018 to 2021 were retrospectively analyzed. Predictive equations were developed to determine theoretical truncation rates in various donor subgroups.

RESULTS

Quantitative variables (pre-procedure cell counts) and qualitative variables (relatedness to recipient, gender, method of venous access, and mobilization strategy) were found to significantly impact CE. However, much of the variability in CE between donors could not be explained by the variables assessed. Analyses of procedures with high pre-collection PB cell counts identified lower CE values for these donors' truncation equations which still allow truncation but minimize risk of collecting less CD34+ cells than requested.

CONCLUSIONS

Individualized CE does not substantially improve truncation volume calculations over use of a fixed CE and adds complexity to these calculations. The optimal fixed CE varies between autologous and allogeneic donors, and donors with high pre-collection PB cell counts in either of these groups. This model will be clinically validated and continuously refined through analysis of future HSC collections.

The effect of increased collect pump rate on collection efficiency in hematopoietic progenitor cell collection by apheresis in allogeneic adult donors-A single center analysis

BACKGROUND

Optimizing CD34 recovery while minimizing harm to hematopoietic progenitor cell donors by apheresis (HPC(A) donors) is critical to the success of allogeneic hematopoietic cell transplantation. We examined the efficacy and safety of starting allogeneic HPC(A) donors at a collect pump rate (CPR) of 2 mL/min on the Spectra Optia regardless of the inlet flow rate and/or pre-apheresis white blood cell (WBC) count (high CPR group).

STUDY DESIGN AND METHODS

A single-center retrospective study was performed on allogeneic adult donors from 10/2020 to 12/2022. From 10/2020 to 6/19/2022, all donors had CPR of ~1 mL/min (historical group). High CPR group started 6/20/2022.

RESULTS

During the study period, 412 donors were in historical group versus 196 (32.2%) in high CPR group. Median CD34 collection efficiency (CE) was higher and more consistent in high CPR group (55.1% vs. 53% in historical group, p < .0001) and remained significant in multivariate analysis. Although product volume was higher in high CPR group, WBC, hematocrit, and platelet concentrations were significantly lower. No difference in engraftment outcomes in patients receiving products from two groups was observed. Moreover, no differences occurred in a significant peri-procedural adverse event or percent decrease in platelets (6.87% decrease in platelets per 100 × 106 CD34 cells collected versus 6.66% in historical group, p = .89). Furthermore, high CPR group had ~26 min less in collection time for every 100 × 106 CD34 cells collected, resulting in less positive fluid balances.

CONCLUSIONS

Starting allogeneic HPC(A) donor collection at a CPR of 2 mL/min is safe and effective.

Paired Donor and Recipient Immunophenotyping in Allogeneic Hematopoietic Stem Cell Transplantation: A Cellular Network Approach

Success and complications of allogeneic hematopoietic stem cell transplantation (alloHSCT) are closely connected to the transferred graft and immune reconstitution post alloHSCT. Due to the variety of immune cells and their distinct roles, a broad evaluation of the immune cellular network is warranted in mobilization and reconstitution studies in alloHSCT. Here, we propose a comprehensive phenotypic analysis of 26 immune cell subsets with multicolor flow cytometry from only 100µl whole blood per time point. Using this approach, we provide an extensive longitudinal analysis of almost 200 time points from 21 donor-recipient pairs. We observe a broad mobilization of innate and adaptive immune cell subsets after granulocyte-colony stimulating factor (G-CSF) treatment of healthy donors. Our data suggest that the relative quantitative immune cell subset composition in recipients approaches that of healthy donors from day +180 post alloHSCT onwards. Correlation of donor and recipient cell counts reveals distinct association patterns for different immune cell subsets and hierarchical clustering of recipient cell counts identifies distinct reconstitution groups in the first month after transplantation. We suggest our comprehensive immune subset analysis as a feasible and time efficient approach for a broad immune assessment for future clinical studies in the context of alloHSCT. This comprehensive cell composition assessment can be a critical step towards personalized graft composition strategies and individualized therapy management in areas such as GvHD prophylaxis in the highly complex immunological setting of alloHSCT.

Process and procedural adjustments to improve CD34+ collection efficiency of hematopoietic progenitor cell collections in sickle cell disease

BACKGROUND

Adequate CD34+ collection efficiency (CE) is critical to achieve target CD34+ cell doses in hematopoietic progenitor cell (HPC) collections. Autologous HPC collection in sickle cell disease (SCD) is associated with unstable collection interfaces and low CD34+ CEs. We hypothesized that variables specific to SCD, activation of blood cells and elevated viscosity, might contribute to these issues and made adjustments to the collection process and procedure to address our hypothesis.

STUDY DESIGN AND METHODS

In two patients with SCD undergoing autologous HPC collection on our clinical trial (NCT02193191), we therefore implemented adjustments to the process and procedure in the following areas: proximity of RBC exchange to HPC collection, the type of anticoagulation, and the packing factor setting.

RESULTS

There was no collection interface instability. Our CD34+ CE1s were high at 70% and 51%, and granulocyte CE, platelet CE, and product granulocyte % were remarkably low. Product hematocrits were not as high as previously reported to be required to obtain adequate CEs. Interestingly, one HPC product showed a hemoglobin S (HbS) of 91% at the same time that the peripheral blood (PB) showed a HbS of 22%.

DISCUSSION

Adjustments to the HPC collection process and procedure were associated with adequate CD34+ CEs and low granulocyte and platelet contamination in HPC products from SCD patients. Given the discrepancy in the percentage of sickle RBCs in the product versus the PB, we hypothesize that CD34+ cells and RBCs may aggregate. Our interventions and hypothesis should be further investigated in larger studies.