Evaluation of mobilization efficacy with an extended interval following plerixafor administration.

Plerixafor is a hematopoietic stem cell mobilizing agent used in combination with granulocyte-colony stimulating factor to improve collection for autologous stem cell transplantation. Despite a recommendation for administration 11 h prior to apheresis per package labeling, logistical challenges lead many institutions to administer plerixafor at an extended interval. The purpose of this study was to determine if plerixafor effectively and efficiently mobilizes CD34+ cells when given at an extended interval prior to apheresis. This was a retrospective evaluation of adult patients who received plerixafor based on an algorithm reserving daily plerixafor only for patients with a pre-apheresis CD34+ count of < 20 cells/µL (pre-apheresis plerixafor) or with a low CD34+ yield after the first apheresis session (rescue plerixafor). The primary outcome was achievement of a disease-specific collection goal of ≥ 6 ×106 CD34+ cells/kg for multiple myeloma and ≥ 4 ×106 CD34+ cells/kg for lymphoma. The mean interval between plerixafor administration and apheresis was 17 h in this study. Despite this extended interval, 64% of patients met their disease-specific collection goal. A minimum collection goal of ≥ 2 ×106 CD34+ cells/kg was achieved by 95% of patients. Mobilization remained efficient with a median of two days to complete collection. Based on this data, plerixafor effectively and efficiently mobilizes CD34+ cells when given at an extended interval prior to apheresis.

Evaluation of a Test Dose Strategy for Pharmacokinetically-Guided Busulfan Dosing for Hematopoietic Stem Cell Transplantation.

Targeted busulfan dosing helps limit chemotherapy-related toxicity and optimize disease outcomes in hematopoietic stem cell transplantation (HCT). The objective of this study was to evaluate busulfan exposure from a pharmacokinetic (PK)-guided dosing strategy using a test dose. This retrospective evaluation included adult patients who underwent HCT at our institution with busulfan-based myeloablative (>9 mg/kg) conditioning between January 2014 and October 2015. A weight-based test dose of 0.8 mg/kg was used with PK assessments to predict area under the curve (AUCpred) achieved with weight-based dosing, with a target AUC of 4800 µM*minute (AUCtarget). PK from the test dose was then used to calculate a PK-guided first myeloablative busulfan dose. PK assessments were also done after the first dose to assess if the goal area under the curve (AUC) had been achieved (AUCfirst). A PK-guided first dose resulted in achievement of target AUC with target ranges of ±10% in 50% of patients, ±15% in 75%, and ±20% in 94%. This was an improved rate of target achievement compared with the 33%, 44%, and 63% of patients who achieved the desired AUC for these respective target ranges when using weight-based dosing (P = .12, .004, and <.001, respectively). The PK-guided strategy also decreased the variability of AUC from 3.6-fold in AUCpred from the weight-based test doses (2700.8 to 9631 µM*minute; SD, 1211.6 µM*minute) to 1.8-fold in AUCfirst from the PK-guided first doses (3672.1 to 6609.8 µM*minute; SD, 574.7 µM*minute). This reflects a 2-fold improvement in AUC variability with a PK-guided dosing strategy. This is also improved from the 3-fold variability in AUC reported in other studies. Weight and body surface area were significantly associated with the likelihood of AUCfirst being within the ±10% target range (P = .04 for both associations). There was no significant association between AUCfirst and death, relapse, or a composite of the two. These results demonstrate a significant improvement in target AUC attainment and less interpatient variability with PK-guided dosing using a test dose strategy compared with weight-based dosing.

Increased BCR responsiveness in B cells from patients with chronic GVHD.

Although B cells have emerged as important contributors to chronic graft-versus-host-disease (cGVHD) pathogenesis, the mechanisms responsible for their sustained activation remain unknown. We previously showed that patients with cGVHD have significantly increased B cell-activating factor (BAFF) levels and that their B cells are activated and resistant to apoptosis. Exogenous BAFF confers a state of immediate responsiveness to antigen stimulation in normal murine B cells. To address this in cGVHD, we studied B-cell receptor (BCR) responsiveness in 48 patients who were >1 year out from allogeneic hematopoietic stem cell transplantation (HSCT). We found that B cells from cGVHD patients had significantly increased proliferative responses to BCR stimulation along with elevated basal levels of the proximal BCR signaling components B cell linker protein (BLNK) and Syk. After initiation of BCR signaling, cGVHD B cells exhibited increased BLNK and Syk phosphorylation compared with B cells from patients without cGVHD. Blocking Syk kinase activity prevented relative post-HSCT BCR hyper-responsiveness of cGVHD B cells. These data suggest that a lowered BCR signaling threshold in cGVHD associates with increased B-cell proliferation and activation in response to antigen. We reveal a mechanism underpinning aberrant B-cell activation in cGVHD and suggest that therapeutic inhibition of the involved kinases may benefit these patients.

B cells from patients with chronic GVHD are activated and primed for survival via BAFF-mediated pathways.

Recent data reveal an important role for B cells in the pathogenesis of chronic GVHD (cGVHD). Patients with cGVHD have delayed B-cell reconstitution and elevated BAFF to B-cell ratios compared to patients without cGVHD. The mechanisms promoting and sustaining B-cell activation in this disease, however, remain unknown. As BAFF increases murine B-cell metabolism and survival and maintains autoreactive B-cell clones, we performed ex vivo analyses of peripheral B cells from 51 patients who either had or did not have active cGVHD and were greater than 1 year from the time of allogeneic hematopoietic stem cell transplantation. We found that B cells from patients with active cGVHD were in a heightened metabolic state and were resistant to apoptosis. Exogenous BAFF treatment amplified cell size and survival in B cells from these patients. We found significantly increased signaling through ERK and AKT that associated with decreased levels of proapoptotic Bim, suggesting a mechanistic link between elevated BAFF levels and aberrant B-cell survival. Thus, we identify a role for BAFF in the pathogenesis of cGVHD and define B-cell activation and survival pathways suitable for novel therapeutic development in cGVHD.

Bone marrow B cell precursor number after allogeneic stem cell transplantation and GVHD development.

Patients without chronic graft-versus-host disease (cGVHD) have robust B cell reconstitution and are able to maintain B cell homeostasis after allogeneic hematopoietic stem cell transplantation (HSCT). To determine whether B lymphopoiesis differs before cGVHD develops, we examined bone marrow (BM) biopsies for terminal deoxynucleotidyl transferase (TdT) and PAX5 immunostaining early post-HSCT at day 30 when all patients have been shown to have high B cell activating factor (BAFF) levels. We found significantly greater numbers of BM B cell precursors in patients who did not develop cGVHD compared with those who developed cGVHD (median = 44 vs 2 cells/high powered field [hpf]; respectively; P < .001). Importantly, a significant increase in precursor B cells was maintained when patients receiving high-dose steroid therapy were excluded (median = 49 vs 20 cells/hpf; P = .017). Thus, we demonstrate the association of BM B cell production capacity in human GVHD development. Increased BM precursor B cell number may serve to predict good clinical outcome after HSCT.

Usefulness of the hematopoietic cell transplantation-specific comorbidity index (HCT-CI) in predicting outcomes for adolescents and young adults with hematologic malignancies undergoing allogeneic stem cell transplant.

BACKGROUND: The HCT-CI helps to predict non-relapse mortality (NRM) and overall survival (OS) in allogeneic hematopoietic cell transplantation (HCT) recipients. The usefulness of this index in a younger, adolescent and young adult (AYA) population is unclear. PROCEDURE: We tested the validity of the HCT-CI as a predictor of mortality in a retrospective cohort of 56 AYA recipients between the ages of 16 and 39, using chart abstraction followed by univariable and multivariate analysis. RESULTS: Only pulmonary dysfunction (46%), hepatic dysfunction (27%), infection (20%), and psychiatric disturbance (11%) had frequencies greater than 5% in this population. HCT-CI scores of 0-2 were present in 54%, and scores of >3 in 46%. The cumulative incidence of NRM at 2 years was 32%, with an OS of 46%; the NRM and OS for patients with an HCT-CI of 0-2 were 24% and 62%, whereas the NRM and OS for patients with an HCT-CI >3 were 38% and 28%. Patients with pulmonary dysfunction prior to transplant had a 29% OS at 2 years, compared to a 61% OS among patients without (P = 0.001). There was no statistically significant difference for patients and a worse NRM (P = 0.08). In multivariable analysis, both an HCT-CI score of >3 and any pulmonary dysfunction remained associated with OS (P = 0.01, P = 0.03), but neither with NRM. CONCLUSIONS: The HCT-CI appears useful in predicting OS in AYAs, though higher scores may reflect prior treatment, with pulmonary dysfunction particularly prevalent. Prospective studies to further validate and explain these findings are warranted.

Infusional mitoxantrone plus bolus melphalan as a stem cell transplant conditioning regimen for multiple myeloma.

This study combined infusional mitoxantrone with bolus melphalan as a transplant preparative regimen for multiple myeloma. Mitoxantrone was infused over 6 hr on days 6 and 5. Melphalan was given as a 15 min bolus on day 1 followed by autologous transplant on day 0. Thirty-five patients were enrolled; 57% of enrollees had received ≥ 2 prior treatments. The median overall survival was 5 years and 8 months, with 37% of the subjects alive >7 years posttransplantation. Myelosuppression and mucositis were the most frequent adverse events. This regimen is well tolerated and the survival compares well to other transplant trials.

Chemomobilization with Etoposide is Highly Effective in Patients with Multiple Myeloma and Overcomes the Effects of Age and Prior Therapy.

The optimal mobilization strategy prior to autologous stem cell transplantation for patients with multiple myeloma remains unclear. Mobilization with cytokines alone appears to yield suboptimal results in older patients as well as patients who have received prior lenalidomide. To avoid the marked cytopenias and risks of hemorrhagic cystitis associated with the administration of cyclophosphamide, we investigated the efficacy and safety of chemomobilization with an intermediate dose etoposide (VP-16; 375 mg/m(2) on days +1 and +2) and granulocyte-colony stimulating factor (G-CSF) (5 µg/kg twice daily from day +3 through the final day of collection). We reviewed our institutional experience with 152 myeloma patients mobilized with this regimen. The addition of VP-16 to G-CSF resulted in successful mobilization in 100% of patients, including 143 (94%) who collected successfully in a single day. A total of 99% of patients, including those with prior XRT and/or prior lenalidomide or thalidomide therapy, collected at least 5 × 10(6) cells/kg in 1 or 2 days of apheresis, and the median total number of CD34(+) cells collected in the entire population was 12 × 10(6) cells/kg. Collection was predictable, with 61% of patients collecting on day +11, and the rest between days +7 and +13. There were no variables, including age, prior imid exposure, radiation therapy, or total amount of prior therapy that were associated with suboptimal mobilization. Adverse effects of the regimen included supportive transfusions required in 31 (20%) patients, and fevers requiring hospitalization or intravenous antibiotics in 26 (17%) patients. VP-16 and G-CSF appears to be a safe and effective mobilization regimen for patients with multiple myeloma undergoing autologous stem cell transplantation, producing excellent stem cell yield with the majority of patients requiring 1 day of apheresis.