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With the US Food and Drug Administration (FDA) approval of four CD19- and one BCMA-targeted chimeric antigen receptor (CAR) therapy for B cell malignancies, CAR T cell therapy has finally reached the status of a medicinal product. The successful manufacturing of autologous CAR T cell products is a key requirement for this promising treatment modality. By analyzing the composition of 214 apheresis products from 210 subjects across eight disease indications, we found that high CD14+ cell content poses a challenge for manufacturing CAR T cells, especially in patients with non-Hodgkin’s lymphoma and multiple myeloma caused by the non-specific phagocytosis of the magnetic beads used to activate CD3+ T cells. We demonstrated that monocyte depletion via rapid plastic surface adhesion significantly reduces the CD14+ monocyte content in the apheresis products and simultaneously boosts the CD3+ content. We established a 40% CD14+ threshold for the stratification of apheresis products across nine clinical trials and demonstrated the effectiveness of this procedure by comparing manufacturing runs in two phase 1 clinical trials. Our study suggests that CD14+ content should be monitored in apheresis products, and that the manufacturing of CAR T cells should incorporate a step that lessens the CD14+ cell content in apheresis products containing more than 40% to maximize the production success.

Administration of pediatric-inspired chemotherapy to adults up to age 60 with acute lymphoblastic leukemia (ALL) is challenging in part due to toxicities of asparaginase as well as myelosuppression. We conducted a multicenter phase II clinical trial (NCT01920737) investigating a pediatric-inspired regimen, based on the augmented arm of the Children’s Cancer Group 1882 protocol, incorporating 6 doses of pegaspargase 2000 IU/m2, rationally synchronized to avoid overlapping toxicity with other agents. We treated 39 adults ages 20-60 years (median, 38 years) with newly-diagnosed ALL (n=31) or lymphoblastic lymphoma (n=8). Grade 3-4 hyperbilirubinemia occurred frequently and at higher rates in patients 40-60 (n=18) vs 18-39 (n=21) years (44 vs 10%, p=0.025). However, 8/9 patients re-challenged with pegaspargase did not experience recurrent grade 3-4 hyperbilirubinemia. Grade 3-4 hypertriglyceridemia and hypofibrinogenemia were common (each 59%). Asparaginase activity at 7-days post-infusion reflected levels associated with adequate asparagine depletion, even among those with antibodies to pegaspargase. Complete response (CR)/CR with incomplete hematologic recovery was observed post-induction in 38/39 (97%) patients. Among patients with ALL, rates of MRD negativity by multiparameter flow cytometry were 33% and 83% following Induction Phase I and Phase II, respectively. Event-free and overall survival at 3 years (67.8 and 76.4%) compare favorably to outcomes observed in other series. These results demonstrate pegaspargase can be administered in the context of intensive multi-agent chemotherapy to adults age ≤60 with manageable toxicity. This regimen may serve as an effective backbone into which novel agents may be incorporated in future frontline studies.

Measurable residual disease is associated with inferior outcomes in patients with acute myeloid leukemia (AML). Measurable residual disease monitoring enhances risk stratification and may guide therapeutic intervention. The European LeukemiaNet working party recently came to a consensus recommendation incorporating leukemia associated immunophenotype-based different from normal approach by multi-color flow cytometry for measurable residual disease evaluation. However, the analytical approach is highly expertise-dependent and difficult to standardize. Here we demonstrate that loss of plasmacytoid dendritic cell differentiation after 7+3 induction in AML is highly specific for measurable residual disease positivity (specificity 97.4%) in a uniformly treated patient cohort. Moreover, loss of plasmacytoid dendritic cell differentiation as determined by a blast-to-plasmacytoid dendritic cell ratio >10 was strongly associated with inferior overall and relapse-free survival (RFS) [Hazard ratio 2.79, 95% confidence interval (95%CI): 0.98-7.97; P=0.077) and 3.83 (95%CI: 1.51-9.74; P=0.007), respectively), which is similar in magnitude to measurable residual disease positivity. Importantly, measurable residual disease positive patients who reconstituted plasmacytoid dendritic cell differentiation (blast/ plasmacytoid dendritic cell ratio

Older adults with acute lymphoblastic leukemia (ALL) continue to have a poor prognosis, in part due to greater chemotherapy-related toxicities. We herein report a 67-year-old man with Philadelphia chromosome (Ph)-negative B-cell ALL, who exhibited refractoriness to 3 different regimens of induction chemotherapy and experienced multiple complications including intracranial bleeding and respiratory failure, who achieved minimal residual disease (MRD)-negative complete response (CR) after a single cycle of inotuzumab ozogamicin (IO). His ALL was characterized by several high-risk mutations, which may have contributed to chemotherapy-refractory disease. Our case supports incorporating IO into front-line induction regimens for older adults with high-risk B-cell ALL. Keywords: Acute lymphoblastic leukemia, Inotuzumab ozogamicin, Older adults, Immunotherapy