Utkarsh Acharya

Despite the availability of an increasing number of targeted therapeutics and wider use of allogeneic hematopoietic stem cell transplantation, many patients with acute myeloid leukemia (AML) ultimately succumb to this disease. Given their remarkable efficacy in B-acute lymphoblastic leukemia and other CD19-expressing B cell malignancies, there is hope adoptive cellular transfer, particularly chimeric antigen receptor (CAR)-modified immune effector cell (IEC) therapies, may afford a novel, potent immune-based approach for the treatment of AML that complements or replaces existing ones and improves cure rates. However, it is unclear how best to translate the success of these therapies from B cell malignancies, where use of highly potent immunotherapies is facilitated by identified target antigens with near ubiquitous expression on malignant cells and non-fatal consequences from “on-target, off-tumor cell” toxicities. Herein, we review the current status of CAR-modified IEC therapies for AML, with considerations regarding suitable, relatively leukemia-restricted target antigens, expected toxicities, and interactions of the engineered cells with a profoundly immunosuppressive tumor microenvironment that restricts their therapeutic efficacy. With these challenges in mind, we will discuss possible strategies to improve the cells’ potency as well as their therapeutic window for optimal clinical use in AML.

“Cytokine release syndrome (CRS) is a systemic inflammatory state with the potential for multisystemic organ dysfunction leading to life-threatening consequences. This toxicity is increasingly recognized as the use of immune effector cellular therapies such as chimeric antigen receptor (CAR) T-cell therapies and bispecific T-cell engagers gains popularity, although this chapter predominantly focuses on CRS associated with adoptive T-cell therapies. The advent and inception of CAR T-cell therapies has transformed the management landscape of various hematologic malignancies. The Food and Drug Administration has approved tisagenlecleucel (Tis-cel) for the treatment of pediatric acute lymphoblastic leukemia (ALL) and relapsed/refractory large-cell lymphoma, and axicabtagene ciloleucel (Axi-cel) for relapsed or resistant aggressive large-cell lymphoma. While early- and late-phase clinical trial data has demonstrated unprecedented response rates and survival advantages of CAR T-cell therapy in various hematologic malignancies, the incidence and respective toxicity profile of CRS have been equitably well reported.”

Factors associated with durable remission after CD19 chimeric antigen receptor (CAR)-modified T cell immunotherapy for aggressive B-cell non-Hodgkin lymphoma (NHL) have not been identified. We report multivariable analyses of factors impacting response and progression-free survival (PFS) in aggressive NHL patients treated with cyclophosphamide and fludarabine (Cy/Flu) lymphodepletion followed by 2x10⁶ CD19 CAR-T cells/kg. The best overall response rate (ORR) was 51%, with 40% of patients achieving complete remission (CR). The median PFS of aggressive NHL patients who achieved CR was 20.0 months (median follow-up 26.9 months). Multivariable analysis of clinical and treatment characteristics, serum biomarkers, and CAR-T cell manufacturing and pharmacokinetic data showed that a lower pre-lymphodepletion serum LDH and a favorable cytokine profile, defined as serum day 0 MCP-1 and peak IL-7 concentrations above the median, were associated with better PFS. MCP-1 and IL-7 concentrations increased after lymphodepletion and higher intensity of Cy/Flu lymphodepletion was associated with higher probability of a favorable cytokine profile. PFS was superior in patients who received high-intensity lymphodepletion and achieved a favorable cytokine profile compared to those who received the same intensity of lymphodepletion without achieving a favorable cytokine profile. Even in high-risk patients with pre-lymphodepletion serum LDH above normal, a favorable cytokine profile after lymphodepletion was associated with a low risk of a PFS event. Strategies to augment the cytokine response to lymphodepletion could be tested in future studies of CD19 CAR-T cell immunotherapy for aggressive B-cell NHL. Key points LDH, MCP-1, and IL-7 are independently associated with PFS in aggressive NHL after CD19 CAR-T cell immunotherapy. Higher intensity of Cy/Flu lymphodepletion is associated with higher probability of a favorable cytokine profile.

Autologous T cells engineered to express a CD19-specific chimeric antigen receptor (CAR) have produced impressive minimal residual disease–negative (MRD-negative) complete remission (CR) rates in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, the factors associated with durable remissions after CAR T-cell therapy have not been fully elucidated. We studied patients with relapsed/refractory B-ALL enrolled in a phase 1/2 clinical trial evaluating lymphodepletion chemotherapy followed by CD19 CAR T-cell therapy at our institution. Forty-five (85%) of 53 patients who received CD19 CAR T-cell therapy and were evaluable for response achieved MRD-negative CR by high-resolution flow cytometry. With a median follow-up of 30.9 months, event-free survival (EFS) and overall survival (OS) were significantly better in the patients who achieved MRD-negative CR compared with those who did not (median EFS, 7.6 vs 0.8 months; P < .0001; median OS, 20.0 vs 5.0 months; P = .014). In patients who achieved MRD-negative CR by flow cytometry, absence of the index malignant clone by IGH deep sequencing was associated with better EFS (P = .034). Stepwise multivariable modeling in patients achieving MRD-negative CR showed that lower prelymphodepletion lactate dehydrogenase concentration (hazard ratio [HR], 1.38 per 100 U/L increment increase), higher prelymphodepletion platelet count (HR, 0.74 per 50 000/μL increment increase), incorporation of fludarabine into the lymphodepletion regimen (HR, 0.25), and allogeneic hematopoietic cell transplantation (HCT) after CAR T-cell therapy (HR, 0.39) were associated with better EFS. These data allow identification of patients at higher risk of relapse after CAR T-cell immunotherapy who might benefit from consolidation strategies such as allogeneic HCT. This trial was registered at www.clinicaltrials.gov as #NCT01865617.

Introduction: Chimeric antigen receptor (CAR) T cell immunotherapy has demonstrated remarkable anti-tumor activity in B-cell malignancies and is under investigation in other hematologic malignancies and solid tumors. While highly efficacious, post-infusion T cell activity often results in massive cytokine release precipitating cytokine release syndrome (CRS), the signature toxicity of CAR T cells. This toxicity is characterized by systemic immune activation resulting in fever, hypotension, respiratory insufficiency and capillary leak. Either in conjunction with or in the absence of CRS, a subset of patients may also develop mild to severe neurotoxicity. Although the precise pathogenesis of CRS and neurotoxicity aren’t fully elucidated, risk factors and mitigation strategies have been reported. Areas covered: This manuscript provides an in-depth overview of the pathogenesis, clinical characteristics, current toxicity management strategies, and future perspectives pertaining to CRS and neurotoxicity. Expert Opinion: As CAR T cell based therapies gain popularity in the management of various malignancies, the complimentary toxicities of CRS and neurotoxicity pose a clinical challenge in practice. Risk adaptive modeling incorporating disease profile, patient demographics, lymphodepletion, cell dosing, CAR T construct, and potentially cytokine gene polymorphisms may be instructive to asses individualized risk and optimal CRS/neurotoxicity management.

Introduction Autologous T cells expressing a CD19-specific chimeric antigen receptor (CAR) have produced impressive minimal residual disease-negative complete remission (MRD-neg CR) rates in relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL) patients (pts). Factors associated with durable remission in pts achieving MRD-neg CR after immunotherapy with T cells engineered with a CD19 CAR (FMC63.41bb.3ζ) have not been elucidated. Methods We studied factors impacting disease-free survival (DFS) of adults with B-ALL treated with lymphodepletion chemotherapy and CD19 CAR-T cells in a phase I/II clinical trial (NCT01865617). Pts were eligible for this analysis if they had bone marrow leukemia identified by flow cytometry and/or extramedullary disease before CAR-T cell therapy, and received CAR-T cells at or below the previously determined maximum tolerated dose (MTD; Turtle, JCI 2016). Anti-tumor response after CAR-T cell infusion was assessed by bone marrow aspiration and biopsy, with PET-CT performed in pts with extramedullary disease. High resolution (1:10,000) flow cytometry was used to identify marrow MRD, and marrow from pts in MRD-neg CR was evaluated by high throughput sequencing (HTS) of IGH, IGK, TRB, TRD, and TRG genes. Cox regression univariate and stepwise multivariable modeling were performed to identify factors associated with DFS. Results Of 57 pts who received lymphodepletion and CD19 CAR-T cells, 53 were evaluable for response and 4 were not evaluable (one MRD-neg CR before CAR-T cell infusion; 2 received CAR-T cells above the MTD; one fatal neurotoxicity prior to restaging). Forty-five of 53 restaged pts (85%) achieved MRD-neg CR after CAR-T cell therapy. With a median follow-up of 30.9 months, DFS and overall survival (OS) were longer in pts who achieved MRD-neg CR compared to those who did not (Fig 1A; median DFS, 7.6 vs 0.8 months, P < .0001; median OS, 20.0 vs 5.0 months, P = .014). Twenty-eight of the 45 pts who achieved MRD-neg CR had a leukemic clone identified by HTS prior to CAR-T cell infusion, and in 20 of these pts (71%), the leukemic clone was not detected in marrow 3 weeks after CAR-T cell infusion. DFS was better in MRD-neg CR pts with no detected malignant clone compared to those with a persistent clone by HTS (Fig 1B; median DFS, 8.4 vs 3.6 months, P = .036). We then used stepwise multivariable modeling to determine factors impacting DFS in the pts who achieved MRD-neg CR (n = 45). Better DFS was seen in pts with a higher pre-lymphodepletion platelet count (hazard ratio, HR 0.65 [95% CI; 0.47-0.88] per 50,000/μL increment P = .006), lower pre-lymphodepletion LDH (HR 1.39 [1.12-1.74] per 100 U/L increment, P = .003), and with incorporation of fludarabine into the cyclophosphamide-based lymphodepletion (Cy/Flu; HR 0.34 [0.15-0.78], P = .011). Similar findings were noted in analysis of MRD-neg CR pts who had no malignant clone by HTS after CAR-T cells. Pts with platelets ≥100,000/μL and normal LDH before lymphodepletion who received Cy/Flu (good risk, n = 15) had 2-year point estimates of DFS and OS of 78% and 86%, respectively. Allogeneic hematopoietic cell transplantation (HCT) is standard of care in suitable R/R adult B-ALL pts after achieving MRD-neg CR. Eighteen pts in MRD-neg CR after CAR-T cells underwent HCT a median of 2.3 months after CAR-T cell infusion. We analyzed the effect on DFS of HCT after CAR-T cell therapy by treating HCT as a time-dependent covariate. After adjusting for LDH, platelets, and Cy/Flu lymphodepletion, pts undergoing HCT after CAR-T cell therapy had lower risk of failure for DFS compared to those who did not undergo HCT (Table 1). No significant interaction effect was seen between HCT and risk group (P = .51). With a median follow-up of 28.4 months after HCT, 2-year point estimates of DFS and OS were 61% and 72% respectively. The 2-year cumulative incidence of relapse was 17% and non-relapse mortality was 23%. Conclusion A high rate of MRD-neg CR was seen following CD19 CAR-T cell therapy in adult B-ALL pts and is associated with improved DFS and OS. Absence of the index clone by HTS after CAR-T cells was associated with better DFS, suggesting deeper responses are associated with improved outcomes. Stepwise multivariable modeling identifies better DFS in pts with higher pre-lymphodepletion platelet count and lower LDH, and with use of Cy/Flu lymphodepletion. After adjusting for these factors, HCT after CD19 CAR-T cells may also be associated with better DFS.

Chronic neutrophilic leukemia (CNL) is a rare myeloproliferative disorder accounting for less than 200 reported cases to date. It is characterized by a sustained neutrophilia, splenomegaly, myeloid marrow hyperplasia, and absence of the breakpoint cluster region/abelson murine leukemia (BCR/ABL) fusion gene. Diagnosis of CNL has been historically challenging, and has ultimately relied on the exclusion of alternate myeloid disorders including chronic myelogenous leukemia (CML) and chronic myel-omonocytic leukemia (CMML). The majority of patients exhibit no overt symptoms, and the diagnosis of CNL is incidentally entertained as a consequence of a protracted and unexplained leukocytosis. Cytogenetic analysis is typically normal in CNL patients; however, various aberrations including del(11q) and del(20q) have been reported in myeloid disorders, but are not specific to CNL. CNL falls within a heterogeneous spectrum of myeloproliferative disorders, and prognostic data are limited given the scarcity of published manuscripts.

Aim: Acute myeloid leukemia (AML) is an aggressive hematopoietic clonal disorder characterized by the increased blasts and poor survival outcome, which is mainly driven by cytogenetic and molecular abnormalities. Here, we investigated the prognostic impact of other demographic parameters on the survival outcomes in AML patients. Method: We reviewed the Surveillance, Epidemiology, and End Result (SEER) database to collect demographic information, including age, diagnosis, gender, race, and geographic region in patients with non-acute promyelocytic leukemia AML, between 2004–2008. The primary end-point of our study was 3-year overall survival (OS), which was estimated by the Kaplan–Meier method and Cox regression model. Results: A total of 13,282 patients were included in our analyses. Increasing age (HR 1.2, p < .0001), male gender (HR 1.05, p = .01), and geographic region of Midwest (HR 1.07, p = .002) were associated with inferior 3-year OS in univariate analysis, and these parameters remained independent prognostic factors in multivariate analyses. Conclusions: AML is a heterogeneous myeloid neoplasm with patient outcomes largely dictated by the cytogenetics and somatic mutations. In our study, additional demographic factors, including advanced age, male gender, and geographic region of AML diagnosis were associated with OS outcome in non-APL AML patients.