CD19-directed chimeric antigen receptor (CAR) T cells have evolved as new standard-of-care (SOC) treatment in patients with relapsed/refractory large B-cell lymphoma (LBCL). Here, we report the first German real-world data on SOC CAR-T cell therapies with the aim to explore risk factors associated with outcome. Patients who received SOC axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel) for LBCL and were registered with the German Registry for Stem Cell Transplantation (DRST) were eligible. Main outcomes analyzed were toxicities, response, overall survival (OS), and progression-free survival (PFS). We report 356 patients who received axi-cel (n=173) or tisa-cel (n=183) between November 2018 and April 2021 at 21 German centers. Whereas the axi-cel and tisa-cel cohorts were comparable for age, sex, LDH, IPI, and pretreatment, the tisa-cel group comprised significantly more patients with poor performance status, ineligibility for ZUMA-1, and need for bridging, respectively. With a median follow-up alive of 11 months, Kaplan-Meier estimates of OS, PFS, and non-relapse mortality (NRM) 12 months after dosing were 52%, 30%, and 6%, respectively. While NRM was largely driven by infections subsequent to prolonged neutropenia and/or severe neurotoxicity and significantly higher with axi-cel, significant risk factors for PFS on multivariate analysis included bridging failure, elevated LDH, age, and tisa-cel use. In conclusion, this study suggests that important outcome determinants of CD19-directed CAR-T cell treatment of LBCL in the real-world setting are bridging success, CAR-T product selection, LDH, and the absence of prolonged neutropenia and/or severe neurotoxicity. These findings may have implications for designing risk-adapted CAR-T cell therapy strategies.

Signal transduction of FMS-like tyrosine kinase 3 (FLT3) is regulated by proteintyrosine phosphatases (PTPs). IntroductionAcute myeloid leukemia (AML) is the most frequent leukemia in adults with improving but still limited treatment possibilities, notably in elderly patients. 1,2 It arises by malignant transformation of myeloid progenitor cells. Among the contributing genetic lesions, mutations in the class III receptor tyrosine kinase (RTK) FMS-like tyrosine kinase 3 (FLT3) occur in approximately 30% of patients. 3 The prevalent type of FLT3 mutations are internal tandem duplications (ITD) of amino acid stretches in the juxtamembrane domain or in the tyrosine kinase domain, 4,5 which confer cytokineindependent proliferation and resistance to apoptosis, and causally contribute to AML in combination with additional genetic lesions. 1 Compared with the ligand-activated wild-type (WT) FLT3, FLT3 ITD mutants exhibit not only elevated but also altered signaling quality, with very pronounced activation of signal transducer and activator of transcription (STAT)5 as one characteristic feature. 6,7 FLT3 ITD also causes the production of high levels of reactive oxygen species (ROS). 8,9 Signal transduction of RTKs is regulated by protein-tyrosine phosphatases (PTPs). PTPs prevent ligand-independent RTK activation, and contribute to modulation and termination of ligand-induced signaling. 10 The activity of PTPs is regulated at several different levels. 11 One regulatory principle is the reversible oxidation of the PTP active-site cysteine, which leads to reversible inactivation. 12,13 Temporary inactivation of negatively regulating PTPs by this mechanism is believed to be important for efficient RTK signal propagation in the cell. 14 A major ROS causing cellular PTP oxidation is hydrogen peroxide (H 2 O 2 ), which can be generated by a dismutase reaction from superoxide anions, the reaction products of NADPH-oxidases. Activation of the NADPH oxidase isoform 1 (NOX1) occurs downstream of RTK activation, and involves activation and membrane translocation of the small guanosine triphosphate (GTP)ase Rac1. 15 ROS generation in the cell is counteracted by efficient ROS decomposing systems. 16 These include peroxiredoxins (Prx), which have a very low K m for H 2 O 2 and can eliminate it even at low concentrations. 17 Relatively little is known about PTPs regulating FLT3 signal transduction. We have previously shown that the nontransmembrane PTPs PTP1B and SHP-1 can potently dephosphorylate FLT3 on overexpression. Further, PTP1B appears important for suppressing signaling of newly synthesized FLT3. 7,18 SHP-2 acts as a positive regulator, because it is important for Erk activation and proliferation induced by ligand-activated WT FLT3. However, it is dispensable for FLT3 ITD-mediated transformation. 19 We previously performed a shRNA-based screen to identify PTPs regulating WT FLT3. The initial screen assessed the effects of shRNAs for 20 PTPs on FL-induced Erk1/2 activation in WT FLT3-expressing 32D cells. Among several potentia...

Treatment of FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD)-positive acute myeloid leukemia (AML) remains a challenge despite the development of novel FLT3-directed tyrosine kinase inhibitors (TKI); the relapse rate is still high even after allogeneic stem cell transplantation. In the era of next-generation FLT3-inhibitors, such as midostaurin and gilteritinib, we still observe primary and secondary resistance to TKI both in monotherapy and in combination with chemotherapy. Moreover, remissions are frequently short-lived even in the presence of continuous treatment with next-generation FLT3 inhibitors. In this comprehensive review, we focus on molecular mechanisms underlying the development of resistance to relevant FLT3 inhibitors and elucidate how this knowledge might help to develop new concepts for improving the response to FLT3-inhibitors and reducing the development of resistance in AML. Tailored treatment approaches that address additional molecular targets beyond FLT3 could overcome resistance and facilitate molecular responses in AML.

Infectious complications continue to be one of the major causes of morbidity and mortality in patients with acute myeloid leukemia (AML). Several single-nucleotide polymorphisms (SNPs) of Toll-like receptors (TLRs) can affect the genetic susceptibility to infections or even sepsis. We sought to investigate the impact of different SNPs on the incidence of developing sepsis and pneumonia in patients with newly diagnosed AML following induction chemotherapy. We analyzed three SNPs in the TLR2 (Arg753Gln) and TLR4 (Asp299Gly and Thr399Ile) gene in a cohort of 155 patients with AML who received induction chemotherapy. The risk of developing sepsis and pneumonia was assessed by multiple logistic regression analyses. The presence of the TLR2 Arg753Gln polymorphism was significantly associated with pneumonia in AML patients (odds ratio (OR): 10.78; 95% confidence interval (CI): 2.0-58.23; P=0.006). Furthermore, the cosegregating TLR4 polymorphisms Asp299Gly and Thr399Ile were independent risk factors for the development of both sepsis and pneumonia (OR: 3.55; 95% CI: 1.21-10.4, P=0.021 and OR: 3.57, 95% CI: 1.3-9.86, P=0.014, respectively). To our best knowledge, this study represents the first analysis demonstrating that polymorphisms of TLR2 and TLR4 influence the risk of infectious complications in patients with AML undergoing induction chemotherapy.