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Key Points The kidney microvasculature was quantified reliably in human autosomal dominant polycystic kidney disease early on, using super-resolution ultrasound localization microscopy. Microvascular parameters correlated with structural and functional indices, constituting promising biomarkers to evaluate noncystic parenchyma. Microvascular parameters may serve to assess disease severity and monitor progression from the early stages of the disease. Background In vitro studies in individuals with autosomal dominant polycystic kidney disease (ADPKD) have shown extensive intrarenal microvascular remodeling. However, analyses have been limited to the time of kidney failure because of the invasive nature of current methodologies to assess the intrarenal microvasculature. We hypothesized that super-resolution ultrasound microvascular imaging, known as ultrasound localization microscopy, enabled by high-framerate ultrasound imaging and microbubble localization and tracking postprocessing techniques, would safely, reliably, and reproducibly assess the intrarenal microvasculature in individuals with ADPKD at an early stage of the disease. Methods We prospectively enrolled young (<40 years of age), well-characterized, early-stage (eGFR >90 ml/min per 1.73 m 2 ) individuals with ADPKD, and sex–age 1:1 matched controls ( n =17 each) and assessed the intrarenal microvasculature using ultrasound localization microscopy. We determined the intersonographer reliability, intraobserver repeatability, and interobserver reproducibility of microvascular parameters in both groups, and the day-to-day variability in the control group. Microvascular parameters were correlated with structural (total kidney volume) and functional (eGFR) markers in individuals with ADPKD. Results Ultrasound localization microscopy provided a super-resolved map of the intrarenal microvasculature in ADPKD and matched controls. Intrarenal microvascular parameters ( e.g ., vessel density) were quantified in a safe, reliable (intraclass correlation coefficients, 0.96; 95% confidence interval, 0.91 to 0.98), reproducible (intraclass correlation coefficient, 0.96; 95% confidence interval, 0.93 to 0.98), and repeatable (coefficient of variations, 3.6%) manner. In control individuals, the day-to-day variability of most parameters was low, with coefficient of variation ranging from 1.8% to 10.7%. Microvascular parameters differed in individuals with ADPKD compared with controls, despite preserved eGFR. Interestingly, cortical vessel density and its derived perfusion correlated directly with eGFR, whereas tortuosity indices presented an inverse correlation. Conclusions Ultrasound localization microscopy provided a safe and reliable in vivo assessment of the human intrarenal microvasculature.

Abstract Introduction Many couples who do not achieve pregnancy with intrauterine insemination (IUI) subsequently pursue in vitro fertilization (IVF). While the impact of semen parameters on IUI outcomes is well established, it remains unclear whether characteristics of sperm following IUI preparation predict future IVF success. Many couples who do not achieve pregnancy with intrauterine insemination (IUI) subsequently pursue in vitro fertilization (IVF). While the impact of semen parameters on IUI outcomes is well established, it remains unclear whether sperm characteristics following IUI preparation predict future IVF success. Here we study a novel, clinically accessible marker of sperm quality – percent change in total motile sperm (TMS) after IUI sperm wash-that may predict fertilization and blastulation outcomes in subsequent IVF cycles. Objective This aims to evaluate the association between changes in total motile sperm (TMS) after IUI sperm wash and fertilization rates in subsequent IVF cycles.This study aims to evaluate the association between changes in TMS after IUI sperm wash and fertilization and blastulation rates in subsequent IVF cycles. Methods In this retrospective study, we identified couples at a single academic center who failed to achieve a live birth following IUI and subsequently underwent IVF with the same partner. To minimize confounding, only couples with a diagnosis of unexplained infertility or male factor infertility were included. In patients who underwent multiple IUIs (median of 2), the cycle with the greatest percent decrease in TMS was selected for analysis. Additional predictive variables of female partner age, male partner age, pre-wash TMS, and insemination method were assessed. A stepwise variable selection method was utilized to identify predictors of fertilization rate and complete blastulation failure, with linear and logistic regression models of selected variables developed, respectively. Results From the cohort of 388 couples, the median fertilization rate during IVF was 56% (IQR 43%–70%). Thirteen percent of couples experienced complete blastulation failure. Change in TMS was selected as a predictor of both fertilization rate and blastulation failure. A 10% greater decline in TMS after IUI sperm wash was associated with a 1.02% lower fertilization rate (p=0.052), after adjustment for insemination method. A 10% greater decrease in TMS was associated with a 1.22-times (95% CI 1.04, 1.48) increased odds of blastulation failure (p=0.023) after adjusting for female partner age. Conclusions A greater percent decrease in TMS following IUI sperm wash is associated with lower fertilization rates and a higher odds of blastulation failure in subsequent IVF cycles. These findings support the hypothesis that significant declines in TMS after sperm preparation may reflect underlying sperm quality defects not detected by routine semen analysis, yet still relevant to fertility outcomes. By identifying sperm quality issues not apparent on standard semen analysis, these findings offer a new tool for risk stratification and counseling of couples transitioning from IUI to IVF. Disclosure No

Localized cutaneous squamous cell carcinoma (cSCC) has a favorable prognosis, unlike advanced disease, especially with clinical perineural invasion (PNI), which poses substantial management challenges due to aggressivity and higher recurrence, metastasis, and mortality risks. PNI, a high-risk staging feature, has worse outcomes, particularly when clinically evident rather than incidental. Clinical PNI (cPNI) is evident by clinical symptoms (such as pain, paresthesia, or motor deficits) or radiologic findings, whereas incidental PNI (iPNI) is identified only histologically without associated symptoms or radiologic evidence. PNI remains a novel area with varying practice patterns across institutions. Improving risk stratification and tailoring multidisciplinary approaches are critical for optimizing outcomes. Our review outlines clinical practice patterns at our institution, providing insights into managing cSCC with PNI, focusing on diagnosis, imaging, staging, and emerging immunotherapies. A structured search was conducted using the terms “perineural invasion,” “cutaneous squamous cell carcinoma,” and “immunotherapy.” cPNI has a poor prognosis and requires nuanced clinical decision-making. Surgery and radiation remain central to management. Adjuvant therapy offers substantial survival benefit in cSCC with PNI, with improved disease-free and overall survival compared with surgery alone, supporting its use in appropriately selected high-risk patients. Traditional systemic therapies, including cisplatin and cetuximab, remain foundational but have shown only moderate response rates and limited durability in advanced or neurotropic cSCC. In contrast, immunotherapy—now preferred for advanced or unresectable cases—has transformed management, with programmed cell death protein-1 (PD-1) inhibitors showing promising results (up to 69% response rate) and disease stabilization. Neoadjuvant immunotherapy may enable tumor downstaging, improve radiation planning, and reduce surgical morbidity. Imaging for squamous cell carcinoma (SCC) with PNI aids staging and surveillance, but symptoms remain key for detecting recurrence. Our multidisciplinary approach emphasizes personalized care. Larger trials are needed to define the optimal role and sequencing of immunotherapy in this high-risk patient population.

To improve synthetic CT (sCT) generation from cone-beam CT (CBCT) in radiotherapy, we propose a multiscale segmentation-guided diffusion framework. The proposed model integrates anatomical priors across multiple spatial resolutions through a segmentation mask pyramid and introduces a scale-specific loss function to guide learning at each level. When evaluated on the SynthRAD2023 brain dataset, our model achieves a mean absolute error (MAE) of 61.82 HU, a peak signal-to-noise ratio (PSNR) of 32.05 dB, and a structural similarity index (SSIM) of 0.90, outperforming baseline models. These results suggest that multiscale anatomical guidance can improve the fidelity and anatomical consistency of sCT images, thus facilitating high-quality CBCT-to-CT translation in radiotherapy applications.

Abstract Pyroptosis is a form of programmed cell death characterized by the cleavage of the gasdermin (GSDM) family proteins that form pores in the plasma membrane, cell rupture, and the release of proinflammatory cytokines. In this study, we performed immunohistochemistry for cleaved gasdermin D (GSDMD), gasdermin E (GSDME) N-terminus, and gasdermin C (GSDMC) in 2 different cohorts of diffuse large B-cell lymphoma (DLBCL) and analyzed the impact of GSDM expression on prognosis and immunity. The results showed frequent cleaved GSDMD (N-terminal) expression. Only cytoplasmic GSDMD N-terminal expression correlated with significantly better patient survival in the 2 cohorts. In contrast, GSDME was mainly expressed in the vascular endothelium, and correlated with significantly adverse prognostic effect. Correlating with the multiplex fluorescent immunohistochemistry results, we found that cytoplasmic GSDMD N-terminal expression was associated with increased CD38+ (activated) M1 macrophages in both cohorts, cognate interactions between live DLBCL cells and activated M1 macrophages (and T cells), and lower PD-1/PD-L1 expression in the analyzed cases. In contrast, T-cell pyroptosis, lymphoma cell-resistance to cell death, and phagocytosis by M2 macrophages were observed in tissues with predominantly nuclear GSDMD N-terminal expression. Bulk gene expression profiling and deconvolution analysis revealed associations of cytoplasmic GSDMD N-terminal expression with downregulation of “Don’t eat me”–signaling genes, upregulation of many RNA genes, decreased frequency of “inflammatory” lymphoma microenvironment subtype, increased frequencies of prognostically favorable cell states and ecotypes, and decreased frequency of T-cell exhaustion state. In summary, this study showed distinct cellular and subcellular patterns of 3 GSDM proteins and their associated immune response phenotypes and prognostic effects, with implications for novel therapeutic strategies for B-cell lymphoma.

Abstract Chimeric antigen receptor (CAR) T-cell therapy has demonstrated remarkable response rates in relapsed/refractory aggressive B-cell non-Hodgkin's lymphoma. However, durable remissions occur in only 40% of treated patients, highlighting mechanisms of therapeutic resistance and immune escape. While cytotoxicity is principally executed by CAR T-cells, monocytes shape CAR-T cell efficacy and orchestrate cytokine-driven immunity. In this study, we defined distinct metabolic profiles of T-cell and monocyte subsets based on clinical response. Single-cell RNA sequencing (scRNA-seq) and T-cell receptor sequencing (scTCR-seq) were performed on peripheral blood mononuclear cells at three timepoints: before lymphodepletion (BL), at peak CAR-T expansion (PK), and one-month post-infusion (M1). Data were processed with CellRanger v7.0.1 and analyzed with the immunopipe pipeline (Wang et al., 2025). Seurat v4.3.0 was utilized for unsupervised hierarchical clustering analysis; subsets identified included classical monocytes (CM), intermediate monocytes (IM), non-classical monocytes (NM), and monocytic myeloid derived suppressor cells (mMDSC). Metabolic profiles were compared across patients achieving ≥6-month complete remission (CR, n=16), primary refractory disease (PD1, n=4), or relapsed after a prior response (PD2, n=12). A total of 107035 T cells and 129981 monocytes from 77 serial samples in 32 patients were analyzed. CR patients had a higher T-cell:monocyte ratio than PD1/PD2 at all time points, especially at BL and PK (BL 1.2 vs 0.4, p=0.011; PK 1.3 vs 0.3, p=0.027). Clinical responses were compared with metabolic pathway analysis and identified oxidative phosphorylation (OXPHOS) as the dominant pathway. OXPHOS was consistently enriched in PD cohorts across T-cell subsets, particularly in PD1 vs CR at BL (mucosal-associated invariant T-cell (MAIT) and T peripheral memory (Tpm)), and at PK (CD4/CD8 memory precursor effector cells (MPEC) and activated MPECs (MPECa), CD4 T-helper 1 proliferating (Th1p), CD4 Th2 activated (Th2a), regulatory T-cell (Treg), CD8 naive senescent (CD8NS), CD8 T effector memory (Tem) tumor recirculating (TR), CD8 Tpm, CD8 T resident memory (Trm) TR and MAIT Tpm). By M1, OXPHOS enrichment in CD4/CD8MPECa, CD4Th2a, CD8NS, CD8TemTR reversed, now predominant in CR although CD8Tpm and CD8TrmTR remained enriched in PD1. In the monocyte subsets at BL, PD2 showed OXPHOS enrichment in CD163+ monocytes (mono), IM IL1, mMDSC SIRPA, mMDSC TGFβ, and CM IL6 subsets compared to PD1 and CR, while PD1 showed OXPHOS enrichment in IM CD38, CM TGFβ, and mMDSC HIF1A vs CR and PD2. This persisted at PK. By M1, the pattern reversed and mirrored that of T-cells, with CR patients showing OXPHOS enrichment in CD163+mono, CM IL6, CM TGFβ, IM CD38, mMDSC HIF1A, mMDSC SIRPA and mMDSC TGFβ, and additionally in CM EMT, CM p53, NM, NM CD36 vs PD1/PD2. Glycolysis/gluconeogenesis (GLY) was also enriched across subsets. In T-cells, PD1 vs CR showed GLY enrichment in CD4Th2a, CD8Tpm, CD8Tpm proliferating and MAIT Tpm at PK. In monocytes, GLY was enriched in PD1/2 vs CR at BL (CD163+mono, CM IL6) and PK (CD163+mono, IM CD18, mMDSC SIRPA). By M1, GLY metabolism was enriched in CR vs PD1/PD2 in CD163+mono, CM IL6, mMDSC SIRPA. Additional GLY enriched subsets at CR vs PD1 included CM, CM p53, EMT, IM CD38, IM IL1, mMDSC HIF1A, NM, NM CD36. Inositol phosphate metabolism (IP) was predominantly enriched in PD2 vs CR at BL (CD8NS, CD8Tcm, CD8Tpm activated), PK (CD4Th2, CD8NS, CD8Tem TR, CD8Tpm proliferating, γδT Tem) and M1 (CD4/CD8 MPECa, CD4 Th1/Th2, CD8NS, CD8Tpm, CD8 Tpm proliferating, Treg and MAIT Tpm). Notably, Treg was the only T-cell subset enriched for IP at PK in CR vs PD1/PD2. Additionally, the TCA cycle was enriched in PD1 Tregs and Th2 cells at BL and PK vs CR/PD2. A higher T-cell:monocyte ratio in CR vs PD1/PD2 supports prior evidence that elevated pre-lymphodepletion lymphocyte:monocyte ratios predict better outcomes. We identified distinct metabolic signatures in T-cells and monocytes between CR and PD1/PD2. OXPHOS enrichment in T-cells and monocytes at M1 in CR patients may reflect oxidative programming as a hallmark of sustained anti-tumor immunity. Conversely, GLY enrichment in PD1 T-cells at PK may reflect short-lived effector states lacking persistence. Overall, these findings highlight metabolic profiling as a promising predictive biomarker and therapeutic programming target to enhance CAR T-cell outcomes.

Abstract Background: The International Consensus Classification (ICC) for systemic mastocytosis (SM) recognizes mast cell leukemia (MCL) and SM with associated myeloid neoplasm (SM-AMN) as distinct categories of advanced SM (SM-Adv; Arber et al. Blood 2022;140:1200). Contemporary risk models in SM, including the Mayo Alliance Prognostic System (MAPS), do not account for the prognostic heterogeneity among ICC-defined SM-Adv subcategories. Methods: Mayo Clinic databases were utilized to access patient information. Diagnoses of SM and its morphological subcategories were confirmed through clinical evaluations and review of BM pathology. Diagnostic criteria were retrospectively fitted to be consistent with those of the ICC (Arber et al. Blood 2022;140:1200); diagnosis of MCL required the presence of immature cytomorphology of mast cells and only myeloid neoplasms were listed under the category of SM-AMN.Next-generation sequencing and cytogenetic studies was performed in a subset of the study patients according to previously described methodologies. Statistical analyses were conducted on clinical and laboratory data collected at the time of initial diagnosis while survival analysis was censored at the time of allogeneic stem cell transplant (ASCT). Results: A total of 910 Mayo Clinic patients with SM (median age 56 years, range 12-89; males 50%) were accessed in order to conduct a series of multivariable analyses (MVA) in search of independent risk factors for transplant-censored overall survival (OS). All patients were evaluable for assignment to specific ICC categories of SM: indolent (ISM; N=553), aggressive (ASM; N=114), SM-AMN (N=235), and MCL (N=8); the AMN components in SM-AMN included acute myeloid leukemia (N=18), chronic myelomonocytic leukemia (N=70), myelodysplastic syndromes (N=32), MDS/myeloproliferative overlap (N=81), myelofibrosis (N=7), polycythemia vera or essential thrombocythemia (PV/ET; N=19), and others (N=8). In addition, subsets of patients were evaluable for hemoglobin level (N= 865), white blood cell count (WBC; N=858), platelet count (N= 859), serum alkaline phosphatase (ALP; N=761), serum tryptase level (N=706), karyotype (N=574), and mutations (N=240). Median follow-up for living patients was 70 months (range, 0-520); during this time 346 (38%) deaths, 16 leukemic transformations, and 20 ASCTs were documented. ROC analysis-determined optimal cutoff levels for predicting OS included age at ≥60 years, platelet count &lt;150 x 109/L, tryptase level ≥100 ng/mL, WBC ≥10 x 109/L, hemoglobin below sex-adjusted lower limit of normal (anemia), and ALP &gt;210 U/L in women or &gt;170 U/L in men (increased). All except WBC ≥10 x 109/L retained significance during MVA that included ICC-specified SM categories: MCL (HR 74.8, 26.0-215.3; p&lt;0.01); SM-AMN (HR 3.9, 2.5-6.0; p&lt;0.01); ASM (HR 2.2, 1.4-3.5; p&lt;0.01); age ≥60 years (HR 3.3, 2.2-4.7; p&lt;0.01); platelets &lt;150 x 109/L (HR 2.8, 2.0-3.9; p&lt;0.01); tryptase ≥100 ng/mL (HR 2.1, 1.5-2.9; p&lt;0.01); anemia (HR 1.7, 1.1-2.4; p&lt;0.01); and increased ALP (HR1.5, 1.1-2.0; p=0.01). A subsequent HR-weighted risk model effectively delineated 5 risk levels ranging in median survivals from 11 months to 372 months (Figure 1). Figure 2 outlines complementary subtype-specific risk models; to that end, risk factors for ISM included age ≥60 years (HR 4.5, 2.5-7.9), tryptase ≥100 ng/mL (HR 3.5, 2.1-6.0); platelets &lt;150 x 109/L (HR 3.4, 1.5-7.9), and anemia (HR 2.4, 1.2-4.8); for ASM age ≥60 years (HR 2.3, 1.3-4.3), platelets &lt;150 x 109/L (HR 2.4, 1.4-4.0), and anemia (HR 2.0, 1.2-3.4); and for SM-AMN age ≥60 years (HR 2.9, 1.6-5.2), platelets &lt;150 x 109/L (HR 2.5, 1.6-3.9), and tryptase ≥100 ng/mL (HR 2.5, 1.6-3.9) [Figure 2]. In SM-AMN, additional prognostic relevance from subcategorization into PV/ET vs. all other types of AMN was appreciated (Figure 3; HR 4.0, 1.6-3.9) and incorporated into the risk model for SM-AMN (Figure 2). Abnormal karyotype (AK) and high risk mutations(HRM; ASXL1, SRSF2, RUNX1, NRAS)clustered withSM-AMN with AK and ASXL1MUT displaying independent prognostic relevance that was most apparent in SM-AMN. Conclusions : MAPS-R relies on the prognostic eminence of ICC-defined morphologic subcategories and allows for additional SM subtype-specific risk stratification. SM associated with ET or PV is a prognostically unique subcategory of SM-AMN and should be recognized as such in future classification schemes. SM-AMN must be thoroughly ruled out in the presence of AK or HRM.

Abstract Introduction: Patients with triple-class exposed (TCE) relapsed/refractory multiple myeloma (RRMM) have historically experienced poor clinical outcomes, prompting the development of novel therapeutic options. Idecabtagene vicleucel (ide-cel) was the first chimeric antigen receptor (CAR) T cell therapy approved for this population, while teclistamab became the first approved bispecific antibody. Both target B-cell maturation antigen (BCMA) and are increasingly used in real-world (RW) settings. Most comparative evidence to date is derived from single-arm clinical trials with cross-trial adjustments. RW studies offer an opportunity to directly compare these therapies and assess their relative effectiveness in routine clinical practice. Methods: We conducted a comparative effectiveness analysis of ide-cel and teclistamab in patients with TCE RRMM using RW data from the United States Flatiron Health electronic health record-derived, deidentified database (January 2011 to April 2025 data cut). Adults who received either index therapy at any line of treatment after becoming TCE (ie, previously exposed to an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody) were included. Exclusion criteria were prior exposure to CAR T cell therapy, bispecific antibodies, or belantamab mafodotin; absence of index treatment; or lack of post-index follow-up. Index dates (T0) represent the date of infusion for ide-cel and the start of treatment for teclistamab. Seventeen prognostic covariates were selected a priori based on published rankings and used to balance treatment groups via inverse probability of treatment weighting (IPTW) with average treatment effect weights. Cox proportional hazards models were used to estimate unadjusted and IPTW-adjusted HRs with 95% CIs for progression-free survival (PFS) and overall survival (OS). As the ide-cel cohort only included infused patients, additional analyses were performed to emulate a real-world intention-to-treat population given the potential immortal time bias (patients in the ide-cel cohort were required to survive between apheresis and infusion). Specifically, patients in the teclistamab cohort who died within the first 24 days (median turnaround time for ide-cel manufacturing in United States in 2024) were excluded and 2 scenarios were performed to re-align T0 based on this 24-day period (either shifting teclistamab T0 forward or ide-cel T0 backward). Lastly, sensitivity analyses assessed differences in restricted mean survival time (dRMST) at 12 and 24 months. Results: A total of 281 patients met the inclusion criteria (ide-cel, N=106; teclistamab, N=175), with median follow-up of 22.4 and 13.7 months, respectively. IPTW adjustment balanced all covariates between groups (effective sample size: ide-cel, n=68; teclistamab, n=135). Adjusted analyses showed improved PFS with ide-cel versus teclistamab (HR, 0.67; 95% CI, 0.47–0.97), with median PFS of 11.3 versus 6.5 months. OS was also improved with ide-cel (HR, 0.59; 95% CI, 0.35–0.98); median OS was not reached in either group due to insufficient follow-up. There was a consistent trend of HRs favoring ide-cel versus teclistamab for both PFS and OS in both scenario analyses addressing the potential immortal time bias. Further, sensitivity analyses using dRMST confirmed statistically significant improvements in both PFS and OS with ide-cel across all scenarios at all time points evaluated. Conclusions: In this RW analysis, ide-cel was associated with superior PFS and OS compared with teclistamab in patients with TCE RRMM. These findings support emerging RW evidence favoring BCMA-directed CAR T cell therapies over bispecific antibodies and may inform treatment sequencing decisions in this high-risk population.

Abstract E1910 evaluated the addition of blinatumomab to chemotherapy in adults with B-acute lymphoblastic leukemia (ALL). The addition of blinatumomab in patients (pts) with measurable residual disease (MRD) negative (neg) B-ALL significantly improved both relapse-free and overall survival (NEJM 2024; 391: 320-33)1. Given the increasing use of blinatumomab and the E1910 backbone chemotherapy regimen, we evaluated &gt; Grade 3 toxicities on this trial in further detail. We assessed toxicity among the MRD-neg pts by age, gender, body mass index (BMI), combined cytogenetic-molecular risk, and number of cycles of blinatumomab received. We also evaluated toxicities during induction since this trial used a modified chemotherapy backbone. Methods: The eligibility, combined cytogenetic-molecular risk, and treatment have been previously described.1 All toxicities were &gt; Grade 3 by CTCAE version 4 with at least a possible relationship to treatment. Descriptive statistics were used to summarize the occurrence and rates of toxicities and Fisher's exact test was used to compare differences in proportions between groups. Analysis of induction included all pts who started treatment. Analysis of Step 3 toxicities included MRD-neg pts who started treatment on the blinatumomab (n=111) or chemotherapy only arm (n=112). Results: Pt characteristics: For induction (n=488), median age was 51 years (yrs) (range 30-70); 48.6% female. Combined cytogenetic-molecular risk: favorable (13.5%); intermediate (12.9%); no risk assigned (16.2%); unfavorable (57.4%). For induction, we compared toxicities for E1910 (n=488) to pts treated on a prior young adult study (n=289) (C10403) (Blood Adv 2021; 5(2): 504-12). The incidence of hyperglycemia (8% vs. 31.1%, p&lt; 0.001), aspartate aminotransferase (AST) increase (6.1% vs. 12.8%, p=0.002), alanine aminotransferase increase (ALT) (11.7% vs. 28.7%, p&lt; 0.001), and hyperbilirubinemia (11% vs. 19%, p=0.002) were significantly lower in E1910 pts. The incidence of pancreatitis (1.8%), thromboembolic events (4.5%), and febrile neutropenia (25.4%) in E1910 was similar to C10403. Toxicities in the MRD-neg pts in the blinatumomab arm (n=111): Despite a high incidence of neutropenia (74.8%) and thrombocytopenia (55.9%) in Step 3, there was a relatively low incidence of sepsis (7.2%), bacteremia (1.8%), cytokine release syndrome (CRS) (3.6%) and neurologic adverse events (0-6.3%). There was a higher incidence of neurological or psychiatric events in the blinatumomab arm (23%) versus chemotherapy arm (5%) (p &lt; 0.001) when all events were combined. There was a numerically higher incidence of ataxia (4.4% vs. %, p=0.16) and dysphasia (11.1% vs. 3%, p=0.12) in pts &gt; 55 yrs and a higher incidence of neutropenia (80.3% vs. 66.7%, p=0.12) and thrombocytopenia (62.1% vs. 46.7%, p=0.12) in the younger pts (age &lt; 55 yrs). In pts with a BMI &lt; 30 kg/m2 (vs. &gt; 30 kg/m2), there was a significantly higher incidence of leukopenia (51.7% vs. 26.4%, p=0.007) and thrombocytopenia (65.5% vs. 45.3%, p=0.037). However, this did not translate into an increased incidence of bleeding or infectious complications. By gender, females had a higher numerical incidence of AST increase (8.8% vs. 0%, p=0.057) and CRS (7% vs. 0% p=0.12); whereas males had a higher incidence of catheter- related infections (7.4% vs. 0%, p=0.05) and hyperglycemia (11.1% vs. 3.5%, p=0.16). A little more than half (56.8%) of pts received 4 cycles of blinatumomab with the remainder of pts receiving 1 (10.8%), 2 (28.8%), or 3 cycles (3.6%). Pts receiving 3-4 cycles of blinatumomab vs. 1-2 cycles of blinatumomab had a statistically higher incidence of anemia (38.8% vs. 6.8%, p&lt; 0.001), neutropenia (98.5% vs. 38.6%, p&lt; 0.001), and thrombocytopenia (83.6% vs. 13.6%, p&lt; 0.001), likely related to being on treatment for a longer period of time. Conclusions: Blinatumomab was well tolerated with no significant toxicity differences noted by age, gender, or number of cycles of blinatumomab received. Pts with a lower BMI did have an increased incidence of leukopenia and thrombocytopenia, possibly related to flat dosing of the drug. However, this did not translate into increased complications. Toxicites during induction were notably few, which suggests that this backbone with age adjustments may serve as a good backbone for future trials. Blinatumomab is being evaluated with low dose chemotherapy and other targeted agents in ongoing trials.