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Alternative strategies are needed for patients with B-cell malignancy relapsing after CD19-targeted immunotherapy. Here, cell surface proteomics revealed CD72 as an optimal target for poor-prognosis KMT2A/MLL1-rearranged (MLLr) B-cell acute lymphoblastic leukemia (B-ALL), which we further found to be expressed in other B-cell malignancies. Using a recently described, fully in vitro system, we selected synthetic CD72-specific nanobodies, incorporated them into chimeric antigen receptors (CAR), and demonstrated robust activity against B-cell malignancy models, including CD19 loss. Taking advantage of the role of CD72 in inhibiting B-cell receptor signaling, we found that SHIP1 inhibition increased CD72 surface density. We establish that CD72-nanobody CAR-T cells are a promising therapy for MLLr B-ALL.Significance:Patients with MLLr B-ALL have poor prognoses despite recent immunotherapy advances. Here, surface proteomics identifies CD72 as being enriched on MLLr B-ALL but also widely expressed across B-cell cancers. We show that a recently described, fully in vitro nanobody platform generates binders highly active in CAR-T cells and demonstrate its broad applicability for immunotherapy development.This article is highlighted in the In This Issue feature, p. 1861

Supplementary Data from Surface Proteomics Reveals CD72 as a Target for In Vitro–Evolved Nanobody-Based CAR-T Cells in KMT2A/MLL1-Rearranged B-ALL

Supplementary Figure from Surface Proteomics Reveals CD72 as a Target for In Vitro–Evolved Nanobody-Based CAR-T Cells in KMT2A/MLL1-Rearranged B-ALL

Alternative strategies are needed for patients with B-cell malignancy relapsing after CD19-targeted immunotherapy. Here, cell surface proteomics revealed CD72 as an optimal target for poor-prognosis KMT2A/MLL1-rearranged (MLLr) B-cell acute lymphoblastic leukemia (B-ALL), which we further found to be expressed in other B-cell malignancies. Using a recently described, fully in vitro system, we selected synthetic CD72-specific nanobodies, incorporated them into chimeric antigen receptors (CAR), and demonstrated robust activity against B-cell malignancy models, including CD19 loss. Taking advantage of the role of CD72 in inhibiting B-cell receptor signaling, we found that SHIP1 inhibition increased CD72 surface density. We establish that CD72-nanobody CAR-T cells are a promising therapy for MLLr B-ALL. Significance: Patients with MLLr B-ALL have poor prognoses despite recent immunotherapy advances. Here, surface proteomics identifies CD72 as being enriched on MLLr B-ALL but also widely expressed across B-cell cancers. We show that a recently described, fully in vitro nanobody platform generates binders highly active in CAR-T cells and demonstrate its broad applicability for immunotherapy development. This article is highlighted in the In This Issue feature, p. 1861

Hematopathology fellowship education has grown in complexity as patient-centered treatment plans have come to depend on integration of clinical, morphologic, immunophenotypic, molecular, and cytogenetic variables. This complexity is in competition with the need for timely hematopathology care with stewardship of patient, laboratory, and societal resources. Accreditation Council for Graduate Medical Education Milestones provide a guidance document for hematopathology training, but fellows and their educators are in need of a simple framework that allows assessment and feedback of growth toward independent hematopathology practice. Entrustable professional activities provide one such framework, and herein, we provide proposed Hematopathology Fellowship Entrustable Professional Activities based on review of pertinent guidelines and literature, with multiple rounds of expert and stakeholder input utilizing a modified mini-Delphi approach. Ten core entrustable professional activities deemed essential for graduating hematopathology fellows were developed together with skills and knowledge statements, example scenarios, and corresponding Accreditation Council for Graduate Medical Education Milestones. Application of these entrustable professional activities in program design, fellow evaluation, and decisions regarding level of supervision is discussed with consideration of benefits and barriers to implementation. These entrustable professional activities may be used by hematopathology fellowship directors and faculty to provide fellows with timely constructive feedback, determine entrustment decisions, provide the Clinical Competency Committee with granular data to support Milestone evaluations, and provide insight into areas of potential improvement in fellowship training. Fellows will benefit from a clear roadmap to independent hematopathology practice with concrete and timely feedback.

IntroductionThe Accreditation Council for Graduate Medical Education requires residents to examine 1500 cytology specimens by the end of residency. Cytology cases of the week (COWs) were instituted in 2010-2011 in an effort to increase trainee exposure to cytology.Materials and methodsImages of 2 to 5 cases with basic clinical information are sent to residents weekly. Residents have 1 week to respond by e-mail; after which, correct answers are e-mailed. Cytology resident in-service examination (RISE) scores were used to assess the effectiveness of COWs. Additionally, a feedback survey was distributed to trainees to determine the perception of COWs as a teaching tool.ResultsAn unpaired two-sided t test showed residents who participated in COWs scored 15.4% higher on the RISE than residents who participated minimally or not at all over the 5-year period (P < 0.05). In 2014-2015 and 2015-2016, when COWs were minimally and not at all offered, we saw a significant decrease in average cytology RISE scores compared with prior years when COWs were offered (P

Alternate strategies are needed for B-cell malignancy patients relapsing after CD19-targeted immunotherapy. Here, cell surface proteomics revealed CD72 as an optimal target for poor-prognosis KMT2A/MLL1-rearranged (MLLr) B-ALL, which we further found to be expressed in other B-cell malignancies. Using a recently-described, fully-in vitro system we selected synthetic CD72-specific nanobodies, incorporated them into CARs, and demonstrated robust activity against B-cell malignancy models, including CD19 loss. Taking advantage of CD72’s role in inhibiting B-cell receptor signaling, we found that pharmacologic SHIP1 inhibition increased CD72 surface density. We establish CD72-nanobody CAR T’s as a promising therapy for MLLr B-ALL.

BackgroundDespite the intensity of hematopoietic stem cell transplantation (HCT), relapse remains the most common cause of death in juvenile myelomonocytic leukemia (JMML). In contrast to other leukemias where therapy is used to reduce leukemic burden prior to transplant, many patients with JMML proceed directly to HCT with active disease. The objective of this study was to elucidate whether pre-HCT therapy has an effect on the molecular burden of disease and how this affects outcome post-HCT.ProcedureTwenty-one patients with JMML who received pre-HCT therapy and were transplanted at UCSF were analyzed in this study. The mutant allele frequency of the driver mutation was assessed before and after pre-HCT therapy, using custom amplicon next-generation sequencing.ResultsOf the 21 patients, seven patients (33%) responded to therapy with a significant reduction in their mutant allele frequency and were classified as molecular responders. Six of these patients received moderate-intensity chemotherapy, one patient received only azacitidine. The 5-year progression-free survival after HCT of molecular responders was 100%versus 61% for nonresponders (P=.12). Survival of molecular nonresponders was not improved by use of high-intensity conditioning, but patients were salvaged if they experienced severe graft versus host disease. There were no baseline clinical characteristics that were associated with response to pre-HCT therapy.ConclusionsDespite the myelodysplastic nature of JMML, patients treated with pre-HCT therapy can achieve molecular remissions. These patients experienced a trend toward improved outcomes post-HCT. Importantly, molecular testing can be helpful to distinguish between responders and nonresponders and should become an integral part of clinical care.

Background Fine-needle aspiration biopsy (FNAB) is a minimally invasive, cost-effective diagnostic tool that can be used in low-resource settings. However, adequacy and accuracy of FNAB is highly dependent on the skills of the operator and requires specialized training. Poor technique can preclude definitive diagnoses because of insufficient quality or quantity of FNAB samples. We evaluated the efficacy of an intensive training experience in Tanzania on improving ultrasound-guided FNAB techniques. Methods A 2-day workshop offered didactic lectures, demonstrations, and hands-on practicum on fundamentals of ultrasound imaging and FNAB technique. A prospective interventional study design was used with pre- and postintervention surveys and assessments to measure the effect of the workshop on specific skills related to slide smearing and ultrasound-guidance among participants. Results Twenty-six pathologists and radiologists, including trainees in each specialty, participated in the workshop. Pre- and postworkshop assessments demonstrated that most participants improved significantly in nearly all technical skills for slide smearing and ultrasound-guided FNAB. After the workshop, most participants demonstrated substantial improvements in ability to prepare the ultrasound equipment, measure the lesion in three dimensions by ultrasound, target lesions in one pass using both parallel and perpendicular approaches, and prepare high-quality aspirate smears. Conclusion An in-country 2-day workshop in Tanzania was efficacious in transferring basic skills in FNAB smear preparation and ultrasound-guided FNAB, resulting in skills enhancement among participating pathologists and radiologists. Although mastery of skills was not the goal of this short workshop, participants demonstrated proficiency in most technical elements after workshop completion, and the workshop generated interest among select participants to pursue additional intensive training in cytopathology.

Introduction: B-cell acute lymphoblastic leukemia (B-ALL) patients that harbor rearrangements of the Mixed-lineage leukemia gene (MLLr; also known as KMT2Ar) have particularly dismal clinical outcomes. Although CAR T immunotherapies targeting CD19 have shown impressive responses treating MLLr B-ALL and other B cell malignancies, relapse, often with loss of relevant CD19 epitope, remains a major clinical concern. The mixed results of CD19 CAR T as a monotherapy underscores the need to pursue additional immunotherapy targets and novel therapeutic modalities for high-risk patients. Results and Methods: Data with existing CAR-T's suggest that increased target antigen density frequently correlates with increased tumor elimination. Therefore, we aimed to define the cell surface proteomic landscape of B-ALL to identify novel, MLLr-enriched candidates for targeted immunotherapy of this poor-prognosis subtype. As an initial screen, using N-glycoprotein capture and mass spectrometry, we quantified differentially abundant cell surface proteins in MLLr (n= 4) versus non-MLLr (n= 5) B-ALL cell lines (Figure 1). Label-free proteomics (n= 3 replicates) quantified >900 high-confidence membrane proteins (FDR=0.05). Principal component analysis identified unique cell surfaceome signatures between B-ALL subtypes, implying different surface landscapes associated with specific genetic alterations. The MLLr B-ALL "surfaceome" is notably characterized by increased expression of adhesion molecules not identified by RNA-sequencing alone. We focused on CD72 as a novel immunotherapy target given significant enrichment on MLLr B-ALL vs. other B-ALL subtypes, near equivalent antigen density to CD19, undetectable expression on HSPCs, T-cells, and other normal tissues, and reported widespread expression on other mature B-cell malignancies. Analysis of transcriptome and ChIP-seq data suggested increased CD72 expression in MLLr B-ALL is not regulated directly by the MLL-AF4 oncoprotein but instead a function of increased CD72 expression at pro-B-cell stage. Flow cytometry and immunohistochemistry on primary samples confirmed high expression of CD72 both in MLLr B-ALL as well as DLBCL. Recombinant CD72 ECD was panned against a fully in vitro nanobody yeast display library (McMahon et al., Nat Struct Mol Biol(2018)) resulting in isolation of multiple unique, highly-specific CD72 nanobody binders with KD's < 5nM. Nanobodies were incorporated into 2nd generation CAR constructs and transduced into normal donor CD8+ T-cells and assessed in vitro for tumor cell lysis, cytokine release, and exhaustion marker expression. Nanobody clone Nb.D4 outperformed others in lysis of B-ALL and DLBCL cells lines displaying a broad range of CD72 expression, had no activity versus CD72 negative cells, and showed similar efficacy to that found with a clinically-used CD19 CAR. To assess in vivo activity, CD72(Nb.D4) CAR-T's at 1:1 CD4:CD8 ratio were injected at an effector:tumor ratio of 5:1 into tumor-bearing NSG mice (luciferase-labeled SEM or MLLr PDX). In vivo results confirmed strong anti-tumor effect of CD72 nanobody CAR-T's, equivalent to clinical CD19 CAR, and significantly increased survival in mice (Figure 2). A CRISPR interference-generated antigen escape model of CD19 was also effectively eliminated by CD72 CAR-T's. We also introduce "antigen escape profiling", where cell surface proteomics of a CRISPRi CD72-knockdown model demonstrated extensive surfaceome rewiring with potential implications for leukemia cell trafficking and adhesion in the setting of acquired resistance. Given CD72's role as a BCR signaling inhibitory receptor, we are currently examining its influence on proximal B-cell receptor signaling and relationship to combination therapies affecting this pathway. Conclusions:By characterizing the surface proteomic landscape of B-ALL, we develop a resource for the research community and identify CD72 as a promising therapeutic target. We demonstrate that a novel, fully recombinant nanobody library can generate potent cellular therapies, which may be extended to other targets in the future. We anticipate that antigen escape profiling will prove broadly useful for anticipating mechanisms of resistance to novel immunotherapies. CD72 CAR-T's are a promising strategy across a range of B-cell malignancies, particularly those refractory to CD19 therapy. Disclosures Nix: UCSF: Patents & Royalties. Wiita:UCSF: Patents & Royalties; Indapta Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Protocol Intelligence: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

Context.—Statistical literacy can be defined as understanding the statistical tests and terminology needed for the design, analysis, and conclusions of original research or laboratory testing. Little is known about the statistical literacy of clinical or anatomic pathologists. Objective.—To determine the statistical methods most commonly used in pathology studies from the literature and to assess familiarity and knowledge level of these statistical tests by pathology residents and practicing pathologists. Design.—The most frequently used statistical methods were determined by a review of 1100 research articles published in 11 pathology journals during 2015. Familiarity with statistical methods was determined by a survey of pathology trainees and practicing pathologists at 9 academic institutions in which pathologists were asked to rate their knowledge of the methods identified by the focused review of the literature. Results.—We identified 18 statistical tests that appear frequently in published pathology studies. On average, pathologists reported a knowledge level between “no knowledge” and “basic knowledge” of most statistical tests. Knowledge of tests was higher for more frequently used tests. Greater statistical knowledge was associated with a focus on clinical pathology versus anatomic pathology, having had a statistics course, having an advanced degree other than an MD degree, and publishing research. Statistical knowledge was not associated with length of pathology practice. Conclusions.—An audit of pathology literature reveals that knowledge of about 12 statistical tests would be sufficient to provide statistical literacy for pathologists. On average, most pathologists report they can interpret commonly used tests but are unable to perform them. Most pathologists indicated that they would benefit from additional statistical training.

We report the case of a 73-year-old American traveler who presented with 3 weeks of fatigue, fevers, chills, and pancytopenia. Clinical and laboratory findings were consistent with hemophagocytic lymphohystiocytosis (HLH) and bone marrow biopsy revealed amastigotes consistent with visceral leishmaniasis. The range of endemic visceral leishmaniasis transmission now extends into northern Spain and travelers to this region should use personal protective measures against sand fly exposure.