Nonclinical Time for Family Medicine Residency Faculty: National Survey Results

Introduction: Recent changes to the Accreditation Council for Graduate Medical Education (ACGME) requirements eliminated minimum standards for protected nonclinical time for core faculty. Faculty perform many nonclinical tasks to maintain family medicine residencies. The objective of this study is to describe the landscape of nonclinical time for family medicine residency faculty. Methods: Program directors at ACGME-accredited family medicine residencies were electronically surveyed in August 2019 to describe nonclinical time of their faculty. Survey information requested included program demographics, the amount of nonclinical time allocated, and the estimated amount of nonclinical time spent per year completing their faculty duties. Results: A total 156 of 635 program directors (24.6%) returned the survey and 58 (9.1%) completed the entire survey for analysis inclusion. An average of 3,394 hours per year, per program were estimated to be spent on nonclinical activities. The greatest amount of time was spent on program administration (39%) and the least amount of time on curriculum development (5%). There was variation in the use of nonphysician faculty to complete these tasks. Allocated faculty time was comparable to estimated time spent performing nonclinical tasks. On average, a 24-resident program devoted 1.9 full-time equivalent faculty salary support to complete nonclinical activities. Conclusions: Family medicine residency faculty spend significant time completing nonclinical tasks required to meet ACGME requirements and need the protected time to complete these necessary tasks. Direct data on the use of faculty nonclinical time is needed to more accurately define its use.

Patient and Caregiver Attitudes Towards Gene Therapy for Sickle Cell Disease: A Need for Partnership and Education

Background: Fewer than 20% of patients with sickle cell disease (SCD) have access to curative matched sibling donor bone marrow transplantation (MSD-BMT). Development of novel therapies to ameliorate the serious morbidity and early mortality caused by SCD is a National Institute of Health research priority. Gene therapy for SCD has emerged as a promising approach in early-stage clinical trials approach with the potential to reach greater numbers of patients than MSD-BMT. Knowledge and attitudes of individuals with SCD towards this investigational new therapy and their willingness to participate in early-stage clinical trials have not been systematically described. Methods: Patients with SCD at least 13 years of age (n=66) and caregivers of children with SCD (n=38) were surveyed about knowledge, attitudes, and beliefs regarding gene therapy for SCD. Most questions utilized a 5-item Likert response scale while The Newest Vital Sign was used to assess health literacy. To explore attitudes around gene therapy in further detail, we identified a regionally diverse focus group comprised of 12 patients/caregivers with SCD from across the United States. We audio-recorded, transcribed verbatim, and analyzed five focus group discussions using thematic content analysis to identify salient themes related to attitudes towards gene therapy for SCD. Our goal was to identify the educational needs and preferences of this patient / caregiver stakeholder group. Results: Survey: Of the 104 survey respondents 96% identified as Black and 4% as Hispanic. Respondents were between 13-64 years (mean 29.6, Std Dev 11.9 years). HbSS and HbSC were the most common genotypes (61.5% and 24%, respectively). Only 4.8% of participants (N=5) felt "extremely knowledgeable" about gene therapy for SCD while most (63.4%) reported no/slight knowledge. We found no association between health literacy levels and gene therapy knowledge (p=0.361). Nearly 30% of participants reported that the risk of cancer as a potential side effect would "probably not prevent their enrollment" on a gene therapy trial while 48% said it "definitely/probably would preclude their participation". Most respondents had a neutral attitude regarding the safety of gene therapy for SCD and how good of a treatment it was (56.7% and 58.6%, respectively). Only a few respondents endorsed the idea that gene therapy was "unsafe" or "not a good treatment for SCD" (5.8% and 4.8% respectively). There was an association between increasing knowledge about gene therapy and agreement that it is safe (p=0.012) and a good treatment for SCD (p=0.031). Focus Groups: Among the focus group participants, there was consensus that communication about gene therapy is suboptimal. Participants noted that clinicians frequently use medical jargon, do not tailor their approach to the individual patient/caregiver, and fail to adequately disclose important details. Focus group members desired more information about side effects and risks associated with conditioning chemotherapy, immunosuppression, risk of infertility, and hair loss. Participants, particularly parents of children with SCD, were worried about future unknown risks and described the enormity of the decision to enroll in an early-phase trial. Focus group members verbalized the need for inclusion of patients with SCD as partners during the informed consent/assent process and ideally, at the outset of the clinical trial design. Conclusion: Very few patients with SCD described feeling knowledgeable about gene therapy for SCD; a majority have neutral feelings about the safety and utility ("good treatment for SCD") of this new approach. Patient/caregiver-centered education about gene therapy in a manner that meets stakeholder informational needs is urgently needed. Given the temporary hold on lentiviral gene therapy trials for SCD (after some participants developed a myeloid neoplasm on an industry sponsored trial in February 2021) and the risk of cancer as a probable or definite barrier to enrollment in a gene therapy trial for many patients, transparency of information about these risks is essential. For the successful execution of novel trials in SCD, a community-based participatory research approach is vital. Disclosures Sharma: Medexus Inc: Consultancy; Spotlight Therapeutics: Consultancy; Novartis: Other: Salary support paid to institution; Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Vindico Medical Education: Honoraria; CRISPR Therapeutics: Other, Research Funding. Johnson: CRISPR Therapeutics: Research Funding.

CD45RO+ T-Cell Add Back and Prophylactic Blinatumomab Administration Post Tcrαβ/CD19-Depleted Haploidentical Transplantation in Pediatric Patients with High Risk Acute Leukemia

For patients receiving haploidentical donor (haplo) hematopoietic cell transplant (HCT), depletion of TCRαβ T cells from the haplo-graft allows for excellent outcomes and low rates of graft-versus-host disease (GVHD), albeit with a significant delay in immune reconstitution (IR). The adoptive transfer of donor T-cells has been used to optimize IR but increases the risk of GVHD. CD45RA-depleted (memory) T-cells are associated with low rates of alloreactivity and thereby GVHD but retain specificity for leukemic and viral antigens. We implemented a prospective trial utilizing escalating doses of CD45RA-depeleted T-cell as addback following TCRαβ/CD19-depleted haploHCT to improve IR. Patients with acute lymphoblastic leukemia (ALL) also received prophylactic Blinatumomab (Blina) following infusion of CD45RA-depeleted T-cell to overcome the risk immune escape secondary to HLA-loss and relapse (NCT03849651). Between 2019 to 2020, 30 pediatric patients (9 males, 21 females) with high-risk acute leukemia were enrolled. Median age at HCT was 8.7 years (range 0.9-18.8). Nineteen patients had ALL, 11 patients had AML. Ten patients were in CR1, 13 in CR2 and 7 in CR3/>. Five patients received prior CD19-CAR T-cell therapy. The donors used were mothers (n=15), fathers (n=13), or sibling/others (n=2). All patients received a reduced intensity preparative regimen consisting of Fludarabine, Melphalan, Cyclophosphamide and Thiotepa. ATG was given on days -5, -4 and -3. Mobilized peripheral blood graft were infused on day 0 with a median number of CD34+ cells, γδ+ T-cells, αβ+ T cells, and B cells of 14.8, 22.7, 0, and 0.09x 10 6/kg, respectively. No GVHD prophylaxis was used post-HCT. Two weeks following engraftment, patients received CD45RA-depleted T-cell addback in 3 escalating doses (DL1: 1x10 5cells/kg, DL2: 1x10 6 cells/kg, DL3:1x10 7 cells/kg). All 30 patients engrafted with a median time for neutrophil and platelet engraftment of 10 (range: 9-11) and 15 (range: 13-20) days, respectively. Infusion of escalating doses of CD45RA-depleted T-cells was well tolerated. One month post infusion, there was a significant increase in the median number of CD3 T-cells, including CD8 and CD45RO+ T-cell subsets (**p<0.01, ***p<0.001, Fig 1A). There was also significant expansion of virus-specific T-cells (VSTs) directed towards Cytomegalovirus (CMV), Adenovirus (AdV), BK, or HHV-6 as shown by Elispot assays (**p<0.01, Fig. 1B). TCR repertoire, as assessed by Vb spectratyping, was broad and comparable to the donor by month 6 post-HCT. The incidence of CMV, AdV, and HHV-6 viremia was 60%, 6.7%, and 16.7% respectively. The median duration of viremia was 4 weeks for CMV (range: 1-13), 3 weeks for AdV (range: 2-13) and 2.5 weeks for HHV-6 (range: 2-20). There were 11 episodes of viral disease (7 colitis, 3 pneumonitis, 1 lymphadenitis). All episodes of viral disease resolved, except 2 that were ongoing at the time of death. The incidence of acute GVHD within 28 days post-infusion after dose level 1, 2 and 3 was 0%, 20% and 10% respectively (p=NS). The cumulative incidence of aGVHD and grade III-IV aGVHD for the entire cohort was 26.7% (12.4-43.3%) and 13.3% (4.1-28.1%) respectively. There was no chronic GVHD; however, follow up is short. Sixteen patients received and tolerated prophylactic Blina infusions. The median time to receiving Blina after CD45RO+ infusion was 29 days (range 15-56). Four of the 16 patients who received Blina relapsed: 3 with CD19+ disease and 1 with CD19-negative disease. With a median follow up of 12.7 months (range 3.5-24.5), 1 year OS and LFS for the cohort was 86.3% (74.6-99.7%) and 69.8% (55.2-88.4%) respectively. The cumulative incidence of relapse was 31.8% (15.3-49.8%) and of non-relapse mortality was 3.3% (0.2-14.8%) respectively. In this interim analysis, addback of CD45RA- depleted T-cells following TCRαβ/CD19-depleted haplo HCT was safe and led to enhanced functional immune reconstitution. Prophylactic infusion of Blina is well tolerated and its use post-transplant warrants further investigation. Analyses into the effect of ATG on immune reconstitution are underway. Figure 1 Figure 1. Disclosures Sharma: CRISPR Therapeutics: Other, Research Funding; Novartis: Other: Salary support paid to institution; Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Spotlight Therapeutics: Consultancy; Medexus Inc: Consultancy; Vindico Medical Education: Honoraria. Gottschalk: Catamaran Bio: Consultancy; Immatics: Membership on an entity's Board of Directors or advisory committees; Other: Other: patents and patent applications in the field of cancer cell and gene therapy ; Novartis: Consultancy; Tidal: Consultancy; Tessa Therapeutics: Consultancy. Triplett: Miltenyi: Other: Travel, meeting registration.

Exposure to Anti-Anaerobic Antimicrobials Around Hematopoietic Cell Transplant (HCT) Is Associated with Poor Outcomes in Pediatric Patients

Background Survival rates in pediatric hematopoietic cell transplant (HCT) have improved over the last several decades. However, the factors that influence suboptimal outcomes continue to be less well understood. Low diversity of the gut microbiota and dysbiosis are known to be associated with poor outcomes after HCT. Exposure to broad-spectrum antibiotics, particularly those with anti-anaerobic coverage, during the course of HCT can induce both loss of gut microbial diversity and worsen dysbiosis. We explored the relationship of exposure to antibiotics with outcomes after HCT among pediatric patients, specifically with respect to the development of acute graft versus host disease (aGVHD). Methods We performed a single institution, retrospective cohort study to evaluate the association of peri-HCT antibiotic exposures with post-HCT outcomes. All patients who underwent their first transplant between 2008-2019 at our institution were included in this study. Patient, disease, HCT, and antibiotic exposure related data were abstracted from patient medical charts. The primary independent variable of interest was exposure to antibiotics for at least 48 hours at any time point from the start of conditioning and up to 100 days after the graft infusion. Antibiotics were further classified based on anti-anaerobic activity. Antibiotic exposure was censored 7 days prior to aGVHD diagnosis. Descriptive statistics are provided. Overall survival (OS) and event-free survival (EFS) curves/functions were estimated by the Kaplan-Meier method, and compared using the log-rank test. Cumulative incidence curve/function of aGVHD (any organ), gastrointestinal aGVHD, relapse and non-relapse mortality (NRM) was estimated by the Kalbafleisch-Prentice method accounting for competing risks and compared by Gray's test. Statistical analyses were performed with SAS version 9.4 Results A total of 492 patients underwent their first HCT at our center during the study time period. The majority of patients underwent HCT for an underlying malignant disorder (n=408, 83%). A total of 174 patients died (35%); causes of death included GVHD (n=7, 4%), infection (n=31, 17.8%), organ dysfunction (n=34, 19.5%), or relapse (n=102, 58.6%). The cohort was then divided into 2 groups based on exposure to anti-anaerobic antibiotics (n=366, 74%), and no exposure to anti-anaerobic antibiotics (n=126, 26%). Overall survival at 2 years was 59% in the group exposed to any anti-anaerobic antibiotics vs. 82% in the unexposed cohort (p<0.01). EFS at 2 years post- transplant was 61% in the group exposed to any anti-anaerobic antibiotics compared to 77% in the non-exposed group (p<0.01). Non-relapse mortality was higher in those receiving anti-anaerobic antimicrobials at 19 vs. 5%. (p<0.01). There was no significant difference in relapse incidence in the two cohorts ( Twenty-three percent (n=116) of all patients were diagnosed with any grade II-IV aGVHD by day +100 with no difference between the 2 groups (p=0.2). Cumulative incidence of grades II-IV gastrointestinal aGVHD was 5.1% (n=27), with a higher incidence in those patients who did not receive anti-anaerobic antimicrobials (11 vs. 3%, p<0.01). Discussion In our cohort, exposure to anti-anaerobic antimicrobials in the peri-transplant setting was associated with increased mortality. The OS and EFS were significantly lower among those exposed to even short periods of anti-anaerobic antimicrobials. No corresponding increase in relapse was seen in those who received anti-anaerobic antibiotics. Infection and organ dysfunction were the leading causes of death in both exposed and unexposed cohorts. The decreased survival does not appear to be driven by aGVHD, as the overall incidence of aGVHD was not significantly different between the two groups. The exact cause-effect relationship between antibiotic exposure and outcomes after HCT in pediatric patients remains to be elucidated. Further studies should focus on the interaction of the nascent immune system, recipient microbiota, and exposure to broad-spectrum antimicrobials, particularly as they relate to the development of GVHD. Figure 1 Figure 1. Disclosures Sharma: Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Spotlight Therapeutics: Consultancy; Vindico Medical Education: Honoraria; CRISPR Therapeutics: Other, Research Funding; Medexus Inc: Consultancy; Novartis: Other: Salary support paid to institution.

COVID-19 in Pediatric Hematopoietic Cell Transplant Recipients: A CIBMTR Study

Background: Adult recipients of hematopoietic cell transplantation (HCT) are at a very high risk of adverse outcomes after COVID-19 (Sharma A, Bhatt NS, et al. Clinical characteristics and outcomes of COVID-19 in haematopoietic stem-cell transplantation recipients: an observational cohort study. The Lancet Haematology. 2021 Mar 1;8(3): e185-93). While children are known to have better outcomes after COVID-19 compared to adults in general, data on risk factors and outcomes of COVID-19 among pediatric recipients of HCT are lacking. Methods: Using the data reported to the Center for International Blood and Marrow Transplant Research (CIBMTR) between March 2020 and May 2021, we describe characteristics, severity, treatment approaches, and outcomes of pediatric HCT recipients who were ≤21 years of age at COVID-19 diagnosis. All diagnoses, donor choice/graft sources, and conditioning regimens were included. Patient, disease, and HCT-related factors were described as frequency for categorical variables and median, range, and interquartile range (IQR) for continuous variables. The probability of overall survival after COVID-19 was calculated using the Kaplan Meier estimator. Additionally, an analysis was performed in the subset of allogeneic HCT COVID-19 cases from the United States (US) to identify risk factors for developing COVID-19. COVID-19 cases were compared with a cohort of all pediatric allogeneic HCT recipients without COVID-19 matched by the transplant center. Impact of hematopoietic cell transplant comorbidity index (HCT-CI), HCT indication, donor type, conditioning intensity, graft vs. host disease (GVHD) prophylaxis, and occurrence of acute and chronic GVHD on development of COVID-19 was examined using Cox proportional hazards model. Hazard ratio (HR) and 95% confidence intervals (CI) were provided. Cumulative incidence of COVID-19 among the US centers reporting at least 1 COVID-19 infection was also calculated, using death from any cause as a competing risk. P value <0.05 was considered statistically significant for the analyses. Results: A total of 167 pediatric HCT recipients (allogeneic, allo: 135 and autologous, auto: 32) met study inclusion criteria. Median age at COVID-19 diagnosis for allo and auto HCT recipients were 15 years (range <1-21y) and 7 years (range 1-21y), respectively. Median time from HCT to COVID-19 diagnosis was 15 months (IQR 7-45) for allo recipients and 16 months (IQR 6-59) for auto HCT recipients. Forty-two percent (42%) of the patients had at least one comorbidity prior to HCT. Thirteen percent (13%) were receiving immunosuppression within six months prior to COVID-19 diagnosis. COVID-19 disease severity was mild in 87% of patients, while 4% of patients had severe disease requiring mechanical ventilation or supplemental oxygen. Only 36 HCT recipients (22%) received any COVID-19 directed therapy. Median follow-up from COVID-19 diagnosis was 53 days (range 1-270) and 37 days (range 1-179) for allo and auto HCT recipients, respectively. The overall probability of survival at 45 days was 95% (95% CI 90-99%) and 90% (95% CI 74-99%) for allo and auto HCT recipients, respectively (Figure 1). Forty-five (45) day survival was lower among recipients transplanted at the transplant centers outside the US [non-US recipients 85% (95% CI 71-95%) versus US recipients 98% (95% CI 93-99%)]. No deaths occurred in patients who had received a transplant between 2000-2013. The primary cause of death was COVID-19 in 54% of patients and primary disease in 38% of patients. In the subset analysis restricted to pediatric allogeneic HCT recipients transplanted at the US centers (n=34), the cumulative incidence of COVID-19 infection was noted to be 1.9% (95% CI 1.2-2.9%) at 6 months post-HCT and increased to 4.7% (95% CI 3.4-6.3%) by 1-year post-HCT. Cox regression analysis showed that compared to HCT-CI score of 0, patients with HCT-CI score of 1-2 were more likely to develop COVID-19 (HR 1.95; 95% CI 1.03-3.69, p=0.042). Underlying diagnosis, donor type, treatment exposures, or GVHD did not predict COVID-19 incidence. Conclusions: This is the largest series to date summarizing the cumulative incidence, risk factors, and outcomes of pediatric HCT recipients with COVID-19. Patients with pre-HCT comorbidities were more likely to develop COVID-19. However, the overall disease severity and mortality after COVID-19 were low in this patient cohort. Figure 1 Figure 1. Disclosures Bhatt: Rite Aid Corporation: Divested equity in a private or publicly-traded company in the past 24 months; Pfizer Inc.: Divested equity in a private or publicly-traded company in the past 24 months; Moderna, Inc.: Divested equity in a private or publicly-traded company in the past 24 months; Johnson & Johnson: Divested equity in a private or publicly-traded company in the past 24 months. Sharma: Medexus Inc: Consultancy; Spotlight Therapeutics: Consultancy; Vindico Medical Education: Honoraria; CRISPR Therapeutics: Other, Research Funding; Novartis: Other: Salary support paid to institution; Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution. Riches: ATARA Biotherapeutics: Other: Payment; Jazz Pharmaceuticals: Other: Payment; BioIntelect: Membership on an entity's Board of Directors or advisory committees. Dandoy: Omeros: Other: Consulted and received Honorarium.

Major ABO Incompatibility Significantly Influences the Survival and Outcomes after Allogeneic Hematopoietic Cell Transplantation in Leukemia - CIBMTR Analysis

Background: Allogeneic hematopoietic cell transplantation (allo-HCT) is a potentially curative treatment for acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). While many factors influence the outcomes of allo-HCT in these leukemias, the independent impact of ABO mismatching between the patient and donor remains unclear. Methods: Using the CIBMTR database, we identified adults aged ≥18 years with AML or ALL who underwent allo-HCT from HLA-matched sibling donor (MSD) or 8/8 matched unrelated donor (MUD) between 2008-2018. We excluded patients who underwent transplant from a mismatched donor source or who received an ex-vivo T-cell depleted graft. Patients were stratified into cohorts based on ABO status (match, minor mismatch, major mismatch, bidirectional mismatch). Outcomes such as overall survival (OS), disease free survival (DFS), non-relapse mortality (NRM), relapse, incidence of acute graft versus host disease (GVHD), chronic GVHD, neutrophil engraftment, platelet engraftment and graft failure were evaluated. Survival analysis was done using Kaplan-Meier method and significant predictors were evaluated using Cox-proportional hazard regression method. Multivariate regression model included main effect (ABO status) and covariates (patient age, gender match, disease type, disease status, HCT-CI, Karnofsky performance status, donor type, conditioning intensity/use of TBI, stem cell source, GVHD prophylaxis, ATG/alemtuzumab use, transplant year). Results: Of 4946 patients who met the study criteria, 2741 patients (55.4%) were ABO matched, 1030 patients (20.8%) had minor ABO mismatch, 899 patients (18.1%) had major ABO mismatch and 276 patients (5.6%) had bidirectional ABO mismatch. Graft manipulation for ABO incompatibility was performed in 900 patients (minor ABO mismatch=532; major ABO mismatch=226; bidirectional mismatch=142), however, the information on individual graft manipulation techniques was limited. In multivariable analysis (table 1), major ABO mismatch significantly affected the OS, platelet engraftment and primary graft failure. Compared to ABO matched allo-HCT, major ABO mismatched allo-HCT was associated with worse OS (major mismatch - HR 1.16, 95% CI 1.05-1.29; p=0.005), inferior platelet engraftment (HR 0.83, 95% CI 0.77-0.90; p=<0.001), and higher risk of primary graft failure [4.5% (major mismatch) vs. 3.2% (ABO matched) - HR 1.60, 95% CI 1.12-2.30, p=0.01]. There was a significant interaction between the ABO status and graft type (peripheral blood vs. bone marrow) for the acute GVHD grades 2-4 model, and they are presented separately (table 1). Bidirectional ABO mismatch also significantly impacted the outcomes such as acute GVHD grades 2-4 (in bone marrow stem cell subgroup, HR 0.50, 95%CI 0.27-0.93, p=0.02) in addition to a trend towards inferior survival and NRM (p-value not significant). Other outcomes such as relapse (p=0.41), acute GVHD grades 3-4 (p=0.13), and chronic GVHD (p=0.30) were not significantly influenced by the ABO status. Conclusions: Our study demonstrates that pre-transplant ABO status is an independent predictor of survival and other post-transplant outcomes in a large cohort of patients with AML and ALL undergoing allo-HCT in the recent era. This demonstrates the importance of considering ABO status in the donor selection algorithms and potential strategies to mitigate its adverse impact. Due to the limited information available on graft manipulation strategies, the impact of graft manipulation techniques on the outcomes could not be evaluated and needs to be investigated in future studies. Figure 1 Figure 1. Disclosures Guru Murthy: Techspert: Consultancy; Guidepoint: Consultancy; Cancerexpertnow: Honoraria; Qessential: Consultancy; TG therapeutics: Other: Advisory board; Cardinal Health Inc.: Honoraria. Devine: Magenta Therapeutics: Current Employment, Research Funding; Tmunity: Current Employment, Research Funding; Sanofi: Consultancy, Research Funding; Johnsonand Johnson: Consultancy, Research Funding; Orca Bio: Consultancy, Research Funding; Be the Match: Current Employment; Vor Bio: Research Funding; Kiadis: Consultancy, Research Funding. Farhadfar: Incyte: Consultancy. Sharma: Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Novartis: Other: Salary support paid to institution; Spotlight Therapeutics: Consultancy; Medexus Inc: Consultancy; CRISPR Therapeutics: Other, Research Funding; Vindico Medical Education: Honoraria. Stefanski: Novartis: Honoraria. Pulsipher: Equillium: Membership on an entity's Board of Directors or advisory committees; Adaptive: Research Funding; Jasper Therapeutics: Honoraria. Shaw: mallinkrodt: Other: payments; Orca bio: Consultancy.

Reduced Intensity Hematopoietic Cell Transplantation Improves Cerebral Hemodynamics in Children with Sickle Cell Disease

Introduction Allogeneic hematopoietic cell transplantation (HCT) is increasingly being utilized in patients with sickle cell disease (SCD) to prevent progressive organ dysfunction, including for primary or secondary stroke prevention. However, outcomes after HCT have mostly been evaluated using broad measures such as overall survival and event free survival with limited direct physiologic evidence of improved cerebral hemodynamics. Cerebral blood flow (CBF; mL blood/100 g tissue/min) is increased in SCD to compensate for chronic anemia, reduced oxygen carrying capacity and to maintain adequate oxygen delivery to the brain tissue. In SCD patients, CBF is inversely associated with intelligence quotient (Strouse JJ, et al. Blood. 2006;108(1):379-381.) and working memory (Prussien KV, et al. Stroke. 2021;52(5):1830-1834.) and has been shown to improve with blood transfusions (Guilliams KP, et al. Blood. 2018;131(9):1012-1021.). Assessment of CBF may help predict long-term neurocognitive outcomes in patients with SCD and assess therapeutic responses to therapies. Additionally, the high metabolic demand of the brain potentially makes assessment of CBF a sensitive predictor of future multiorgan damage in patients with SCD and hence may be useful to help determine eligibility of patients for curative therapies. Methods We performed anatomical and hemodynamic magnetic resonance imaging (MRI) of the brain prior to, and at 6 months after HCT in children with SCD undergoing a reduced intensity conditioning based HCT on a clinical study (NCT04362293). All patients received pretransplant conditioning with hydroxyurea, azathioprine, alemtuzumab, thiotepa and low dose total body irradiation (200-400 cGy). All patients received an unmanipulated mobilized peripheral blood derived hematopoietic stem and progenitor cell graft. One patient who received the graft from a haploidentical (HAPLO) donor also received post-transplant cyclophosphamide. Graft versus host disease prophylaxis comprised of sirolimus. A 3-dimensional (3D) T1 sequence was used for gray/white matter segmentation. 3D-pulsed arterial spin labeling (ASL) perfusion imaging (3 mm isotropic) was acquired to measure resting CBF. Mean CBF values were calculated from gray matter. Mean ± standard deviation and median values for various variables are presented. Results Four consecutive patients had 2 serial MRIs performed (one before HCT and another 6 months after HCT). Median age at HCT was 14.5 years. Indications for HCT, donor type and whether patients were receiving chronic transfusion therapy (CTT) prior to HCT are indicated in the Table. No patient had prior evidence of overt stroke. All patients engrafted and had >99% donor myeloid chimerism at the time of the post-HCT imaging. Mean pre-HCT hemoglobin was 8.7 ± 0.8 g/dL (median 8.6 g/dL) and it increased to 12.5 ± 2.1 g/dL (median 12.4 g/dL) at 6 months after HCT. All patients exhibited elevated resting CBF values prior to HCT (123.8 ± 32.2 mL blood/100 g tissue/min, median 112.8 mL blood/100 g tissue/min), that decreased following HCT (71.1 ± 32.1 mL blood/100 g tissue/min, median 72.8 mL blood/100 g tissue/min) (Table and Figure). None of the patients had any clinical neurological complications or imaging evidence of new infarcts or anatomical abnormalities in the follow up period. Conclusion Our preliminary results indicate that it is feasible to quantify CBF in patients with SCD before and after HCT using MRI. We demonstrate that cerebral hemodynamics improve after HCT in children with SCD, indicated by a decrease in CBF to near normal values (normal CBF ~80 mL blood/100 g tissue/min). The more substantial changes (-50% and -78%) are seen in children who were not receiving CTT, suggesting that CTT might partially mitigate CBF elevation prior to HCT. Nevertheless, 2 patients receiving CTT prior to HCT also had a further modest decrease in CBF after HCT (-5% and -18%). We plan to follow these changes at serial time points annually after HCT and correlate them with changes in neurocognitive functioning and other functional MRI measures. Improved CBF is expected to reduce stroke risk and may also preserve or improve neurocognitive functioning, and prospective monitoring of these outcomes are underway. Data on all the study participants who have undergone an HCT and had 2 serial MRIs performed by the ASH annual meeting will be presented. Figure 1 Figure 1. Disclosures Sharma: Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Medexus Inc: Consultancy; CRISPR Therapeutics: Other, Research Funding; Novartis: Other: Salary support paid to institution; Spotlight Therapeutics: Consultancy; Vindico Medical Education: Honoraria. Triplett: Miltenyi: Other: Travel, meeting registration. Hankins: Vindico Medical Education: Consultancy; UpToDate: Consultancy; Global Blood Therapeutics: Consultancy; Bluebird Bio: Consultancy.

Antibody and T-Cell Responses to Covid-19 mRNA Vaccines in Patients with B-Cell Lymphomas and Chronic Lymphocytic Leukemia (CLL)

Introduction: While the approval of three commercial vaccines for the SARS-CoV-2 virus has provided upwards of 95% protection against the coronavirus for healthy subjects, the efficacy among patients with hematologic malignancies remains unknown. Immune dysfunction and impaired humoral responses to other vaccines are well documented in patients with CLL and B-cell lymphomas. Furthermore, they suffer increased risk of morbidity and mortality with Covid-19 infections compared to healthy controls. As such, the immune response elicited by the available Covid-19 vaccines in these patients is of utmost importance to investigate. Methods: We performed a prospective exploratory analysis in CLL and B-cell lymphoma patients to evaluate humoral and T-cell responses to the commercially available mRNA Covid-19 vaccines. The objective was to obtain samples at baseline and 2-3 weeks post-vaccination, although some samples were obtained outside of this timeframe. IgG to the SARS-CoV-2 spike receptor-binding domain (RBD) was quantified using the ImmunoCAP platform (Thermo Fisher); results were compared to data from 167 subjects in a healthy vaccine cohort at the University of Virginia. T-cell responses to spike protein of SARS-CoV-2 were measured in 3 NHL patients and 3 matched healthy controls at 2-3 weeks post-2nd vaccine dose, by T cell receptor dependent activation-induced marker (AIM) assay using pooled peptides spanning spike protein. Results: Among 18 patients currently evaluable, median age is 67 y and 72% are male. Diagnoses include CLL (5), marginal zone lymphoma (MZL; 4), diffuse large B-cell lymphoma (3), follicular lymphoma (1), mantle cell lymphoma (MCL;4), and Waldenstrom's macroglobulinemia (1). All patients except 1 MZL patient are currently receiving or have received systemic treatment for their hematologic malignancy. Treatments include immunochemotherapy in 5 patients, Bruton's tyrosine kinase inhibitors (BTKi) with or without anti-CD20 monoclonal antibody therapy in 5, single agent anti-CD20 monoclonal antibody in 4, and other targeted therapy in 4 patients including venetoclax, lenalidomide, and bortezomib. Two patients had received prior autologous stem cell transplantation, 1 patient allogeneic transplantation, and 1 patient chimeric antigen receptor T-cell therapy. Among patients on therapy (n=10), median time from start of current treatment to Covid-19 vaccine was 136 days (range 13 - 829d). In patients who had completed therapy (n=8), median time from end of last treatment to vaccine was 153 days (range 37 - 355d). Seven patients had a blood sample drawn between 1 week and 1 month post-second mRNA vaccine dose. IgG antibody levels to spike RBD were markedly lower in NHL/CLL patients compared to those observed in the control cohort (median 2.1 µg/mL [IQR 0.23-7.6 µg/mL] versus 60.3 µg/mL [IQR 42.5-87.0 µg/mL], Mann-Whitney P<0.001, Figure 1). Of the 16 samples that were obtained post-vaccine dose 2, nine had IgG levels less than 2 µg/mL (manufacturer lower threshold of detection), whereas only 5 of 252 samples from the control cohort were less than this level (Chi-square P<0.001, RR =39.6 (95%CI 15.1-100)). Antibody responses were independent of type of therapy (Figure 2). The percentage of total lymphocytes and T cells was generally reduced in NHL patients versus controls; however, CD4+ T cells responding to spike protein were readily detected, despite the absence of antibody responses in 2 of these patients, both of whom had MCL. Curiously, 2 patients (1 MZL with and 1 MCL patient without antibodies) displayed a higher percentage of activated CD4+ T cells compared to controls, and CD8+ T cells also responded in each of these patients. T-cell responses were specific for spike protein as evidenced by no response to peptides of whole nucleoprotein. Conclusions: Compared to a reference cohort, patients with B-cell malignancies, both treatment-naïve and on treatment, have impaired antibody response to the commercially available mRNA Covid-19 vaccines. Despite this, virus-responsive T-cells can be readily detected, even in the absence of antibodies. Further research is needed to determine whether antibody levels can be used as a biomarker for vaccine efficacy, whether the presence of virus-specific T-cells confers protection in the absence of antibodies, and to determine the effect of booster doses of vaccine on immune response. Figure 1 Figure 1. Disclosures Wilson: Thermo-Fisher Phadia: Research Funding. Woodfolk: Regeneron: Other: Salary Support, Research Funding; NIH/NIAID: Other: Salary support, Research Funding; University of Virginia: Other: Salary Support; Regeneron: Other: research sponsor and salary support; FDA: Membership on an entity's Board of Directors or advisory committees; Clinical and Experimental Allergy: Other: Editorial Board. Portell: Abbvie: Research Funding; Aptitude Health: Honoraria; Merck: Honoraria, Research Funding; Xencor: Research Funding; Pharmacyclics: Honoraria; BeiGene: Honoraria, Research Funding; Targeted Oncology: Honoraria; Morphosys: Honoraria; SeaGen: Research Funding; TG Therapeutics: Honoraria, Research Funding; Acerta/AstraZeneca: Research Funding; Kite: Honoraria, Research Funding; Genentech: Research Funding; VelosBio: Research Funding. Williams: Janssen: Consultancy, Research Funding; Pharmacyclics: Research Funding.

Performance Evaluation Study of a Novel Digital Microscopy System for the Quantitative Analysis of Bone Marrow Aspirates

Background. We report here a trial in progress for the evaluation of a novel system aimed to provide an all-digital standardized bone marrow aspirate (BMA) analysis, Scopio Labs X100, empowered by artificial intelligence (AI) based cell pre-classification. Current methods for the analysis and reporting of BMA specimens are based on analog microscopy, as whole slide imaging at x100 magnification is not practically available. The lack of uniformity between experts in the field, originating from a subjective manual review, can lead to inconsistencies in disease diagnosis and classification, and thereby affect treatment and clinical outcomes. For example, ICSH and WHO guidelines require that at least 500 cells should be counted in at least two smears when a precise percentage of an abnormal cell type is required for diagnosis and classification. It is also recommended that in order reduce imprecision from sampling error, the total number of cells counted in the differential should be increased, specifically if the abnormal cell count is very close to a critical threshold for disease stratification or response assessment. For the general evaluation of hematopoiesis, Myeloid to Erythroid (M:E) ratio is reported. Considering the complexity of the manual BMA analysis, even more so in routine laboratory settings with competitive turnaround times, a digital transformation can sustain the desired standardization, and increase sensitivity and efficiency in routine workflow. Study Design and Methods. This multisite study is taking place at: Hospital of the University of Pennsylvania (HUP), Oregon Health and Science University (OHSU), and Tel Aviv Sourasky Medical Center (TASMC). BMA analysis is performed with a manual microscope as the reference arm and in Scopio Labs X100 Full Field BMA application as the test arm (Figure 1A). Two hematopathologists at each site independently review 265 BMA specimens, including 205 with a Romanowsky stain and 60 with a Prussian Blue stain, in both the test and the reference arms. There is a 3 week washout period between arms (Figure 1B, right). ICSH guidelines were rigorously translated into a comprehensive report format used in both study arms. The report presents 27 primary and 13 secondary characteristics for the morphological assessment of BMA (Figure 1C). These include evaluation of specimen quality, evaluation of count, maturation and morphology of trilineage hematopoietic elements (myeloid, erythroid and megakaryocytic), as well as lymphocytes and plasma cells. For a repeatability study, 8 representative samples are analyzed through 20 days, 2 daily runs and 2 replicas in one site. For reproducibility study, 8 representative samples are analyzed in all sites for 5 days with 5 replicas (Figure 1B, left). The collected BMA samples hold a distribution of 55.61% males, with 2.02%, 9.46%, 16.39%, 54.73% and 17.40% of ages 13-21, 22-39, 40-55, 56-75 and >75 respectively. All samples were diagnosed by WHO criteria. Diagnoses include AML, ALL, MPN, MDS, PCN, lymphoid neoplasms, aplastic anemia, ITP and normal morphology marrow and hemodiluted samples. All samples were retrieved from the sites' bone marrow sample storage. For the method comparison study, the primary and secondary characteristics are aggregated into three primary and secondary evaluation categories of specimen quality, count, and morphology and maturation assessments (Figure 1B, left, 1C). For the primary groups, confusion matrix will be produced. For the secondary groups, contingency tables will be generated (Figure 1B, left). For the repeatability and reproducibility (R&R) studies, two-way nested ANOVA tables will be created (Figure 1, right). Primary groups will be measured for accuracy in the form of efficiency, sensitivity and specificity. Secondary groups will be measured for overall agreement. R&R will be measured for SD and CV. The introduction of Scopio's full field morphological evaluation of BMA smears, promotes an accurate diagnosis of hematological disorders including hematological malignancies, and enables a remote evaluation of BMA smears. By reviewing the entire BMA smear, and by counting a very large number of cells, this novel approach provides a new and highly accurate tool for early detection of pathological conditions, including residual disease following therapy. Figure 1 Figure 1. Disclosures Bagg: Scopio Labs: Research Funding. Raess: Scopio Labs: Research Funding. Jengehino: Scorpio Labs: Other: Partial Salary Support. Wiszniewska: Scopio Labs: Research Funding. Huynh: Scorpio Labs: Other: Salary Support. Fan: Scopio Labs: Research Funding. Bhattacharyya: Scorpio Labs: Other: Partial Salary Support. Avivi: Novartis: Speakers Bureau; Kite, a Gilead Company: Speakers Bureau. Katz: Scopio Labs: Consultancy.

Assessment of Cardiac Abnormalities in Sickle Cell Disease Patients Using Cardiac Magnetic Resonance Imaging (CMR)

Introduction Sickle cell disease (SCD) is characterized by chronic hemolytic anemia which predisposes patients to high output heart failure. Recently it has been recognized that repetitive microvascular ischemic insults and reperfusion injury result in diffuse myocardial fibrosis and cardiac remodeling that eventually leads to irreparable myocardial injury. Superimposed on these cardiac insults, patients with SCD often have iron overload related to chronic transfusions. Together, these insults produce a unique SCD-related cardiomyopathy characterized by restrictive physiology with LV dilation. Cardiac Magnetic Resonance Imaging (CMR) is the only non-invasive technique for assessing and quantifying diffuse myocardial fibrosis with simultaneous highly accurate assessment of heart size and systolic and diastolic function. Diffuse myocardial fibrosis is measured by a CMR technique called T1 mapping and calculated as extracellular volume (ECV), which may serve as an early marker of sickle cell related cardiomyopathy. An early marker for SCD-related cardiomyopathy would allow for efficient screening, prevention, and institution of treatment strategies. We describe utilization of CMR to evaluate cardiac pathology in a cohort of pediatric SCD patients. Methods Twenty-six children with SCD underwent CMR, as clinically indicated, between January 2020 and July 2021 at our institution. We analyzed cardiac chamber size (left atrium [LA], left ventricle [LV], right ventricle [RV]), systolic and diastolic function parameters, and quantitative myocardial parametric mapping values (T1 pre- and post-contrast and T2*) for these patients. ECV was calculated for all patients using T1 pre- and post-contrast values in conjunction with current hemoglobin values. Four patients underwent an allogeneic hematopoietic cell transplant (HCT) for SCD and had serial CMR performed before and 1 month after HCT. Results Median age of patients was 17 years; 12 (70%) were female; 22 (84%) had HbSS, 3 (12%) had HbSC and 1 (4%) had Hb S beta thalassemia. 15 (58%) patients had LA enlargement and only a few had ventricular enlargement (LV, 11 [42%]; RV, 9 [35%]). Patients rarely had had LV (4 [15%]) or RV (1 [4%]) systolic dysfunction. Twenty-five (96%) patients had increased ECV; median 30.5% (IQR 28-34%, reference normal 20.8% +/- 2.4). All patients had normal myocardial T2* values indicating no myocardial iron deposition. Additional details are provided in Table. Among those who underwent HCT, all 4 had elevated ECV at baseline, which improved in 1 patient 1-month post-HCT (27% [pre] to 21% [post]). One patient had a dilated LA at baseline with the other 3 developing LA dilation at 1-month post HCT. Conclusion CMR provides accurate and reproducible measurements of chamber sizes/ventricular volumes, myocardial mass, and ventricular function. Multiparametric mapping enabled quantitative evaluation of myocardial fibrosis in patients with SCD. We found that diffuse myocardial fibrosis is often present in children with SCD, even those with apparently normal cardiac function. This indicates damage to the myocardium occurs before symptoms or measurable changes on echocardiography, calling into question our current screening procedures. T1 mapping to monitor the progression of fibrosis could help evaluate response to current therapies including SCD directed therapies, cardioprotective medications, and curative options such as HCT and gene therapy. Hence, we believe that cardiac MRI is complementary to echocardiography and provides additional clinically relevant information that will help guide treatment in patients with SCD. Additionally, it has been shown that patients with SCD who undergo successful HCT exhibit significant improvements in cardiac size, function, and diastolic filling parameters as early as 3 months after the procedure, with improvements continuing slowly up to 1 year after HCT. Early post-HCT evaluation in our cohort did show moderate improvement in ECV in one HCT recipient. Further follow up with serial monitoring is ongoing to evaluate long term changes in these patients. Data on additional patients who have undergone serial CMR monitoring after HCT will be presented at the ASH annual meeting. Figure 1 Figure 1. Disclosures Sharma: CRISPR Therapeutics: Other, Research Funding; Medexus Inc: Consultancy; Spotlight Therapeutics: Consultancy; Novartis: Other: Salary support paid to institution; Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Vindico Medical Education: Honoraria. Hankins: UpToDate: Consultancy; Global Blood Therapeutics: Consultancy; Vindico Medical Education: Consultancy; Bluebird Bio: Consultancy. Triplett: Miltenyi: Other: Travel, meeting registration.