Thompson, Alexis A.

Abstract Introduction: The Duffy null variant (genotype or phenotype) is associated with lower circulating absolute neutrophil counts (ANC) without increased risk for infection. It is found in ~66% of people identifying as Black or African American vs <1% of people of Asian or European ancestry. Many ANC reference intervals (RI) are not representative of the Duffy null population. There are no adult Duffy null WBC RI and no pediatric Duffy null ANC or WBC RI. Thus, we aimed to assess Duffy null ANC and WBC distributions as well as develop WBC and ANC RI for adults and pediatrics. Methods: Twenty-three sites across the United States collected samples with all sites excluding participants with conditions or medications that could impact ANC or WBC. Only Duffy null participants were included. Sex, race, ethnicity, age, sample collection type, practice setting, Duffy testing method, ANC, and WBC were recorded. The non-parametric method for determining lower limit of normal (LLN), upper limit of normal (ULN), and 90% confidence intervals (CI) around the limits was performed according to the Clinical and Laboratory Standards Institute guidelines. Specific ULN and LLN are not reported as these are preliminary data. The Mann-Whitney U test was used to compare sex and prior data; differences by age groups were assessed with Kruskal-Wallis test. Results: 316 participants 18+ years-old (y/o) were assessed of whom 62.3% (n=197) are female, 97.5% (n=308) identified as Black or African American, and 94.9% (n=300) identified as non-Hispanic. Median age was 47 y/o (IQR: 32-60.5). Median ANC was 2600/uL (IQR: 1860-3530; range: 400-7400); 28.6% (n=90) of participants had ANC <2000/uL, 13.6% (n=43) had ANC <1500/uL, and 2.5% (n=8) had <1000/uL. The 90% CI around the LLN was 810-1070/uL and 5570-7130/uL around the ULN. Consistent with prior data, there was a difference in median ANC by sex (male: 2400/uL; female: 2710/uL; p=0.02). There was no significant difference between this ANC data and previously published Duffy null ANC data (p=0.28). Median WBC was 5.4x109/L (IQR: 4.4-6.5; range: 2.10-11.64) with 4.1% (n=13) of participants with WBC <3.0x109/L. The 90% CI around the LLN is 3.68-4.30x109/L and 11.02-12.97x109/L around the ULN. 515 participants between 0-17 y/o were assessed with 51.8% (n=267) females, 94.8% (n=488) identified as Black or African American, and 94.0% (n=484) identified as non-Hispanic. Among pediatric participants, 56.8% (n=291) had ANC <2000/uL, 38.7% (n=198) had ANC <1500/uL, and 14.4% (n=74) had ANC <1000/uL. For those <1 y/o (n=29), median ANC was 950/uL (IQR: 840-1360; range: 111-3910). There are currently too few samples to predict ULN and LLN. Median WBC was 8.85x109/L (IQR: 7.03-10.16; range: 4.17-13.53). For those 1-5 y/o (n=143), median ANC was 1735/uL (IQR: 1100-2550; range: 207-5810) with a 90% CI around the LLN of 207-820/uL and 4020-5810/uL around the ULN. Median WBC was 6.72x109/L (IQR: 5.64-8.25; range: 3.68-12.97). For those 6-11 y/o (n=128), median ANC was 1590/uL (IQR: 1090-2470; range: 420-5490) with a 90% CI around the LLN of 420-910/uL and 4340-5490/uL around the ULN. Median WBC was 5.42x109/L (IQR: 4.45-6.70; range: 2.80-10.50). For those 12-17 y/o (n=215), median ANC was 2190/uL (IQR: 1460-2930; range: 204-5850) with a 90% CI around the LLN of 540-930/uL and 4350-5510/uL around the ULN. Median WBC was 5.06x109/L (IQR: 4.26-6.20; range of 2.04-9.91). There is a significant difference in ANC by age category (p<0.0001). Conclusion: This is the first report of healthy pediatric Duffy null ANC and WBC data and the first large-scale verification of adult Duffy null ANC and WBC data. Final RI are expected in September 2025. Among adults with the Duffy null phenotype, ANC LLN are likely between 810-1070/uL. Pediatric ANC LLN are likely as low as 207-820/uL (1-5 y/o), 420-910/uL (6-11 y/o), and 540-930/uL (12-17 y/o). These findings redefine “normal” as a significant proportion of healthy participants have ANC or WBC below current RI or below thresholds typically defined as disease. Limitations include heterogeneous sample populations and collection methods. Future analyses will assess differences between collection sites or methods. Ultimately, this work lays the foundation for a more scientifically sound and equitable approach to medical care by ensuring that RI accurately reflects health for the entire community. Healthcare systems are strongly encouraged to adopt Duffy null-specific ANC and WBC RI.

Abstract Introduction Elevated levels of fetal hemoglobin (HbF) ameliorate sickle cell disease (SCD) manifestations. BEAM-101 is an investigational cell therapy comprising ex vivo base-edited autologous CD34+ hematopoietic stem and progenitor cells (HSPCs) that directly target the HBG1/2 promoters to disrupt BCL11A binding, switching production from sickle (HbS) to majority anti-sickling HbF. We present ongoing data from the BEACON study (NCT05456880), a Phase 1/2, single-arm, open-label study evaluating a single dose of BEAM-101 in individuals with SCD and severe vaso-occlusive crises (sVOCs). Methods Eligible patients were aged 12–35 years with SCD and ≥4 sVOCs in the 2-year period prior to informed consent. After mobilization with weight-based or tiered fixed-dose plerixafor, autologous CD34+ HSPCs were collected by leukapheresis and genetically modified with an adenine base editor. Following conditioning with pharmacokinetically adjusted myeloablative busulfan (target cumulative AUC 80 hr*mg/L), patients received a single dose of BEAM-101 (≥3.0×106 viable CD34+ cells/kg). Patients were then monitored for neutrophil and platelet engraftment, adverse events (AEs), total Hb, Hb fractions, % F-cells, hemolysis markers, sVOCs, and additional protocol endpoints for up to 24 months. Results As of June 16, 2025, enrollment has been completed and 46 patients have initiated mobilization. Of the 26 patients who have received BEAM-101, mean duration of follow-up was 6.2 (range 1.0–18.7) months. Baseline demographics were: age 18–34 years, 24 βS/βS genotype, 21 self-reported Black/African American, and 11 female. One patient, who successfully engrafted and obtained stable HbF levels >60%, withdrew consent 5 months post-infusion. For the 26 treated patients, the median number of stem cell collection cycles was 1 (range 1–4); 18 (69.2%) required a single cycle, 4 required 2 cycles, and 4 required >2 cycles. Target cell dose was achieved with a median of 3 (1–12) collection days. Patients received a mean BEAM-101 dose of 8.4 (range 3.2–23.4) ×106 viable CD34+ cells/kg. By the data cut, patients achieved neutrophil (n=26) and platelet (n=24) engraftment at a median of 18 (12–30) days and 19 (11–50) days, respectively, with a median duration of 7 (4–17) days of neutropenia. Of the 24 evaluable patients, 9 (37.5%) achieved platelet engraftment without requiring platelet transfusion through the transplant process. No patients had ≥Grade 3 AEs or serious AEs related to BEAM-101. One patient died due to respiratory failure, assessed as likely related to busulfan conditioning, 4 months post-infusion as previously reported. Mean total Hb increased to 12.1 (range 9.0–14.7) g/dL by Month (M) 1 (n=24), 15.6 (11.9–18.6) g/dL by M6 (n=11), and was sustained through follow-up. Four patients had total Hb levels above the normal range beyond M6 without any associated clinical manifestations or need for therapeutic intervention. Erythropoietin levels trended towards normal in all patients, including those with elevated total Hb. Mean endogenous HbF (HbF/[HbF+HbS]) was >60% and HbS was <40% by M1, which was sustained through last follow-up. At M6, mean % F-cells were 99.2% (97.0–99.9; n=10) and mean HbF/F-cell was 20.8 (18.0–23.9; n=9) pg, exceeding the protective threshold of 10 pg against sickling. Peripheral blood editing was at a mean of 68.5% by M3 (n=16), 69.6% by M6 (n=10), and 72.8% by M12 (n=5). Hemolysis markers and sickling parameters normalized or improved for all patients. No patients experienced any investigator-reported sVOCs post-engraftment. Conclusions The BEAM-101 treatment process is characterized by a low number of mobilization and collection cycles and high editing efficiency, resulting in rapid neutrophil and platelet engraftment and robust pancellular HbF expression, with durability observed up to 18 months. Additionally, there is a corresponding reduction in HbS levels to <40%, and improvements or resolution of hemolysis parameters and anemia, along with resolution of investigator-reported sVOCs post-engraftment. The safety profile of the BEAM-101 treatment regimen is consistent with busulfan conditioning, autologous HSCT, and underlying SCD. These results demonstrate the potential for base editing of the HBG1/2 promoters as a safe and effective therapeutic modality for the treatment of SCD that also has the potential to minimize hospitalization and treatment process burden for patients, families, and sites.

Fetal hemoglobin (HbF) is anti-sickling and elevated HbF ameliorates sickle cell disease (SCD) manifestations. BEAM-101 is an investigational cell therapy comprised of autologous CD34+ hematopoietic stem and progenitor cells (HSPCs) that are base edited ex vivo to introduce naturally occurring A-to-G substitutions into the promoters of the HBG1/2 genes that encode γ-globin to disrupt BCL11A transcriptional repressor binding sites, leading to increased HbF production. We previously demonstrated in pre-clinical studies that base editing potently induced HbF (>60%) and proportionately reduced sickle hemoglobin (HbS) (<40%) without relying on double-stranded DNA breaks. We present initial data from BEACON (NCT05456880), a Phase 1/2, single-arm, open-label study evaluating the safety and efficacy of a single dose of BEAM-101 in patients with SCD with severe vaso-occlusive crises (VOCs). Patients 18-35 years diagnosed with SCD and ≥4 severe VOCs in the 2-year period prior to screening per trial criteria were eligible. After plerixafor mobilization, autologous CD34+ HSPCs were collected by leukapheresis/isolation and genetically modified with an adenine base editor. After myeloablative conditioning with pharmacokinetically adjusted busulfan, patients received a single infusion of BEAM-101 (≥3.0 × 106 viable CD34+ cells/kg) and are monitored for neutrophil and platelet engraftment, adverse events (AEs), total hemoglobin (Hb), Hb fractions, % F-cells, hemolysis markers, peripheral blood editing, and VOCs for 24 months. As of July 2, 2024, >20 patients are enrolled and BEAM-101 has been manufactured for 8 patients, of whom 6 patients have been dosed. One patient not included in this analysis discontinued during the mobilization/collection period prior to BEAM-101 treatment for non-medical reasons. Baseline demographics were as follows: 5/6 patients βS/βS, 1/6 patients βS/β0, all self-reported Black/African American, 50% female, aged 19-27 years. Of the 6 patients, half (n=3) required only a single mobilization cycle and the other half required 2. Patients received a mean BEAM-101 dose of 11.9 × 106 (5.2-23.4) viable CD34+ cells/kg. Excepting safety data that include all patients dosed (n=6), the following data are from patients dosed with ≥1 month of follow up (n=4; 6, 5, 2, and 1 month[s] post-treatment, each). All 4 patients with ≥1 month of follow up achieved neutrophil and platelet engraftment at a median of 17 (15-19) and 20 (11-34) days, respectively. One patient died due to respiratory failure, likely related to busulfan conditioning, 4 months after infusion. In all patients dosed (n=6), there have been no ≥Grade 3 AEs or serious AEs related to BEAM-101. Using the central laboratory data, patients' total Hb increased from baseline (mean 9.3 [7.9-10.9] g/dL) to 17.9, 18.2, 11.0, and 11.8 g/dL at last time point (LTP) available for P1, P2, P3, and P4, respectively. No signs/symptoms or interventions were undertaken for high total Hb. All patients achieved >60% HbF of non-transfused Hb (total Hb − HbA) at Month (M) 1 and sustained this elevation to the LTP available. By M1, HbS% in non-transfused blood dropped to ≤36% in all 4 patients and was sustained through LTP. In total blood, % F-cells were 99.6% in P1 at M6, 94.4% in P2 at M4, 52.0% in P3 at M2, and 13.3% in P4 at M1 with all patients having >19 pg HbF/F-cell at LTP available. Peripheral blood editing in nucleated cells, measured in P1 (at M6) and P2 (at M3), was 69.9% and 76.1%, respectively. Markers of hemolysis (lactate dehydrogenase, indirect bilirubin, haptoglobin, and reticulocyte counts) have normalized or improved for all patients. No VOCs have been reported by investigators following BEAM-101 treatment. These initial data show a safety profile for BEAM-101 consistent with busulfan conditioning and autologous HSCT. Treatment with BEAM-101 resulted in rapid engraftment, improvement in hemolysis markers, and marked improvement of anemia in all 4 dosed patients. We observed rapid and robust HbF induction consistent with pre-clinical data by M1 (>60%) and corresponding HbS reduction (≤36%) in non-transfused blood in all post-treatment assessments. No VOCs were reported by investigators post-treatment. These initial data support base editing of the HBG1/2 promoters as an effective therapeutic modality for the treatment of SCD and will continue to be investigated in the ongoing BEACON study. Updated data to be presented.

Abstract In 2003, the Institute of Medicine noted the need to improve workforce diversity. The American Society of Hematology (ASH) responded by developing the Minority Recruitment Initiative (MRI) to recruit diverse physicians/scientists into hematology. We evaluated the outcomes of the program. From 2004 to 2022, there were 405 awardees. Compared with national estimates, MRI awardees were less likely to discontinue their degree programs. MRI graduate student awardees had 0% attrition (97.5% confidence interval [CI], 10.6), whereas the national minority graduate student attrition was 36%. Medical student awardees had 2.2% (95% CI, 0.61-5.6) attrition, compared with the minority medical school attrition of 5.6%. Awardees were more likely than expected to pursue hematology-oncology (5.7% minority national estimate) because 14.4% (95% CI, 8.1-23.0) of medical student awardees and 88.5% (95% CI, 70.0-97.6) of early career awardees remain in the field. ASH has developed a successful program, but continued efforts are needed to advance equity in hematology.