ABSTRACT Steroid‐refractory chronic cutaneous graft‐versus‐host disease (GVHD) causes substantial morbidity, prolonged hospitalization, and non‐relapse mortality after allogeneic hematopoietic cell transplantation. We report a young adult with multisystem chronic GVHD and recurrent life‐threatening inflammatory skin flares refractory to multiple standard therapies, with cumulative inpatient care exceeding 1 year. Under an institutional review board‐approved compassionate‐use protocol, he received a non‐cytotoxic monoclonal antibody targeting CD162 (P‐selectin glycoprotein ligand‐1). Treatment was associated with durable resolution of active cutaneous GVHD, corticosteroid reduction, improved mobility, and meaningful recovery in daily function and quality of life. Trial Registration The author has confirmed clinical trial registration is not needed for this submission.

Practice variation in allogeneic hematopoietic cell transplantation may contribute to preventable toxicity, nonrelapse mortality, and excess cost. We evaluated outcomes occurring with the implementation of a program-wide standardization initiative in a medium-sized program. We conducted a single-center retrospective cohort study of consecutive patients undergoing first allogeneic hematopoietic cell transplantation in 2024 during implementation of a system-level redesign. The intervention emphasized high-reliability operations through concise standard operating procedures, formal quality management, standardized recipient and donor selection, a limited conditioning regimen formulary, fluid-sparing conditioning and graft infusion practices, post-transplant cyclophosphamide-based graft-versus-host disease prophylaxis, and an early-discharge outpatient care model. The primary endpoint was 1-year overall survival. Secondary endpoints included graft-versus-host disease-free, relapse-free survival, nonrelapse mortality, acute and chronic graft-versus-host disease, length of stay, and pharmaceutical cost. Ninety-four patients underwent a first allogeneic hematopoietic cell transplantation in 2024. One-year overall survival was 92.6%, graft-versus-host disease-free, relapse-free survival was 56%, and nonrelapse mortality was 1%. The cumulative incidence of grade II to IV acute graft-versus-host disease was 32%, with grade III to IV acute graft-versus-host disease in 5%, and chronic graft-versus-host disease requiring systemic therapy in 18% at 1 year. Median hospital length of stay was 19 days overall and 14 days among adults. Average pharmaceutical cost per patient decreased from $88,810 across the preceding 3 fiscal years to $39,019 under the redesigned care model. In this single-center cohort, implementation of a standardized, high-reliability allogeneic hematopoietic cell transplantation care model was associated with excellent 1-year survival, low nonrelapse mortality, and lower pharmaceutical cost. These findings support the potential value of disciplined operational standardization as a complement to contemporary transplant platforms.

Solitary plasmacytoma of bone (SPB) is a localized plasma cell neoplasm associated with a substantial risk of progression to multiple myeloma (MM), yet the role of adjuvant systemic therapy following definitive radiation therapy (RT) remains undefined. We conducted a randomized phase III trial (Alliance A061402) to evaluate whether the addition of systemic therapy with ixazomib, lenalidomide, and dexamethasone (IXA-LEN-DEX) to zoledronic acid (ZA) improves outcomes compared with ZA alone in patients with SPB and minimal (< 10%) bone marrow plasma cell involvement following RT. Patients were randomized to receive six 28-day cycles of IXA-LEN-DEX-ZA or ZA alone. The primary endpoint was time to progression (TTP) to MM. The study was closed early due to poor accrual after enrolling 11 patients (IXA-LEN-DEX-ZA, n = 5; ZA, n = 6). All patients completed RT and planned treatment without dose reductions. The combination regimen was well tolerated, with limited grade ≥ 3 toxicities, including hypophosphatemia and lymphopenia. At follow-up extending beyond 4 years, the 1- and 4-year progression rates to MM in the IXA-LEN-DEX-ZA arm were 0% and 33%, respectively, compared with 37.5% and 58.3% at 1 and 2 years in the ZA-alone arm. Although underpowered, these findings demonstrate the feasibility and tolerability of an all-oral adjuvant systemic regimen in SPB and provide prospective data supporting further investigation of systemic strategies to delay progression to MM.

Solitary plasmacytomas (SPs) are rare localized tumors of clonal plasma cells, either in the bone (solitary bone plasmacytoma) or in soft tissue/extraosseous (extramedullary) with either no or with minimal bone marrow (BM) infiltration (<10% clonal plasma cells by immunohistochemistry) and no evidence of systemic involvement or myeloma defining events. Approximately 50% of SPs will progress to symptomatic myeloma within 5 years after initial definitive local radiotherapy. Increased availability of improved diagnostic and monitoring tools has increased the sensitivity of detection of additional lesions and marrow involvement and has implications for the follow-up strategy after treatment. Thus, the definitions and requirements for the diagnosis and follow-up of SPs are evolving. The diagnosis of SP requires the careful exclusion of multiple myeloma (MM) that would require systemic therapy, by using all the available methods to detect systemic disease (advanced imaging, sensitive BM assessment methods, blood and urine tests). Local radiotherapy remains the mainstay of therapy, and despite the availability of innovative drugs for MM, the clinical benefit of systemic therapy currently remains poorly defined. The International Myeloma Working Group provides here updated recommendations for the diagnosis, evaluation, treatment, and response assessment of patients with SPs, incorporating recent data and advances in diagnostic tools.

Background: A single nucleotide polymorphism (SNP) in ACKR1/DARC results in erythrocyte Duffy null phenotype in ~66% of African American (AA) and <1% of White pts. This is associated with lower absolute neutrophil count (ANC) and has a key role in cytokine homeostasis, which may influence MM pathobiology, response to inflammatory stressors, and treatment (tx) outcomes. DETERMINATION found a PFS benefit with RVd+ASCT (RVd-alone vs RVd+ASCT: hazard ratio [HR] 1.53; 95% confidence interval (CI) 1.23–1.91), but subgroup analysis showed differential PFS effect by race (AA pts: HR 1.07, 95% CI 0.61–1.89; White pts: HR 1.67, 95% CI 1.29–2.15). As race is a social construct, and with equitable access to care and cost-free therapy provision in DETERMINATION, we sought a pathobiological explanation. Given the prevalence of Duffy null and its known impact on the inflammasome, we hypothesized that Duffy status may affect magnitude of PFS benefit. We report updated PFS analyses in all pts in DETERMINATION with Duffy status available. Methods: Pts received RVd-alone or RVd+ASCT followed by R maintenance until progression in both groups. Peripheral blood samples underwent genomics analysis for the SNP rs2814778 and were classified as C/C (Duffy null) or non-C/C (Duffy non-null). Impact of Duffy status on PFS was evaluated with Cox proportional hazards regression in univariate models. Heterogeneity of tx effect was assessed by a test for interaction. Results: Overall, 592 enrolled pts were evaluable for Duffy status; consistent with US population data, 63.3% (n=62/98) of AA pts and 1.1% (n=5/465) of White/other pts were Duffy null (n=4/29 pts with missing race). 493 randomized pts had Duffy status evaluated (68.3% of intent-to-treat [ITT] population, N=722), with 238 assigned to RVd-alone and 255 to RVd+ASCT. Pts were broadly representative of the ITT population. PFS with RVd-alone vs RVd+ASCT in the analysis cohort, overall and by race, was consistent with the ITT population. Of the 493 pts, 59 (12.0%) pts were Duffy null (53 [89.8%] AA, 5 [8.5%] white/other race, 1 missing), and 434 (88.0%) were Duffy non-null (403 [92.9%] white/other race, 28 [6.5%] AA, 3 missing). Median (interquartile range) baseline ANC was 2.8 (2.1–4.3) x 109/L in Duffy null pts vs 3.4 (2.6–4.6) x 109/L in Duffy non-null pts. In Duffy null vs Duffy non-null pts, median duration of tx from randomization (35.1 vs 33.8 months [mos]) and of R maintenance (42.1 vs 36.4 mos) were similar in the RVd-alone arm but numerically shorter (30.3 vs 40.4 mos; 32.5 vs 42.4 mos) in the RVd+ASCT arm. Rates of grade ≥3 neutropenia in the RVd-alone vs RVd+ASCT arms (for all tx) were 48.3% vs 80.0% in Duffy null pts and 40.7% vs 88.9% in Duffy non-null pts; rates of grade ≥3 febrile neutropenia (FN) were 0% vs 3.3% in Duffy null pts and 7.2% vs 9.3% in Duffy non-null pts. Overall pooled PFS was similar in Duffy null vs Duffy non-null pts (median 62.5 vs 56.7 mos; HR 0.94, 95% CI 0.62–1.42). Duffy non-null pts had PFS findings consistent with the ITT analysis (RVd-alone vs RVd+ASCT: 120/209 vs 85/225 events/pts; median 46.7 vs 67.5 mos; HR 1.76, 95% CI 1.33–2.34). In contrast, Duffy null pts had longer PFS with RVd-alone vs RVd+ASCT (9/29 vs 16/30 events/pts; median NR vs 44.0 mos; HR 0.64, 95% CI 0.27–1.50) (interaction p-value 0.005). When these analyses were restricted to AA pts, the same PFS pattern was seen with RVd-alone vs RVd+ASCT among Duffy null (8/25 vs 15/28 events/pts; median NR vs 45.4 mos; HR 0.66, 95% CI 0.27–1.60) compared to Duffy non-null pts (6/13 vs 3/15 events/pts; median 64.4 mos vs NR; HR 5.29, 95% CI 1.20–23.4). On univariate analysis by Duffy status (null vs non-null), PFS HR was 0.51 (95% CI 0.26–1.00) with RVd-alone and 1.63 (95% CI 0.95–2.78) with RVd+ASCT. Conclusions: These exploratory analyses of DETERMINATION suggest that Duffy status drives a difference in tx effect that is more pronounced than for PFS by race. With RVd-alone vs RVd+ASCT, PFS appeared better in Duffy null pts and poorer in Duffy non-null pts. In Duffy null vs non-null pts, PFS appeared better with RVd-alone and poorer with RVd+ASCT. Similar trends were seen in analyses restricted to AA pts, indicating Duffy status may provide a biological rationale for observed differential tx effects, rather than race. Further studies are warranted to assess impact of Duffy status on clinical outcomes such as treatment response, overall survival, and effects on the inflammasome, as well as ANC and FN.

7030 Background: Common toxicities associated with infusion of Chimeric antigen receptor T-Cell (CAR T-cell) therapy include cytokine release syndrome (CRS) and immune-effector-cell-associated neurotoxicity syndrome (ICANS). While early steroid use has correlated with a reduced risk of high-grade CRS and ICANS, there is conflicting data regarding its impact on CAR-T efficacy. We aim to study the impact of prophylactic steroid use on toxicities and outcomes at our institution. Methods: We performed a single-center comparative analysis between two patient cohorts at higher risk of CRS and ICANS based on elevated inflammatory markers, (ferritin ≥400 ng/mL and CRP ≥4 mg/dL). One cohort received prophylactic dexamethasone 10 mg on days 0,1, and 2. Univariate statistics were calculated using X2, Fisher’s exact tests, and ANOVAs, where appropriate. Kaplan Meier was used to estimate overall survival (OS) and progression-free survival (PFS) and compared using the log-rank test. Results: Out of 63 patients with high ferritin and CRP, 10 patients received prophylactic steroids (Group PS) and 53 patients did not (Group NPS). In the NPS group, 46 patients had a primary diagnosis of non-Hodgkin lymphoma and 7 had a diagnosis of multiple myeloma. In the PS group, 9 had non-Hodgkin lymphoma and 1 had multiple myeloma. The median age at CAR-T was 58 years in PS and 64 years in NPS group (p=0.48). The rate of CRS grade ≥3 was higher in the NPS group compared to the PS group, (47.2 vs 20%, p=0.26) whereas ICANS grade ≥3 was similar (32% in NPS and 30% in PS group). More patients achieved a complete response in the PS group (60%) compared to the NPS group (30.2%). The1-year PFS was higher in PS group compared to NPS (60% vs 28%,p=0.08) which was also reflected in the 1-year OS (70% vs 38%, p=0.10). At a median follow-up of 22 months, 70% patients were alive in the PS group compared to 28.3% patients in the NPS group. Conclusions: Our study shows lower rates of CRS and a pattern towards higher rates of complete remission and survival benefit in patients undergoing CAR T-cell therapy receiving prophylactic steroids. The data must be interpreted with caution given the small sample size, but it warrants the need for future studies. Outcomes of patients by prophylactic steroid status (n=63). Parameter NPS (n=53) % PS (n=10) % p-value* Best Response 0.42 Complete Response 16 30.2 6 60.0 Partial Response 4 7.5 1 10.0 Stable Disease 2 3.8 0 0.0 Progressive Disease 24 45.3 3 30.0 NE* 7 13.2 0 0.0 Disease progression 0.30 No 25 47.2 7 70.0 Yes 28 52.8 3 30.0 Time to disease progression, days, median (range) 66.5 5-996 96 92-158 0.75 Median follow-up among survivors (n=22), months (range) 46.5 9-73.8 11.4 8.3-24.2 <0.01 Alive 15 28.3 7 70.0 Dead 38 71.7 3 30.0 2nd Cancer 1 2.6 1 33.3 CNS failure 2 5.3 0 0.0 COVID 1 2.6 0 0.0 Disease 23 60.5 2 66.7 Hemorrhage 1 2.6 0 0.0 Infections 9 23.7 0 0.0 Unknown 1 2.6 0 0.0 NE*= not included in analysis.

The gut microbiome has been studied in preclinical inflammatory disease models. Dysbiosis, where normal gut bacteria are replaced by aberrant organisms, can worsen inflammation. Altered microbiomes are associated with more severe graft-versus-host disease (GvHD) after allogeneic hematopoietic cell transplantation (allo-HCT). Microbiome regulation and its impact on GvHD is not fully understood. Galectin 3 (Gal-3), a Galectin family member, can alter inflammation. We showed how donor T cell expression of Gal-3 decreases GvHD severity (Mohammadpour et al Cell Rep 2023). We now examine how recipient Gal-3 expression during murine allo-HCT impacts the gut microbiome and GvHD. We used the following murine allo-HCT models 1) (Donor BALB/c (H-2d)→Recipient C57BL/6 (H-2b)) (T cell depleted (TCD) BM+/-CD90.2+ spleen T cells); 2) C57BL/6 wild type (WT) and Gal-3 deleted (Gal-3-/-) recipients, 3) Four BM chimera types were generated by HCT post total body irradiation (TBI) in C57BL/6 mice: WT→WT, Gal-3⁻/⁻→WT, WT→Gal-3⁻/⁻, and Gal-3⁻/⁻→Gal-3⁻/⁻. 4)We made selective Gal-3-/- in LGR5+ Intestinal stem cells (ISCs) by crossing Gal-3fl/fl mice with LGR5Cre mice, leading to Gal-3fl/flLGR5Cre mice. To induce Gal-3-/- in LGR5+ ISCs, Gal-3fl/flLGR5Cre mice were given Tamoxifen. For all first HCTs, TBI was given at 11Gy. For the 2nd allo-HCTs (chimeras), 8 Gy was used. After allo-HCT, mice were followed for weight and survival. Fecal pellets were saved weekly for microbiome analysis. Intracellular inflammatory cell cytokine flow cytometry analyses were done on isolated tissue. Multicolor immunofluorescence imaging (MFI) detected Gal-3 and other intestinal cell markers. For Graft-versus Leukemia (GvL) studies, Gal-3-/- and WT mice received TBI followed by syngeneic- or allo-HCT with donor TCD-BM+/-lower T cell doses to decrease GvHD but preserve GvL. Luciferase expressing C1498 AML cells were injected 4 hours post allo-HCT with weekly bioluminescence imaging. After allo-HCT with donor TCD-BM+T cells, Gal-3-/- mice had inferior survival compared to WT by day 60 (25% vs 60%, p<0.0135). Survival for Gal-3-/- and WT donor TCD-BM only, was 100%. TNF-α, IFN-γ, GM-CSF and IL-17 levels in donor H2kd+CD3+CD4+ T cells were not different in spleen, liver and intestine in WT and Gal-3-/- recipients. Distinct microbiome profiles were seen in WT and Gal-3⁻/⁻ mice pre and post allo-HCT, denoting an inflammatory Gal-3⁻/⁻ gut environment, including the phyla Verrucomicrobia and Proteobacteria. Co-housing to normalize microbiomes did not change the impact of Gal-3⁻/⁻ on GvHD severity. Antibiotic treatment prior to allo-HCT decreased microbial diversity in WT and Gal-3⁻/⁻ recipients, increasing GvHD severity, with Gal-3⁻/⁻ mice having the worst survival. Chimeras received allo-HCT with donor TCD-BM+/-T cells, testing the impact of Gal-3 on hematopoietic and non-hematopoietic tissue. Chimeras with Gal-3-/- non-hematopoietic tissue had the worst survival when compared to WT non-hematopoietic tissue chimeras. MFI identified Gal-3 expression in the intestinal epithelial (Villin+) (28%), IS (LGR5+) (12%) and <5% in Paneth (Lysozyme+), Goblet (Muc2+), Enteroendocrine (CHG-A+) cells. We theorized that ISC Gal-3 expression would impact gut GvHD. MFI analysis of Gal-3fl/flLGR5Cre mice confirmed the absence of Gal-3 on LGR5+ ISCs. WT, Gal-3fl/fl and Gal-3fl/flLGR5Cre mice received allo-HCT with donor TCD-BM+/-T cells. The highest day 60 mortality was seen in Gal-3fl/flLGR5Cre mice (95%) followed by Gal-3fl/fl recipients (50%) (p=0.0154). Gal-3fl/fl and Gal-3fl/flLGR5Cre mice receiving TCD-BM only, had 100% survival. GvL studies showed no difference in survival between Gal-3-/- and WT mice receiving T cells, both with a strong GvL effect. Gal-3 expression impacts the gut microbiome and allo-HCT outcome. The lack of Gal-3 in recipient non-hematopoietic tissue led to significant dysbiosis and increased GvHD mortality. Altering the microbiome in WT and Gal-3-/- recipients increased GvHD severity while not affecting the impact of Gal-3 on GvHD incidence and severity. Lack of Gal-3 on ISCs increases the severity and mortality of GvHD. This study showed that Gal-3 protects ISCs, sustaining gut integrity post allo-HCT. Future studies aimed at strategies to enhance the effect of Gal-3 in non-hematopoietic gut cells may improve preclinical GvHD with the potential to translate to clinical trials to decrease GvHD severity without affecting GvL.

ABSTRACT:Understanding the roles of myeloid cells in the tumor microenvironment (TME) has emerged as a promising strategy to identify novel targets to counteract the immunosuppressive barriers protecting multiple myeloma (MM). Neutrophils are a new cancer research focus due to their potential to reduce the efficacy of immune-based therapies. This study aimed to deepen understanding of neutrophil function in MM by analyzing freshly isolated myeloid cells from paired focal lesions (FLs) and bone marrow using single-cell RNA sequencing, immunofluorescence imaging, and functional assays. We describe 3 distinct CXCR2+ mature neutrophil subsets: TREM1+CD10+, RETN+LCN2+, and TNFAIP3+CXCL8+, each exhibiting unique phenotypes within the TME. Notably, the TREM1+CD10+ subset was highly prevalent, particularly in FLs, demonstrating potent immunosuppressive effects on T cells. This subset's gene signature was correlated with shorter overall survival (OS) in a large data set of patients with MM, underscoring its clinical significance. Targeted inhibition of neutrophil activity through CXCR2 blockade, alone or combined with standard anti-MM therapies, significantly reduced tumor burden, improving OS in preclinical MM models. These insights into neutrophil-mediated immunosuppression in MM provide valuable knowledge regarding mechanisms driving immune evasion, and reveal new therapeutic approaches to enhance the efficacy of MM treatment.

INTRODUCTION:Monoclonal gammopathy of undetermined significance (MGUS) is a benign precursor of multiple myeloma, but little is known about the role of comorbidities in progression. MATERIALS AND METHODS:A retrospective review of medical records of patients with MGUS (n = 150) or a negative MGUS workup (n = 96) seen at a comprehensive cancer center between 2007 and 2023 was performed. Charlson Comorbidity Index (CCI) scores, descriptive characteristics, and overall (OS) and progression-free (PFS) survival were abstracted. Group differences (MGUS vs negative) in CCI and other characteristics were tested with Student's t-tests and Pearson's chi-square tests. Univariate and multivariate Cox proportional hazard models were used to model the association between CCI and OS and PFS in patients with MGUS. RESULTS:Patients with MGUS had a higher mean CCI (P = .01) and prevalence of diabetes mellitus with end-organ damage (P < .05) and solid tumors (P = .01) than patients with a negative MGUS workup. Each additional CCI point was associated with shorter OS (HR 1.50, P< .01) and PFS (HR 1.25, P < .01). Results were not confounded by age, body mass index, or sex. CONCLUSIONS:Our study suggests that comorbidities are relevant to risk of MGUS and that prevention and management of comorbidities in patients with MGUS is indicated and may be associated with improved outcomes.

Introduction: Primary graft failure (PGF) after hematopoietic cell transplant is a life-threatening complication due to the absence of early diagnostic tests, precluding expedited re-transplantation. Two primary mechanisms contribute to PGF: i) impaired donor stem cells and/or host stroma and ii) immune-mediated rejection by host lymphocytes. Thus, we hypothesized that patients with PGF and/or their donors would have higher frequency of germline deleterious variants in cancer predisposition genes and that engraftment-associated cytokines would be higher in recipients preceding the diagnosis of confirmed PGF than matched controls. Methods: Under IRB approved protocols, a case:control study (1:3 where possible) was performed to identify likely germline pathogenic (P) or likely pathogenic (LP) variants in cancer predisposition genes (CPGs) in either the donor or host from patients enrolled on BMTCTN1202 using augmented whole exome sequencing. Controls were matched on: disease indication, preparative regimen and intensity, donor source, and recipient age, and were alive without relapse nor acute GVHD on day 100. Quality filtered variants were culled by a 0.005 gnomAD allele frequency threshold, except those with high frequency, for which 0.05 was employed. CPGs were curated for pathogenicity per established protocols. Weekly plasma (from infusion to 4 weeks) was assayed for relevant analytes using Mesoscale per manufacturers guidelines. Presence of CPGs were compared between cases and controls using an odds ratio with 95% confidence interval (CI). A mixed model with an interaction was used to compare cases and controls across time (0, 7, 14, 21, 28 days post transplant). An alpha of 0.05 was used. Results: Among the 34 patients with graft failure, between4 and 71 years old, and 79 controls (21 matched on 3, 3 partially match, 9 unable to be matched), we observed 21% cases and 9% of controls have P/LP likely germline CPGs variants in the donor or recipient, yielding an odds ratio of 2.7 (95% CI 0.9,7.7). There was a high rate of CPGs in genes associated with Noonan syndrome (e.g., LZTR1, NRAS, and PTPN11) in pediatric cases. Of the cytokines/chemokines evaluated, FLT3L on days 14, 21, and 28 (p<0.0001), and IL-15 on days 7 (p=0.0005), 14, 21, and 28 (p<0.0001) were significantly higher in those with graft failure compared to those without graft failure. P-selectin on days 14 (p=0.0151), 21 (p<0.0001), and 28 (0.0002) was significantly lower for those without graft failure compared to those with graft failure. Conclusions: Recipients who developed graft failure had more P/LP CPG variants in the case or donor, although the difference was not statistically significant in this small cohort. Several cytokines linked to engraftment were statistically significantly different between cohorts and were biologically rationale. Elevated FLT3L levels have previously inversely correlated with hematopoietic stem cell number and has been linked to certain CPGs as well. IL-15 is a T cell consumptive cytokine that would remain high in those without T cell recovery. P-selectin is upregulated with immune cell activation; thus, low P-selectin could reflect the lack of immune recovery and recognition of organ injury after HCT. Our data suggest that integrating pre-HCT genetic markers with post-HCT analyte profiles may identify those at highest risk for graft failure, permitting pre-emptive interventions, decreasing the morbidity and mortality from primary graft failure.

Introduction: Hyperleukocytosis is traditionally defined as White Blood Count (WBC) greater than 100000/microliter. It is seen in Acute Leukemia (AL) and Chronic Leukemia (CL). However, the complications of leukocytosis with leukostasis, Diffuse Intravascular Coagulation (DIC) and tumor lysis (TLS) are usually hallmarks of AL particularly Acute Myeloid Leukemia (AML). There is no standard for management and controversy exists regarding the use of leukapheresis (Stahl M et al Leukaemia 2020) versus initiation of chemotherapy (Zhao J et al. Leuk Lymphoma 2021). Venetoclax is a bcl2 inhibitor that is being used in the management of AL. Here we report our experience using novel combination targeted therapy with Venetoclax for cytoreduction. Methods: This is a retrospective analysis of AL patients seen in a public tertiary care hospital in the emirates of Abu Dhabi in United Arab Emirates. The study period is between January 2023 to June 2024. Data was abstracted from the electronic medical records including patient demographics, diagnosis, laboratory values and treatment. Results: During the study period sixty-five patients presented with clinical features suggestive of AL. Fourteen (21 %) patients had hyperleukocytosis. The median age of the patients was 30 years (range 19 to 60 years). The median WBC was 134000/microliter (range 104-432,000/microliter). Diagnostic work up included bone marrow biopsy with flow cytometry, karyotype analysis, Fluorescence in situ hybridization (FISH) and molecular studies (30 gene panel and FLT3 PCR). The median period of reporting of the bone marrow result was 3 days (range 0-7 days). Cytoreductive therapy was given with Dexamethasone 20 -40 mg intravenously daily with Hydroxyurea 2000 mg orally daily and Venetoclax orally (escalating from 100 mg day 1, 200 mg day 2 and 400 mg day 3 and onwards) while awaiting diagnosis. There was a 50 % reduction of WBC by day 3 in most patients (64%). A WBC of less than 50000/microliter was achieved by day 4 in 57% of the cohort. There was biochemical evidence of tumor lysis. This was managed medically by hydration, prevention of hyperuricemia and correction of electrolytes. Dialysis and critical care were not required. Six patients refused further therapy and were lost to follow-up. Three patients died during induction period. Two patients went for allogeneic hematopoietic stem cell transplant, two patients had relapsed and refractory disease while one patient is in sustained remission post consolidation chemotherapy. Conclusion: The current experience using dexamethasone, Hydroxyurea and Venetoclax gives an alternate (leukapheresis and Cyclophosphamide/Cytarabine) and safe option for cytoreduction prior to exact diagnosis and initiation of therapy.

BMT CTN 1401 is a phase II trial of 140 multiple myeloma (MM) patients undergoing autologous hematopoietic cell transplant (HCT) followed by lenalidomide maintenance with or without a personalized DC/MM vaccine. Vaccination was associated with increased MM-reactive T cells and clonotypic expansion of activated T cells 1-year post-HCT. Here, we identify private or shared antigenic targets in pre-HCT bone marrow (BM) samples, along with corresponding T cell clonotypic patterns. We also further analyzed the peripheral blood (PB) immune landscape of the study patients, exploring the correlation between disease response and the T cell repertoire, including dominant clonotypes. Pre-HCT BM samples from 16 patients underwent bulk RNAseq and whole exome sequencing. With an in silico-experimental framework developed by our team, we predicted tumor antigens by considering factors including translation potential, RNA expression, peptide-MHC binding affinity, immunogenicity, clonality, and physicochemical properties. 10 samples were further analyzed by single cell (sc) immunoprofiling to assess the antigens expression in MM cells. Additionally, PB samples from 40 study patients underwent sc immunoprofiling to investigate the T cell repertoire in stringent complete response/complete response (sCR/CR, N=26), very good partial response (VGPR, N=9), partial response (PR; N=4) or progressive disease (PD; N=1). We observed a high prevalence of tumor-specific (neo)antigens, with 50% shared among more than 2 patients. 19 neoantigens were prioritized based on high immunogenicity and expression in multiple patients, including four expressed in immune-privileged tissues (MAGEC1, TPTE, UCHL1). UCHL1 showed an 80-fold higher median expression in MM samples than in healthy controls. We observed a significant enrichment of shared tumor antigenic peptides (n=33) across up to 10 patients, originating from regions not typically expressed or translated, such as retroelements and downstream/upstream open reading frames. PB T cells immunoprofiling revealed higher T cell clonotypic expansion in sCR/CR and VPGR, with sCR/CR associated with higher proportion of cytotoxic CD8 T cells and fewer Tregs 1-year post-HCT. A high degree of TCR sharing between clonally expanded T cells in the PB and BM was observed. To identify novel immunotherapy targets for MM, we characterized the MM antigenic landscape, identifying personal and shared tumor antigens. In addition, we demonstrated that sCR/CR is associated with clonal expansion of cytotoxic T cells with clonal dynamics in the PB reflecting those in the BM. We are correlating the dominant T cell clonotypes with the identified antigens and assessing the impact of DC/MM fusion vaccination in this setting. Giulia Cheloni, Dimitra Karagkouni, Shivani Nanda, Lina Bisharat, Isabella Saldarriaga, MA Yuling, Shuoshuo Wang, Xanti-Lida Katopodi, Yered Pita-Juarez, Jessica Liegel, Hazal Toros, Prateek Pophali, David Chung, Nina Shah, Natalie Callander, Binod Dhakal, Thinle Chodon, Nikhil Munshi, Kenneth Anderson, Yvonne Efebera, Peiman Hematti, Hillard Lazarus, Ehsan Malek, Philip McCarthy, Ajay Nooka, Krina Patel, Aaron Rapoport, Robert Soiffer, Edmund Waller, Marcelo Pasquini, Jacalyn Rosenblatt, Ioannis Vlachos, David Avigan. Neoantigen expression and expansion of cytotoxic T cell clonotypes in multiple myeloma patients receiving a personalized cancer vaccine post-transplant: Insights from the BM CTN 1401 multicenter trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 7128.

PURPOSENewly approved drugs and combinations treating multiple myeloma (MM) have resulted in substantial improvements in patients' survival. To deliver rapid access to newer therapies, an earlier end point to expedite clinical trials is needed. Our objective was to evaluate the minimal residual disease-negative complete response (MRD-CR) as an intermediate end point for progression-free survival (PFS) and overall survival (OS) in newly diagnosed (ND) transplant-eligible (NDTE) patients, ND transplant-ineligible (NDTinE) patients, and patients with relapsed/refractory (RR) MM.PATIENTS AND METHODSIndividual patient data from 20 randomized multicenter trials were collected. Eleven studies (4,773 patients) with sufficient data were analyzed to evaluate whether 9- or 12-month MRD-CR classified at a 10-5 threshold could be reasonably likely to predict the clinical benefit of new agents regarding PFS and OS. Global odds ratio (OR) was estimated using the bivariate Plackett Copula model. Supportive evaluation included correlations of the treatment effects on MRD-CR end points and PFS/OS, evaluated by both linear regression (R2weighted least squared) and Copula (R2Copula) models.RESULTSThe analysis demonstrated that both 9- and 12-month MRD-CR strongly correlated with PFS at patient level in NDTE patients, NDTinE patients, and patients with RRMM. Global ORs ranged from 3.06 to 16.24, all with 95% CIs excluding 1.0. Encouraging trial-level correlations (R2, 0.61-0.70) were observed by pooling three populations and were stronger (R2, 0.67-0.78) in the ND population. Similar results were observed for OS.CONCLUSIONOur findings provided the support for use of MRD-CR classified at a 10-5 threshold at either 9 or 12 months after starting of the treatment, as an intermediate end point to support accelerated approvals, in future trials in NDTE patients, NDTinE patients, and patients with RRMM.

Introduction Bone marrow biopsies (BMBx) are an integral part of the diagnosis and management of plasma cell disorders (PCD) because they provide access to the tumor cells themselves but also to the immune microenvironment relevant to these disorders. However, due to the invasiveness, discomfort, and expense, BMBx are only utilized at a very limited number of timepoints during diagnosis and treatment. With the evolving role of liquid biopsy techniques in the management of hematologic malignancies, a deeper understanding of how closely the peripheral blood (PB) immune milieu reflects that of the BM, has the potential to add another dimension to the pursuit of less invasive, less costly methods for diagnosis and monitoring disease response. Furthermore, immune recovery is a new area of interest in patients having received effective therapies, but the timepoint for the assessment is unclear. PB tests allow for more frequent and less invasive testing than BMBx. The current study provides insight into which lymphocyte populations and functional subsets are most closely correlated in paired PB and BM. Methods The patients included in this analysis (n=65) were being worked up for PCDs and were ultimately diagnosed with multiple myeloma (n=36), smoldering multiple myeloma (n=5), monoclonal gammopathy of undetermined significance (n=11), Waldenström macroglobulinemia (n=4), light chain amyloidosis (n=3), or another hematologic condition (n=6). Sampling of paired PB and BM were done within 15 days of one another and were done on treatment-naïve patients. A comprehensive flow cytometry panel was utilized to assess the PB and BM frequency of lymphocyte populations, including CD4+, CD8+, and gamma-delta (γδ) T cells, B cells, natural killer (NK) cells, and NKT cells. The current analysis includes 47 markers of interest representing absolute cell counts (per μL) of these populations and major functional subsets, such as naïve, memory, exhausted, and terminally differentiated, as well as key ratios of interest. Correlations between populations in PB and BM are estimated using Spearman's rank correlation coefficients (ρ), with p-values ≤.05 considered significant. The false discovery rate (FDR) is controlled using the Benjamini-Hochberg procedure. Results Patients included in the study have a mean age at sampling of 67.0 years. More than two-thirds (69%) of the patients are male. As expected, the median absolute counts of most lymphocyte populations are greater in the BM than PB, with the exception of CD4+ T cells. Overall, there is strong correlation between the paired specimens, with the median correlation of all 47 markers being ρ=.80. All p-values are <.0001, and all immune markers remain significantly correlated after correction for FDR. There are 9 markers with very strong correlation (ρ>.90), 31 with strong correlation (ρ>.70), and 7 with moderate correlation (ρ>.50). The major lineages had the following correlations between PB and BM: CD4+ T cells (ρ=.81), CD8+ T cells (ρ=.84), γδ T cells (ρ=.85), B cells (ρ=.86), NK cells (ρ=.65), and NKT cells (ρ=.92). The functional subsets that are very strongly (ρ>.90) correlated between PB and BM are CD4+ naïve T cells (ρ=.92), naïve B cells (ρ=.91), non-class switched memory B cells (ρ=.91), NKT cells (ρ=.92), terminally differentiated NKT (ρ=.95), and the following ratios: CD4/CD8 (ρ=.94), CD4+ naïve/memory (ρ=.94), CD4+ exhausted/non-exhausted T cells (ρ=.92), and CD8+ exhausted/non-exhausted T cells (ρ=.93). The populations with the lowest correlations between PB and BM include CD4+ effector memory (TEM) (ρ=.69), CD4+ terminally differentiated effector memory (ρ=.68), CD4+ regulatory T cells (ρ=.65), CD8+ TEM (ρ=.66), the ratio of CD8+ TEM to central memory (TCM) (ρ=.59), class-switched memory B cells (ρ=.68), and NK cells (ρ=.65). Symptomatic and asymptomatic patients had similarly strong correlations between PB and BM, with the exception of CD4+ TIGIT and PD1 exhausted populations and CD8+ TEM being more strongly correlated in asymptomatic, and CD8+ naïve and B cells being more strongly correlated in symptomatic patients. Conclusion The current study presents evidence that the PB immune profile is strongly correlated with that of BM. Additional work is needed to study rarer and more specifically defined populations, to examine how these relationships hold up in different PCD diagnoses, and to examine whether treatment impacts these PB-BM correlations.