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Background Advancements in imaging techniques, diagnostic procedures, and increased routine health care visits are anticipated to lead to a higher number of patients with an incidental diagnosis of cancer, including the most common lymphoma DLBCL. In parallel, multiple cancer early detection (MCED) blood assays are emerging to screen for cancer in asymptomatic, average risk individuals. Assays that use methylated DNA markers (MDM) are of special interest and have been shown to detect evidence of DLBCL in the blood in 80% of DLBCL cases (Witzig TE et al ASCO 2022). While these MDMs are candidates for inclusion in MCED assays, the impact of early detection of lymphoma in general and DLBCL specifically remains controversial. Since the outcomes for patients with an incidental diagnosis of DLBCL have not been previously studied and to give further insight to the early detection question, we investigated clinical characteristics and outcome differences between patients with DLBCL found incidentally and those with symptoms or obvious signs of disease that led them to seek medical evaluation. Methods We conducted a retrospective analysis of newly diagnosed DLBCL patients enrolled into the Molecular Epidemiology Resource (MER) of the University of Iowa/Mayo Clinic Lymphoma Specialized Program of Research Excellence from 2002-2015. We reviewed the medical records of the Mayo component to assign a mode of diagnosis (incidental vs symptomatic). We examined disease characteristics and impact on event-free survival (EFS) and overall (OS) survival according to the mode of diagnosis. EFS was the time from diagnosis to relapse, progression, retreatment, or death from any cause. OS was defined as the time from diagnosis to death from any cause. Results 1140 patients with DLBCL (90.6%), high grade B cell lymphoma (2.4%) or primary mediastinal B cell lymphoma (7.0%) were reviewed; 85 (7.5%) patients presented incidentally (incidental group), while 1055 (92.5%) presented with a lymphoma-related symptom or sign, e.g., palpation of a lump/mass, B symptoms and/or other symptoms caused by the lymphoma such as abdominal pain (symptomatic group). In the incidental group, 67.5% (65/85) of patients were diagnosed after an incidental finding on imaging or diagnostic/surgical procedure, 14.1% (12/85) were diagnosed after an incidental lab finding, and 9.4% (8/85) were diagnosed after a clinical health care professional incidentally identified a lump/mass. Compared to the symptomatic group, patients with incidental diagnosis were older at diagnosis (median age 66 vs 63 years, P=0.01) and more likely to present with an earlier stage I/II (62.4% vs 38.9%, P<0.001). Patients who presented with symptoms were more likely to have ≥ 1 extra-nodal site involvement (29.8% vs 15.5%, P=0.005), elevated LDH level (55.4% vs 40.8%, P=0.01), and high-risk IPI score (13.7% vs 5.9% P=0.03) compared to the incidental group. The median diagnosis to treatment interval (DTI) was significantly longer in the incidental group (21 days, IQR 12-34) compared to the symptomatic group (15 days, IQR 9-24) (P = 0.0014). The median follow-up time was 152.3 months in the incidental group and 123.7 months in the symptomatic group. We observed no difference in early failure rates as measured by failure to achieve event-free status at 24 months (EFS24) for incidentally vs symptomatic diagnosis (25.9% vs 31.9%, P=0.25). There was no difference in EFS between the two groups in univariate (HR=1.08, 95%CI=0.8-1.45) or multivariable analysis adjusted for IPI (aHR=0.97, 95%CI=0.72-1.31). There was also no difference in OS in univariate (HR=0.98, 95%CI=0.72-1.34) or multivariable analysis adjusted for IPI (aHR=0.87, 95%CI=0.64-1.19). Conclusion In this large cohort of aggressive B-cell lymphoma, incidental diagnosis occurred in only 7.5% of cases and these patients had earlier stage, lower IPI score, lower LDH levels and less extranodal involvement. These differences in clinical characteristics did not translate into EFS or OS differences. Our findings are the first to describe presentation and outcomes of incidentally diagnosed DLBCL and provide data regarding what investigators may find with MCED assays. Finding more early stage DLBCL patients with lower tumor burden may influence type of treatment, enable the use of fewer chemotherapy cycles, and avoid symptoms and complications of advanced stage disease such as tumor lysis syndrome and organ compression.

Background: Data from the ASH Research Collaborative COVID-19 Registry for Hematology demonstrated that patients with multiple myeloma and other immune compromise had elevated risk for severe complications from COVID-19 infection. To address current evidence gaps and to demonstrate proof of concept for a pandemic preparedness and response network, the ASH Research Collaborative Multiple Myeloma Program developed a prospective, decentralized study within a site-based provider network to investigate COVID-19 infections, vaccinations, and quality of life in patients with multiple myeloma. Methods: We designed and established the COVID-19 OutcomeS in Myeloma and the Impact of VacCines (COSMIC) to study COVID-19 in patients with multiple myeloma at ASH Research Collaborative network sites. A study application was accessed with a QR code and shared with patients during usual clinical care. Patients provided consent, optionally gave permission for electronic health record data collection, and completed patient-reported outcomes (EORTC QLQ-C30 and MY20) at baseline, Day 30, and Day 180 through the study portal. Clinicians at participating sites facilitated study enrollment and shared best practices monthly to accelerate study execution. Study objectives related to feasibility of data collection in a decentralized format are reported in a separate abstract. Here, we report interim results related to SARS-CoV-2 vaccination history, COVID-19 infection, and how these relate to patient reported outcomes and clinical outcomes in enrolled participants. Results: The COSMIC study rapidly accrued and consented 200 patients from eight participating ASH Research Collaborative sites over four months (1/22/2024 through 5/17/2024). Consented participants' ages ranged from 29 to 93 years, with median of 67 years; 46% were female, 69% were non-Hispanic White (NHW), 17% were non-Hispanic Black (NHB), and 8% were Hispanic/Latino. Of the 196 patients who reported COVID-19 data, 111 (57%) reported at baseline that they had a history of COVID-19 infection, with 12 having required hospitalization for this (12/111=11%). Overall, 95% (186/196) reported a history of COVID-19 vaccination, where the median number of vaccinations was 4 (range: 1 to 6); 44 patients (23%) expressed willingness to discuss getting a yearly booster vaccine with their provider. At 1-month follow-up, there were 3 additional patients who reported a COVID-19 infection and 18 patients who received an additional COVID-19 vaccination. The baseline EORTC QLQ-C30 median Global Health Status/QOL score was 66.7 (mean=64.4, range: 8.3 - 100, n=196). This overall global QOL score was not significantly different between those who did vs. did not have a history of COVID-19 infection (mean [SD]: 63.7 [19.3] vs. 65.8 [17.6]; p=0.57). In analyses adjusted for age, biological sex, and race/ethnicity group, history of COVID-19 infection was not associated with HRQOL (odds ratio=0.93, 95% CI: 0.78 - 1.10; p=0.38). Data collection is ongoing and final study results will be reported at a later date. Conclusion: COSMIC is a prospective, decentralized study within a site-based provider network conducted by the ASH Research Collaborative Multiple Myeloma Program that demonstrates the feasibility of using an innovative evidence generation strategy to drive rapid accrual of patients to address a rapidly evolving area of need. The COSMIC study also provides proof of concept that a real-world evidence generation network can play an important role in national pandemic preparedness and response. The COSMIC experience reinforces the ability to accrue diverse patient populations representing the demographic of myeloma patients in the US.

Introduction: Ven is a BCL2 inhibitor that has shown clinical efficacy in RRMM patients (pts) particularly those that harbor t(11;14). Ven has been evaluated in clinical trials as a single agent, in combination with dexamethasone (dex), immunomodulatory drugs (IMiD), proteasome inhibitors (PI), and anti-CD38 monoclonal antibodies (MAb) yet its place in the therapeutic landscape remains in question. In this retrospective analysis, we aim to evaluate the real-world efficacy of Ven-based regimens in RRMM pts treated outside of a clinical trial across the 3-site MCCC. Methods: We retrospectively analyzed the medical records of pts with RRMM treated with Ven-based regimens between January 2015 and October 2023 at the MCCC. Refractoriness was defined by progression on or within 60 days of stopping treatment. Categorical variables were compared with Chi-square tests and continuous variables were compared with t-tests. Outcomes were estimated using the Kaplan-Meier method and curves were compared between the groups using log-rank tests. Results: 83 pts were included in the analysis. The median age was 71 (39-93), 63% were male, 93% were white, 27% had ISS III, 18% had high risk cytogenetics (HRCyto), 76% had t(11;14), the median prior lines of therapy (LOT) was 4 (1-15), 68% received ≥ 4 prior LOT, 87% received prior autologous transplant, 58% were triple-class refractory (TCR), 64%/23% were penta-drug exposed/refractory (PDE/R), 8% received prior BCMA-directed therapies (BDT), 58% received Ven+dex, 25% received Ven+PI +/-dex, 6 % received Ven+anti-CD38 MAb+/-dex and 11% received Ven+other. The median follow-up time from start of a Ven-based regimen was 29 months (mo). The median Ven dose was 800mg (20-1600) with 25% of pts receiving Ven ramp-up dosing. The overall response rate (ORR) to a Ven-based regimen was 58% and was 64% for pts with t(11;14) and 40% for pts without t(11;14); p=0.06. Ven-treated pts with HRCyto had inferior PFS (3mo) and OS (8mo) compared to patients who did not have HRCyto who had a PFS of 9mo (p=0.020) and OS of 80mo (p<0.001). The ORR for TCR and PDR pts were 52% and 42%, respectively. No significant ORR differences were noted across the different Ven-based regimens (p=0.32). The median PFS for pts with t(11;14) was 10mo compared to 2mo for pts w/o t(11;14); p=<0.001. The median OS for pts with t(11;14) was 80mo compared to 10mo for pts without t(11;14); p=0.001. Ven-treated pts who received 1-3 prior LOT has superior ORR, median PFS, and median OS; 89%, 25mo, and 99mo, respectively, compared to pts who received ≥4 prior LOT who achieved an ORR of 43% (p<0.001), median PFS of 5mo (p<0.001) and median OS of 25mo (p<0.001). Ven-treated pts that were TCR had inferior PFS (5mo) and OS (26mo) compared to pts who were not TCR who achieved a PFS of 12mo (p<0.001) and a median OS of 80mo (p=0.02).Ven-treated pts that were PDR had inferior PFS (4mo) and OS (22mo) compared to pts who were not PDR who achieved a PFS of 9mo (p<0.001) and a median OS of 80mo (p=0.02).Ven-treated pts who received prior BDT (n=7) achieved an ORR of 29% and had a median PFS and OS of 2mo and 6mo, respectively on a Ven-based therapy. 59 pts received additional therapy in the post Ven-progression setting. The ORR to post-Ven progression therapies was 53% (n=31/59), the median PFS was 9mo and median OS was 35mo. The most common post-Ven progression regimens used were PI-based (n=16; ORR=56%), anti-CD38 MAb-based (n=14; ORR=50%), BDT (n=12; ORR=83%), selinexor-based (n=3; ORR=0%) with BDT resulting in highest ORR (p=0.048) and PFS (p=0.005). Conclusions: Ven-based regimens are effective in heavily pre-treated pts with RRMM however they are more effective when used within 1-3 prior LOT, in pts with t(11;14), and in pts without HRCyto, TCR or PDR MM. BDT appear to be the most efficacious therapies in the post-Ven progression setting.

Activating mutations in the calcium sensor STIM1 underlie Stormorken Syndrome (SS), a rare congenital disorder that causes thrombocytopenia and tubular aggregate myopathy. We recently identified two patients with SS and confirmed mutations in STIM1 (R304W and S88G), who were found to have features consistent with myelofibrosis (MF), as indicated by bone marrow biopsies demonstrating megakaryocyte hyperplasia and atypia in conjunction with marked reticulin fibrosis. The unusual MF findings in these two patients raised the hypothesis that altered calcium signaling represents a shared hallmark of congenital platelet disorders such as Stormorken Syndrome and myeloproliferative neoplasms (MPNs) including MF. Analyzing gene expression data from public datasets, we found increased expression of STIM1 in megakaryocyte progenitors and platelets, as well as CD34+ hematopoietic stem/progenitor cells (HSPCs), from MPN patients (including those with CALR or JAK2 mutations) vs healthy controls. These findings led us to hypothesize that dysregulation of STIM1 and store operated calcium entry (SOCE) signaling may contribute to altered megakaryopoiesis and development of fibrosis in both SS and MPNs. To further delineate these processes, we analyzed samples from our two SS patients, demonstrating constitutive activation of SOCE causing increased calcium flux, as well as decreased aggregation in mature platelets. We also performed transmission electron microscopy (TEM) and identified platelets with abnormal granularity in dense and alpha granules. We also performed single cell RNA-seq on SS patient peripheral blood mononuclear cells, which revealed enhanced NFkB inflammatory signaling, suggesting that altered signaling driven by STIM1 mutations may drive aberrant inflammation to contribute to MF development. To corroborate these initial observations, we identified a separate family cohort of 9 individuals in Italy with SS and confirmed STIM1 mutation (L92V). In ex vivo megakaryocytic differentiation assays, cells derived from these patients demonstrated a defect in thrombopoiesis with significantly decreased pro-platelet formation and adhesion to extracellular matrix. To further characterize the effects of the gain of function STIM1 mutations seen in our patients, we developed a novel, conditional knock-in mouse model of the heterozygous R304W mutation in the coiled coil (CC) domain of Stim1. Induction of hematopoietic-specific expression of mutant Stim1 via Vav-Cre resulted in recapitulation of hematological features of SS, including thrombocytopenia and a mild bleeding tendency, with confirmation of increased SOCE activity and calcium flux. Notably, we confirmed the development of bone marrow fibrosis, as well as findings of severe osteosclerosis, in these mice. TEM imaging confirmed that platelets from Stim1R304W/+Vav-Cre mice exhibit abnormal granularity, similar to what we observed from our SS patients. Noting that we identified increased STIM1 expression in samples from MPN patients harboring either JAK2 or CALR mutations, we further characterized the role of STIM1 in MPN disease development. NSGS mice were engrafted with CALR-mutant CD34+ cells subjected to CRISPR ablation of STIM1. Recipient mice exhibited decreased human CD45+ cell engraftment in conjunction with prolonged survival. In contrast, targeting of STIM1 in JAK2-mutant CD34+ cells led to exacerbated disease phenotypes, as manifested by enhanced human CD45+ cell engraftment, worsened splenomegaly, and early lethality. Taken together, these findings suggest a striking, differential relationship between mutant JAK2 and CALR and STIM1 activity and their relationship to MF development. Altogether, this study represents the first demonstration of MF development in patients with Stormorken Syndrome, and reveals a previously unrecognized hallmark of altered calcium signaling via aberrant STIM1 activation underlying SS and MPNs. We further demonstrate recapitulation of these hematologic features in a novel knock-in Stim1R304W/+Vav-Cre mouse model. These findings implicate an important role for STIM1and SOCE activity in MF development, and further uncover important distinctions between JAK2 vs CALR mutations and their interaction with altered STIM1 activity. These studies may contribute to the development of novel therapeutic approaches for these disorders.

Background: Philadelphia (Ph)-like acute lymphoblastic leukemia (ALL) is a heterogenous subtype of B-ALL defined by the presence of gene expression profiling similar to Ph+ ALL in the absence of a BCR::ABL1 fusion. Ph-like ALL has lower response rates to standard frontline therapies and carries a poorer prognosis when compared to other B-ALL subtypes. However, the role in which specific patient characteristics may impact responses is not well described. Our aim for this retrospective study was to evaluate the characteristics and outcomes of a real-world cohort of patients (pts) with Ph-like ALL across multiple institutions, including describing key patient characteristics, treatments, and factors that may contribute to minimal residual disease (MRD) status and treatment response. Methods: We conducted a retrospective review of adult pts with Ph-like ALL diagnosed and treated at the University of New Mexico, Mayo Clinic Phoenix, University of Chicago, and University of Michigan between 1/1/18 - 2/1/2024. Pts were eligible if they carried a diagnosis of B-ALL, and were determined to have Ph-like ALL according to each institutional diagnostic algorithm. Descriptive statistics, ANOVA, and Fisher's exact test were employed to summarize various clinical characteristics and their associations. Cox regression analysis was utilized to estimate the median survival time and assess the relationship between clinical characteristics and survival outcomes, including overall survival and progression-free survival. All statistical analyses were conducted using the R statistical software. Results: 67 pts were identified with a median age of 34.2 (IQR 28.5) and 35.8% were female. Twenty-eight pts identified as Hispanic or Latino (H/L) (43.1%), 25 (38.5%) identified as non-Hispanic White/Caucasian (NHW), 10 (15.4%) as American Indian/Alaska Native (AI/AN), and 2 (3.1%) as Asian/Pacific Islander. Thirteen pts (19.4%) had central nervous system (CNS) involvement at diagnosis, 22.4% of pts had extramedullary disease, and, in those who had NGS or cytogenomic microarray testing (n=49), 51% had an identified mutation/deletion in IKZF1. Initial treatment varied widely with pts receiving most commonly: Children's Oncology Group (COG) protocols (22.4%), CALGB 10403 (22.4%), HyperCVAD (11.9%), and CALGB 8811 (10.4%). Fifty-eight percent achieved a CR/CRi and 21% were refractory to initial therapy. Thirteen percent of pts received a Jak inhibitor and 6% of pts were treated with a TKI. Thirty pts (50.8%) underwent allogeneic stem cell transplant, with 8 of those pts (26.7%) experiencing a relapse post-transplant. Nine pts (13.4%) underwent treatment with CAR-T therapy with few pts experiencing grade 2 or higher cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS). Pts with CNS disease at diagnosis were less likely to achieve a CR/CRi compared to those without CNS disease at diagnosis (33.3% vs 64.0%; p=0.12). Pts identifying as AI/AN were more likely to be refractory to their first treatment compared to other racial/ethnic groups (75%, p=0.002). Forty two percent of pts never achieved MRD negativity (< 0.01% by flow cytometry) during treatment; pts identifying as H/L and AI/AN had a higher rate of MRD positivity after induction compared to NHW pts (56% and 70% vs. 25%; p=0.02). In pts with IKZF1 mutation, 57.1% did not achieve MRD negativity compared to 21.7% in pts without a mutation (p=0.029). The median overall survival (OS) was 66.3 months (mos) and the median progression-free survival (PFS) was 15.7 mos. Pts who did not achieve MRD negativity after initial treatment had shorter OS compared to those who did achieve MRD negativity, 33.9 mos vs 66.3 mos (p=0.086). Progression-free survival (PFS) was significantly shorter for patients who did not achieve MRD negativity after initial treatment compared to those who did, 3.9 mos vs 43.9 mos (p=0.001). PFS was shorter in pts who identify as AI/AN compared to H/L and NHW pts (2 mos vs 35.7 mos and 35.7 mos; p=0.046). Conclusion: Pts with Ph-like ALL experience poor response rates to therapies used to treat B-ALL, highlighting the urgent need for novel therapies and treatment strategies. We identified race/ethnicity and CNS disease at diagnosis as risk factors for poor treatment response. In addition, race/ethnicity and the presence of an IKZF1 mutation was associated with worse rates of MRD negativity during treatment.

Introduction: MPAL is a rare and heterogenous subtype of acute leukemia characterized by a single blast population with phenotypic expression of both myeloid and lymphoid lineages (biphenotypic) or multiple co-existing lineages of blasts that satisfy criteria for both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). MPAL presents both a diagnostic and therapeutic challenge given its rarity and resistance to traditional therapies. Data suggest ALL-directed or hybrid therapies are most effective at inducing durable remissions as a bridge to allogeneic stem cell transplantation (Allo-SCT; Lazzarotto 2023, Rasekh 2021); however, many are single-institution with limited sample sizes. Methods: A retrospective analysis at 7 US academic centers was performed. Adult patients (pts) with a confirmed diagnosis of MPAL between 2003-2023 were included. Comparisons of categorical and continuous variables utilized the Fisher exact test and Wilcoxon rank-sum or Kruskal-Wallis test as appropriate. Time-to-event outcomes were calculated using the Kaplan-Meier method and compared using log-rank test. Results: A total of 79 pts with MPAL were included in this study. Median age at diagnosis was 61 years (range, 18-89); 52% were ≥ 60 years. Majority of pts were male (60%), non-Hispanic white (64%), and had an ECOG ≤ 1 (83%). Of the 50 pts with baseline CSF analysis, 5 (10%) had CNS disease. Phenotypically, the predominant blast population was biphenotypic in 68%, myeloid in 17%, and lymphoid in 15% of cases. KMT2A-rearrangement and BCR::ABL1 translocation constituted 4% and 14% of cases, respectively, and 30% of pts had complex cytogenetics. Most common mutations at baseline included RUNX1 (33%), DNMT3A (30%), FLT3-ITD (26%), TET2 (19%), WT1 (19%), NRAS (18%), TP53 (17%), and ASXL1 (14%) mutations. Of the 79 pts, 61 (77%) received intensive chemotherapy (IC), 12 (15%) received HMA-based regimens, 4 (5%) received other non-intensive regimens, and 2 (3%) transitioned to hospice prior to therapy. Among those receiving IC, 37 (61%) received ALL-directed therapies, 16 (26%) AML-directed, and 8 (13%) received hybrid regimens which included FLAG-VIPR (6/8), 7+3+vincristine (1/8), and cladrabine/low-dose cytarabine/vincristine/dexamethasone (1/8). Therapies were phenotype-discordant in 4/61 pts receiving IC; 3 myeloblast-predominant MPAL pts received ALL-directed therapy and one lymphoid-predominant pt received AML-directed therapy. Among 54 pts with predominant biphenotypic blasts, 52% received ALL-directed regimens. Of the 11 pts with BCR::ABL1 translocation, 8 (73%) received dasatinib, 2 (18%) ponatinib, and 1 (9%) received both. Only 30% of pts with FLT3-ITD mutated MPAL (5/17) received a FLT3 inhibitor. Overall, 56% of pts achieved complete remission (CR) or CR with incomplete count recovery (CRi), with a median duration of response of 16.7 months (IQR: 8.1-46.1). The rates of CR/CRi were 39%, 56%, and 75% for myeloid, biphenotypic, and lymphoid MPAL, respectively. All pts with CNS disease (5/5) cleared after induction. Thirty-seven percent of pts proceeded with Allo-SCT in first remission (23% of myeloid pts, 58% lymphoid, 35% biphenotypic). Thirty-two percent of responders (CR/CRi; 14/44) relapsed with a median time to relapse of 9.4 months (range, 0.5-42). Median overall survival (OS) for the entire cohort was 51 months (95% CI: 15-89). The 2-year OS rate was higher in pts with lymphoid-predominant phenotype (83%) compared to biphenotypic (55%) or myeloid-predominant phenotype (38%; p=0.16). Median OS was significantly longer in transplant versus non-SCT recipients (121 vs 14 months) with a 1-year OS rate of 97% vs. 59% (p<0.0001), respectively. Among pts who achieved CR/CRi, median OS significantly longer in transplant versus non-SCT recipients (121 vs 55 months, p=0.031), with a 2-year OS rate of 91% vs 75%. Conclusions In this large multi-center study, there were differences in survival based on predominant blast phenotype, with improved OS in lymphoid-predominant MPAL. Although most pts with biphenotypic-predominant MPAL received ALL-directed regimens, OS was worse in this subtype compared to lymphoid-predominant MPAL. There was significantly improved OS among Allo-SCT recipients underscoring the importance of Allo-SCT in this subtype of acute leukemia. Additional studies are needed to understand this rare and heterogenous disease.

Introduction ABBV-383 is a differentiated BCMA x CD3 bispecific antibody (fully humanized IgG4) T-cell engager composed of a bivalent BCMA binding domain with high avidity, a low-affinity CD3-binding domain, and a present but silenced-Fc tail retaining the FcRn binding allowing for an extended half-life and thereby, enabling dosing convenience. ABBV-383 monotherapy has shown promising activity and improved CRS safety profile with modified dexamethasone (Dex) premedication in patients (pts) with RRMM (NCT03933735; Rodriguez et al., JCO 2024;42[suppl 16]:7531). Here, ER and CRS PK/PD analyses supporting the selection of optimal SUD for ABBV-383 are reported. Methods ER-efficacy (N=286) and -safety (N=290) analyses were conducted using logistic regression methodology (R version 4.3.2) combining data from escalation (0.025-120 mg Q3W) and expansion (20, 40, 60 mg Q3W and 60 mg Q4W) cohorts of phase 1 study NCT03933735 and Arm A of phase 1b study NCT05650632 evaluating step-up dose (2 or 4 mg on Day 1) with a full dose (60 mg on Day 4) in pts with RRMM. Pts received modified Dex with full dose in expansion cohorts of 60 mg Q4W and 2/60 mg Q4W. In all other cohorts with or without SUD, pts received low Dex. Based on prior knowledge (JCO 2024;42[suppl 16]:7541), the safety endpoints (CRS: any-grade and ≥ G2) were modeled with Cycle 1 total (unbound + bound to soluble BCMA) Cmax, while objective response rate (ORR) was modeled with free (unbound + partially bound to soluble BCMA) Cavg. CRS ER models included a priori selected Dex (low vs. modified) and SUD (yes vs. no) as predictors. Relevant pt-specific covariates were tested in all models. CRS PK/PD analyses included total PK, IL-6, and CRS data (N=199) from the first 3 cycles of the above phase 1/1b studies. A semi-mechanistic indirect response PK/IL-6 model was developed to correlate total PK and IL-6 (NONMEM 7.5). Maximal IL-6 concentrations were derived using post hoc estimates from the PK/IL-6 model and correlated with CRS events (logistic regression; R version 4.3.2). The models included effects of time-dependent Dex (low vs. modified) and SUD (yes vs. no). The overall modeling approach was assessed by comparing observed and predicted CRS rates. Simulations were conducted for various dosing regimens, including one or two SUD and Dex premedication scenarios to support the selection of the optimal SUD. Results Consistent with clinical observations (separate abstract submission), any-grade CRS model predicted probabilities suggested two key outcomes: 1) premedication with modified Dex improves the CRS safety profile compared to the low Dex (42% vs 69% for 60 mg Q4W); 2) modified Dex with SUD further improves the CRS safety profile of ABBV-383 compared to low Dex with SUD (29% vs 43% for 2/60 mg Q4W). Consistent with prior work, no ER relationship was observed for ≥ G2 CRS (p > 0.05). The ORR model resulted in a predicted probability of 68% ORR (closely matching with overall observed 64% ORR) with no impact of SUD and modified Dex. Only soluble BCMA was selected as a covariate in the ORR ER model. The final semi-mechanistic PK/IL-6 model well captured the observed IL-6 data, and the CRS rates (predicted by the logistic regression models) closely matched with the observed data. The CRS PK/PD analyses findings were consistent with the clinical observations and ER analyses key outcomes 1 and 2. The CRS PK/PD analyses predictions comparing the 1-SUD vs 2-SUD (untested) regimens with modified Dex suggested that 1) among the 2-SUD regimens with modified Dex, the 2/3/60 mg regimen would have the maximum reduction of 4% points in any-grade CRS compared to the 2/60 mg 1-SUD regimen, however, with substantial overlap of confidence intervals and with no decrease in ≥ G2 CRS (< 0.5% point); 2) 4 mg as an intermediate SUD in a 2-SUD regimen would lead to higher any-grade and ≥ G2 CRS rates (~9% and 3% points higher, respectively), compared to the 2/60 mg Q4W regimen. Conclusions ER and CRS PK/PD analyses suggested that modified Dex and SUD improve the CRS safety profile of ABBV-383 with no impact on efficacy (ORR) in pts with RRMM. The CRS PK/PD predictions indicated that implementation of 2-SUDs provide minimal additional or no improvement in CRS safety profile compared to 1-SUD. Overall, the 1-SUD dosing regimen of 2 mg with modified premedication prior to the full dose of 60 mg Q4W showed promising results and can be considered for future evaluation and studies.

Background The vitamin K antagonist, warfarin, is the preferred anticoagulant in patients with antiphospholipid syndrome (APS). Direct oral anticoagulant (DOAC) use in APS is associated with inferior outcomes, including significantly increased odds of arterial thrombotic events, particularly cerebrovascular accidents (CVA). Despite growing evidence supporting warfarin as the preferred first-line agent, DOACs continue to be utilized by providers in the management of APS. The primary aim of this analysis was to scrutinize the patients with a diagnosis of APS and their anticoagulant choices, to identify quality gaps such as unconfirmed diagnosis (with the need for further testing), lack of awareness of the evidence by the prescribing provider or inadequate documentation of risk benefit conversation, versus patient preference and then systematically intervene to reduce the utilization of DOACS in this patient population. Methods We retrospectively reviewed 100 patients with an ICD code diagnosis of APS documented in the electronic health record (EHR) who were recently prescribed a DOAC within Mayo Clinic enterprise. These cases were assessed for appropriateness of the diagnosis (defined as having at least one clinical manifestation of APS, including venous/arterial thrombosis and/or adverse pregnancy outcome in the setting of persistent antiphospholipid antibody (aPL) positivity by Sapporo criteria). aPL positivity was defined as having positive tests on two occasions with a minimum of 12 weeks apart. Antiphospholipid antibody testing included anticardiolipin (aCL) antibodies (IgG and IgM), anti-beta2 glycoprotein I antibodies (IgG and IgM) and lupus anticoagulant (LA). If the patient met diagnostic criteria, they were then risk stratified to identify high-risk cases. High-risk profile was defined as persistently positive levels of all three aPL (triple-positive). Following review for the appropriate diagnosis, intervention gaps were identified, including the need for additional diagnostic testing, provider education, documenting risk-benefits discussion, and removal of APS from the patient's problem list in the EHR. Clinical intervention was done by sending an EHR message to the prescribing provider which included reason for communication, intervention and recommendation. Reminders were sent every 2 weeks to providers who did not respond, with maximum of 3 messages per provider. Results Of the 100 patients, 60/100 (60%) did not meet criteria for APS, as either initial or repeat aPL testing was negative, and therefore were excluded from this project. Within the remaining 40 patients, 17/100 (17%) had thrombotic APS and 23/100 (23%) had unconfirmed diagnosis Reasons for no intervention (20/40) included not meeting criteria for APS, no longer on a DOAC, and risk versus benefits discussion documented. After adjudication only 20 patients qualified for intervention, 10/20 (50%) patients required additional testing due to lack of repeat testing or referral to a specialist, 7/20 (35%) required removal of APS from problem list, and 3/20 (15%) needed provider. Only 12/20 (65%) of providers accepted the recommendation, 7/20 (35%) did not, and 1/20 (5%) did not respond. Conclusions Despite syndrome-defining criteria, APS remains a commonly misdiagnosed condition. Our QI analysis found that more than half of patients in our cohort with HER documented diagnosis of APS did not meet the Sapporo diagnostic criteria. The tested intervention was time-intensive and prospective, which may have contributed to limited provider acceptance. We propose a robust system-based intervention to remedy this quality issue, which will leverage the EHR to create smart tools in the form of order sets and a passive Our Best Practice Advisory alert to highlight incomplete testing or suggest follow up lab testing at 12 weeks. We will also integrate just in time provider education resources and material embedded in the orders. Our future goal is to assess the impact of this intervention with a similarly sampled cohort.

Background: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a severe thrombotic thrombocytopenia that predominantly occurs after adenoviral vector-based vaccines. VITT patients produce anti-platelet factor 4 (PF4) antibodies with restricted clonality (i.e., mono/oligoclonal) with lambda light chains. Long-term follow-up studies in VITT show a disconnect in the persistence of anti-PF4 antibodies, whereby ELISA-positive antibodies persist significantly longer than platelet-activating antibodies. The mechanistic basis of this is unclear and could be explained by a couple of hypotheses: (1) Epitope spreading where, with time, the specificity of platelet-activating anti-PF4 antibodies may “spread” to recognize only PF4 complexed to heparin vs. (2) Persistence of clonally restricted platelet-activating anti-PF4 antibodies which decrease in titers with time such that their levels are insufficient to crosslink platelet FcGRIIa and induce platelet activation. Methods: Acute, convalescent patient sera and affinity-purified anti-PF4 antibodies were evaluated in antigen-based, functional (platelet-activation-based), and mass spectrometry studies as previously described (Blood, 2022 Jul 7;140(1):73-77). The median time to last follow-up was 243 days after the acute episode (range: 114-664 days). Results: Follow-up samples were obtained from 6 VITT patients after Ad26.COV2.S vaccination. At last follow-up, anti-PF4 IgG antibodies reactive in PF4/polyanion ELISA were detected in the sera of 5/6 VITT patients. However, only one of these samples stimulated platelet activation in the PF4-dependent P-selectin expression assay (PEA; 199 days after acute presentation). Affinity-purified anti-PF4 antibodies were detected by ELISA in all follow-up samples and three of the six affinity-purified anti-PF4 antibody samples activated platelets in the PEA. Four of the six VITT patients demonstrated a monoclonal anti-PF4 antibody, while one each had a biclonal and triclonal profile. Five VITT patients produced IgG lambda light chain antibodies, while one produced an IgG kappa. All six VITT patients demonstrated synonymous anti-PF4 antibody profiles when comparing acute and follow-up antibody repertoires, without evidence of VITT patients producing new anti-PF4 antibodies after the acute episode. In all cases, levels of anti-PF4 antibodies were significantly lower in convalescent samples relative to acute samples. Given this data on the persistence of clonally-restricted VITT antibodies, samples from another VITT patient with thrombocytopenia (100-150,000/uL) persisting for more than three years were similarly evaluated. This patient, who experienced severe thrombosis after ChAdOx1 nCoV19 vaccination, demonstrated persistent ELISA and PEA positivity even three years after symptom onset but had not experienced breakthrough thrombosis while on anticoagulation therapy. Serum protein electrophoresis (SPEP) did not detect a monoclonal gammopathy. Anti-PF4 antibodies immuno-enriched from a sample obtained >2 years after acute presentation demonstrated a monoclonal profile. While non-availability of an acute sample for anti-PF4 antibody characterization precluded a firm determination of whether this “Long VITT” case represented a subset of monoclonal gammopathy of thrombotic significance (MGTS; Blood 2023 Apr 6;141(14):1772-1776; New Eng J Med 2024 Aug 8), the chronicity of thrombocytopenia, presence of a monoclonal anti-PF4 antibody and persistently positive anti-PF4 serology supports this diagnosis. Conclusions. Clonally-restricted VITT antibodies persist for months-years with no evidence for the production of novel anti-PF4 antibodies after the acute event. Decreased abundance of anti-PF4 antibodies leads to negative functional results with follow up samples. Some platelet-activating antibodies can persist for very long periods (>3 years) and mediate persistent thrombocytopenia, representing an SPEP-negative MGTS-like state. This study also demonstrates the first example of a VITT antibody with a kappa light chain. The requirement for anticoagulation in patients demonstrating ELISA-positive/functional test-negative results is not clear, but the persistence of mono/oligoclonal anti-PF4 antibodies raises the possibility for the upregulation of pathogenic antibody production in proinflammatory settings.

Introduction: Chronic myelomonocytic leukemia (CMML) is a myeloid stem cell neoplasm with few effective therapies and poor prognosis. This disease is characterized by an expansion of malignant monocytes which express high and homogeneous levels of the homing chemokine receptor CCR2. We have developed a CCR2 targeting Cytotoxicity Targeting Chimera (CCR2-CyTAC, STX-0712), which potently binds CCR2 on cells, and when combined with the CyTAC platform antibody, eliminates target cells via enhanced effector mediated killing. We present here the characterization of CCR2 expression in CMML patient samples, ex vivo depletion of CMML cells via treatment with STX-0712, and the dose dependent depletion of MO1 monocytes (classical monocytes) in non-human primates, supporting CMML as a promising indication for STX-0712. Methods: IRB approval was obtained from Mayo Clinic for patient sample use. For CCR2 characterization and depletion experiments, we used bone marrow biopsy specimens and peripheral blood mononuclear cells (PBMCs) obtained from CMML patients and controls from healthy donors. CCR2 expression and monocyte depletion were evaluated via flow cytometry, as previously described. In vivo pharmacokinetic (PK) and pharmacodynamic (PD) studies were conducted in cynomolgus monkeys. Results: First, we evaluated CCR2 expression in peripheral blood and bone marrow in CMML samples by flow cytometry. In 6/6 (100%) peripheral blood samples CCR2 was highly expressed on >98% of the monocytes. Also, in 3/3 (100%) bone marrow samples, CCR2 was expressed on a subset of CD34+ progenitors, while low/no expression was observed in healthy controls. This progenitor subpopulation had characteristics of the inflammatory granulocyte-macrophage progenitor (GMP)-like cells. Next, STX-0712 was added to freshly isolated PBMCs from CMML donors and CCR2+ monocyte depletion, mediated by endogenous Fc gamma receptor 3a positive (FcγRIIIa) effector cells, was assessed. In 5/5 (100%) CMML patient samples, the drug selectively induced depletion of CD14+, CCR2+ cells with an average potency of 3nM and 66-91% target cell killing vs no drug control. Finally, we evaluated the effects of STX-0712 in cynomolgus monkeys to evaluate PK and PD effects on CCR2 MO1 monocytes in vivo. STX-0712 demonstrated PK supportive of dosing in man. In 9/9 (100%) animals, STX-0712 effectively depleted >95% of CCR2+ monocytes which returned after drug levels dropped below ~10ng/mL. All doses were well tolerated and the findings of comprehensive immunophenotyping were to be as expected, predictable and mechanism directed. Conclusion: These results demonstrate high and homogenous CCR2 expression on malignant monocytes, ex vivo human target engagement and pharmacodynamics, and in vivo depletion of CCR2 MO1 monocytes in a potent and dose dependent manner. Based on this data we plan a First in Human, phase 1 clinical trial for patients with relapsed/refractory CMML.