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Introduction: Adults older than 60 years constitute 20-25% of newly diagnosed classic Hodgkin lymphoma (cHL) and have inferior outcomes compared to younger patients (pts). Salvage therapy followed by an autologous stem cell transplant (ASCT) is a potentially curative option for pts with relapsed/refractory (R/R cHL). There is limited data regarding outcomes of older adults with R/R cHL who undergo ASCT in the current era where novel agents are employed in the R/R setting, in comparison with younger patients. Methods: This multicenter, international, retrospective study of 18 participating institutions included adults with R/R cHL who underwent ASCT from January 1, 2010 through December 31 2020. Retrospective chart review was performed to collect data on patient and disease characteristics at relapse, including lines and type of salvage therapy, pre-ASCT response by PET, and use of brentuximab vedotin (BV) as consolidation post-ASCT. Study objectives were to assess progression-free survival (PFS), overall survival (OS), and the probability of non-relapse mortality (NRM) with relapse as a competing event. NRM was defined as death without preceding relapse. Results: Of the total 1172 adults with R/R cHL enrolled in the parent cohort, 96 (8.1%) were age 60 years or older at the time of ASCT. In this older cohort, the median age was 66 years (range: 60-72). 54 (56%) were age 60-64, 31 (32%) were of age 65-69 and 11 (11%) were of age 70-72. 59 (61%) were male, 63 (66%) had advanced stage disease, 17 (18%) had bulky disease, 37 (39%) had B symptoms and 38 (40%) had extranodal disease. All patients (pts) received ABVD or ABVD-like frontline therapy. The median time to relapse was 6 months (range: 0-174). 48 pts (50%) relapsed within a year after completion of frontline treatment and 25 (26%) had primary refractory disease. Salvage therapy prior to ASCT included platinum-based chemotherapy (65%), BV-based regimen (34%), and PD-1 inhibitor-based regimens (3%). 16 pts (16%) underwent ASCT after >1 line of salvage therapy and 75 (78%) underwent ASCT after achieving a complete metabolic response (CMR). 14 pts (14.6%) received BV consolidation. Median follow-up for entire population was 53.4 months (range: 0.3-199.0). In older adults, the 5-year PFS was 54.2% (CI95: 43.4-67.6) not statistically different compared to pts <60 years (67.7% (CI95: 64.3-71.3), p=0.2). However, 5-year OS was inferior in older adults: 71.9% (CI95: 43.4-67.6) vs. 82.6% (CI95: 43.4-67.6) in pts <60 years (p <0.0001)). In pts ≥60, 26 (27%) died including 12 (12.5%) without preceding relapse. Older adults had 3-month, 1-year and 5-year probability of NRM of 5.2% (CI95: 2.2-12.2), 7.5% (CI95: 3.6-15.3), and 10.9% (CI95: 5.8-20.8), respectively. NRM was significantly higher in older adults compared to pts <60 who had 3-month, 1-year and 5-year probability of NRM of 0.3% (CI95: 0.1-1.0), 0.9% (CI95: 0.5-1.7), and 2.5% (CI95: 1.6-3.9), respectively (p<0.0001). Older adults had 3-month, 1-year and 5-year probability of relapse of 1% (CI95: 0.2-7.3), 7.5% (CI95: 3.6-15.3), and 28.6% (CI95: 19.1-42.1), respectively, which did not differ significantly from younger pts (p=0.3) who had 3-month, 1-year and 5-year probability of relapse of 0.6% (CI95: 0.3-1.3), 5.1% (CI95: 3.8-6.6), and 29.9% (CI95: 26.6-33.5), respectively. Conclusions: Although older adults with cHL are more likely to relapse after frontline treatment, only a minority of pts (<10%) in this large multicenter cohort underwent ASCT at age ≥60. In select older adults who underwent ASCT, the risk of relapse was similar to younger pts, but NRM was significantly higher, especially in the early post-ASCT period. Detailed assessment of comorbidity scores, toxicities of salvage therapies, and prognostic factors will be presented at the conference.

Background Hepcidin, a central regulator of iron homeostasis, is pathologically elevated in patients with myelofibrosis (MF) and anemia. Chronic hepcidin elevation limits iron availability for red blood cell production and contributes to onset and severity of anemia, for which there is a large unmet need for safe and effective treatments. DISC-0974 is an investigational, first-in-class, monoclonal antibody that blocks hemojuvelin, a co-receptor in the bone morphogenetic protein-signaling pathway driving hepcidin expression. A completed healthy volunteer study demonstrated serum hepcidin reductions, serum iron increases, and increasing trends in hematologic parameters, with no safety signal identified. Aims This Phase 1b/2, open-label, multiple-ascending dose study (NCT05320198) assessed safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), and initial efficacy of DISC0974 in patients with MF and anemia. Methods Eligible participants were ≥18 years of age with intermediate-2 or high-risk MF and anemia. Anemia was defined as baseline hemoglobin (Hgb) <10 g/dL with or without intermittent transfusion requirement (non-transfusion dependent [nTD]) or transfusion dependent (TD), as defined by the IWG-MRT. A stable dose of concomitant hydroxyurea and/or Janus kinase (JAK) inhibitor was allowed. Major exclusion criteria included liver iron concentration ≥7 mg/g dry weight and nutritional, genetic, infectious, or autoimmune anemia. Dose escalation was based on a Bayesian optimal interval design with accelerated titration. DISC-0974 was administered subcutaneously monthly for 6 doses. Primary endpoints included evaluating DISC-0974 safety and tolerability. Secondary endpoints included PK/PD markers of iron regulation and hematologic parameters. Hematologic response was defined for TD as transfusion independence (TI) during any 12-week consecutive period and for nTD as ≥1.5 g/dL Hgb increase from baseline at any time point. Durability was evaluated as mean Hgb ≥1.5 g/dL above baseline during any 12-week period. Data were summarized using descriptive statistics. Results At the time of data cut, 34 participants were enrolled at 5 dose levels: 14 mg (n=1), 28 mg (n=7), 50 mg (n=12), 75 mg (n=8), and 100 mg (n=6). Treatment with DISC-0974 resulted in meaningful and sustained hepcidin reductions with mean change from baseline (mean 88.2 ng/mL; range [8.7, 374.7]) reaching over 80% across treated participants. This corresponded to iron mobilization at all dose levels. Efficacy Hematologic responses were evaluated in participants dosed at 28 to 100 mg. Responses were achieved independent of baseline transferrin saturation (TSAT) values. Initial hematologic responses in nTD participants were observed around the time of administration of the second dose, with a rise in absolute reticulocyte count preceding responses. Mean erythropoietin values decreased from baseline (mean 68.2 mIU/mL; range [13.2, 1815]) in participants treated at 50 to 100 mg. Hemoglobin responses were achieved in 69% (20/29) of nTD participants; 60% of nTD participants (9/15) achieved a durable response. TSAT values above normal range (50%) were observed in all participants with a durable response. One of two evaluable TD participants achieved TI at the end of study. All evaluable participants with a baseline transfusion requirement (n=8) had ≥50% reduction in transfusions over a rolling 8-week window compared to baseline. Hematologic response was observed in 6 of 10 participants with concomitant JAK inhibitor therapy. Safety One adverse event (AE), diarrhea, was at least possibly related to DISC-0974 and reported in ≥2 participants. Grade 3 AEs included headache reported in 1 participant treated at 28 mg (not related to DISC-0974) and Grade 3 anemia reported in 2 participants treated at 28 mg and 4 participants treated at 50 mg (1 at 50 mg was deemed related to DISC-0974; all others were deemed not related). One serious AE of Grade 2 arthralgia was reported and deemed not related to DISC-0974. Summary/Conclusions DISC-0974 demonstrated acceptable safety and tolerability at all evaluated dose levels. Hematologic responses were achieved in nTD and TD participants, regardless of concomitant JAK inhibitor use. Sustained hepcidin reduction with DISC-0974 led to increased serum iron that preceded hematological response. Additional Phase 1b data, including longer follow-up, will be presented.

Introduction Symptom burden in myeloproliferative neoplasms (MPN) is quantified using total symptom scores (TSS) calculated from the patient-reported scores for clinically meaningful symptoms. The impact of demographic, clinical, and laboratory features on these symptoms remains unclear and warrants further investigation. Methods Patients with polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF) were identified from the retrospective chart review. TSS, scores of individual symptoms (fatigue, early satiety, abdominal discomfort, inactivity, concentration difficulties, fever, night sweats, itching, bone pain, weight loss), demographic characteristics (race, ethnicity, age, and gender), clinical features (time since diagnosis, depression status, obesity status), laboratory results and season at the time of visit when the first TSS assessment was performed were recorded. Multicollinearity and homoscedasticity were assessed using variance inflation factors and visual inspection of the data, respectively. A multivariable regression analysis was performed using a robust variance estimator. A p-value <0.05 indicated a statistically significant association with the symptom scores. Results The chart review identified 557 (PV: 201; ET: 191; MF: 165) patients. The median age of patients with PV, ET, and MF was 65 (range: 27-93), 65 (20-96), and 69 (27-96) years, respectively. Most patients were white (PV: 92%; ET: 90%; MF: 93%) and non-Hispanic or Latino (PV: 93%; ET: 96%; MF: 92%). Most patients with PV and ET were female (PV: 51%; ET: 73%), while most patients with MF were male (55%). Among the included patients 22% (PV: 21%; ET: 27%; MF: 18%) had the diagnosis of depression at the time of the clinical visit. TSS was highest in MF (mean (SD): 18.1±14.6), followed by PV (15.7±14.5) and ET (15.1±14.0) patients. Fatigue was the most reported symptom by the patients (PV: 81%; ET: 82%; MF: 84%), whereas weight loss was the least reported symptom (PV: 4.5%; ET: 6.3%; MF: 16%). With regards to the TSS multivariable regression analysis showed that age (beta coefficient: 0.2; p=0.01), depression (7.2; 0.008), and low hemoglobin (1.2; 0.003) in PV, depression (11.7; 0.001) in ET, and depression (9.5; 0.001), splenomegaly (6.9; 0.01), and WBC count (0.16; 0.048) in MF patients were significantly associated with TSS. In terms of individual symptoms in PV, depression was associated with fatigue (beta coefficient: 1.31; p-value: 0.01) and concentration difficulties (1.7; <0.001), high WBC count was associated with early satiety (0.09; 0.03), and non-white race was associated with fever (1.4; 0.007). In ET, depression was associated with fatigue (1.6; <0.001), abdominal discomfort (1.4; <0.001), inactivity (2.5; <0.001), concentration difficulties (2.4; <0.001) and night sweats (1.4; <0.001), anemia was associated with fatigue (1.2; 0.03), fewer months since diagnosis was associated with inactivity (0.01; 0.02) and young age was associated with bone pain (0.02; 0.03). In MF, depression was associated with fatigue (1.8; 0.001), concentration difficulties (1.3; 0.01), fever (1.1; 0.02), and night sweats (2.2; 0.03), low hemoglobin was associated with fatigue (0.46; <0,001) and early satiety (0.31; 0.003), high WBC count was associated with fatigue (0.03; 0.04) and early satiety (0.04; 0.02), low platelet count was associated with abdominal discomfort (0.002; 0.03), splenomegaly was associated with inactivity (2.27; 0.003) and female gender was associated with itching (0.57; 0.01). Conclusions This study demonstrates that depression in PV and ET and depression, low hemoglobin, and a high WBC count in MF contribute to multiple symptoms seen in these patients. Identifying demographic groups at risk of a higher symptom burden and addressing the comorbidities that drive symptoms, in addition to disease-directed therapy, is crucial to improving the quality of life in these patients.

Background: Erdheim-Chester Disease (ECD) is an exceedingly rare inflammatory myeloid neoplasm characterized by infiltration and accumulation of clonal histiocytes within multiple organ systems. These histiocytes usually carry gain-of-function mutations that affect the MAPK-ERK or PI3K-AKT pathways. The most common mutation is BRAFV600E, occurring in greater than 50% of patients, often with a low variant allele frequency (i.e. <5%). ECD presents as a spectrum of clinical manifestations that include symmetric osteosclerosis of the distal femora and proximal tibiae and/or fibulae (almost always present), ataxia from cerebellar/brainstem involvement, diabetes insipidus, periorbital xanthelasmas, pleuropulmonary disease, pseudotumor of the right atrioventricular groove, encasement of the (coated) aorta, and retroperitoneal involvement with ‘hairy’ kidneys. Patients may be asymptomatic or critically ill. Treatment options include targeted agents like BRAF or MEK inhibitors, as well as systemic agents such as interferon or chemotherapy. A recent combined report from France and Italy suggested incidence rates of 3.5 per 10 million adults (not age-adjusted). ECD was officially considered a hematopoietic malignancy by the World Health Organization in 2016 and a reportable cancer in the United States (US) beginning in 2021. For the first time, we report the incidence of ECD in the US. Methods: We obtained ECD data in 2021, the only year available so far, from the Surveillance Epidemiology and End Results (SEER) program. The SEER program prospectively collects data from population-based cancer registries covering about 48% of the US population and is updated annually. Data elements include patient demographics, primary tumor site, tumor morphology and stage at diagnosis, first course of treatment, and follow-up for vital status. Twentytwo cancer registries (SEER 22) were included and screened for cases with the ECD International Classification of Diseases for Oncology (ICD-O) code 9749/3 for inclusion in this study. We used SEERstat version 8.4.3 to calculate the annual incidence. All incidence rates were age-adjusted to the 2000 US standard population. Confidence intervals (CI; 95%) were provided whenever available. Results: In 2021, SEER documented 16 patients diagnosed with ECD. The median age at diagnosis was 52 years (range, 25-74). The most common age range at diagnosis was 55-59 years (31%). There was an even distribution of sexes (53% male), but greater proportion of minority patients (38% non-Hispanic White, 25% non-Hispanic Black, 25% Hispanic, 6% Asian/Pacific Islander, 6% unknown race/ethnicity). Most patients (94%) were diagnosed in large metropolitan areas. The overall incidence rate was 0.9 [CI: 0.2-5.2] per 10 million population. The incidence rates for various demographic subgroups were as follows (per 10 million): males (1.0 [0.4-1.9]), females (0.8 [0.4-1.7), non-Hispanic Blacks (1.9 [0.5-5.2]), Hispanic (1.1 [0.3-2.8]), non-Hispanic Whites (0.5 [0.2-1.2]), Asian/Pacific Islander (0.5 [0.0-3.4]), and ages 25-74 years (1.5 [0.8 - 2.5]). The most reported primary site was subcutaneous (25%), followed by bone (19%) and breast (19%). A greater number of cases had distant disease (56%; 31% localized, 13% unknown). Almost half of the patients received chemotherapy (44%) and few underwent radiation (13%) or surgery (13%). Conclusion: We report the first estimate of ECD incidence in the US, highlighting the rarity of this entity. It should be noted that our reported incidence rates are likely underestimated. This could be due to the COVID-19 pandemic that resulted in social quarantine from 2020-2021. ECD is also a very challenging diagnosis to make. Future investigations of annual SEER updates and collective incidence data over several years will be required to strengthen our findings and further characterize the epidemiological features of ECD in the US.

Background: Two National Cancer Institute-funded pharmacovigilance programs have identified 49 serious hematology-related ADRs since 1998. The programs, called RADAR (Research on Adverse Drug events and Reports) and then SONAR (Southern Network on Adverse Reactions) involve > 50 institutions and > 75 co-investigators worldwide. The work builds on three prior studies evaluating “Davids and Goliaths” in medical oncology and in cardiology (PLOS One, eClinicalMedicine, and Journal of Scientific and Professional Integrity). Here we review the hematology focused safety investigations of RADAR/SONAR. Methods: Data were based on initial safety signals being identified by a RADAR/SONAR co-investigator. Then, case-series were derived. Collaborations with basic scientists allowed for basic science correlative studies. Results were disseminated primarily as Brief Report in the literature and Black Box warnings on the related drug. In some instances, studies identified hematologic toxicities that prevent FDA from approving a submitted drug application. Results: sADRs were frequently identified based on very small case series, including ticlopidine-and clopidogrel associated thrombotic thrombocytopenic purpura (22 and 10 patients, respectively), thalidomide- and lenalidomide-associated venous thromboembolism (9 and 5 patients, respectively), rituximab-associated progressive multi-focal leukoencephalopathy (22 patients), peginesatide-associated fatal anaphylaxis (5 patients), and COVID-19 vaccine associated immune thrombocytopenia (1 patient). Meta-analyses provided data for epoetin- and darbepoetin-associated mortality among cancer patients and lenalidomide- and thalidomide-associated venous thromboembolism. Following the onset of the COVID-19 pandemic, RADAR/SONAR investigated social media and pre-prints (COVID-19 vaccine associated cerebral vein thrombosis and immune thrombocytopenia). Time from FDA approval to sADR discovery was a median of 5 years (range, 0 months (thalidomide-associated venous thromboembolism) to 34 years (ciprofloxacin-associated neuropsychiatric toxicity). Basic science correlative studies identified ADAMTS13 autoantibodies (ticlopidine), leachates that developed in a multi-dose vial (peginesatide), anti-red blood cell antibodies (epoetin-associated pure red cell aplasia), and high-risk genes (fluoroquinolones and rituximab). Overall, RADAR/SONAR studies are estimated to have saved over 1 million lives and also resulted in overall payments to the Department of Justice of $1.5 billion (related to marketing of unsafe drugs). Discussion: RADAR/SONAR has proven to be a very important adjunct to FDA and pharmaceutical manufacturer-led safety investigations for hematology, paralleling the success in medical oncology and in cardiology. Going forward, independent centers of excellence for safety-focused investigations such as the CERSI network and the SENTINEL network (both are NIH funded) should be broadened to include a hematology-focused safety center.

Background and significance: Light chain (AL) amyloidosis is a plasma cell malignancy characterized by the production of amyloidgenic clonal light chains that deposit in various tissues. The addition of daratumumab to bortezomib, cyclophosphamide and dexamethasone (Dara-VCD) has improved the depth of hematologic and organ responses and is an approved induction therapy in newly diagnosed AL amyloid patients (DOI: 10.1056/NEJMoa2028631). However, this approach has not yet demonstrated an overall survival (OS) benefit and follow up remains short. With strict adherence to eligibility criteria, in particular severity of cardiac involvement, autologous stem cell transplantation (ASCT) as consolidative therapy is safe with transplant related mortality on par with multiple myeloma. This approach generates deep and sustained responses, but it is unclear if it offers an additional survival benefit following Dara-VCD induction. The only randomized trial evaluating the role of ASCT in AL amyloid is outdated (DOI: 10.1056/NEJMoa070484) and no randomized data exist to inform the optimal use of ASCT in the era of Dara-VCD induction. Furthermore, multi-organ involvement in AL amyloid drives morbidity and mortality thus the impact of any consolidative therapy on cardiac and renal involvement in addition to overall survival but must be defined. Finally, the approval of Dara-VCD therapy was based on complete hematologic response rates but there is increasing data demonstrating that achieving minimal residual disease (MRD) negativity by either bone marrow next generation flow cytometry (DOI: 10.1002/ajh.26562) or peripheral blood mass spectrometry (DOI: 10.1038/s41408-020-0291-8) generates improved organ response, hematologic progression free survival, and possibly OS. Methods: This randomized phase 3 SWOG led intergroup trial (S2213; NCT06022939) is being conducted within the United States and will accrue a total of 143 participants per arm. The primary endpoint will compare MOD-PFS (major organ deterioration progression free survival: defined as time from randomization to death, cardiac/renal progression, or hematologic progression) between participants receiving an ASCT with those receiving 3 cycles of Dara-VCD consolidation following 3 cycles of uniform Dara-VCD induction. Following the assigned consolidation, all patients will receive 18 months of daratumumab maintenance therapy. A median MOD-PFS of 31 months is anticipated in the non-ASCT arm. This study has 90% power and a two-sided significance level of 0.05 to detect a hazard ratio of 0.62 corresponding to a MOD-PFS of 50 months in the ASCT arm. Important additional endpoints include OS, hematologic PFS, cardiac and renal responses, MRD negativity both by peripheral blood mass spectrometry and bone marrow next generation flow cytometry, delayed utilization of ASCT, and quality of life. Key inclusion criteria include non-severe cardiac AL amyloid (NT-proBNP <5000; TnT < 0.06; NYHA I or II, EF ≥ 40%), CrCl ≥30 mL/min, serum dFLC > 2 mg/dL, and supine systolic BP ≥ 90 mmHg. Importantly, patients are permitted to have up to one full cycle or 28 days of any plasma cell directed therapy prior to enrollment. This trial was activated on 12/1/2023 with the first patient enrolled 07/01/2024. Funding: NIH/NCI/NCTN grants U10CA180888, U10CA180819; and in part by Janssen Pharmaceuticals Inc. of Johnson & Johnson (now J&J Innovative Medicine).

Background: Light chain (AL) amyloidosis is a rare and understudied plasma cell disorder. It is caused by abnormal misfolding of monoclonal immunoglobulin light chains, leading to extracellular deposition of amyloid, ultimately resulting in organ dysfunction and death. Since AL amyloidosis is uncommon, therapies are adapted from the more common plasma cell disorders like multiple myeloma. Daratumumab, a monoclonal antibody targeting CD38, was first tested in several prospective and retrospective studies in AL patients with relapsed refractory disease. The ANDROMEDA study (Kastritis E et al, NEJM 2021) established daratumumab in combination with CyBorD (Cyclophosphamide-Bortezomib-Dexamethasone) followed by daratumumab maintenance as the new standard of care compared to CyBorD alone for newly diagnosed patients. Consequently, daratumumab maintenance has become universally offered to all newly diagnosed AL amyloidosis patients. Notably, there was no second randomization before the initiation of maintenance therapy in ANDROMEDA. Hence, a critical question that remains is whether the superior efficacy observed in the investigational arm of the ANDROMEDA trial is solely a result of the addition of daratumumab during the induction phase or if the maintenance phase contributed to the favorable outcomes in the investigational arm. We hypothesize that a shorter duration of maintenance would prove non-inferior to the standard duration of daratumumab maintenance in patients with AL amyloidosis that have responded to Daratumumab-CyBorD induction. To answer this question we are conducting a pragmatic phase 2 randomized trial assessing the optimal duration of daratumumab maintenance in patients with AL amyloidosis who have responded to Daratumumab-CyBorD induction. Study Design, Patients and Methods: We use broadened eligibility criteria consistent with pragmatic trial design. The estimated total enrollment is up to 96 patients. The main eligibility criteria are patients with biopsy-proven AL Amyloidosis who have completed 6 cycles of Dara-CyBorD-based induction treatment and achieved an adequate response to induction (defined as hematological complete response (CR), hematological very good partial response (VGPR), or hematological partial response (PR) with at least one organ response). Patients in whom bortezomib and/or cyclophosphamide were omitted from induction due to toxicity concerns or adverse effects are allowed. The major exclusion criteria are patients who were concomitantly diagnosed with multiple myeloma based on International Myeloma Working Group (IMWG) criteria. This phase II, open-label, multicenter trial (NCT05898646) randomizes patients who have attained an adequate response to 6 cycles of Dara-CyBorD-based induction in a 1:1 ratio, using a dynamic allocation procedure that balances the marginal distributions of the stratification factors (age, cardiac stage, and t(11;14) status). Randomization is to either single-agent daratumumab maintenance of 6 cycles duration (experimental arm) or 18 cycles of daratumumab maintenance (control arm) (cycle = 28 days). Treatment is allowed to be given at a local facility After completing maintenance treatment, patients will follow up every 3 months for up to 36 months from registration. The primary endpoint of the trial is to evaluate the non-inferiority of a shorter (6 cycles) daratumumab maintenance measured by event-free survival (EFS) compared to the standard maintenance of 18 cycles in newly diagnosed AL amyloidosis who receive 6 cycles of daratumumab-CyBorD based induction. EFS in this study is defined as time from registration to any of the following events: hematological progression, organ progression, subsequent anti-plasma cell therapy in the absence of hematological progression but with persistent organ dysfunction or death, whichever occurs first. Secondary endpoints are depth of hematological and organ response, bone marrow measurable residual disease negativity rate, duration of response, quality of life, and survival. By investigating whether a shorter duration of maintenance is non-inferior to the standard duration, we aim to inform clinical practice and potentially reduce the toxicities associated with prolonged maintenance therapy, including hypogammaglobulinemia, recurrent infections, the need for intravenous gammaglobulin replacement, and financial toxicity.

Background:Patients (pts) with multiple myeloma (MM) often receive immunomodulatory drugs (IMiDs; eg, lenalidomide), proteasome inhibitors (eg, bortezomib), and anti-CD38 monoclonal antibodies (mAbs) as part of their initial treatment. However, most pts relapse following initial treatment, with increasing attrition rates observed at each subsequent line of therapy (LOT), creating an unmet need for treatment options for pts with relapsed/refractory MM (RRMM) who have prior exposure to these agents. Current regimens for pts who have prior exposure to lenalidomide and anti-CD38 mAbs include elotuzumab, pomalidomide, and dexamethasone (EPd; approved in Europe and the US) and pomalidomide, bortezomib, and dexamethasone (PVd; approved in Europe and Australia), but disease control, as well as depth and durability of response, could be improved. Talquetamab (tal) and teclistamab (tec), targeting CD3 and either G protein-coupled receptor family C group 5 member D (GPRC5D, tal) or B-cell maturation antigen (tec), are the first T-cell redirecting bispecific antibodies (BsAbs) approved as monotherapies in Europe and the US for the treatment of pts with triple-class exposed (TCE) RRMM. Use of these novel immunotherapies in earlier LOTs, either with a dual-antigen targeting approach or by enhancing the activity of the BsAb with an IMiD (pomalidomide), may provide deeper, more durable responses and improve pt quality of life. Preliminary data using these combination treatments have shown promising results: in the phase 1b MonumenTAL-2 study (NCT05050097), tal+pomalidomide (tal-P) demonstrated overall response rates (ORRs) of >84% in pts with RRMM with ≥2 prior LOTs and in the phase 1b/2 RedirecTT-1 study (NCT04586426), tal+tec (tal-tec) showed ORRs of >77% in pts with TCE RRMM. MonumenTAL-6 (NCT06208150) is a randomized, open-label, multicenter, phase 3 study comparing the efficacy of tal-P vs investigator's choice of EPd or PVd and tal-tec vs investigator's choice of EPd or PVd in pts with RRMM with 1-4 prior LOTs, including lenalidomide and an anti-CD38 mAb. Study Design and Methods: Eligibility includes pts aged ≥18 years with documented MM per International Myeloma Working Group (IMWG) criteria, with measurable disease at screening, an Eastern Cooperative Oncology Group performance status of 0-2, who have received 1-4 prior LOTs (including lenalidomide and an anti-CD38 mAb in any prior LOT), and have progressive disease on or after their last therapy. Pts with prior exposure to pomalidomide, tec, or GPRC5D-directed therapies are excluded. Approximately 795 pts are randomized 1:1:1 to receive tal-P, tal-tec, or investigator's choice of EPd or PVd. Tal is administered subcutaneously at 0.8 mg/kg every other week (Q2W), and tec is administered subcutaneously at 3.0 mg/kg every 4 weeks (Q4W) following step-up doses of each. Pts are permitted to switch from Q2W to Q4W tal dosing following a confirmed very good partial response or better (≥VGPR) at cycle 5. Pomalidomide, EPd, and PVd are administered per approved dosing schedules. Randomization is stratified by number of prior LOTs (1 vs ≥2), International Staging System stage at screening (I vs II/III), and investigator's choice of treatment (EPd vs PVd). Pts receive study treatment until disease progression, start of subsequent anti-MM treatment, death, intolerable toxicity, withdrawal of consent, or end of study, whichever occurs first. A finite dosing approach is employed for tal and tec. The primary endpoint is progression-free survival (PFS). Secondary endpoints include ORR assessed per IMWG 2016 criteria, ≥VGPR rate, complete response (CR) or better rate, rate of minimal residual disease-negative CR, overall survival, PFS on next LOT, time-to-next treatment, and pt-reported outcomes. This study is actively recruiting, with more than 160 locations in 26 countries. Results will provide insights into the efficacy of the combination of BsAbs in therapeutic strategies that exploit their different mechanisms of action to overcome treatment resistance and improve outcomes of pts with TCE RRMM in earlier LOTs.

Introduction Intravenous Immunoglobulin G (IVIg) is a pooled antibody Immunoglobulin G product that is used for a large and ever-growing number of medical indications. It is also known to be associated with an increased risk of thromboembolic complications such that the Food and drug administration (FDA) has mandated a “black box” warning alerting physicians to this risk. Particular lots of IVIg preparations have been recalled due to a higher-than-expected rate of thromboembolic adverse events (“Evaluation of the Risk of Thromboembolic Events After Immunoglobulin Administration, 2006-2012”. Sentinel Product Assessment, US FDA, 7/13/2017). While a number of mechanisms have been proposed to explain the thromboembolic risk, platelet activation induced by small amounts of aggregated IgGs in IVIg preparations remains the leading hypothesis. Currently, testing of IVIg lots specifically looking at their ability to induce platelet activation is not routinely performed due to challenges with acquisition of fresh platelets for testing, and lack of availability of technically simple platelet activation endpoints. Recent breakthroughs in platelet storage technology have demonstrated that platelet viability can be preserved for long periods (months-years) by controlled-rate cryopreservation which also allows platelets to retain FcγRIIa-mediated signaling (FcγRIIa is the IgG receptor on platelets). This technology has been successfully leveraged for the detection of platelet-activating heparin-induced thrombocytopenia (HIT) and Vaccine-induced immune thrombotic thrombocytopenia (VITT) antibodies (Blood, 140 (25) 2722-2729, 2022). Goals of the study We hypothesized that long-term stored cryopreserved platelets could be used to detect platelet-activating IVIg preparations using a technically simple ELISA endpoint that measures levels of thrombospondin-1 (TSP-1), a platelet granule protein, released upon platelet activation. If successful, this tool could help de-risk IVIg from the standpoint of thrombotic adverse reactions. Methods Aggregated IgG was prepared by heat treatment of IVIg (Pel-Freez- Rogers, AR) as previously described (Immunol. Lett. (15) 311-316, 1987). Platelets were cryopreserved as previously described (Blood, 140 (25) 2722-2729, 2022) with minor modifications. Cryopreserved platelets were thawed and treated with heat-aggregated or untreated IVIg at concentrations ranging from 19 to 75mcg/mL. After incubation, supernatants were collected by centrifugation and were assayed for TSP-1 by an antigen capture ELISA which has been shown previously to correlate with platelet activation. Results 10-month-old “off-the-shelf” cryopreserved platelets treated with buffer control displayed minimal platelet activation as measured by the TSP1 ELISA (Optical density, OD: 0.21). Similarly, platelets treated with IVIg (non-aggregated IgG) at concentrations ranging from 19 to 75mcg/mL displayed little-to-no platelet activation in the TSP1 ELISA (OD: 0.22-0.29). In contrast, cryopreserved platelets treated with heat aggregated IVIg demonstrated marked platelet activation in the TSP1 ELISA with ODs in the 0.60-0.82 range, correlating with increasing concentrations of heat-aggregated IVIg in the reaction. Conclusions De-risking IVIg from a prothrombotic standpoint has been challenging due to the need for fresh platelets for testing and the lack of technically simple means to assess platelet activation. Here, we leveraged breakthrough platelet storage technology coupled to a technically simple ELISA endpoint that allowed for rapid and easy identification of platelet activating forms of IVIg. This easy-to-use self-contained test kit could be implemented as a quality control/patient safety tool to de-risk IVIg preparations from the standpoint of platelet activation-mediated thrombosis. Future studies aim to test a large number of IVIg lots, including “problem” lots associated with thromboembolic events to assess the incidence of platelet activating IgG molecules in IVIg preparations. Acknowledgments This work was supported in part by a grant from the National Institutes of Health (C.G.J.: HL147734).

Introduction. Platelet-activating anti-Platelet factor 4 (PF4) antibodies mediate a number of thrombotic thrombocytopenic syndromes, including heparin-induced thrombocytopenia (HIT), and more recently recognized conditions, vaccine-induced immune thrombotic thrombocytopenia (VITT), adenovirus-associated thrombotic thrombocytopenia, and monoclonal gammopathy of thrombotic significance (MGTS). In MGTS (Blood. 2023 Apr 6;141(14):1772-1776), a monoclonal IgG antibody to PF4 mediates a chronic prothrombotic state characterized by recurrent thrombosis. More recent evidence suggests that MGTS may present with negative results in HIT enzyme-linked immunosorbent assay (ELISA) and serotonin release assay (SRA), and positivity only in PF4-dependent functional assays such as the PF4-dependent P-selectin expression assay (PEA; submitted). The presence of MGUS in patients has long been associated with high risks of thrombotic disease (Blood. 2010 Jun 17;115(24):4991-8), but the mechanism by which they predispose to thrombosis has been relatively unexplored. In this study, we evaluated a cohort of MGUS patients who experience thrombosis for the presence of platelet-activating anti-PF4 antibodies. M ethods. An administrative database search was performed of Mayo Clinic records to identify patients who had a diagnosis of MGUS, and thrombosis. Research samples from 134 MGUS patients with IgG monoclonal protein and thrombosis were obtained from Mayo Clinic's dysproteinemia biobank and subjected to PF4 antigen-based and functional screening. Research studies were approved by the Institutional Review Board of Mayo Clinic. Results. Of the 134 patients, 17 (12.7%) activated platelets in the PEA (≥19%). To exclude non-specific activation (e.g. due to HLA antibodies), secondary PEA testing was performed to assess whether platelet activation was mediated by a HIT-like antibody (i.e., PF4- and IgG-dependent, and inhibitable with high concentrations of heparin). Four patients, hereafter referred to as patients 1-4, were identified as having a HIT-like antibody, as demonstrated by PF4-dependent platelet activation that could be inhibited with high concentrations of heparin (100 U/mL), and blockade of the platelet IgG receptor, FcγRIIa. Patients 1 and 2 had persistent, platelet-activating anti-PF4 antibodies based on PEA testing of multiple samples obtained several years apart. Patient 1 had a recurrent, multi-year history of deep venous thrombosis (DVT), while patient 2 had one DVT episode. Patient 3 demonstrated a HIT antibody-like profile in the PEA in two of three samples available for testing and had a history of thrombotic cerebrovascular accident (CVA). Patient 4 demonstrated a HIT-like platelet-activating antibody in only one of four samples tested, and consistent with this finding, had an MGUS identified on clinical testing at only one time point (“small” IgG lambda, not quantified), 3 months prior to the platelet-activating sample. This patient experienced multiple thrombotic events including DVTs, left atrial thrombus and embolic CVA, pulmonary embolism and acute limb ischemia. All patients tested negative in two FDA-approved antigen-based HIT assays tested (Immucor PF4 IgG and Zymutest HIA IgG), similar to a recent MGTS case (submitted). SRA was negative in both Patients 1 & 2, weakly positive in Patient 3 (33%, with high CV), and positive (72%) in Patient 4. Conclusions. Definitive diagnosis of patients with MGTS provides insight into a mechanism of “unexplained” thrombosis and may offer additional treatment pathways for these patients with recurrent thrombosis (New Eng J of Med, 2024 Aug 8). Serologic testing in two patients correlated strongly with observations of thrombosis, and the study confirmed recent findings that anti-PF4 antibodies may present with unusual serology that is neither HIT- nor VITT-like (with negative results in both ELISA and SRA). The incidence of confirmed/suspected MGTS was 3% (4/134) in this population of MGUS patients with thrombosis. Prospective studies are needed to confirm these observations.