Despite several approved therapies, multiple myeloma (MM) remains an incurable disease with high unmet medical need. "Off-the-shelf" T-cell bispecific antibodies (TCBs) targeting BCMA and GPRC5D have demonstrated high objective response rates (ORR) in heavily pre-treated MM patients, however, primary resistance, short duration of response and relapse driven by antigen shift frequently occurs. Although GPRC5D represents the most selective target in MM, recent findings indicate antigen loss occurs more frequently than with BCMA. Thus, anti-GPRC5D immunotherapies must hit hard during a short period of time to kill as many myeloma cells as possible. Here, we characterize forimtamig, a novel GPRC5D-targeting TCB with 2+1 format, using preclinical models of MM. Bivalent binding of forimtamig to the N-terminus of GPRC5D confers higher affinity as compared to classical 1+1 TCB formats correlating with formation of more stable immunological synapses and higher potency in tumor cell killing and T cell activation. Using an orthotopic mouse model of MM, forimtamig recruited T effector cells to the bone marrow and induced rapid tumor killing even after the introduction of step-up dosing to mitigate cytokine release. Combination of forimtamig with standard-of-care (SoC) agents including anti-CD38 antibodies, immunomodulatory drugs and proteasome inhibitors improved depth and duration of response. The combination of forimtamig with novel therapeutic agents including BCMA-TCB and Cereblon E3 Ligase Modulatory Drugs (CELMoDs) was potent and prevented occurrence of GPRC5D-negative tumor relapse. Forimtamig is currently being evaluated in Phase 1 clinical trials in relapsed and refractory myeloma (RRMM) patients for monotherapy and in combination treatments. NCT04557150.

BCR::ABL1-negative myeloproliferative neoplasms (MPN) are clonal hematological malignancies resulting from the proliferation of myeloid cells harboring a JAK-STAT pathway activating driver mutation. MPN management recommendations are based on the evaluation of different risks to prevent disease evolution associated events while preserving patients' quality of life. Such risks can be common across all MPN or specific to each subtype (polycythemia vera (PV), essential thrombocythemia (ET), prefibrotic myelofibrosis (pre-MF), primary myelofibrosis (PMF)). MF-patients harbor the worse prognosis and hematopoietic stem cell transplantation (HSCT) is the only curative treatment, at the expense of a high morbi-mortality. Therefore, accurate scoring systems to estimate overall survival are crucial for MF patients' management and selection for HSCT. In PV and ET, vascular events prediction is prioritized given their higher incidence and related morbi-mortality. Finally, quality of life evaluation is important for all subtypes. To predict these risks and adapt MPN therapeutic strategies, clinical risk scores have been developed over the past decades, more recently including molecular risk factors for more accurate risk stratification. The large number of scoring systems available in combination with disease heterogeneity and the necessity to predict diverse outcomes, make it difficult for clinicians to choose the most appropriate score to evaluate their patients' risk in 2024. Here, we provide an overview of MPN disease evolution associated events incidence and conduct an exhaustive comparative review of the scoring systems currently available for each risk. Finally, we propose an algorithm for the use of these scores in clinical practice in each MPN subtype.

An open prospective, multicenter study enrolled 48 selected patients with chronic immune thrombocytopenia who achieved complete response for 1 year on thrombopoietin receptor agonists, half of the patients maintained a sustained response off treatment 4 years after treatment discontinuation. NCT03119974.

SAMD9 and SAMD9L (SAMD9/9L) are paralogous genes encoding antiviral proteins that negatively regulate cell proliferation. Heterozygous germline gain-of-function (GoF) SAMD9/9L variants cause multisystem syndromes with variable manifestations. The unifying features are cytopenia, immunodeficiency, infections, bone marrow failure (BMF), myelodysplasia (MDS) and monosomy 7. Non-hematopoietic presentations can affect almost every organ system. Growth impairment and adrenal insufficiency are typical in SAMD9, while progressive neurologic deficits characterize SAMD9L. Most patients (>90%) carry germline missense GoF variants. A subgroup of patients presenting with SAMD9L-associated inflammatory disease (SAAD) carry frameshift truncating variants that are also GoF. Somatic genetic rescue occurs in >2/3 of patients and involves monosomy 7, which may spontaneously disappear (transient monosomy 7) or progress to MDS/leukemia, and adaptive clones with somatic SAMD9/9L compensatory mutations or uniparental disomy 7q (UPD7q), both associated with remission. This manuscript examines the clinical and genetic spectrum, therapies and outcome based on 243 published patients compiled in our registry with additional genetic information on 62 unpublished cases. We consolidate the diverse clinical manifestations and diagnostic challenges of SAMD9/9L syndromes to enhance recognition and improve patient care. We highlight the knowledge gaps in pathomechanisms and emphasize the importance of genetic surveillance assessing disease remission versus disease progression. Insights are provided into variant curation and the necessity of testing for somatic SAMD9/9L mutations and UPD7q. Multidisciplinary care in specialized centers is critical to manage these complex disorders. Future natural history studies, especially in patients with monosomy 7, will help formulate evidence-based surveillance protocols and optimize transplant timing and outcomes.

Venetoclax, a first-in-class BH3 mimetic drug targeting BCL-2, has improved outcomes for patients with chronic lymphocytic leukemia (CLL). Early measurements of the depth of the venetoclax treatment response, assessed by minimal residual disease, are strong predictors of long-term clinical outcomes. Yet, there are limited data concerning the early changes induced by venetoclax treatment that might inform strategies to improve responses. To address this gap, we conducted longitudinal mass cytometric profiling of blood cells from patients with CLL during the first five weeks of venetoclax monotherapy. At baseline, we resolved CLL heterogeneity at the single-cell level to define multiple subpopulations in all patients distinguished by proliferative, metabolic and cell survival proteins. Venetoclax induced significant reduction in all CLL subpopulations coincident with rapid upregulation of pro-survival BCL-2, BCL-XL and MCL-1 proteins in surviving cells, which had reduced sensitivity to the drug. Mouse models recapitulated the venetoclax-induced elevation of survival proteins in B cells and CLL-like cells that persisted in vivo, with genetic models demonstrating that extensive apoptosis and access to the B cell cytokine, BAFF, were essential. Accordingly, analysis of patients with CLL that were treated with venetoclax or the anti-CD20 antibody obinutuzumab exhibited marked elevation of BAFF and increased pro-survival proteins in leukemic cells that persisted. Overall, these data highlight the rapid adaptation of CLL cells to targeted therapies via homeostatic factors and support co-targeting of cytokine signals to achieve deeper and more durable long-term responses.

Mosunetuzumab, a CD20xCD3 T-cell engaging bispecific antibody, redirects T cells to eliminate malignant B cells. We present updated efficacy and safety data of a pivotal phase 1/2 study after a median follow-up of 37.4 months in 90 patients with relapsed/refractory (R/R) follicular lymphoma (FL) and ≥2 prior lines of therapy treated with fixed-duration mosunetuzumab. Investigator-assessed complete response (CR) rate and objective response rate (ORR) were 60.0% (95% confidence interval [CI], 49.1-70.2) and 77.8% (95% CI, 67.8-85.9), respectively. Among 70 responders, median duration of response was 35.9 months (95% CI, 20.7-not estimable [NE]). Among 54 patients who achieved CR, 49 remained in CR at the end of treatment; median duration of complete response was not reached (NR) (95% CI, 33.0-NE); Kaplan-Meier-estimated 30-month remission rate was 72.4% (95% CI, 59.2-85.6). Estimated 36-month overall survival (OS) rate was 82.4% (95% CI, 73.8-91.0); median OS was NR (95% CI, NE-NE). Median progression-free survival was 24.0 months (95% CI, 12.0-NE). Median time to CD19+ B-cell recovery was 18.4 months (95% CI, 12.8-25.0) following 8 cycles of mosunetuzumab treatment. No new cytokine release syndrome events or fatal, serious, or Grade ≥3 adverse events were reported. With extended follow-up, mosunetuzumab demonstrated high response rates, durable remissions and manageable safety with no long-term concerns. This supports outpatient mosunetuzumab administration as an off-the-shelf, fixed-duration, safe and effective treatment for patients with R/R FL, including those with high-risk disease. Trial registration: www.clinicaltrials.gov (NCT02500407).

Glutamine dependency has been shown to be a metabolic vulnerability in acute myeloid leukemia (AML). Prior studies using several in vivo AML models showed that depletion of plasma glutamine induced by the long-acting crisantaspase (pegcrisantaspase or PegC) was synergistic with the BCL-2 inhibitor venetoclax (Ven), resulting in significantly reduced leukemia burden and enhanced survival. Here, we report a phase 1 study (NCT04666649) of Ven and PegC combination (VenPegC) for treating adult patients with relapsed or refractory AML, including patients who had previously received Ven. The primary endpoints were incidence of regimen limiting toxicities (RLT) and maximum tolerated dose (MTD). Twenty-five patients received at least one PegC dose with Ven and 18 efficacy-evaluable patients completed at least one VenPegC cycle; 12 (67%) had previously received Ven. Hyperbilirubinemia was the RLT and occurred in 60% of patients treated with VenPegC; 20% had Grade ≥3 bilirubin elevations. MTD was determined to be Ven 400 mg daily with biweekly PegC 750 IU/m2. The most common treatment-related adverse events of any Grade in 25 patients who received VenPegC included antithrombin III decrease (52%), elevated transaminases (36-48%), fatigue (28%), and hypofibrinogenemia (24%). No thromboembolic or hemorrhagic adverse events or clinical pancreatitis were observed. The overall complete remission rate in efficacy-evaluable patients was 33%. Response correlated with alterations in proteins involved in mRNA translation. In patients with RUNX1 mutations, the composite complete rate was 100%.

The structure of human coagulation factor XIII (FXIII), a heterotetrameric plasma pro-transglutaminase that covalently crosslinks pre-formed fibrin polymers, remains elusive until today. The heterotetrameric complex is composed of two catalytic FXIII-A and two protective FXIII-B subunits. Structural etiology underlying FXIII deficiency has so far been derived from crystallographic structures, all of which are currently available for the FXIII-A2 homodimer only. Here, we present the cryo-electron microscopy structure of a native, human plasma-derived FXIII-A2B2 complex at 2.4 Å resolution. The structure provides detailed information on FXIII subunit interacting interfaces as the two subunits interact strongly in plasma. The native FXIII-A2B2 complex reveals a pseudo-symmetric heterotetramer of two FXIII-B monomers intercalating with a symmetric FXIII-A2 dimer forming a "crown-like" assembly. The symmetry axes of the A2 and B2 homodimers are twisted relative to each other such that Sushi domain 1 interacts with the catalytic core of the A subunit and Sushi domain 2 with the symmetry related A' subunit and vice versa. We also report four novel mutations in the F13A1 gene encoding the FXIII-A subunit from a cohort of patients with severe FXIII deficiency. Our structure reveals the etiological basis of homozygous and heterozygous pathogenic mutations and explains the conditional dominant negative effects of heterozygous mutations. This atomistic description of complex interfaces is consistent with previous biochemical data and shows a congruence between the structural biochemistry of the FXIII complex and the clinical features of FXIII deficiency.

Soluble B-cell maturation antigen (sBCMA) is overexpressed on multiple myeloma (MM) cells. We investigated whether sBCMA levels correlated with other myeloma tumor volume indicators and its utility in monitoring oligo-secretory/non-secretory (O-S/Non-S) MM. In 115 patients with newly diagnosed MM, sBCMA was compared with M-protein levels, bone marrow plasma cells (BMPCs), circulating tumor cells (CTCs), and total diffusion volume (tDV; estimated by whole-body diffusion-weighted magnetic resonance imaging) at diagnosis. sBCMA levels increased significantly with International Staging System stage, chromosome 1q21 gain/amplification and CTC levels. sBCMA also correlated strongly with %BMPC (r = 0.65), moderately with tDV (r = 0.55) and paraprotein levels (involved immunoglobulin in IgG and IgA subtypes, r = 0.44 and 0.4; involved free light-chain levels in light-chain-only MM, r = 0.61, all P < 0.05). Longitudinal changes in sBCMA were consistent with disease status in both 17 O-S/Non-S and other secretory MM cases. Furthermore, sBCMA levels increased as early as 6 months pre-relapse in almost all O-S/Non-S relapsed patients. Thus, sBCMA correlates strongly with total tumor volume in MM, as assessed using different modalities. We suggest that sBCMA is useful, not only for monitoring responses in patients with O-S/Non-S MM but also for early relapse detection and prediction.

Antibiotic-induced microbiome dysbiosis is widespread in oncology, adversely affecting outcomes and side effects of various cancer treatments, including immune checkpoint inhibitors and chimeric antigen receptor T (CAR-T) cell therapies. In this study, we observed that prior exposure to broad-spectrum ABX with extended anaerobic coverage like piperacillin-tazobactam and meropenem was associated with worsened anti-CD19 CAR-T therapy survival outcomes in large B-cell lymphoma patients (n=422), compared to other ABX classes. In a discovery subset of these patients (n=67), we found that the use of these ABX was in turn associated with substantial dysbiosis of gut microbiome function, resulting in significant alterations of the gut and blood metabolome, including microbial effectors such as short-chain fatty acids (SCFAs) and other anionic metabolites, findings that were largely reproduced in an external validation cohort (n=58). Broader evaluation of circulating microbial metabolites revealed reductions in indole and cresol derivatives, as well as trimethylamine N-oxide, in patients who received ABX treatment (discovery n=40, validation n=28). These findings were recapitulated in an immune-competent CAR-T mouse model, where meropenem-induced dysbiosis led to a systemic dysmetabolome and decreased murine anti-CD19 CAR-T efficacy. Furthermore, we demonstrate that SCFAs can enhance the metabolic fitness of CAR-T cells, leading to improved tumor killing capacity. Together, these results suggest that broad-spectrum ABX deplete metabolically active commensals whose metabolites are essential for enhancing CAR-T efficacy, shedding light on the intricate relationship between ABX exposure, microbiome function and their impact on CAR-T cell efficacy. This highlights the potential for modulating the microbiome to augment CAR-T immunotherapy.