Air pollution exposure may induce procoagulant effects, and chronic exposure may be linked to greater risk of venous thromboembolism (VTE). We tested the hypothesis that air pollution is associated with increased VTE risk in the prospective Multi-Ethnic Study of Atherosclerosis, which has well-characterized air pollution measures and information on potential confounding factors. We included 6651 participants recruited in 2000 to 2002 (baseline age range, 45-84 years; 53% female). Air pollution was assessed with a validated spatiotemporal model that incorporates cohort-specific monitoring. Four indexes of air pollution updated each fortnight over follow-up were averaged to estimate participant-level chronic exposure: fine particulate matter ≤2.5 micrometers in aerodynamic diameter (PM2.5), oxides of nitrogen (NOx), nitrogen dioxide (NO2), and ozone (O3). Mean±SD PM2.5 was 13.5±3.0 μg/m3, NO2 17.9±8.2 parts per billion (ppb), NOx 36.1±19.6 ppb, and O3 22.2±3.7 ppb. Incident VTE was identified using hospitalization discharge codes through 2018. A total of 248 VTE events accrued over a median follow-up of 16.7 years. After adjustment for baseline demographics, health behaviors, and body mass index, the hazard ratio (95% confidence interval) for incident VTE associated per 3.6 μg/m3 higher PM2.5 was 1.39 (1.04-1.86); per 13.3 ppb higher NO2 concentration was 2.74 (1.57-4.77); and per 30 ppb higher NOx was 2.21 (1.42-3.44). O3 was not related. In this prospective community-based cohort with individual-level estimation of chronic air pollution exposure, higher average ambient concentrations of PM2.5, NO2, and NOX were associated with greater risk of developing VTE. Findings add to accumulating evidence of adverse health effects attributed to air pollution exposure.

Chimeric antigen receptor T-cell (CAR-T) therapy has emerged as a breakthrough treatment for relapsed and refractory multiple myeloma (RRMM). However, these products are complex to deliver, and alternative options are now available. Identifying biomarkers that can predict therapeutic outcomes is crucial for optimizing patient selection. There is a paucity of data evaluating the utility of both serum soluble B-cell maturation antigen (sBCMA) levels and metabolic tumor volume (MTV) at baseline in patients with RRMM undergoing CAR-T therapy. We identified a cohort of 183 patients with available serum to measure sBCMA and/or pretreatment MTV, derived from positron emission tomography-computed tomography scans obtained per standard of care. Expectedly, high pretreatment levels of sBCMA correlated with other established markers of tumor burden (eg, bone marrow plasma cells and β2 microglobulin) and inflammation and were highly prognostic for CAR-T-related toxicities and inferior progression-free survival (PFS). High MTV values were also associated with shorter PFS and inferior overall survival. The poor correlation observed between these 2 measures prompted evaluation of those with discordant results, identifying that those with low sBCMA and high MTV frequently had low/absent BCMA expression on plasma cells and suboptimal response. Our findings highlight the potential utility of sBCMA and MTV to facilitate more personalized treatment strategies in the management of RRMM eligible for BCMA-directed CAR-T.

Immunomodulatory drugs (IMiDs) are a major class of drugs for treating multiple myeloma (MM); however, acquired resistance to IMiDs remains a significant clinical challenge. Although alterations in cereblon and its pathway are known to contribute to IMiD resistance, they account for only 20% to 30% of cases, and the underlying mechanisms in the majority of the resistance cases remain unclear. Here, we identified adenosine deaminase acting on RNA1 (ADAR1) as a novel driver of lenalidomide resistance in MM. We showed that lenalidomide activates the MDA5-mediated double-stranded RNA (dsRNA)-sensing pathway in MM cells, leading to interferon (IFN)-mediated apoptosis, with ADAR1 as the key regulator. Mechanistically, ADAR1 loss increased lenalidomide sensitivity through endogenous dsRNA accumulation, which in turn triggered dsRNA-sensing pathways and enhanced IFN responses. Conversely, ADAR1 overexpression reduced lenalidomide sensitivity, attributed to increased RNA editing frequency, reduced dsRNA accumulation, and suppression of the dsRNA-sensing pathways. In summary, we report the involvement of ADAR1-regulated dsRNA sensing in modulating lenalidomide sensitivity in MM. These findings highlight a novel RNA-related mechanism underlying lenalidomide resistance and underscore the potential of targeting ADAR1 as a novel therapeutic strategy.

Initial clinical trials with drugs targeting epigenetic modulators, such as bromodomain and extraterminal protein (BET) inhibitors, demonstrate modest results in acute myeloid leukemia (AML). A major reason for this involves an increased transcriptional plasticity within AML, which allows the cells to escape therapeutic pressure. In this study, we investigated the immediate epigenetic and transcriptional responses after BET inhibition and demonstrated that BET inhibitor-mediated release of bromodomain-containing protein 4 from chromatin is accompanied by acute compensatory feedback that attenuates downregulation or even increases the expression of specific transcriptional modules. This adaptation is marked at key AML maintenance genes and is mediated by p300, suggesting a rational therapeutic opportunity to improve outcomes by combining BET and p300 inhibition. p300 activity is required during all steps of resistance adaptation; however, the specific transcriptional programs that p300 regulates to induce resistance to BET inhibition differ, in part, between AML subtypes. As a consequence, in some AMLs, the requirement for p300 is highest during the earlier stages of resistance to BET inhibition, when p300 regulates transitional transcriptional patterns that allow leukemia-homeostatic adjustments. In other AMLs, p300 shapes a linear resistance to BET inhibition and remains critical throughout all stages of the evolution of resistance. Altogether, our study elucidates the mechanisms that underlie an "acute" state of resistance to BET inhibition, achieved through p300 activity, and how these mechanisms remodel to mediate "chronic" resistance. Importantly, our data also suggest that sequential treatment with BET and p300 inhibition may prevent resistance development, thereby improving outcomes.

We have identified a new inherited bone marrow failure syndrome with severe congenital neutropenia (CN) caused by autosomal recessive mutations in the coatomer protein complex I (COPI) subunit zeta 1 (COPZ1) gene. A stop-codon COPZ1 mutation and a missense (MS) mutation were found in 3 patients from 2 unrelated families. Although 2 affected siblings with a stop-codon COPZ1 mutation suffered from CN that involves other hematologic lineages and nonhematologic tissues, the patient with a MS COPZ1 mutation had isolated neutropenia. Both COPZ1 mutations were localized to a highly evolutionarily conserved region. The resulting truncated (TR) COPZ1 protein was predicted to display diminished interaction with its COPI complex partner, COPG1. These findings were consistent with the observed block in retrograde protein transport from the Golgi apparatus to the endoplasmic reticulum (ER) in human fibroblasts carrying TR COPZ1. Human CD34+ cells with TR or MS COPZ1 had significantly impaired granulocytic differentiation, and in zebrafish embryos, TR Copz1 also resulted in defective myelopoiesis. Intracellularly, TR COPZ1 downregulated JAK/STAT/CEBPE/G-CSFR signaling and hypoxia-responsive pathways, while inducing STING, interferon-stimulated genes, stimulating oxidative phosphorylation activity, and increasing reactive oxygen species levels in hematopoietic cells. MS COPZ1 deregulated interferon and JAK/STAT signaling but less than the TR protein. Finally, treatment with the small molecule HIF1α stabilizer IOX2 or transduction of cells with COPZ2 restored defective granulopoiesis in COPZ1-mutated human CD34+ cells, offering potential therapeutic options.

Acute myeloid leukemia (AML) remains a dismal disease with poor prognosis, particularly in the relapsed/refractory (R/R) setting. Chimeric antigen receptor (CAR) therapy has yielded remarkable clinical results in other leukemias and thus has, in principle, the potential to achieve similar outcomes in R/R AML. Redirecting the approved CD19-specific CAR designs against the myeloid antigens CD33, CD123, or CLEC12A has occasionally yielded morphologic leukemia-free states but has so far been marred by threatening myeloablation and early relapses. These safety and efficacy limitations are largely due to the challenge of identifying suitable target antigens and designing adequate receptors for effective recognition and safe elimination of AML. Building on lessons learned from the initial clinical attempts, a new wave of CAR strategies relying on alternative target antigens and innovative CAR designs is about to enter clinical evaluation. Adapted multiantigen targeting, logic gating, and emerging cell engineering solutions offer new possibilities to better direct T-cell specificity and sensitivity toward AML. Pharmacologic modulation and genetic epitope engineering may extend these approaches by augmenting target expression in AML cells or minimizing target expression in normal hematopoietic cells. On/off switches or CAR T-cell depletion may curb excessive or deleterious CAR activity. Investigation of AML-intrinsic resistance and leukemic microenvironmental factors is poised to reveal additional targetable AML vulnerabilities. We summarize here the findings, challenges, and new developments of CAR therapy for AML. These illustrate the need to specifically adapt CAR strategies to the complex biology of AML to achieve better therapeutic outcomes.

Interferon alfa has activity against multiple myeloma (MM). Modakafusp alfa is an immunocytokine comprising 2 attenuated interferon alfa-2b molecules and an anti-CD38 immunoglobulin G4 antibody, targeting delivery of interferon alfa to CD38-expressing (CD38+) immune and myeloma cells. This phase 1/2 trial enrolled patients with relapsed/refractory multiple myeloma with ≥3 prior lines of treatment and refractory to, or intolerant of, ≥1 proteasome inhibitor and ≥1 immunomodulatory drug. During dose escalation, modakafusp alfa was administered at 10 doses in 4 schedules across 13 cohorts. The primary end point was safety for dose escalation, and overall response rate (ORR) for dose expansion. We enrolled 106 patients who had received a median of 6.5 lines of prior therapy; 84% of patients had myeloma previously refractory to an anti-CD38 antibody. The most feasible dosing schedule was every 4 weeks (Q4W), at which the maximum tolerated dose was 3 mg/kg. Among 30 patients treated at 1.5 mg/kg Q4W, the ORR was 43.3%, with a median duration of response of 15.1 months (95% confidence interval [CI], 7.1-26.1); median progression-free survival was 5.7 months (95% CI, 1.2-14). Grade ≥3 adverse events (AEs) occurred in 28 (93.3%) patients, the most common were neutropenia (66.7%) and thrombocytopenia (46.7%); infections were reported in 8 (26.7%) patients (including grade 3 in 4 [16.7%]). Modakafusp alfa therapy induced upregulation of the type 1 interferon gene signature score, increased CD38 receptor density in CD38+ cells, and innate and adaptive immune cell activation. Modakafusp alfa resulted in antitumor activity and immune activation in patients with MM. AEs were primarily hematologic. This trial was registered at www.clinicaltrials.gov as #NCT03215030.

Langerhans cell histiocytosis (LCH) is a clonal hematopoietic disorder defined by tumorous lesions containing CD1a+/CD207+ cells. Two severe complications of LCH are systemic hyperinflammation and progressive neurodegeneration. The scarcity of primary samples and lack of appropriate models limit our mechanistic understanding of LCH pathogenesis and affect patient care. We generated a human in vitro model for LCH using induced pluripotent stem cells (iPSCs) harboring the BRAFV600E mutation, the most common genetic driver of LCH. We show that BRAFV600E/WT iPSCs display myelomonocytic skewing during hematopoiesis and spontaneously differentiate into CD1a+/CD207+ cells that are similar to lesional LCH cells and are derived from a CD14+ progenitor. We show that BRAFV600E modulates the expression of key transcription factors regulating monocytic differentiation and leads to an upregulation of proinflammatory molecules and LCH marker genes early during myeloid differentiation. In vitro drug testing revealed that BRAFV600E-induced transcriptomic changes are reverted upon treatment with mitogen-activated protein kinase (MAPK) pathway inhibitors (MAPKis). Importantly, MAPKis do not affect myeloid progenitors but reduce only the mature CD14+ cell population. Furthermore, iPSC-derived neurons (iNeurons) cocultured with BRAFV600E/WT iPSC-derived microglia-like cells, differentiated from iPSC-derived CD34+ progenitors, exhibit signs of neurodegeneration with neuronal damage and release of neurofilament light chain. In summary, the iPSC-based model described here provides a platform to investigate the effects of BRAFV600E in different hematopoietic cell types and provides a tool to compare and identify novel approaches for the treatment of BRAFV600E-driven diseases.

Treatment options for stage I/II bulky and advanced-stage disease have recently extensively changed. For decades in North America, ABVD (doxorubicin hydrochloride [Adriamycin], bleomycin sulfate, vinblastine sulfate, and dacarbazine) has been a frontline standard-of-care option for patients with advanced classical Hodgkin lymphoma (cHL). Recent data on combining brentuximab vedotin, doxorubicin, vinblastine, and dacarbazine demonstrated improved overall survival compared with ABVD but increased adverse events (AEs). We hypothesized that replacing vinblastine with nivolumab (brentuximab vedotin and nivolumab [AN] + doxorubicin and dacarbazine [AD]; AN+AD) may improve efficacy and safety. This phase 2, open-label multipart, multicenter study enrolled patients with treatment-naive stage II bulky or III/IV cHL. Patients received ≤6 cycles of AN+AD; granulocyte-colony stimulating factor (G-CSF) prophylaxis was optional, per institutional guidelines. At the time of planned analysis (N = 57), complete response (CR) and objective response rates were 88% (95% confidence interval [CI], 76.3-94.9) and 93% (95% CI, 83.0-98.1), respectively. With a median follow-up of 24.2 months (95% CI, 23.4-26.9), the 2-year progression-free survival rate was 88% (95% CI, 75.7-94.6); 88% (95% CI, 75.7-94.6) had a response lasting >2 years. Most common grade ≥3 treatment-related AEs were alanine aminotransferase increased (11%) and neutropenia (9%); 44% had treatment-related peripheral sensory neuropathy (grade 1/2, 40%; grade 3, 4%). No febrile neutropenia occurred; 49% received G-CSF prophylaxis. AN+AD led to a high CR rate and favorable safety profile. Further evaluation of programmed death receptor 1 inhibitor and CD30 antibody-drug conjugate combination regimens in frontline advanced-stage cHL is warranted. This trial was registered at www.clinicaltrials.gov as #NCT03646123 and www.clinicaltrialsregister.eu as #EudraCT 2020-004027-17.

In this issue of Blood, Reis et al1 identify a monoclonal antibody, INCA033989, that selectively targets mutant calreticulin (mutCALR) in myeloproliferative neoplasms (MPNs), inhibiting its oncogenic activity without affecting normal hematopoiesis.