Multiple myeloma (MM) is driven by clonal plasma cell (cPC)-intrinsic factors and changes in the tumor microenvironment (TME). To investigate whether residual polyclonal PCs (pPCs) are disrupted, single-cell (sc) RNA sequencing (scRNA-seq) and sc B-cell receptor analysis were applied in a cohort of 46 samples with PC dyscrasias and 21 healthy donors (HDs). Of 234 789 PCs, 64 432 were genotypically identified as pPCs with frequencies decreasing over different disease stages, from 23.66% in monoclonal gammopathy of undetermined significance to 3.23% in MMs (P = .00012). Both cPCs and pPCs had a comparable expression of typical lineage markers (ie, CD38 and CD138), whereas others were more variable (CD27 and ITGB7). Only cPCs overexpressed oncogenes (eg, CCND1/2 and NSD2), but CCND3 was often expressed in pPCs. B-cell maturation antigen was expressed on both pPCs and cPCs, whereas GPRC5D was mostly upregulated in cPCs with implications for on-target, off-tumor activity of targeted immunotherapies. In comparison with HDs, pPCs from patients showed upregulated autophagy and disrupted interaction with TME. Importantly, interferon-related pathways were significantly enriched in pPCs from patients vs HDs (adjusted P < .05) showing an inflamed phenotype affecting genotypically normal PCs. The function of pPCs was consequently affected and correlated with immunoparesis, driven by disrupted cellular interactions with TME. Leveraging our scRNA-seq data, we derived a "healthy PC signature" that could be applied to bulk transcriptomics from the CoMMpass data set and predicted significantly better progression-free survival and overall survival (log-rank P < .05 for both). Our findings show that genotypic sc identification of pPCs in PC dyscrasias has relevant pathogenic and clinical implications.

The thrombopoietin:cMPL signaling axis is a critical regulator of early hematopoiesis. However, the utility of cMPL as a standalone marker for identifying long-term repopulating hematopoietic stem cells (LT-HSCs) within the adult human CD34+ hematopoietic stem and progenitor cell (HSPC) population has not been validated. In this study, we established high cMPL surface expression as a defining feature of human LT-HSCs. Targeting the cMPL receptor facilitated the separation of human LT-HSCs from mature progenitors, a delineation not achievable with c-KIT (CD117). Leveraging this finding, we explored the therapeutic potential of cMPL as a novel target for pretransplant conditioning regimens. We developed a cMPL-targeting immunotoxin and demonstrated its ability to preferentially deplete host cMPLhigh LT-HSCs in murine xenograft models. Evaluation in rhesus macaques confirmed these findings and highlighted a favorable safety profile with rapid systemic clearance within 24 hours of administration. Proof of concept experiments validated the immunotoxin as a novel conditioning agent, enabling donor HSPC engraftment without the use of chemotherapy or irradiation. These findings advance our understanding of the molecular determinants of human hematopoiesis and underscore the potential of cMPL-targeting preparative regimens to improve therapeutic transplantation outcomes.

Rovadicitinib (TQ05105) is a novel, oral dual Janus kinase 1/2 and rho-associated coiled-coil-containing protein kinase-1/2 inhibitor targeting inflammatory and fibrotic components of chronic graft-versus-host disease (cGVHD). This phase 1b/2a, multicenter, open-label study enrolled patients with moderate or severe glucocorticoid-refractory or -dependent cGVHD to evaluate the safety and efficacy of rovadicitinib. The study followed a 3+3 design with 2 escalating doses (rovadicitinib 10 and 15 mg twice daily) and a dose expansion cohort. Primary end points included safety and recommended phase 2 dose (RP2D); the best overall response (BOR) was the key secondary end point. A total of 44 patients were enrolled (29 at 10 mg, 15 at 15 mg twice daily). Rovadicitinib was well tolerated without dose-limiting toxicity at both dosages, and no rovadicitinib-related adverse events (AEs) led to discontinuation. The most prevalent hematological AE was anemia (38.6%), with grade ≥3 of 4.6%. The RP2D was 10 mg twice daily. The BOR was 86.4% (95% confidence interval [CI], 72.6-94.8), with no difference between the 2 dosage cohorts. Besides, BOR was 72.7% in the steroid-refractory cohort and 90.9% in the steroid-dependent cohort. All affected organs exhibited responses regardless of prior therapy. The failure-free survival rate was 85.2% (95% CI, 64.5-94.3) at 12 months. Rovadicitinib reduced corticosteroid doses in 88.6% of patients and improved cGVHD symptoms in 59.1%. Rovadicitinib has favorable tolerability and notable clinical response rates, ameliorating the quality of life and reducing corticosteroid dose requirements in patients with glucocorticoid-refractory or -dependent cGVHD. This trial was registered at www.ClinicalTrials.gov as #NCT04944043.

Patients with TP53-mutated acute myeloid leukemia (AML) have an extremely poor prognosis, necessitating new treatments. The global, randomized, phase 3 ENHANCE-2 trial evaluated the anti-CD47 monoclonal antibody magrolimab plus azacitidine (Magro/Aza) for previously untreated TP53-mutated AML. Patients determined ineligible for intensive therapy were randomized to receive Magro/Aza or venetoclax plus Aza (Ven/Aza); those eligible for intensive therapy were randomized to receive Magro/Aza or 7+3 induction chemotherapy. The primary end point was overall survival (OS) in the nonintensive arm. At interim analysis, nonintensive-arm OS hazard ratio (HR) between treatment groups was 1.191 (95% confidence interval [CI], 0.744-1.906), meeting the study's definition for futility and resulting in study termination. At final analysis, median OS was 4.4 vs 6.6 months (HR, 1.132; 95% CI, 0.783-1.637; P = .5070) in the nonintensive arm (n = 205) and 7.3 vs 11.1 months (HR, 1.434; 95% CI, 0.635-3.239; P = .3798) in the intensive arm (n = 52) between Magro/Aza and control groups, respectively. Incidences of grade ≥3 adverse events were similar across Magro/Aza and control groups (nonintensive, n = 194: 96.9% and 95.9%; intensive, n = 50: 92.6% and 95.7%), including grade ≥3 anemia (nonintensive: 27.1% and 23.5%; intensive: 25.9% and 21.7%). Grade ≥3 infections were observed in 50.0% and 53.1% of patients in the nonintensive arm and 44.4% and 65.2% of intensive-arm patients. ENHANCE-2 did not meet its primary end point of OS in TP53-mutated AML but provides important data informing future studies in this challenging population. This trial was registered at www.clinicaltrials.gov as #NCT04778397.

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy that is characterized by an expansion of T-cell progenitors and DNA mutations that lead to overactive NOTCH1 signaling in >50% of T-ALL cases. Using synthetic models of human T-ALL, we report that NOTCH1 dimeric signaling was crucial for the leukemogenesis of human hematopoietic stem/progenitor cells (HSPCs) from cord blood. We also identified a Notch dimerization-dependent gene signature, including the HES4 transcription factor, which induced a proliferative advantage in human HSPCs and in Notch dimerization-dependent, patient-derived xenografts of T-ALL. Interestingly, in human T-ALL cells, HES4 enforced the expression of the Δ133p53 isoform with the concomitant block of proapoptotic p53 target genes and the induction of BCL2L1 gene expression and antiapoptotic B-cell lymphoma extra-large protein. In addition, through an integrated experimental approach that included genetically modified cell lines, RNA/chromatin immunoprecipitation sequencing, and single-cell RNA sequencing profiles of primary T-ALL samples, we revealed cell subsets with Notch dimerization-dependent gene signatures, which indirectly correlated with proapoptotic genes and directly associated with cell markers of poor clinical outcome in primary T-ALL samples. Taken together, these findings highlight the crucial role of NOTCH1 dimeric signaling in human T-cell leukemogenesis and T-ALL maintenance, suggesting that a possible benefit can be obtained with a therapeutic strategy that target NOTCH1 dimer signaling or its downstream effectors.

Venetoclax (VEN) combined with hypomethylating agents is approved for frontline therapy in older/unfit patients with acute myeloid leukemia (AML). However, prospective data on this low-intensity therapy in treatment-naive younger patients with AML are lacking. This study investigated the efficacy and safety of VEN plus decitabine (VEN-DEC) as induction in untreated young fit patients with AML in a randomized trial. Patients aged 18 to 59 years eligible for intensive chemotherapy were randomized 1:1 to receive VEN-DEC or IA-12 (idarubicin and cytarabine). All patients achieved composite complete remission (CRc) underwent high-dose cytarabine consolidation. The primary end point was CRc rate after induction. Of 255 screened, 188 were enrolled and randomly assigned, with 94 in each group. In the intention-to-treat population, CRc was 89% (84/94) in the VEN-DEC group vs 79% (74/94) in the IA-12 group (noninferiority P = .0021), with measurable residual disease negativity rates of 80% (67/84) vs 76% (56/74), respectively. VEN-DEC showed superior CRc in patients aged ≥40 years (91% vs 75%) and those with adverse risk (91% vs 42%) or epigenetic mutations (91% vs 67%), but lower CRc in RUNX1::RUNX1T1 fusion cases (44% vs 88%) than IA-12. Patients in the VEN-DEC group experienced fewer grade ≥3 infections (32% vs 67%) and shorter severe thrombocytopenia duration (median, 13 vs 19 days; P < .001). At a median follow-up of 12.1 months, overall and progression-free survival were similar between groups. In conclusion, VEN-DEC demonstrated noninferior response rates with superior safety over IA-12 in young patients with AML. The trial was registered at www.clinicaltrials.gov as #NCT05177731.

Discontinuation of lenalidomide maintenance after autologous stem cell transplantation is a burning question within the multiple myeloma (MM) community, especially after the inclusion of minimal residual disease (MRD) in the disease response criteria. In this prospective study, we evaluated the conversion to MRD positivity, the treatment-free survival (TFS), and the progression-free survival (PFS) in 52 patients with MM who discontinued lenalidomide maintenance after achieving sustained bone marrow and imaging MRD negativity for 3 years. Patients who developed MRD positivity after lenalidomide discontinuation restarted lenalidomide maintenance at the same dose. The median follow-up from lenalidomide discontinuation was 3 years. Overall, 12 (23%) patients obtained MRD positivity and restarted lenalidomide maintenance. Only 4 (7.6%) patients progressed; 3 had a biochemical progression and 1 had a clinical progression. The overall median PFS was not reached, whereas the 7-year PFS from diagnosis was 90.2%. The 1-, 2-, and 3-year TFS rates were 93.9%, 91.6%, and 75.8%, respectively, whereas the 1-, 2-, and 3-year landmark PFS rates from maintenance discontinuation (study entrance) were 96.0%, 96.0%, and 92.9%, respectively. There were no statistically significant associations among age, sex, Second Revision International Staging System, type of induction therapy, and use of consolidation therapy and the effect outcomes of PFS and TFS. We conclude that maintenance discontinuation after 3 years of sustained marrow and imaging MRD negativity is associated with low rates of MRD conversion and progressive disease. Thus, in the era of modern antimyeloma treatments, a subgroup of patients may remain treatment free while in complete remission without jeopardizing disease response.

The combination of ibrutinib plus venetoclax (IV) in chronic lymphocytic leukemia (CLL) treatment leverages their complementary mechanisms of action. Studies investigating IV typically begin with a short initial course of ibrutinib, followed by venetoclax introduction for a limited duration, typically 12 months. The Swiss Group for Clinical Cancer Research (SAKK) 34/17 study is a single-arm, multicenter, phase 2 trial evaluating the effectiveness of a modified IV schedule in patients with relapsed/refractory (R/R) CLL. No prior exposure to BTK or BCL2 inhibitors was allowed. The lead-in phase with ibrutinib was extended to 6 months to reduce the tumor burden and related tumor lysis syndrome (TLS) risk. Additionally, the treatment phase with IV is prolonged to a minimum of 24 months to enhance the undetectable minimal residual disease (uMRD; 10-4) rate. The primary end point was the rate of complete response or complete response with incomplete bone marrow recovery (CR/CRi) with uMRD in both bone marrow (BM) and peripheral blood (PB). Secondary end points included assessing the proportion of patients transitioning to a low-risk category for TLS after receiving ibrutinib lead-in. Of the 30 enrolled patients with R/R CLL, 40.0% achieved uMRD CR/CRi by intention-to-treat analysis, and 53.3% showed uMRD in the BM and PB. After the lead-in period with ibrutinib, 57.1% of patients achieved a low risk of TLS. At cycle 31, the progression-free survival rate was 89.9%. These results contribute to the increasing body of evidence supporting the idea that a longer IV duration is beneficial for enhancing therapeutic effectiveness. This trial was registered at www.clinicaltrials.gov as #NCT03708003.

Fixed-duration venetoclax-rituximab (VenR) in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) in the phase 3 MURANO trial resulted in superior progression-free survival (PFS) and overall survival (OS) vs bendamustine-rituximab (BR). We report the final analyses of MURANO (median follow-up, 7 years). Patients were randomized to VenR (venetoclax 400 mg daily for 2 years plus monthly rituximab for 6 months; n = 194) or BR (6 months; n = 195). In a substudy, patients with progressive disease (PD) received VenR as retreatment or crossover from BR. At the final data cut (3 August 2022), the median PFS with VenR was 54.7 months vs 17.0 months with BR. The 7-year PFS with VenR was 23.0%. The 7-year OS was 69.6% and 51.0%, respectively. Among VenR-treated patients with undetectable minimal residual disease (MRD; uMRD) and no PD at end of treatment (EOT; n = 83), the median PFS from EOT was 52.5 vs 18.0 months in patients with MRD at EOT (n = 35; P < .0001). Fourteen patients had enduring uMRD. Three distinct mutations in BCL2 in 4 patients were identified. In the substudy, 25 patients were retreated with VenR, and 9 patients crossed over to VenR; the median PFS was 23 and 27 months, and the best overall response rate was 72% and 89%, respectively. At the end of combination treatment (EOCT), after retreatment or crossover, 8 and 6 patients achieved uMRD, respectively. No new safety findings were observed. Overall, these final MURANO analyses support consideration of fixed-duration VenR therapy for patients with relapsed/refractory CLL. This trial was registered at www.clinicaltrials.gov as #NCT02005471.

The non-O blood group is a well-established risk factor for venous thromboembolism (VTE). However, the association between plasma levels of the histo-blood group ABO system transferase (BGAT), the gene product of the ABO locus, and VTE risk remains unclear. We aimed to investigate the association between plasma BGAT levels and risk of future VTE, and whether this relationship was mediated by plasma von Willebrand factor (VWF) or coagulation factor VIII (FVIII), as VWF is glycosylated by BGAT. Incident VTE-cases (n = 294) and a randomly sampled age- and-sex-weighted subcohort (n = 1066) were derived from the third survey of the Trøndelag Health Study. Baseline plasma samples (2006-2008) were subjected to the SomaScan aptamer-based-7K platform for protein measurements. Weighted Cox regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) across BGAT quartiles. We found that ABO haplotypes (A1/A2/B/O1/O2) explained ≈80% of the BGAT plasma variability. Participants with BGAT levels in the highest quartile had 2-fold higher VTE risk (HR, 2.12; 95% CI, 1.39-3.22) compared with those with BGAT in the lowest quartile in age-, sex-, and sample batch-adjusted models. The associations were particularly pronounced for unprovoked VTE (HR, 3.71; 95% CI, 1.79-7.67) and deep vein thrombosis (HR, 3.28; 95% CI, 1.63-6.59). The HRs were similar after further adjustment for body mass index, C-reactive protein, and estimated glomerular filtration rate, and moderately attenuated when adding VWF or FVIII plasma levels to the models. Our findings indicate that elevated BGAT plasma levels are associated with increased risk of future VTE beyond what is explained by VWF and FVIII.

The Gruppo Italiano Malattie EMatologiche dell'Adulto (GIMEMA) Leucemia Acuta Linfoblastica (LAL) 2317 protocol investigated the frontline chemotherapy-blinatumomab combination in adult Philadelphia chromosome/BCR::ABL1 rearrangement-negative (Ph-) CD19+ B-lineage acute lymphoblastic leukemia (B-ALL) to improve minimal residual disease (MRD) response and clinical outcome. Two cycles of IV blinatumomab were administered after chemotherapy cycles 3 and 6. The primary end point was the rate of molecular MRD negativity after blinatumomab 1. One hundred forty-nine patients were enrolled (median age, 41 years [range, 18-65]); 132 entered remission, 122 received blinatumomab, and 109 had a pre- and post-blinatumomab 1 MRD assessment. MRD negativity increased from 72% to 93% (P < .001) after blinatumomab, with 23 of 30 MRD-positive patients (73%) becoming MRD negative, fulfilling the primary end point. At a median follow-up of 38.1 months (range, 0.5-62.8), the median overall survival (OS) and disease-free survival (DFS) were not reached, and the estimated 3-year OS and DFS were 71% and 65%, respectively, with an excellent outlook for the patients aged 18 to 40 years who achieved an early MRD negativity (DFS, 92%). Pre-blinatumomab MRD predicted a worse outcome, especially in genetically high-risk patients. Notably, the 3-year survival of blinatumomab-treated patients was 82%. Survival and relapse rates were 91% and 15% in patients assigned to standard chemotherapy, 59% and 35% in patients assigned to hematopoietic stem cell transplantation, and 69% and 19% in transplant recipients, respectively. Blinatumomab toxicity was manageable, with only 8 permanent discontinuations. This chemotherapy-blinatumomab risk-oriented program yielded remarkable results that need further improvement in higher-risk patients displaying early MRD persistence. Blinatumomab should be considered as a standard component of induction/consolidation for adult Ph- B-ALL. This trial was registered at www.ClinicalTrials.gov as #NCT03367299.

MDM2 inhibitors are promising therapeutics for acute myeloid leukemia (AML) with wild-type TP53. Through an integrated analysis of functional genomic data from primary patient samples, we found that an MDM2 inhibitor, idasanutlin, like venetoclax, is ineffective against monocytic leukemia (French-American-British [FAB] subtype M4/M5). To dissect the underlying resistance mechanisms, we explored both intrinsic and extrinsic factors. We found that monocytic leukemia cells express elevated levels of CEBPB, which promote monocytic differentiation, suppress CASP3 and CASP6, and upregulate MCL1, BCL2A1, and the interleukin (IL-1)/tumor necrosis factor alpha (TNF-α)/NF-κB pathway members, thereby conferring drug resistance to a broad range of MDM2 inhibitors, BH3 mimetics, and venetoclax combinations. In addition, aberrant monocytes in M4/M5 leukemia produce elevated levels of IL-1 and TNF-α, which promote monocytic differentiation and upregulate inflammatory cytokines and receptors, thereby extrinsically protecting leukemia blasts from venetoclax and MDM2 inhibition. Interestingly, IL-1β and TNF-α only increase CEBPB levels and protect M4/M5 cells from these drugs but not M0/M1 leukemia cells. Treatment with venetoclax and idasanutlin induces compensatory upregulation of CEBPB and the IL-1/TNF-α/NF-κB pathway independent of the FAB subtype, indicating drug-induced compensatory protection mechanisms. The combination of venetoclax or idasanutlin with inhibitors that block the IL-1/TNF-α pathway demonstrates synergistic cytotoxicity in M4/M5 AML. As such, we uncovered a targetable positive feedback loop that involves CEBPB, IL-1/TNF-α, and monocyte differentiation in M4/M5 leukemia and promotes both intrinsic and extrinsic drug resistance and drug-induced protection against venetoclax and MDM2 inhibitors.

Despite the approval of several new treatments for patients with B-cell lymphoma, there is still a large unmet need. Diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) are the 2 most common B-cell lymphoma subtypes, accounting for ∼50% of all cases. EZH2 heterozygous gain-of-function somatic driver mutations are frequently found in germinal center B-cell DLBCLs and FLs. An EZH2 inhibitor has shown durable responses in patients with relapsed or refractory FL, however a considerable fraction of the patients did not show an objective response. To identify alternative therapeutic strategies, we performed CRISPR/Cas9 knockout screens in B-cell lymphoma cells treated with or without an EZH2 inhibitor. This led to the identification of the histone methyltransferase DOT1L as a potential therapeutic target. Specifically, we showed that an EZH2 inhibitor synergizes with a DOT1L inhibitor in a panel of B-cell lymphoma cell lines regardless of the EZH2 mutation status. Mechanistically, we demonstrated that the 2 inhibitors cooperatively suppress DOT1L-regulated cell cycle genes, upregulate genes involved in interferon signaling, including antigen presenting genes, and ultimately drive B-cell differentiation by derepressing EZH2-regulated plasma cell signature genes. Furthermore, we demonstrated the effectiveness of this epigenetic combination strategy in a xenograft model, which led to significant abrogation of tumor growth. Together, our studies provide preclinical proof-of-concept for an epigenetic combination therapy to overcome resistance and improve durability of response for the treatment of B-cell lymphoma, warranting clinical investigation and illustrating an important convergent role of EZH2 and DOT1L in B-cell lymphomagenesis.

T-cell-recruiting bispecific antibodies (BsAbs) are in clinical development for relapsed/refractory acute myeloid leukemia (AML). Despite promising results, early clinical trials have failed to demonstrate durable responses. We investigated whether activation of the innate immune system through stimulator of interferon (IFN) genes (STING) can enhance target cell killing by a BsAb targeting CD33 (CD33 bispecific T-cell engager molecule; AMG 330). Indeed, we show that cytotoxicity against AML mediated by AMG 330 can be greatly enhanced when combined with the STING agonist 2',3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) or diamidobenzimidazole (diABZI). We used in vitro cytotoxicity assays, immunoblotting, transcriptomic analyses, and extensive CRISPR-Cas9 knockout experiments to investigate the enhancing effect of a STING agonist on the cytotoxicity of AMG 330 against AML. Importantly, we validated our findings with primary AML cells and in a xenograft AML model. Mechanistically, in addition to direct cytotoxic effects of STING activation on AML cells, activated T cells render AML cells more susceptible to STING activation through their effector cytokines, IFN-γ and tumor necrosis factor, resulting in enhanced type I IFN production and induction of IFN-stimulated genes. This feeds back to the T cells, leading to a further increase in effector cytokines and an overall cytotoxic T-cell phenotype, contributing to the beneficial effect of cGAMP/diABZI in enhancing AMG 330-mediated lysis. We established a key role for IFN-γ in AMG 330-mediated cytotoxicity against AML cells and in rendering AML cells responsive to STING agonism. Here, we propose to improve the efficacy of CD33-targeting BsAbs by combining them with a STING agonist.

The transglutaminase coagulation factor XIII (FXIII) is critical for the stability and function of intravascular fibrin clots. Prorepair extravascular fibrin(ogen) deposits are potentially subject to cross-linking by FXIII and other transglutaminases not typically resident in plasma. However, the impact of these alternative modifiers on fibrin(ogen) structure and function is not known. We tested the hypothesis that tissue transglutaminase (TG2) modifies FXIII-directed fibrin(ogen) cross-linking in vitro and within injured tissue. Global proteomic analysis after experimental acetaminophen (APAP)-induced acute liver injury revealed that intrahepatic fibrin(ogen) deposition was associated with hepatic TG2 levels that exceeded that of FXIII. Mass spectrometry-based cross-link mapping of in vitro fibrin matrices uncovered, to our knowledge, the first evidence of synergistic fibrin(ogen) α-α cross-linking catalyzed by both transglutaminases. Fibrin(ogen) cross-linking was increased in livers from patients with APAP-induced acute liver failure. APAP-challenged TG2-/- mice displayed an altered pattern of FXIII-dependent fibrin(ogen)-γ and fibrin(ogen)-α chain cross-linking aligned with the impact of TG2 on fibrin cross-linking in vitro. This shift in fibrin(ogen) cross-linking exacerbated pathologies including hepatic necrosis and sinusoidal congestion. The results, to our knowledge, are the first to indicate that TG2 impacts FXIII-directed fibrin(ogen) cross-linking, both in vitro and in vivo. The results suggest that TG2 functions to dynamically alter the structure of extravascular fibrin(ogen) to mitigate liver damage, a novel mechanism likely applicable across types of tissue injury.

Microbial dysbiosis and metabolite changes in the gastrointestinal (GI) tract have been linked to pathogenesis and severity of many diseases, including graft-versus-host disease (GVHD), the major complication of allogeneic hematopoietic stem cell transplantation. However, published studies have only considered the microbiome and metabolome of excreted stool and do not provide insight into the variability of the microbial community and metabolite composition throughout the GI tract or the unique temporal dynamics associated with different gut locations. Because such geographical variations are known to influence disease processes, we used a multi-omics approach to characterize the microbiome and metabolite profiles of gut contents from different intestinal regions in well-characterized mouse models of GVHD. Our analysis validated analyses from excreted stool, but importantly, uncovered new biological insights from the microbial and metabolite changes between syngeneic and allogeneic hosts that varied by GI location and time after transplantation. Our integrated analysis confirmed the involvement of known metabolic pathways, including short-chain fatty acid synthesis and bile acid metabolism, and identified additional functional genes, pathways, and metabolites, such as amino acids, fatty acids, and sphingolipids, linked to GI GVHD. Finally, we validated a biological relevance for one such newly identified microbial metabolite, phenyl lactate, that heretofore had not been linked to GI GVHD. Thus, our analysis of the geographic variability in the intestinal microbiome and metabolome offers new insights into GI GVHD pathogenesis and potential for novel therapeutics.

Refractory and/or relapsing T-cell acute lymphoblastic leukemia (T-ALL) remains a major therapeutic challenge. The pre-T-cell receptor (TCR) pathway has recently emerged as a therapeutic target via LCK inhibition in this context. However, there is a need for simple and quickly assessable biomarkers to predict sensitivity to LCK inhibitors. Moreover, targeting LCK alone by tyrosine kinase inhibitors, such as dasatinib, often results in transient clinical responses, emphasizing the need for efficient combination strategies. Here, we assessed pre-TCR α chain (pTα) surface expression by flow cytometry in a unique series of 50 adult T-ALL patient-derived xenografts (PDXs). We show that cases displaying a cortical phenotype often express high levels of surface pTα (pre-TCR+ T-ALL) and that the latter associates with LCK activation. Furthermore, we show that ectopic interleukin-7 receptor (IL-7R) expression can rescue pre-TCR+ T-ALL from dasatinib cytotoxicity (5 PDXs). We tested whether coinhibition of pre-TCR and IL-7R signaling pathways could be synergetic in pre-TCR+ IL-7R+ T-ALL (11 PDXs). Combination of JAK inhibitors, ruxolitinib or tofacitinib, with dasatinib elicited strong and specific synergy in IL-7R+ pre-TCR+ T-ALL in vitro, including in the relapse setting (4 of 28 patient-derived primary samples). Using 3 adult-PDX models, we show that in vivo treatment with this combination significantly delayed leukemic progression and prolonged survival compared with either monotherapy. This preclinical study thus proposes the use of pTα as a biomarker of LCK-inhibitor sensitivity in T-ALL, and suggests that dual targeting of IL-7R and pre-TCR signaling pathways may be a relevant therapeutic strategy in a substantial proportion of adult T-ALL.

Chronic graft-versus-host disease (cGVHD) remains the leading cause of nonrelapse morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Effective therapeutic agents targeting dysregulated cytokines including interleukin-17 (IL-17) and colony-stimulating factor 1 (CSF-1) have been defined in preclinical models of cGVHD, and efficacy in subsequent clinical trials has led to their recent US Food and Drug Administration approval. Despite this, these agents are effective in only a subset of patients, expensive, difficult to access outside the United States, and used in a trial-and-error fashion. The ability to readily discern druggable, dysregulated immunity in these patients is desperately needed to facilitate the selection of appropriate treatment and to potentially identify high-risk individuals for preemptive therapy. We used single-cell sequencing-based approaches in our informative preclinical cGVHD models to "reverse engineer" temporal IL-17 and CSF-1 signatures in mouse blood that could be used to interrogate patients. We defined distinct, nonintuitive IL-17 and CSF-1 signatures in mouse blood monocytes that could be identified in relevant monocyte populations within 70% of patients at diagnosis of cGVHD and in half of patients at day +100 after HCT who subsequently developed cGVHD. These signatures can now be evaluated prospectively in clinical studies to help delineate potential responder and nonresponders to relevant therapeutics targeting these pathways.