Clonal Hematopoiesis and Therapy-Related Myeloid Neoplasms After Autologous Transplant for Hodgkin Lymphoma.

PURPOSE: Therapy-related myeloid neoplasm (t-MN) is a life-threatening complication of autologous peripheral blood stem cell transplantation (aPBSCT) for Hodgkin lymphoma (HL). Although previous studies have reported an association between clonal hematopoiesis (CH) in the infused PBSC product and subsequent post-aPBSCT risk of t-MN in patients with non-HL, information about patients with HL treated with aPBSCT is not available. METHODS: We constructed a retrospective cohort of 321 patients with HL transplanted at a median age of 34 years (range, 18-71). Targeted DNA sequencing of PBSC products performed for CH-associated or myeloid malignancy-associated genes identified pathogenic mutations in these patients. RESULTS: CH was identified in the PBSC product of 46 patients (14.3%) with most prominent representation of DNMT3A (n = 25), PPM1D (n = 7), TET2 (n = 7), and TP53 (n = 5) mutations. Presence of CH in the PBSC product was an independent predictor of t-MN (adjusted hazard ratio [aHR], 4.50 [95% CI, 1.54 to 13.19]). Notably all patients with TP53 mutations in the PBSC product developed t-MN, whereas none of the patients with DNMT3A mutations alone (without co-occurring TP53 or PPM1D mutations) did. Presence of TP53 and/or PPM1D mutations was associated with a 7.29-fold higher hazard of t-MN when compared with individuals carrying no CH mutations (95% CI, 1.72 to 30.94). The presence of TP53 and/or PPM1D mutations was also associated with a 4.17-fold higher hazard of nonrelapse mortality (95% CI, 1.25 to 13.87). There was no association between CH and relapse-related mortality. CONCLUSION: The presence of TP53 and/or PPM1D mutations in the PBSC product increases the risk of post-aPBSCT t-MN and nonrelapse mortality among patients with HL and may support alternative therapeutic strategies.

Atrial Fibrillation and Clonal Hematopoiesis in TET2 and ASXL1.

Importance: Clonal hematopoiesis of indeterminate potential (CHIP) may contribute to the risk of atrial fibrillation (AF) through its association with inflammation and cardiac remodeling. Objective: To determine whether CHIP was associated with AF, inflammatory and cardiac biomarkers, and cardiac structural changes. Design, Setting, and Participants: This was a population-based, prospective cohort study in participants of the Atherosclerosis Risk in Communities (ARIC) study and UK Biobank (UKB) cohort. Samples were collected and echocardiography was performed from 2011 to 2013 in the ARIC cohort, and samples were collected from 2006 to 2010 in the UKB cohort. Included in this study were adults without hematologic malignancies, mitral valve stenosis, or previous mitral valve procedure from both the ARIC and UKB cohorts; additionally, participants without hypertrophic cardiomyopathy and congenital heart disease from the UKB cohort were also included. Data analysis was completed in 2023. Exposures: CHIP (variant allele frequency [VAF] ≥2%), common gene-specific CHIP subtypes (DNMT3A, TET2, ASXL1), large CHIP (VAF ≥10%), inflammatory and cardiac biomarkers (high-sensitivity C-reactive protein, interleukin 6 [IL-6], IL-18, high-sensitivity troponin T [hs-TnT] and hs-TnI, N-terminal pro-B-type natriuretic peptide), and echocardiographic indices. Main Outcome Measure: Incident AF. Results: A total of 199 982 adults were included in this study. In ARIC participants (4131 [2.1%]; mean [SD] age, 76 [5] years; 2449 female [59%]; 1682 male [41%]; 935 Black [23%] and 3196 White [77%]), 1019 had any CHIP (24.7%), and 478 had large CHIP (11.6%). In UKB participants (195 851 [97.9%]; mean [SD] age, 56 [8] years; 108 370 female [55%]; 87 481 male [45%]; 3154 Black [2%], 183 747 White [94%], and 7971 other race [4%]), 11 328 had any CHIP (5.8%), and 5189 had large CHIP (2.6%). ARIC participants were followed up for a median (IQR) period of 7.0 (5.3-7.7) years, and UKB participants were followed up for a median (IQR) period of 12.2 (11.3-13.0) years. Meta-analyzed hazard ratios for AF were 1.12 (95% CI, 1.01-1.25; P = .04) for participants with vs without large CHIP, 1.29 (95% CI, 1.05-1.59; P = .02) for those with vs without large TET2 CHIP (seen in 1340 of 197 209 [0.67%]), and 1.45 (95% CI, 1.02-2.07; P = .04) for those with vs without large ASXL1 CHIP (seen in 314 of 197 209 [0.16%]). Large TET2 CHIP was associated with higher IL-6 levels. Additionally, large ASXL1 was associated with higher hs-TnT level and increased left ventricular mass index. Conclusions and Relevance: Large TET2 and ASXL1, but not DNMT3A, CHIP was associated with higher IL-6 level, indices of cardiac remodeling, and increased risk for AF. Future research is needed to elaborate on the mechanisms driving the associations and to investigate potential interventions to reduce the risk.

Targeting the mevalonate or Wnt pathways to overcome CAR T-cell resistance in TP53-mutant AML cells.

TP53-mutant acute myeloid leukemia (AML) and myelodysplastic neoplasms (MDS) are characterized by chemotherapy resistance and represent an unmet clinical need. Chimeric antigen receptor (CAR) T-cells might be a promising therapeutic option for TP53-mutant AML/MDS. However, the impact of TP53 deficiency in AML cells on the efficacy of CAR T-cells is unknown. We here show that CAR T-cells engaging TP53-deficient leukemia cells exhibit a prolonged interaction time, upregulate exhaustion markers, and are inefficient to control AML cell outgrowth in vitro and in vivo compared to TP53 wild-type cells. Transcriptional profiling revealed that the mevalonate pathway is upregulated in TP53-deficient AML cells under CAR T-cell attack, while CAR T-cells engaging TP53-deficient AML cells downregulate the Wnt pathway. In vitro rational targeting of either of these pathways rescues AML cell sensitivity to CAR T-cell-mediated killing. We thus demonstrate that TP53 deficiency confers resistance to CAR T-cell therapy and identify the mevalonate pathway as a therapeutic vulnerability of TP53-deficient AML cells engaged by CAR T-cells, and the Wnt pathway as a promising CAR T-cell therapy-enhancing approach for TP53-deficient AML/MDS.

Clonal Hematopoiesis of Indeterminate Potential With Loss of Tet2 Enhances Risk for Atrial Fibrillation Through Nlrp3 Inflammasome Activation.

BACKGROUND: Clonal hematopoiesis of indeterminate potential (CHIP), a common age-associated phenomenon, associates with increased risk of both hematological malignancy and cardiovascular disease. Although CHIP is known to increase the risk of myocardial infarction and heart failure, the influence of CHIP in cardiac arrhythmias, such as atrial fibrillation (AF), is less explored. METHODS: CHIP prevalence was determined in the UK Biobank, and incident AF analysis was stratified by CHIP status and clone size using Cox proportional hazard models. Lethally irradiated mice were transplanted with hematopoietic-specific loss of Tet2, hematopoietic-specific loss of Tet2 and Nlrp3, or wild-type control and fed a Western diet, compounded with or without NLRP3 (NLR [NACHT, LRR {leucine rich repeat}] family pyrin domain containing protein 3) inhibitor, NP3-361, for 6 to 9 weeks. Mice underwent in vivo invasive electrophysiology studies and ex vivo optical mapping. Cardiomyocytes from Ldlr-/- mice with hematopoietic-specific loss of Tet2 or wild-type control and fed a Western diet were isolated to evaluate calcium signaling dynamics and analysis. Cocultures of pluripotent stem cell-derived atrial cardiomyocytes were incubated with Tet2-deficient bone marrow-derived macrophages, wild-type control, or cytokines IL-1ß (interleukin 1ß) or IL-6 (interleukin 6). RESULTS: Analysis of the UK Biobank showed individuals with CHIP, in particular TET2 CHIP, have increased incident AF. Hematopoietic-specific inactivation of Tet2 increases AF propensity in atherogenic and nonatherogenic mouse models and is associated with increased Nlrp3 expression and CaMKII (Ca2+/calmodulin-dependent protein kinase II) activation, with AF susceptibility prevented by inactivation of Nlrp3. Cardiomyocytes isolated from Ldlr-/- mice with hematopoietic inactivation of Tet2 and fed a Western diet have impaired calcium release from the sarcoplasmic reticulum into the cytosol, contributing to atrial arrhythmogenesis. Abnormal sarcoplasmic reticulum calcium release was recapitulated in cocultures of cardiomyocytes with the addition of Tet2-deficient macrophages or cytokines IL-1ß or IL-6. CONCLUSIONS: We identified a modest association between CHIP, particularly TET2 CHIP, and incident AF in the UK Biobank population. In a mouse model of AF resulting from hematopoietic-specific inactivation of Tet2, we propose altered calcium handling as an arrhythmogenic mechanism, dependent on Nlrp3 inflammasome activation. Our data are in keeping with previous studies of CHIP in cardiovascular disease, and further studies into the therapeutic potential of NLRP3 inhibition for individuals with TET2 CHIP may be warranted.

Induced protein degradation for therapeutics: past, present, and future.

The concept of induced protein degradation by small molecules has emerged as a promising therapeutic strategy that is particularly effective in targeting proteins previously considered "undruggable." Thalidomide analogs, employed in the treatment of multiple myeloma, stand as prime examples. These compounds serve as molecular glues, redirecting the CRBN E3 ubiquitin ligase to degrade myeloma-dependency factors, IKZF1 and IKZF3. The clinical success of thalidomide analogs demonstrates the therapeutic potential of induced protein degradation. Beyond molecular glue degraders, several additional modalities to trigger protein degradation have been developed and are currently under clinical evaluation. These include heterobifunctional degraders, polymerization-induced degradation, ligand-dependent degradation of nuclear hormone receptors, disruption of protein interactions, and various other strategies. In this Review, we will provide a concise overview of various degradation modalities, their clinical applications, and potential future directions in the field of protein degradation.

Risk factors for clonal hematopoiesis of indeterminate potential in people with HIV: a report from the REPRIEVE trial.

ABSTRACT: Clonal hematopoiesis of indeterminate potential (CHIP), the clonal expansion of myeloid cells with leukemogenic mutations, results in increased coronary artery disease (CAD) risk. CHIP is more prevalent among people with HIV (PWH), but the risk factors are unknown. CHIP was identified among PWH in REPRIEVE (Randomized Trial to Prevent Vascular Events in HIV) using whole-exome sequencing. Logistic regression was used to associate sociodemographic factors and HIV-specific factors with CHIP adjusting for age, sex, and smoking status. In the studied global cohort of 4486 PWH, mean age was 49.9 (standard deviation [SD], 6.4) years; 1650 (36.8%) were female; and 3418 (76.2%) were non-White. CHIP was identified in 223 of 4486 (4.97%) and in 38 of 373 (10.2%) among those aged ≥60 years. Age (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.05-1.09; P < .0001) and smoking (OR, 1.37; 95% CI, 1.14-1.66; P < .001) associated with increased odds of CHIP. Globally, participants outside of North America had lower odds of CHIP including sub-Saharan Africa (OR, 0.57; 95% CI, 0.4-0.81; P = .0019), South Asia (OR, 0.45; 95% CI, 0.23-0.80; P = .01), and Latin America/Caribbean (OR, 0.56; 95% CI, 0.34-0.87; P = .014). Hispanic/Latino ethnicity (OR, 0.38; 95% CI, 0.23-0.54; P = .002) associated with significantly lower odds of CHIP. Among HIV-specific factors, CD4 nadir <50 cells/mm3 associated with a 1.9-fold (95%CI, 1.21-3.05; P = .006) increased odds of CHIP, with the effect being significantly stronger among individuals with short duration of antiretroviral therapy (ART; OR, 4.15; 95% CI, 1.51-11.1; P = .005) (Pinteraction= .0492). Among PWH at low-to-moderate CAD risk on stable ART, smoking, CD4 nadir, North American origin, and non-Hispanic ethnicity associated with increased odds of CHIP. This trial was registered at www.ClinicalTrials.gov as NCT02344290.

Clonal Hematopoiesis Risk Score and All-Cause and Cardiovascular Mortality in Older Adults.

Importance: Clonal hematopoiesis (CH) with acquired pathogenic variants in myeloid leukemia driver genes is common in older adults but of unknown prognostic value. Objective: To investigate the prevalence of CH and the utility of the CH risk score (CHRS) in estimating all-cause and disease-specific mortality in older adults with CH. Design, Setting, and Participants: This population-based prospective cohort study involved community-dwelling older adults (aged 67-90 years) without hematologic malignant neoplasms (HMs) who were participants in the Atherosclerosis Risk in Communities Visit 5 at 4 US centers: Forsyth County, North Carolina; Jackson, Mississippi; Minneapolis, Minnesota; and Washington County, Maryland. Samples were collected from 2011 to 2013, sequencing was performed in 2022, and data analysis was completed in 2023. Exposure: The exposure was a diagnosis of CH. CHRS scores (calculated using 8 demographic, complete blood cell count, and molecular factors) were used to categorize individuals with CH into low-risk (CHRS ≤9.5), intermediate-risk (CHRS >9.5 to <12.5), and high-risk (CHRS ≥12.5) groups. Main Outcomes and Measures: The primary outcome was all-cause mortality, and secondary outcomes were HM mortality, cardiovascular disease mortality, and death from other causes. Results: Among 3871 participants without a history of HM (mean [SD] age, 75.7 [5.2] years; 2264 [58.5%] female individuals; 895 [23.1%] Black individuals; 2976 White individuals [76.9%]), 938 (24.2%) had CH. According to the CHRS, 562 (59.9%) were low risk, 318 (33.9%) were intermediate risk, and 58 (6.2%) were high risk. During a median (IQR) follow-up of 7.13 (5.63-7.78) years, 570 participants without CH (19.4%) and 254 participants with CH (27.1%) died. Mortality by CHRS risk group was 128 deaths (22.8%) for low risk, 93 (29.2%) for intermediate risk, and 33 (56.9%) for high risk. By use of multivariable competing risk regression, subdistribution hazard ratios (sHRs) for all-cause mortality were 1.08 (95% CI, 0.89-1.31; P = .42) for low-risk CH, 1.12 (95% CI, 0.89-1.41; P = .31) for intermediate-risk CH, and 2.52 (95% CI, 1.72-3.70; P < .001) for high-risk CH compared with no CH. Among individuals in the high-risk CH group, the sHR of death from HM (6 deaths [10.3%]) was 25.58 (95% CI, 7.55-86.71; P < .001) and that of cardiovascular death (12 deaths [20.7%]) was 2.91 (95% CI, 1.55-5.47; P < .001). Conclusions and Relevance: In this cohort study, the CHRS was associated with all-cause, HM-related, and cardiovascular disease mortality in older adults with CH and may be useful in shared decision-making to guide clinical management and identify appropriate candidates for clinical trials.

Mezigdomide is effective alone and in combination with menin inhibition in preclinical models of KMT2A-r and NPM1c AML.

ABSTRACT: Small molecules that target the menin-KMT2A protein-protein interaction (menin inhibitors) have recently entered clinical trials in lysine methyltransferase 2A (KMT2A or MLL1)-rearranged (KMT2A-r) and nucleophosmin-mutant (NPM1c) acute myeloid leukemia (AML) and are demonstrating encouraging results. However, rationally chosen combination therapy is needed to improve responses and prevent resistance. We have previously identified IKZF1/IKAROS as a target in KMT2A-r AML and shown in preclinical models that IKAROS protein degradation with lenalidomide or iberdomide has modest single-agent activity yet can synergize with menin inhibitors. Recently, the novel IKAROS degrader mezigdomide was developed with greatly enhanced IKAROS protein degradation. In this study, we show that mezigdomide has increased preclinical activity in vitro as a single-agent in KMT2A-r and NPM1c AML cell lines, including sensitivity in cell lines resistant to lenalidomide and iberdomide. Further, we demonstrate that mezigdomide has the greatest capacity to synergize with and induce apoptosis in combination with menin inhibitors, including in MEN1 mutant models. We show that the superior activity of mezigdomide compared with lenalidomide or iberdomide is due to its increased depth, rate, and duration of IKAROS protein degradation. Single-agent mezigdomide was efficacious in 5 patient-derived xenograft models of KMT2A-r and 1 NPM1c AML. The combination of mezigdomide with the menin inhibitor VTP-50469 increased survival and prevented and overcame MEN1 mutations that mediate resistance in patients receiving menin inhibitor monotherapy. These results support prioritization of mezigdomide for early phase clinical trials in KMT2A-r and NPM1c AML, either as a single agent or in combination with menin inhibitors.

Clonal haematopoiesis of indeterminate potential predicts incident cardiac arrhythmias.

BACKGROUND AND AIMS: Clonal haematopoiesis of indeterminate potential (CHIP), the age-related expansion of blood cells with preleukemic mutations, is associated with atherosclerotic cardiovascular disease and heart failure. This study aimed to test the association of CHIP with new-onset arrhythmias. METHODS: UK Biobank participants without prevalent arrhythmias were included. Co-primary study outcomes were supraventricular arrhythmias, bradyarrhythmias, and ventricular arrhythmias. Secondary outcomes were cardiac arrest, atrial fibrillation, and any arrhythmia. Associations of any CHIP [variant allele fraction (VAF) ≥ 2%], large CHIP (VAF ≥10%), and gene-specific CHIP subtypes with incident arrhythmias were evaluated using multivariable-adjusted Cox regression. Associations of CHIP with myocardial interstitial fibrosis [T1 measured using cardiac magnetic resonance (CMR)] were also tested. RESULTS: This study included 410 702 participants [CHIP: n = 13 892 (3.4%); large CHIP: n = 9191 (2.2%)]. Any and large CHIP were associated with multi-variable-adjusted hazard ratios of 1.11 [95% confidence interval (CI) 1.04-1.18; P = .001] and 1.13 (95% CI 1.05-1.22; P = .001) for supraventricular arrhythmias, 1.09 (95% CI 1.01-1.19; P = .031) and 1.13 (95% CI 1.03-1.25; P = .011) for bradyarrhythmias, and 1.16 (95% CI, 1.00-1.34; P = .049) and 1.22 (95% CI 1.03-1.45; P = .021) for ventricular arrhythmias, respectively. Associations were independent of coronary artery disease and heart failure. Associations were also heterogeneous across arrhythmia subtypes and strongest for cardiac arrest. Gene-specific analyses revealed an increased risk of arrhythmias across driver genes other than DNMT3A. Large CHIP was associated with 1.31-fold odds (95% CI 1.07-1.59; P = .009) of being in the top quintile of myocardial fibrosis by CMR. CONCLUSIONS: CHIP may represent a novel risk factor for incident arrhythmias, indicating a potential target for modulation towards arrhythmia prevention and treatment.

Optimization of Advanced Molecular Genetic Testing Utilization in Hematopathology: A Goldilocks Approach to Bone Marrow Testing.

PURPOSE: This study investigated the effectiveness of algorithmic testing in hematopathology at the Brigham and Women's Hospital and Dana-Farber Cancer Institute (DFCI). The algorithm was predicated on test selection after an initial pathologic evaluation to maximize cost-effective testing, especially for expensive molecular and cytogenetic assays. MATERIALS AND METHODS: Standard ordering protocols (SOPs) for 17 disease categories were developed and encoded in a decision support application. Six months of retrospective data from application beta testing was obtained and compared with actual testing practices during that timeframe. In addition, 2 years of prospective data were also obtained from patients at one community satellite site. RESULTS: A total of 460 retrospective cases (before introduction of algorithmic testing) and 109 prospective cases (following introduction) were analyzed. In the retrospective data, 61.7% of tests (509 of 825) were concordant with the SOPs while 38.3% (316 of 825) were overordered and 30.8% (227 of 736) of SOP-recommended tests were omitted. In the prospective data, 98.8% of testing was concordant (244 of 247 total tests) with only 1.2% overordered tests (3 of 247) and 7.6% omitted tests (20 of 264 SOP-recommended tests; overall P < .001). The cost of overordered tests before implementing SOP indicates a potential annualized saving of $1,347,520 in US dollars (USD) in overordered testing at Brigham and Women's Hospital/DFCI. Only two of 316 overordered tests (0.6%) returned any additional information, both for extremely rare clinical circumstances. CONCLUSION: Implementation of SOPs dramatically improved test ordering practices, with a just right number of ancillary tests that minimizes cost and has no significant impact on acquiring key informative test results.

Association of Somatic TET2 Mutations With Giant Cell Arteritis.

OBJECTIVE: Giant cell arteritis (GCA) is an age-related vasculitis. Prior studies have identified an association between GCA and hematologic malignancies (HMs). How the presence of somatic mutations that drive the development of HMs, or clonal hematopoiesis (CH), may influence clinical outcomes in GCA is not well understood. METHODS: To examine an association between CH and GCA, we analyzed sequenced exomes of 470,960 UK Biobank (UKB) participants for the presence of CH and used multivariable Cox regression. To examine the clinical phenotype of GCA in patients with and without somatic mutations across the spectrum of CH to HM, we performed targeted sequencing of blood samples and electronic health record review on 114 patients with GCA seen at our institution. We then examined associations between specific clonal mutations and GCA disease manifestations. RESULTS: UKB participants with CH had a 1.48-fold increased risk of incident GCA compared to UKB participants without CH. GCA risk was highest among individuals with cytopenia (hazard ratio [HR] 2.98, P = 0.00178) and with TET2 mutation (HR 2.02, P = 0.00116). Mutations were detected in 27.2% of our institutional GCA cohort, three of whom had HM at GCA diagnosis. TET2 mutations were associated with vision loss in patients with GCA (odds ratio 4.33, P = 0.047). CONCLUSIONS: CH increases risk for development of GCA in a genotype-specific manner, with the greatest risk being conferred by the presence of mutations in TET2. Somatic TET2 mutations likewise increase the risk of GCA-associated vision loss. Integration of somatic genetic testing in GCA diagnostics may be warranted in the future.

Chemical genetic control of cytokine signaling in CAR-T cells using lenalidomide-controlled membrane-bound degradable IL-7.

CAR-T cell therapy has emerged as a breakthrough therapy for the treatment of relapsed and refractory hematologic malignancies. However, insufficient CAR-T cell expansion and persistence is a leading cause of treatment failure. Exogenous or transgenic cytokines have great potential to enhance CAR-T cell potency but pose the risk of exacerbating toxicities. Here we present a chemical-genetic system for spatiotemporal control of cytokine function gated by the off-patent anti-cancer molecular glue degrader drug lenalidomide and its analogs. When co-delivered with a CAR, a membrane-bound, lenalidomide-degradable IL-7 fusion protein enforced a clinically favorable T cell phenotype, enhanced antigen-dependent proliferative capacity, and enhanced in vivo tumor control. Furthermore, cyclical pharmacologic combined control of CAR and cytokine abundance enabled the deployment of highly active, IL-7-augmented CAR-T cells in a dual model of antitumor potency and T cell hyperproliferation.

Acute Lymphoblastic Leukemia with Myeloid Mutations Is a High-Risk Disease Associated with Clonal Hematopoiesis.

Myeloid neoplasms arise from preexisting clonal hematopoiesis (CH); however, the role of CH in the pathogenesis of acute lymphoblastic leukemia (ALL) is unknown. We found that 18% of adult ALL cases harbored TP53, and 16% had myeloid CH-associated gene mutations. ALL with myeloid mutations (MyM) had distinct genetic and clinical characteristics, associated with inferior survival. By using single-cell proteogenomic analysis, we demonstrated that myeloid mutations were present years before the diagnosis of ALL, and a subset of these clones expanded over time to manifest as dominant clones in ALL. Single-cell RNA sequencing revealed upregulation of genes associated with cell survival and resistance to apoptosis in B-ALL with MyM, which responds better to newer immunotherapeutic approaches. These findings define ALL with MyM as a high-risk disease that can arise from antecedent CH and offer new mechanistic insights to develop better therapeutic and preventative strategies. SIGNIFICANCE: CH is a precursor lesion for lymphoblastic leukemogenesis. ALL with MyM has distinct genetic and clinical characteristics, associated with adverse survival outcomes after chemotherapy. CH can precede ALL years before diagnosis, and ALL with MyM is enriched with activated T cells that respond to immunotherapies such as blinatumomab. See related commentary by Iacobucci, p. 142.

Proteolysis-targeting chimeras with reduced off-targets.

Proteolysis-targeting chimeras (PROTACs) are molecules that induce proximity between target proteins and E3 ligases triggering target protein degradation. Pomalidomide, a widely used E3 ligase recruiter in PROTACs, can independently degrade other proteins, including zinc-finger (ZF) proteins, with vital roles in health and disease. This off-target degradation hampers the therapeutic applicability of pomalidomide-based PROTACs, requiring development of PROTAC design rules that minimize off-target degradation. Here we developed a high-throughput platform that interrogates off-target degradation and found that reported pomalidomide-based PROTACs induce degradation of several ZF proteins. We generated a library of pomalidomide analogues to understand how functionalizing different positions of the phthalimide ring, hydrogen bonding, and steric and hydrophobic effects impact ZF protein degradation. Modifications of appropriate size on the C5 position reduced off-target ZF degradation, which we validated through target engagement and proteomics studies. By applying these design principles, we developed anaplastic lymphoma kinase oncoprotein-targeting PROTACs with enhanced potency and minimal off-target degradation.

Clinical Outcomes and Evolution of Clonal Hematopoiesis in Patients with Newly Diagnosed Multiple Myeloma.

Clonal hematopoiesis (CH) at time of autologous stem cell transplant (ASCT) has been shown to be associated with decreased overall survival (OS) and progression-free survival (PFS) in patients with multiple myeloma not receiving immunomodulatory drugs (IMiD). However, the significance of CH in newly diagnosed patients, including transplant ineligible patients, and its effect on clonal evolution during multiple myeloma therapy in the era of novel agents, has not been well studied. Using our new algorithm to differentiate tumor and germline mutations from CH, we detected CH in approximately 10% of 986 patients with multiple myeloma from the Clinical Outcomes in MM to Personal Assessment of Genetic Profile (CoMMpass) cohort (40/529 transplanted and 59/457 non-transplanted patients). CH was associated with increased age, risk of recurrent bacterial infections and cardiovascular disease. CH at time of multiple myeloma diagnosis was not associated with inferior OS or PFS regardless of undergoing ASCT, and all patients benefited from IMiD-based therapies, irrespective of the presence of CH. Serial sampling of 52 patients revealed the emergence of CH over a median of 3 years of treatment, increasing its prevalence to 25%, mostly with DNMT3A mutations. SIGNIFICANCE: Using our algorithm to differentiate tumor and germline mutations from CH mutations, we detected CH in approximately 10% of patients with newly diagnosed myeloma, including both transplant eligible and ineligible patients. Receiving IMiDs improved outcomes irrespective of CH status, but the prevalence of CH significantly rose throughout myeloma-directed therapy.

Enhanced TP53 reactivation disrupts MYC transcriptional program and overcomes venetoclax resistance in acute myeloid leukemias.

The tumor suppressor TP53 is frequently inactivated in a mutation-independent manner in cancers and is reactivated by inhibiting its negative regulators. We here cotarget MDM2 and the nuclear exporter XPO1 to maximize transcriptional activity of p53. MDM2/XPO1 inhibition accumulated nuclear p53 and elicited a 25- to 60-fold increase of its transcriptional targets. TP53 regulates MYC, and MDM2/XPO1 inhibition disrupted the c-MYC-regulated transcriptome, resulting in the synergistic induction of apoptosis in acute myeloid leukemia (AML). Unexpectedly, venetoclax-resistant AMLs express high levels of c-MYC and are vulnerable to MDM2/XPO1 inhibition in vivo. However, AML cells persisting after MDM2/XPO1 inhibition exhibit a quiescence- and stress response-associated phenotype. Venetoclax overcomes that resistance, as shown by single-cell mass cytometry. The triple inhibition of MDM2, XPO1, and BCL2 was highly effective against venetoclax-resistant AML in vivo. Our results propose a novel, highly translatable therapeutic approach leveraging p53 reactivation to overcome nongenetic, stress-adapted venetoclax resistance.

Causes and consequences of clonal hematopoiesis.

ABSTRACT: Clonal hematopoiesis (CH) is described as the outsized contribution of expanded clones of hematopoietic stem and progenitor cells (HSPCs) to blood cell production. The prevalence of CH increases dramatically with age. CH can be caused by somatic mutations in individual genes or by gains and/or losses of larger chromosomal segments. CH is a premalignant state; the somatic mutations detected in CH are the initiating mutations for hematologic malignancies, and CH is a strong predictor of the development of blood cancers. Moreover, CH is associated with nonmalignant disorders and increased overall mortality. The somatic mutations that drive clonal expansion of HSPCs can alter the function of terminally differentiated blood cells, including the release of elevated levels of inflammatory cytokines. These cytokines may then contribute to a broad range of inflammatory disorders that increase in prevalence with age. Specific somatic mutations in the peripheral blood in coordination with blood count parameters can powerfully predict the development of hematologic malignancies and overall mortality in CH. In this review, we summarize the current understanding of CH nosology and origins. We provide an overview of available tools for risk stratification and discuss management strategies for patients with CH presenting to hematology clinics.

Exploration of the Tunability of BRD4 Degradation by DCAF16 Trans-labelling Covalent Glues.

Small molecules that can induce protein degradation by inducing proximity between a desired target and an E3 ligase have the potential to greatly expand the number of proteins that can be manipulated pharmacologically. Current strategies for targeted protein degradation are mostly limited in their target scope to proteins with preexisting ligands. Alternate modalities such as molecular glues, as exemplified by the glutarimide class of ligands for the CUL4CRBN ligase, have been mostly discovered serendipitously. We recently reported a trans-labelling covalent glue mechanism which we named 'Template-assisted covalent modification', where an electrophile decorated small molecule binder of BRD4 was effectively delivered to a cysteine residue on an E3 ligase DCAF16 as a consequence of a BRD4-DCAF16 protein-protein interaction. Herein, we report our medicinal chemistry efforts to evaluate how various electrophilic modifications to the BRD4 binder, JQ1, affect DCAF16 trans-labeling and subsequent BRD4 degradation efficiency. We discovered a decent correlation between the ability of the electrophilic small molecule to induce ternary complex formation between BRD4 and DCAF16 with its ability to induce BRD4 degradation. Moreover, we show that a more solvent-exposed warhead presentation is optimal for DCAF16 recruitment and subsequent BRD4 degradation. Unlike the sensitivity of CUL4CRBN glue degraders to chemical modifications, the diversity of covalent attachments in this class of BRD4 glue degraders suggests a high tolerance and tunability for the BRD4-DCAF16 interaction. This offers a potential new avenue for a rational design of covalent glue degraders by introducing covalent warheads to known binders.

Chemical Specification of E3 Ubiquitin Ligase Engagement by Cysteine-Reactive Chemistry.

Targeted protein degradation relies on small molecules that induce new protein-protein interactions between targets and the cellular protein degradation machinery. Most of these small molecules feature specific ligands for ubiquitin ligases. Recently, the attachment of cysteine-reactive chemical groups to pre-existing small molecule inhibitors has been shown to drive specific target degradation. We demonstrate here that different cysteine-reactive groups can specify target degradation via distinct ubiquitin ligases. By focusing on the bromodomain ligand JQ1, we identify cysteine-reactive functional groups that drive BRD4 degradation by either DCAF16 or DCAF11. Unlike proteolysis-targeting chimeric molecules (PROTACs), the new compounds use a single small molecule ligand with a well-positioned cysteine-reactive group to induce protein degradation. The finding that nearly identical compounds can engage multiple ubiquitination pathways suggests that targeting cellular pathways that search for and eliminate chemically reactive proteins is a feasible avenue for converting existing small molecule drugs into protein degrader molecules.

Long-term longitudinal analysis of 4,187 participants reveals new insights into determinants of incident clonal hematopoiesis.

Clonal hematopoiesis (CH), characterized by blood cells predominantly originating from a single mutated hematopoietic stem cell, is linked to diverse aging-related diseases, including hematologic malignancy and atherosclerotic cardiovascular disease (ASCVD). While CH is common among older adults, the underlying factors driving its development are largely unknown. To address this, we performed whole-exome sequencing on 8,374 blood DNA samples collected from 4,187 Atherosclerosis Risk in Communities Study (ARIC) participants over a median follow-up of 21 years. During this period, 735 participants developed incident CH. We found that age at baseline, sex, and dyslipidemia significantly influence the incidence of CH, while ASCVD and other traditional risk factors for ASCVD did not exhibit such associations. Our study also revealed associations between germline genetic variants and incident CH, prioritizing genes in CH development. Our comprehensive longitudinal assessment yields novel insights into the factors contributing to incident CH in older adults.