Abstract: Acute lymphoblastic leukemia (ALL) is the most common malignancy in childhood. While improved multi-agent chemotherapy regimens with individualized risk stratification have led to increased survival rates of approximately 80 percent, 20 percent of patients respond poorly to therapy or relapse. Therefore, novel therapeutic avenues are urgently needed to improve treatment outcome, overcome resistance and reduce side effects. Failure to undergo cell death represents a key survival mechanism of cancer cells and results in drug resistance and clonal escape. Since inhibitor of apoptosis proteins (IAPs) are often overexpressed in malignant cells and their overexpression correlates with inferior survival rates, they provide an attractive molecular target for therapeutic intervention. Small molecule inhibitors have been developed that act as SMAC mimetics (SMs) to counteract the cell death inhibitory function of IAPs. SMs can activate and/or modulate cell death pathways, and are currently being evaluated in clinical trials. Their successful therapeutic implementation requires identification of patients who could benefit from a SM-based treatment regimen ideally before start of therapy. Here, we analyzed the intrinsic activity of two monovalent (AT406 and LCL161) and two bivalent (Birinapant or BV6) SMs on 29 unselected patient-derived pediatric precursor B-cell (BCP)-ALL samples and identified a subset of BCP-ALL primografts to be sensitive to SM treatment (n=8). When we compared gene expression of SM-sensitive (n=8) and SM-insensitive (n=6) patient-derived BCP-ALL samples, we identified a characteristic gene expression signature with 127 differentially regulated genes, amongst them upregulation of TNFRSF1A (TNFR1) in the SM-sensitive subset. In line with previous reports, we confirmed a critical role of the TNF/TNFR1-axis for SM-induced cell death in BCP-ALL by functional analysis. Expression of TNFRSF1A alone, however, did not correlate with sensitivity to SM-induced cell death indicating that TNFR1 is not the only factor regulating cell fate decisions in response to SM treatment. To identify potential biomarker genes for prediction of patient response to SM monotherapy in BCP-ALL, we compared differentially regulated genes of SM responders and non-responders from our cohort with data from a published cohort. Interestingly, we found 4 genes to overlap between these two cohorts. Of these 4 genes TSPAN7, FAM69C, and TNFRSF1A were upregulated whereas MTX2 was downregulated in SM-sensitive samples. The signature identified may reflect a particular TNF network. Analysis of expression levels of these 4 genes in BCP-ALL cell lines (Nalm6, Reh, UoCB6 and RS4;11) revealed that Reh cells, sensitive to SM-induced cell death, exhibited the biomarker profile of primograft sensitivity, i.e. upregulation of TSPAN7, FAM69C, TNFRSF1A and downregulation of MTX2. Nalm6 cells resembled the expression pattern of SM-insensitive samples with a downregulation of TSPAN7, FAM69C, TNFRSF1A and an upregulation of MTX2 and were resistant to SM-induced cell death. RS4;11 and UoCB6 cells showed no pattern. Based on these findings we hypothesized that the respective expression patterns of TSPAN7, FAM69C, TNFRSF1A and MTX2 could predict sensitivity to SMs. An extended screen of additional primary BCP-ALL samples for their expression levels of TSPAN7, FAM69C, TNFRSF1A and MTX2 and response to SMs substantiated this hypothesis. In summary, the subset of primary BCP-ALL samples with sensitivity to SMs is characterized by a gene signature with MTX2 low and TSPAN7, FAM69C and TNFRSF1A high. By using this expression profile, sensitivity to SMs in BCP-ALL could be identified in cell lines and additional primografts. Based on these results, we suggest the identified gene expression pattern as a biomarker for selecting patients to be treated by SM monotherapy in clinical trials. Disclosures No relevant conflicts of interest to declare.

Abstract: Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by pathologic immune activation in which prompt recognition and initiation of immune suppression is essential for survival. Children with HLH have many overlapping clinical features with critically ill children with sepsis and systemic inflammatory response syndrome (SIRS) in whom alternative therapies are indicated. To determine whether plasma biomarkers could differentiate HLH from other inflammatory conditions and to better define a core inflammatory signature of HLH, concentrations of inflammatory plasma proteins were compared in 40 patients with HLH to 47 pediatric patients with severe sepsis or SIRS. Fifteen of 135 analytes were significantly different in HLH plasma compared with SIRS/sepsis, including increased interferon-γ (IFN-γ)–regulated chemokines CXCL9, CXCL10, and CXCL11. Furthermore, a 2-analyte plasma protein classifier including CXCL9 and interleukin-6 was able to differentiate HLH from SIRS/sepsis. Gene expression in CD8+ T cells and activated monocytes from blood were also enriched for IFN-γ pathway signatures in peripheral blood cells from patients with HLH compared with SIRS/sepsis. This study identifies differential expression of inflammatory proteins as a diagnostic strategy to identify critically ill children with HLH, and comprehensive unbiased analysis of inflammatory plasma proteins and global gene expression demonstrates that IFN-γ signaling is uniquely elevated in HLH. In addition to demonstrating the ability of diagnostic criteria for HLH and sepsis or SIRS to identify groups with distinct inflammatory patterns, results from this study support the potential for prospective evaluation of inflammatory biomarkers to aid in diagnosis of and optimizing therapeutic strategies for children with distinctive hyperinflammatory syndromes.

Abstract: Coronary heart disease is a major cause of death in the western world. Although essential for successful recovery, reperfusion of ischemic myocardium is inevitably associated with reperfusion injury. To investigate a potential protective role of ADAMTS13, a protease cleaving von Willebrand factor multimers, during myocardial ischemia/reperfusion, we used a mouse model of acute myocardial infarction. We found that Adamts13−/− mice developed larger myocardial infarctions than wild-type control mice, whereas treatment of wild-type mice with recombinant human ADAMTS13 (rhADAMTS13) led to smaller infarctions. The protective effect of ADAMTS13 was further confirmed by a significant reduction of cardiac troponin-I release and less myocardial apoptosis in mice that received rhADAMTS13 compared with controls. Platelets adherent to the blood vessel wall were observed in few areas in the heart samples from mice treated with vehicle and were not detected in samples from mice treated with rhADAMTS13. However, we observed a 9-fold reduction in number of neutrophils infiltrating ischemic myocardium in mice that were treated with rhADAMTS13, suggesting a potent anti-inflammatory effect of ADAMTS13 during heart injury. Our data show that ADAMTS13 reduces myocardial ischemia/reperfusion injury in mice and indicate that rhADAMTS13 could be of therapeutic value to limit myocardial ischemia/reperfusion injury.

Abstract: On behalf of the Hokusai VTE Cancer Investigators The treatment of cancer-associated venous thromboembolism (VTE) is challenging because these patients are at increased risk of both recurrent VTE and major bleeding. Low-molecular-weight heparin (LMWH) treatment is standard care for these patients, but requires daily subcutaneous injections. Guidelines recommend LMWH treatment for 6 months, but the risk-benefit beyond this time is uncertain. Direct oral anticoagulants are used for the treatment of VTE in patients without cancer, but their role in patients with cancer- associated VTE is uncertain. In this randomized, open-label non-inferiority trial, cancer patients with acute symptomatic or incidental VTE were assigned to receive LMWH for a minimum of 5 days followed by the oral factor Xa inhibitor edoxaban at a dose of 60 mg once daily (or 30 mg once daily in patients with a creatinine clearance of 30 to 50 ml per minute or a body weight below 60 kg), or subcutaneous dalteparin 200 units per kg once daily for one month followed by 150 units per kg thereafter. Patients received these regimens for up to 12 months. The primary outcome was the composite of the first recurrent VTE or major bleeding event during follow-up for 12 months. Secondary outcomes included recurrent VTE and major bleeding analyzed separately, and survival free of recurrent VTE or major bleeding. The study hypothesis was that edoxaban would be noninferior to dalteparin for the primary outcome with an upper 95% confidence interval [CI] for the hazard ratio below 1.5, and a two-sided alpha of 0.05. All outcomes were independently adjudicated by a committee without knowledge of treatment allocation. This committee also assessed the clinical severity of major bleeding events using categorical criteria defined a priori (categories 1 to 4). From July 2015 through December 2016 a total of 1050 patients were enrolled at 114 centers in 13 countries; 525 were randomized to edoxaban and 525 to dalteparin. At entry, pulmonary embolism with or without deep-vein thrombosis was present in 657 patients (63%) while the remainder had isolated deep-vein thrombosis. Of the 1050 patents, 706 (67%) had symptomatic VTE and the rest were incidental. Active cancer at entry was present in 97% of the patients and 53% had metastatic disease. 1046 patients were included in the modified-intention-to-treat analysis. The primary outcome occurred in 67 of 522 patients (12.8%) in the edoxaban group compared with 71 of 524 patients (13.5%) in the dalteparin group (hazard ratio with edoxaban, 0.97; 95% CI, 0.70 to 1.36; P = 0.0056 for noninferiority) for a risk difference (edoxaban minus dalteparin) of - 0.7% (95% CI, - 4.8 to 3.4). The difference in risk for recurrent VTE was -3.8 % (95% CI, -7.1 to -0.4), whereas the corresponding difference in risk for major bleeding was 3.1% (95% CI, 0.5 to 5.7). The frequencies of severe major bleeding events (categories 3 and 4) were similar during treatment with edoxaban or dalteparin (12 patients in each group respectively). Survival at 12 months free of recurrent VTE and major bleeding in the edoxaban and dalteparin groups was similar (55.0% and 56.5% respectively). Oral edoxaban for up to 12 months is noninferior to subcutaneous dalteparin for the treatment of cancer-associated VTE. Disclosures Raskob: BMS: Consultancy, Honoraria; Eli Lilly: Consultancy; Janssen: Consultancy; Johnson and Johnson: Consultancy; Pfizer: Consultancy, Honoraria; Portola: Consultancy; Boehringer-Ingelheim: Consultancy; Medscape: Honoraria; Bayer Healthcare: Consultancy; Daiichi Sankyo: Consultancy, Honoraria. Van Es:Daiichi Sankyo: Honoraria; Pfizer: Honoraria. Verhamme:Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Bayer Healthcare: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria; Boehringer Ingelheim: Consultancy, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Portola: Consultancy; Medscape: Honoraria; Leo: Honoraria, Research Funding; Sanofi Aventis: Research Funding; Medtronic: Honoraria, Membership on an entity's Board of Directors or advisory committees. Carrier:Daiichi Sankyo: Consultancy, Honoraria; BMS: Consultancy, Research Funding; Leo: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria. Di Nisio:Daiichi: Consultancy, Honoraria. Garcia:Daiichi Sankyo: Honoraria, Research Funding; BMS: Consultancy; Boehringer Ingelheim: Consultancy; Janssen: Consultancy, Research Funding; Pfizer: Consultancy, Honoraria; Medscape: Honoraria; Incyte: Consultancy, Honoraria, Research Funding. Grosso:Daiichi Sankyo: Employment. Kakkar:Daiichi Sankyo: Consultancy, Honoraria; Bayer Healthcare: Consultancy, Research Funding; Boehringer Ingelheim: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Sanofi SA: Consultancy, Honoraria; Verseon: Consultancy, Honoraria. Kovacs:Daiichi Sankyo: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Bayer: Honoraria; Bristol Myers Squibb: Research Funding. Mercuri:Daiichi Sankyo: Employment, Patents & Royalties: pending properties of edoxaban . Meyer:BMS Pfizer: Research Funding; Leo: Other: travel support; Stago: Other: travel support. Segers:Ionis: Research Funding; Daiichi Sankyo: Research Funding; Janssen: Research Funding. Shi:Daiichi Sankyo: Employment. Wang:Daiichi Sankyo: Honoraria. Yeo:Daiichi Sankyo: Honoraria, Research Funding; Bayer Healthcare: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Boehringer Ingelheim: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Leo: Consultancy, Honoraria. Zhang:Daiichi Sankyo: Employment. Zwicker:Daiichi Sankyo: Honoraria; Quercegen Pharma: Research Funding; Parexel: Consultancy. Weitz:Daiichi-Sankyo: Consultancy, Honoraria; Ionis Pharmaceuticals: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Novartis Pharmaceuticals: Consultancy, Honoraria; Merck & Co., Inc.: Consultancy, Honoraria; Pfizer, Inc.: Consultancy, Honoraria; Portola Pharmaceuticals: Consultancy, Honoraria; Bristol-Myers Squibb: Consultancy, Honoraria; Medscape: Consultancy, Honoraria; Boehringer Ingelheim: Consultancy; Bayer HealthCare Pharmaceuticals: Consultancy, Honoraria. Büller:Daiichi Sankyo: Consultancy, Honoraria; Bayer: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Boehringer Ingelheim: Consultancy, Honoraria; Portola: Consultancy; Medscape: Honoraria; Eli Lilly: Consultancy; Sanofi Aventis: Consultancy; Ionis: Consultancy.

Abstract: Somatic missense mutations of BTG1 are exclusive to germinal center (GC)-derived B cell lymphomas (~12% of DLBCLs) and are most prevalent in ABC-DLBCL (p=0.0184 vs GCB-DLBCL), particularly in the MCD/cluster 5 subtype, which features extranodal dissemination and unfavorable outcome. However, the relevance, mechanism of action and biological contribution of BTG1 mutations have not been studied. Using a rigorous genomic covariate analysis, we identified BTG1 mutations as a top genetic driver in DLBCL. Furthermore, molecular dynamics simulations indicated that BTG1 recurrent mutations, including the most frequent Q36H, disrupted the protein structure, with likely deleterious functional consequences. To investigate the effect of BTG1 mutation in GC B cells, we generated a conditional Btg1Q36H knock in mouse crossed to the B cell specific Cd19Cre line. Surprisingly, there was no apparent phenotype in GC B cells or other B cell populations. However, placing Btg1 Q36H and WT GC B cells in competition within the same mouse through adoptive transfer revealed a dramatic competitive advantage of Btg1 Q36H cells, virtually taking over the GC reaction. To gain further insight into this striking fitness advantage, we performed RNAseq in Btg1 Q36H GCs, which showed marked enrichment for genes induced in positively selected GC B cells, including MYC targets and biosynthetic pathways. The same genes were also enriched in BTG1 mutant DLBCL patients in 2 independent cohorts. Furthermore, Btg1 Q36H GC B cells displayed greater RNA content and cell size, reflecting increased fitness. Positive selection normally triggers a brief Myc pulse in GC B cells. We therefore crossed our Btg1Q36H mice to the MycGFPprotein fusion reporter and observed higher proportion of Myc GFP+ cells in Btg1 Q36H GCs. For mechanistic studies, we generated isogenic BTG1 Q36H or BTG1 WT human DLBCL cell lines. BTG1 Q36H cells exhibited enrichment for the same positively selected GC B and MYC target genes, as well as greater RNA content and cell size. BTG1 family members were suggested to interact with RNA. Performing RNA-immunoprecipitation, we discovered that ~800 transcripts associated with BTG1 WT, but not BTG1 Q36H. Notably, these corresponded to the same positively selected GC B and MYC target genes, including MYC itself. BTG1 was shown to regulate mRNA stability in other cell types. However, BTG1 Q36H did not alter MYC mRNA stability and instead facilitated MYC protein synthesis, thus disrupting a novel GC context-specific checkpoint mechanism, whereby BTG1 normally attenuates spurious MYC translation to tightly restrict fitness potential. In GC B cells, Myc induction coincides with S phase entry, but G2/M progression requires re-entry into the proliferative dark zone. To characterize GC dynamics in vivo, we performed targeted single cell RNAseq in competing Btg1 Q36H and WT GC B cells and noted earlier and higher proportion of positively selected Btg1 Q36H GC B cells having committed to G2/M and the proliferative program. We confirmed faster S phase completion in competing Btg1 Q36H GC B cells by in vivo EdU/BrdU labelling and greater re-entry into the proliferative dark zone by in vivo antigen delivery to synchronize GC B cells at the time of positive selection. Given that MCD-DLBCLs express high levels of BCL2, we crossed our Btg1Q36H mice to the VavP-Bcl2 model. As compared to VavP-Bcl2, VavP-Bcl2+Btg1 Q36H mice displayed shorter survival (p=0.0005), earlier onset of lymphoma, dysplastic B cell infiltration into non lymphoid organs and they contained highly mutated, selected and clonal tumor B cells. Moribund VavP-Bcl2+Btg1 Q36H mice uniquely featured sheets of large, immunoblastic lymphoma cells, characteristic of ABC-DLBCLs. Most notably, examining ABC-DLBCLs from 5 independent cohorts showed inferior clinical outcome for BTG1 mutant patients (p=0.0011) and independent association of BTG1 mutation with inferior overall survival by multivariable Cox regression (p=0.0190). Collectively, we find that BTG1 mutations mediate lymphomagenesis through an entirely novel mechanism of action that recapitulates the embryonic MYC-dependent "super-competitive" phenotype originally described in Drosophila imaginal disc cells. In the GC, "super-competition" is provided by BTG1 mutation via a subtle acceleration of MYC induction and GC dynamics, conferring dramatic fitness and the potential to transform into aggressive lymphomas. Disclosures Hoehn: Prellis Biologics: Consultancy. Elemento: Janssen: Research Funding; Freenome: Consultancy, Other: Current equity holder in a privately-held company; Volastra Therapeutics: Consultancy, Other: Current equity holder, Research Funding; Owkin: Consultancy, Other: Current equity holder; Champions Oncology: Consultancy; One Three Biotech: Consultancy, Other: Current equity holder; Eli Lilly: Research Funding; AstraZeneca: Research Funding; Johnson and Johnson: Research Funding. Scott: NanoString Technologies: Patents & Royalties: Patent describing measuring the proliferation signature in MCL using gene expression profiling.; BC Cancer: Patents & Royalties: Patent describing assigning DLBCL COO by gene expression profiling--licensed to NanoString Technologies. Patent describing measuring the proliferation signature in MCL using gene expression profiling. ; AstraZeneca: Consultancy; Abbvie: Consultancy; Celgene: Consultancy; Incyte: Consultancy; Janssen: Consultancy, Research Funding; Rich/Genentech: Research Funding. Melnick: Constellation: Consultancy; Epizyme: Consultancy; Daiichi Sankyo: Research Funding; Sanofi: Research Funding; Janssen Pharmaceuticals: Research Funding; KDAC Pharma: Membership on an entity's Board of Directors or advisory committees.

Abstract: Abstract 548 Background: Excellent results are seen in HL patients with stage I-IIA disease treated with CMT that includes involved field radiation therapy (IFRT), as per GHSG HD10 [Engert NEJM 2010] and HD11 [Eich JCO 2010] or with ABVD alone, as per NCIC CTG/ECOG HD.6 [Meyer NEJM 2012] . Comparing these reports is complicated by differences in eligibility, staging, endpoints and follow-up duration. Our objectives were to use individual patient data from these 3 trials to compare outcomes after standardizing patient eligibility. Methods: Potentially eligible patients were those treated with 2 cycles of ABVD/20 Gy IFRT on GHSG HD10, 4 cycles of ABVD/30 Gy IFRT on GHSG HD11 and 4–6 cycles of ABVD alone on NCIC CTG HD.6. To be included in analysis, patients were required to be eligible for GHSG HD10 or HD11 and NCIC CTG HD.6. Eligibility of HD10/11 patients for HD.6 was determined by the GHSG by applying HD.6 protocol criteria. Anonymized individual patient data of eligible patients was forwarded to NCIC CTG along with reasons for ineligibility of other patients. Eligibility of HD.6 patients for HD10/11 was determined by NCIC CTG by applying HD10/11 protocol criteria with listing of reasons for ineligibility. Eligibility questions were resolved through consensus. Patients meeting mutually inclusive eligibility criteria were stratified by a propensity score (PSc) based on age, gender, stage, ESR and number of disease sites. Outcomes were based on Revised Response Criteria for Malignant Lymphoma [Cheson JCO 2007]; no trial incorporated PET scanning. The primary outcome measure was progression-free survival (PFS), which includes disease progression and death from any cause as events. Secondary outcomes included overall survival (OS) and time to progression (TTP), which includes disease progression and death from HL as events. A priori subsets for analysis included eligibility for HD10 vs. HD11 and CR/CRu status after 2 cycles of ABVD among those eligible for both HD10 and HD.6. Cox models stratified by PSc were used to obtain hazard ratios (HR) for PFS, OS and TTP; HRs are expressed as GHSG HD10/11 relative to NCIC CTG HD.6. Results: Of 655 patients eligible for selected arms of HD10/HD11, 406 were eligible when applying the inclusion criteria for HD.6 (HD10 = 254; HD11 = 152). Most common reasons for ineligibility were B symptoms (n=127) and large mediastinal mass (n=80). Of 196 HD.6 patients, 182 were eligible for HD10 (n=110) or HD11 (n=71; 1 patient not assignable). Median follow-up for both HD10 and HD11 was 91 months and for HD.6 was 134 months. Results that include all eligible patients are shown in table; TTP was superior in GHSG trials. In the HD10/HD.6 subset, 8-yr PFS was 87% vs 82% (HR=0.58; 95% CI=0.32–1.05) and OS was 96% vs 94% (HR=0.65; 95% CI=0.25–1.72). Among those with CR/CRu after 2 cycles of ABVD, 8-yr PFS was 87% vs 95% (HR=2.8; 95% CI=0.64–12.5) and OS was 96% vs 100%. Among those without CR/CRu after 2 cycles of ABVD, 8-yr PFS was 88% vs 74% (HR=0.35; 95% CI=0.16–0.79) and OS was 95% vs 91% (HR=0.42; 95% CI=0.12–1.44). In the HD11/HD.6 subset, 8-yr PFS was 91% vs 91% (HR=1.15; 95% CI=0.45–2.97) and OS was 95% vs 97% (HR=2.03; 95% CI=0.53–7.79). Among 406 HD10/11 patients, there have been 19 deaths; 7 were attributed to HL or immediate treatment toxicity and 12 to other causes. Among 182 HD.6 patients, there have been 10 deaths; 5 were attributed to HL or immediate treatment toxicity and 5 to other causes. Conclusions: In this non-randomized cohort comparison, TTP was superior and PFS trended to being superior in patients treated with CMT on HD10/11. No differences in OS are evident; longer follow-up is needed to assess trade-offs between disease control and risks of late treatment effects. The role of IFRT in attaining long-term disease control appears to be especially important in those who do not attain CR/CRu status after 2 cycles of ABVD. As outcomes of those eligible for HD10/HD.6 and treated with 4–6 cycles of ABVD alone were excellent if CR/CRu was attained after 2 cycles of ABVD, these data support more recent strategies evaluating response-adapted approaches for use of IFRT. Disclosures: Borchmann: Millenium The Takeda Oncology Company: Research Funding; Takeda Pharma GmbH: Travel Grants, Travel Grants Other. Horning:Genentech: Employment; Roche: Equity Ownership. Engert:Millenium The Takeda Oncology Company: Honoraria. Meyer:Lilly: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Amgen Canada: Research Funding; Ariad Pharma: Research Funding; Astex Therapeutics: Research Funding; AstraZeneca: Research Funding; Bristol-Myers Squibb: Research Funding; GlaxoSmithKline: Research Funding; Janssen Ortho: Research Funding; Novartis: Research Funding; Oncothyreon: Research Funding; Pfizer: Research Funding; Roche: Research Funding; Sanofi-Aventis: Research Funding; Schering Canada: Research Funding.

Abstract: Introduction: Telomere biology disorders (TBD) are caused by mutations affecting proper telomere maintenance resulting in premature telomere shortening. Telomere length (TL) assessment is currently being used for screening and diagnosis of TBD of which Dyskeratosis congenita (DKC) is the most prominent TBD subtype typically found in children and adolescents. In adults, TBDs are characterized by a broad spectrum of more "cryptic" diverging mono- or oligosymptomatic clinical manifestations such as bone marrow failure (BMF), hepatopathy or interstitial lung disease (ILD). However, despite growing general clinical awareness and exertion of improved TL screening strategies, insufficient data are available about the clinical course of adult, late-onset TBDs. Here, we present a series of 41 consecutive adult TBD cases from 2014 to 2021 identified through the Aachen Telomeropathy registry. Methods and Patients: Median follow-up of the cohort was 2.0 (range 0-6.2) years. In 39/41 patients TBD diagnosis was established based on coexistence of the following three criteria: 1.) Identification of pathogenic variant in a known TBD-related gene via next-generation panel sequencing (NGS) or sequential whole exome sequencing (WES). 2.) The presence of prematurely shortened TL below the 1% percentile (39/41) or 5% percentile (2/41) in the lymphocyte gate detected by flow-FISH and 3.) the presence of BMF or ILD as predominant clinical manifestation. In 2 out of 41 cases, WES did not identify a definitive pathogenic variant. Here, diagnosis of TBD was established due to short telomere below the 1% percentile, BMF and the presence of typical DKC stigmata, other TBD symptoms and a positive family history. Results: Mean age of our cohort was 35.9 ± 17.6 years. 49% (n=20) of patients were females. Results of the genetic screening revealed heterozygous pathogenic variants in TERC (n=14) and TERT (n=11) as the most frequent variants, followed by RTEL1 (n=6), TIN2 (n=1), CTC1 (n=1) and DKC1 (n=1). Homozygous or compound heterozygous pathogenic variants were found for CTC1 (n=2), NHP2 (n=2) or TCAB1 (n=1). 46% (n=19) of patients had a positive family history. BMF was the most frequent symptom with 93% (n=38) presenting with leukopenia, 78% (n=32) with anemia and 76% (n=31) with thrombocytopenia. ILD was suspected/confirmed clinically in 44% (n=18), hepatopathies in 29% (n=12) and cancer in 12% of the patients in past medical history (n=5, liposarcoma, breast cancer, Hodgkin lymphoma, diffuse large B-cell lymphoma, endometrial cancer). Symptoms of the typical DKC triad (leukoplakia, nail dystrophy, abnormal skin pigmentation) were observed in 41% (n=17). Of those, 76% (13/17) presented with only one or two clinical signs. Based on past medical history, the onset of first TBD manifestation was observed at a mean age of 26.9 ± 18.3 years. Time from first symptom observed to the diagnosis of TBD was 8.2 ± 9.5 years. 22% (n=9) patients died during follow-up with mean time of 11.7 ± 10.1 years from first manifestation of TBD to death. Regarding treatment, 39% (n=16) were listed for allogeneic stem cell transplantation (allo Tx), but only 38% (6/16) of these eventually received allo Tx. Immunosuppressive therapy with ATG and CSA was carried out in 12% (n=5) of the patients with no patient responding to treatment. Eltrombopag was given in 5% of cases (n=2) without response. 15% (n=6) received androgen treatment with danazol as the most frequently used drug in five of the six reported cases. All patients showed a response at least in one hematological lineage. Conclusions: Our data support the notion that despite the recent progress in screening and genetic diagnostics, late-onset TBD is still frequently underdiagnosed with several years from first manifestation of disease to diagnosis. Implementation of routine screening for TBD might improve the rate of correct TBD diagnosis and could help to avoid ineffective treatments. Disclosures Beier: Pfizer: Membership on an entity's Board of Directors or advisory committees; Jazz: Other: Travel reembursement; Alexion: Speakers Bureau. Roeth: Novartis: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Kira: Consultancy, Honoraria; Bioverativ, a Sanofi company: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Research Funding; Apellis Pharmaceuticals: Consultancy, Honoraria; Alexion Pharmaceuticals Inc.: Consultancy, Honoraria. Platzbecker: AbbVie: Honoraria; Novartis: Honoraria; Celgene/BMS: Honoraria; Janssen: Honoraria; Takeda: Honoraria; Geron: Honoraria. Radsak: Novartis: Consultancy, Honoraria, Other: e.g. travel support; JAZZ: Other: e.g. travel support; Takeda: Consultancy, Honoraria; Celgene/BMS: Consultancy, Honoraria, Other: e.g. travel support; Daiichi Sankyo: Consultancy, Honoraria, Other: e.g. travel support; Astellas: Other: e.g. travel support; Incyte: Consultancy, Honoraria; Corat: Consultancy, Honoraria; Cogent Biosciences: Consultancy, Honoraria; TEVA: Consultancy, Honoraria; Otsuka: Consultancy, Honoraria; Amgen: Other: e.g. travel support; Abbvie: Other: e.g. travel support. Schafhausen: Blueprint Medicines: Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Swedish Orphan Biovitrum AB: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Corbacioglu: Gentium/Jazz Pharmaceuticals: Consultancy, Honoraria. Heuser: AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria; BergenBio: Research Funding; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer Pharma AG: Research Funding; Astellas: Research Funding; Karyopharm: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolremo: Membership on an entity's Board of Directors or advisory committees. Koschmieder: Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Karthos: Other: Travel support; Shire: Honoraria, Other; CTI: Membership on an entity's Board of Directors or advisory committees, Other; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Geron: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Alexion: Other: Travel support; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support); Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Baxalta: Membership on an entity's Board of Directors or advisory committees, Other; Abbvie: Other: Travel support; Image Biosciences: Other: Travel support; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; AOP Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: (e.g. travel support), Research Funding. Panse: Blueprint Medicines: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Chugai: Speakers Bureau; Pfizer: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Alexion: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Grunenthal: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Apellis Pharmaceuticals: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Isfort: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel reimbursement; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria; Hexal: Other: Travel reimbursement; Mundipharma: Other: Travel reimbursement; Amgen: Other: Travel reimbursement; Roche: Other: Travel reimbursement; Alexion: Other: Travel reimbursement. Brummendorf: Bristol Myers: Research Funding; Janssen: Honoraria; Novartis: Honoraria, Patents & Royalties, Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Repeat Diagnostics: Research Funding; Takepart Media: Honoraria.

Abstract: Covalent Bruton tyrosine kinase (BTK) inhibitors, such as ibrutinib, have proven to be highly beneficial in the treatment of chronic lymphocytic leukemia (CLL). Interestingly, the off-target inhibition of IL-2-inducible T-cell kinase (ITK) by ibrutinib may also play a role in modulating the tumor microenvironment, potentially enhancing the treatment benefit. However, resistance to covalently binding BTK inhibitors can develop as the result of a mutation in cysteine 481 of BTK (C481S), which prevents irreversible binding of the drugs. In the present study we performed preclinical characterization of vecabrutinib, a next-generation noncovalent BTK inhibitor that has ITK-inhibitory properties similar to those of ibrutinib. Unlike ibrutinib and other covalent BTK inhibitors, vecabrutinib showed retention of the inhibitory effect on C481S BTK mutants in vitro, similar to that of wild-type BTK. In the murine Eμ-TCL1 adoptive transfer model, vecabrutinib reduced tumor burden and significantly improved survival. Vecabrutinib treatment led to a decrease in CD8+ effector and memory T-cell populations, whereas the naive populations were increased. Of importance, vecabrutinib treatment significantly reduced the frequency of regulatory CD4+ T cells in vivo. Unlike ibrutinib, vecabrutinib treatment showed minimal adverse impact on the activation and proliferation of isolated T cells. Lastly, combination treatment with vecabrutinib and venetoclax augmented treatment efficacy, significantly improved survival, and led to favorable reprogramming of the microenvironment in the murine Eμ-TCL1 model. Thus, noncovalent BTK/ITK inhibitors, such as vecabrutinib, may be efficacious in C481S BTK mutant CLL while preserving the T-cell immunomodulatory function of ibrutinib.

Abstract: First-line therapy of acute myeloid leukemia (AML) consists of combinations of cytarabine and an anthracycline. While initial complete remissions are frequent, most patients succumb to resistant disease underlining the need for novel, more effective agents. The most striking progress in AML therapy was achieved by targeting the nuclear receptor RARα with ATRA. Research in our laboratory has demonstrated that the novel synthetic triterpenoid CDDO (2-cyano-3,12- dioxooleana-1,9-dien-28-oic acid) and its more active C28 methyl ester derivative CDDO-Me inhibit growth and induce apoptosis in a variety of cancers including AML, CLL and blast crisis CML. CDDO and to a much higher degree CDDO-Me are potent activators of the nuclear transcription factor Peroxisome Proliferator-Activated Receptor gamma (PPARγ). In a mammalian two-hybrid assay, the CDDO and CDDO-Me induced activation of PPARγ was associated with a marked increase in multiple coactivator recruitment (SRC-1, SRC-2, SRC-3, TRAP220/DRIP205, CARM-1 and PGC-1) that is qualitatively different from that induced by other PPARγ ligands. CDDO induced a higher degree of myelo-monocytic differentiation in DRIP205-overexpressing HL-60 cells suggesting that high cellular levels of DRIP205 co-activator modulate differentiation response to PPARγ ligation. CDDO induced p21 mRNA and protein in leukemic cells and transactivation of the p21 promoter in a p53-independent fashion. We have recently identified the PPARγ-independent depletion of mitochondrial glutathione (GSHm) as a novel mechanism of action resulting in redox disbalance and mitochondrial damage as mechanisms of pro-apoptotic effects of CDDO and CDDO-Me. Gene expression studies using cDNA arrays demonstrate that CDDO induces genes involved in the antioxidant response (AR) including phase II detoxifying enzymes (glutamate cysteine ligase, GSH transferase, etc.) and antioxidant enzymes (heme oxygenase 1, thioredoxin reductase). Cotreatment with the GSH precursor, n-acetyl cystein prevented apoptosis and loss of viability induced by CDDOs, whereas alkylation of intracellular thiols by diethylmaleate decreased the accumulation of a biotinylated derivative of CDDO, TP-301, in U937 leukemic cells suggesting that intracellular reduced thiols are functional targets of CDDO and its derivatives. The in vivo studies using liposomal CDDO-Me in a conditional leukemia model demonstrated significant reduction of leukemia burden as measured by bioluminescence imaging and prolongation of survival. Based on the ample pre-clinical evidence of anti-leukemia effects and on the favorable PK/toxicity profile of the parental compound, CDDO will enter Phase I clinical trials in hematologic malignancies in 3Q 2005 and CDDO-Me in 1Q 2006.