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Background: Aggressive hematological malignancies in relapsed/refractory setting bear a dire prognosis with low cure rates and short survival. Matching these patients to therapies is challenged by complexity due to spatial and temporal tumor evolution and incomplete understanding of genotype to phenotype correlations. Direct functional testing could address these impediments. The EXALT trial is an interventional, one-arm study designed to assess the clinical value of next generation functional drug screening (ngFDS). An interim analysis on 17 patients suggested a clinical benefit (Snijder et al., Lancet Hematol. 2017). Methods: We applied image-based ngFDS to quantify differential ex-vivo sensitivity of primary patient tumor cells to respective non-tumor cells towards 136 small molecule drugs, including EMA approved for any indication or experimental. We screened bone marrow, peripheral blood or lymph node material from 143 patients who suffered from late stage aggressive hematological malignancies (acute leukemias, aggressive B- and T-cell lymphomas) , discussed the results in a multidisciplinary tumor board and recommended treatments to physicians (A). The primary endpoint of this study was the percentage of patients reaching a PFS-ratio (PFS(ngFDS treatment)/PFS(previous treatment)) of ≥1.3 with an H0 hypothesis < 15% patients. The secondary endpoint was overall response rate (ORR) defined as proportion of patients reaching complete remission (CR) or partial remission (PR). Additionally, we performed a post hoc analysis to evaluate the matching of ngFDS to drugs used in actual treatment (matching score of received treatment). Results: 56 (39%) patients were evaluable and treated according to ngFDS based recommendations. With 30 of 56 (54%) ngFDS guided patients experiencing a PFS ratio of ≥1.3, the primary study endpoint was reached. 11 patients (37%) had ongoing response at censoring date (B). The median follow-up was 718 days. The median number of days from sampling to treatment was 21 (range 4-77). The ngFDS treatment regimens consisted of a median of 2 drugs (range: 1-6). ORR was 55% for all evaluable ngFDS treated patients, 60% for the lymphoid subgroup and 41% for the myeloid subgroup. Patients on ngFDS guided treatment with performance status ECOG ≤ 1 had a median PFS of 207 days compared to a median PFS of 29 days for patients with higher ECOG (p < 0.001, C). 24 of 39 (62%) patients with ECOG ≤ 1 had a PFS ratio of ≥1.3 (D). In disease specific subgroup analysis median PFS of T-cell lymphoma patients was 235 days versus 60 days for B-cell lymphoma patients (p = 0.018, E). Age (≤60 vs. >60), sex, lineage (myeloid vs. lymphoid), number of previous treatment lines (≤2 vs. >2), and clinical presentation (leukemia vs. lymphoma) did not have an impact on PFS of ngFDS guided treatment. Post hoc analysis including additional 17 non-ngFDS treated patients demonstrated that only patients receiving treatment with a positive ngFDS matching score demonstrated clinical benefit (HR: 0.53, p=0.005; vs. HR: 1.4, p=0.4). ngFDS matched treatments resulted in higher PFS for patients with tumor samples that had a cancer cell fraction of 10-50% in comparison to patients with samples of lower or higher cancer cell percentage (HR:0.35, p=0.01). Conclusion: ngFDS could be integrated in the routine clinical work flow. ngFDS guided treatments led to high rates of PFS prolongation compared to previous treatments of individual patients. ngFDS guided treatment is feasible and effective in patients with late stage aggressive hematological malignancies. These results prompted a prospective randomized trial comparing treatment guidance based on ngFDS or comprehensive genomic profiling or physician's choice (EXALT-2 trial, NCT04470947). Figure Disclosures Vladimer: Allcyte GmbH: Current Employment, Current equity holder in private company, Other: Founder. Jaeger:Karyopharm: Honoraria; Amgen: Honoraria; Gilead: Honoraria, Research Funding; BMS/Celgene: Consultancy, Honoraria, Research Funding; True North: Honoraria, Research Funding; Miltenyi: Consultancy, Honoraria; CDR Life AG: Consultancy, Research Funding; F. Hoffmann-La Roche: Honoraria, Research Funding; Infinity: Honoraria; Takeda: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; AbbVie: Honoraria. Krall:Allcyte GmbH: Current Employment, Current equity holder in private company, Other: Founder. Valent:Allcyte GmbH: Research Funding; Cellgene: Honoraria, Research Funding; Pfizer: Honoraria. Wolf:Celgene: Honoraria, Research Funding. Zielinski:MSD: Consultancy, Honoraria, Speakers Bureau; Roche: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Imugene: Consultancy, Honoraria, Speakers Bureau; Ariad: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau; Merrimack: Consultancy, Honoraria, Speakers Bureau; Merck KGaA: Consultancy, Honoraria, Speakers Bureau; Fibrogen: Consultancy, Honoraria, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; Tesaro: Consultancy, Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; Servier: Consultancy, Honoraria, Speakers Bureau; Shire: Consultancy, Honoraria, Speakers Bureau; Eli Lilly: Consultancy, Honoraria, Speakers Bureau; Athenex: Consultancy, Honoraria, Speakers Bureau. Superti-Furga:Allcyte GmbH: Current equity holder in private company, Other: Founder. Snijder:Allcyte GmbH: Current equity holder in private company, Other: Founder. Staber:Roche: Consultancy, Honoraria, Research Funding; Astra Zeneca: Consultancy, Honoraria; Celgene/ BMS: Consultancy, Honoraria; msd: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria.

The blood system serves as a key model for cell differentiation and cancer. It is orchestrated by precise spatiotemporal expression of crucial transcription factors. One of the key master regulators in the hematopoietic systems is PU.1. Reduced levels of PU.1 are characteristic for human acute myeloid leukemia (AML) and are known to induce AML in mouse models. Here, we show that transcriptional downregulation of PU.1 is an active process involving an alternative promoter in intron 3 that is induced by RUNX transcription factors driving noncoding antisense transcription. Core-binding factor (CBF) fusions RUNX1-ETO and CBFβ-MYH11 in t(8;21) and inv(16) AML, respectively, activate the PU.1 antisense promoter that results in a shift from sense toward antisense transcription and myeloid differentiation blockade. In patients with CBF-AML, we found that an elevated antisense/sense transcript and promoter accessibility ratio represents a hallmark compared with normal karyotype AML or healthy CD34+ cells. Competitive interaction of an enhancer with the proximal or the antisense promoter forms a binary on/off switch for either myeloid or T-cell development. Leukemic CBF fusions thus use a physiological mechanism used by T cells to decrease sense transcription. Our study is the first example of a sense/antisense promoter competition as a crucial functional switch for gene expression perturbation by oncogenes. Hence, this disease mechanism reveals a previously unknown Achilles heel for future precise therapeutic targeting of oncogene-induced chromatin remodeling.

Introduction: Alterations of core binding factors (CBF), Runx1 and CBFβ are frequent mutational targets in acute myeloid leukemia (AML). Chromosomal translocations t(8;21)(q22;q22) and inv(16)(p13q22), creating the fusion proteins RUNX1-ETO and CBFβ-MYH11 respectively, account for 15% and thus the largest sub-group of AML called CBF-AML. CBF oncogenes induce global changes in chromatin structure and gene regulation, which lead to differentiation blockade. A critical leukemic event could be the inactivation of PU.1 transcription factor. Normal myeloid differentiation needs PU.1 levels to increase, failure to do so leads to a stop of differentiation and AML development. In contrast, T-cell differentiation requires PU.1 to be completely switched off. The exact mechanism of PU.1 suppression, physiological for T-lymphopoiesis or pathological for leukemia, remains elusive. Results: We assessed the activation of the PU.1 locus throughout human hematopoietic differentiation stages using the assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and reverse-transcription quantitative polymerase chain reaction (RT-qPCR). Interestingly, we observed high accessibility of a previously identified antisense promoter (AsPr) in intron 3 and antisense transcript (asRNA) expression during early lymphopoiesis which preceded locus shutdown in T cells. The ratio of AsPr/PrPr accessibility and of antisense/sense transcription clearly indicated cellular fate during hematopoiesis (Figure 1A). T-lymphoid differentiation was related to the timely expression of RUNX transcription factors. RUNX1, RUNX3, and the CBF fusions RUNX1-ETO and CBFβ-MYH11 were capable to transactivate PU.1 AsPr. In CBF-AML patient samples we strikingly found elevated asRNA/mRNA ratios compared to normal karyotype AML or healthy CD34+ cells (Figure 1B) and increased AsPr/PrPr ratios unsing DNaseI-seq data in RUNX1-ETO AML patients. Functionally we found that PU.1 asRNA depletion in t(8;21) xenografted immune-deficient (NOD/SCID) mice restored a normal survival (Figure 1C) demonstrating that PU.1 antisense transcripts are required for CBF leukemia outgrow in vivo. To further dissect the mechanism of how CBFs could drive PU.1 antisense transcription we applied active RNA polymerase mapping (PRO-seq) and chromatin accessibility (ATAC-seq) and found a shift from PU.1 antisense to sense transcription after RUNX1-ETO depletion. Using chromosomal conformation capture sequencing (3C, Hi-C and CHiC) in T-lymphoid, myeloid and RUNX1-ETO cells combined with transcript quantification we observed that competitive interaction of an upstream enhancer with the proximal or the antisense promoter are at the heart of differential PU.1 expression during myeloid and T-cell development (Figure 2A). Leukemic CBF fusions thus utilize a physiologic mechanism employed by T-cells to decrease sense PU.1 transcription (Figure 2B). Conclusion: The data suggest that silencing transcription factor PU.1 is an active process that requires a specific chromosome formation that is induced by CBF fusions. Sense/antisense promoter competition represents a crucial functional switch for gene expression perturbation by oncogenes and provide a potential strategy for future precise therapeutic targeting of oncogene-induced chromatin remodeling. Disclosures Valent: Allcyte GmbH: Research Funding; Pfizer: Honoraria; Cellgene: Honoraria, Research Funding. Staber:Roche: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Astra Zeneca: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; msd: Consultancy, Honoraria; Celgene/ BMS: Consultancy, Honoraria.

Background Patients with refractory or relapsed haematological malignancies have few treatment options and short survival times. Identification of effective therapies with genomic-based precision medicine is hampered by intratumour heterogeneity and incomplete understanding of the contribution of various mutations within specific cancer phenotypes. Ex-vivo drug-response profiling in patient biopsies might aid effective treatment identification; however, proof of its clinical utility is limited. Methods We investigated the feasibility and clinical impact of multiparametric, single-cell, drug-response profiling in patient biopsies by immunofluorescence, automated microscopy, and image analysis, an approach we call pharmacoscopy. First, the ability of pharmacoscopy to separate responders from non-responders was evaluated retrospectively for a cohort of 20 newly diagnosed and previously untreated patients with acute myeloid leukaemia. Next, 48 patients with aggressive haematological malignancies were prospectively evaluated for pharmacoscopy-guided treatment, of whom 17 could receive the treatment. The primary endpoint was progression-free survival in pharmacoscopy-treated patients, as compared with their own progression-free survival for the most recent regimen on which they had progressive disease. This trial is ongoing and registered with ClinicalTrials.gov, number NCT03096821. Findings Pharmacoscopy retrospectively predicted the clinical response of 20 acute myeloid leukaemia patients to initial therapy with 88·1% accuracy. In this interim analysis, 15 (88%) of 17 patients receiving pharmacoscopy-guided treatment had an overall response compared with four (24%) of 17 patients with their most recent regimen (odds ratio 24·38 [95% CI 3·99–125·4], p=0·0013). 12 (71%) of 17 patients had a progression-free survival ratio of 1·3 or higher, and median progression-free survival increased by four times, from 5·7 (95% CI 4·1–12·1) weeks to 22·6 (7·4–34·0) weeks (hazard ratio 3·14 [95% CI 1·37–7·22], p=0·0075). Interpretation Routine clinical integration of pharmacoscopy for treatment selection is technically feasible, and led to improved treatment of patients with aggressive refractory haematological malignancies in an initial patient cohort, warranting further investigation. Funding Austrian Academy of Sciences; European Research Council; Austrian Science Fund; Austrian Federal Ministry of Science, Research and Economy; National Foundation for Research, Technology and Development; Anniversary Fund of the Austrian National Bank; MPN Research Foundation; European Molecular Biology Organization; and Swiss National Science Foundation., The Lancet Haematology, 4 (12), ISSN:2352-3026

Background. Patients with aggressive hematologic malignancies failing at least two lines of therapy are without further standard treatment options and have a poor prognosis. Identifying effective therapies with genomic-based precision medicine is hampered by intratumor heterogeneity and incomplete understanding of the contribution of various mutations within specific cancer phenotypes. Next-generation functional drug screening (ngFDS) in patient samples promises to overcome these challenges, however, proof of its clinical utility is limited. Methods. We investigated the feasibility and clinical impact of ngFDS measured at single-cell resolution using high-throughput automated microscopy in blood, bone marrow, pleural effusions, or excised lymph node biopsies (Figure 1A and Valdimer G et al. Nat Chem Biol. 2017). First, the accuracy of ngFDS to predict clinical outcome was evaluated in a retrospective cohort of 20 previously untreated patients with acute myeloid leukemia (AML). Then, 48 patients with aggressive hematologic malignancies failing at least two lines of treatment were prospectively evaluated for ngFDS guided therapy, of which 17 could receive ngFDS-guided treatment. Individual ngFDS-guided treatment regimens were selected by a committee (EXALT-board) of hemato-oncologists, pathologist, and pharmacists based on top-candidate treatments identified by ngFDS, considering drug availability as well as safety profiles of single agents and previously reported combinations (Figure 1B). The majority of these patients (12/17) presented with aggressive lymphoma and had seen in median three (2-7) prior treatment lines (Figure 2A). Overall response rate (ORR) and progression-free survival (PFS) of ngFDS-guided treatment were compared with ORR and PFS for the most recent regimen (MRR) on which patients had previously progressed. Results. ngFDS accurately predicted individual clinical response of AML patients to initial therapy. From prospectively analyzed patients receiving ngFDS guided treatment the ORR-ngFDS was 88% (15/17) compared to ORR-MRR of 24% (4/17; P Conclusions. Automatedmicroscopy-based ngFDS is feasible and accurately predicts clinical response. It can successfully guide personalized treatment of aggressive refractory hematological malignancies. Figure 1 Figure 1. Disclosures Staber: Takeda: Honoraria; Abbie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; MSD: Honoraria; Amgen: Honoraria; Gilad: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Morphosys: Membership on an entity's Board of Directors or advisory committees. Snijder: Allcyte: Equity Ownership, Other: founder and shareholder of Allcyte GmbH that holds a worldwide exclusive license for and commercializes the Pharmacoscopy high content imaging technology.. Vladimer: Allcyte Gmbh: Equity Ownership. Krall: Allcyte Gmbh: Equity Ownership. Hoermann: Ariad: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Gilead: Honoraria, Research Funding. Sperr: Teva: Honoraria; Meda: Research Funding; Celgene: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Phadia: Research Funding; Novartis: Other: Register. Gisslinger: Janssen Cilag: Honoraria; Takeda: Honoraria; Shire: Honoraria; PharmaEssentia: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; AOP Orphan Pharmaceuticals AG: Consultancy, Honoraria. Valent: Incyte: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Deciphera: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Ariad: Honoraria, Research Funding; Teva: Honoraria; Celgene: Honoraria, Research Funding; Blueprint: Research Funding. Jaeger: Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses; Novartis Pharmaceuticals Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses. Superti-Furga: Allcyte GmbH: Equity Ownership.