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Colony-stimulating factor-1 receptor (CSF1R) is a receptor tyrosine kinase that controls the differentiation and maintenance of most tissue-resident macrophages, and the inhibition of CSF1R has been suggested as a possible therapy for a range of human disorders. Herein, we present the synthesis, development, and structure−activity relationship of a series of highly selectivepyrrolo[2,3-d]pyrimidines, showing subnanomolar enzymatic inhibition of this receptor and with excellent selectivity toward other kinases in the platelet-derived growth factor receptor (PDGFR) family. The crystal structure of the protein and 23 revealed that the binding conformation of the protein is DFG-out-like. The most promising compounds in this series were profiled for cellular potency and subjected to pharmacokinetic profiling and in vivo stability, indicating that this compound class could be relevant in a potential disease setting. Additionally, these compounds inhibited primarily the autoinhibited form of the receptor, contrasting the behavior of pexidartinib, which could explain the exquisite selectivity of these structures.

Overcoming drug-resistance and the subsequent relapse that often occurs with monotherapy is crucial in the treatment of acute myeloid leukemia. We here demonstrate that therapy-resistant leukemia initiating cells can be targeted using a novel inhibitor of mitochondrial transcription (IMT). The compound inhibits mitochondrial RNA polymerase activity and sensitizes the resistant population to the induction of apoptosis. In vitro studies on acute myeloid leukemia cells demonstrate that IMT prevents cell proliferation, and together with a selective BCL-2 inhibitor, venetoclax, induce apoptosis and suppress oxidative phosphorylation (OXPHOS) synergistically. AML mouse models treated with IMT in combination with venetoclax show prolonged survival in venetoclax-resistant models. Our findings suggest that certain therapy-resistant leukemia cell populations display a unique dependency on mitochondrial transcription and can be targeted with IMT.TeaserLeukemia cells resistant to standard treatment are sensitive to a recently developed inhibitor of mitochondrial gene expression.

The inhibition of the nuclear receptor retinoic-acid-receptor-related orphan receptor γt (RORγt) is a promising strategy in the treatment of autoimmune diseases. RORγt features an allosteric binding site within its ligand-binding domain that provides an opportunity to overcome drawbacks associated with orthosteric modulators. Recently, trisubstituted isoxazoles were identified as a novel class of allosteric RORγt inverse agonists. This chemotype offers new opportunities for optimization into selective and efficacious allosteric drug-like molecules. Here, we explore the structure-activity relationship profile of the isoxazole series utilizing a combination of structure-based design, X-ray crystallography, and biochemical assays. The initial lead isoxazole (FM26) was optimized, resulting in compounds with a ∼10-fold increase in potency (low nM), significant cellular activity, promising pharmacokinetic properties, and a good selectivity profile over the peroxisome-proliferated-activated receptor γ and the farnesoid X receptor. We envisage that this work will serve as a platform for the accelerated development of isoxazoles and other novel chemotypes for the effective allosteric targeting of RORγt.

Mutated or amplified Her2 serves as a driver of non-small cell lung cancer or mediates resistance toward the inhibition of its family member epidermal growth factor receptor with small-molecule inhibitors. To date, small-molecule inhibitors targeting Her2 which can be used in clinical routine are lacking, and therefore, the development of novel inhibitors was undertaken. In this study, the well-established pyrrolopyrimidine scaffold was modified with structural motifs identified from a screening campaign with more than 1600 compounds, which were applied against wild-type Her2 and its mutant variant Her2-A775_G776insYVMA. The resulting inhibitors were designed to covalently target a reactive cysteine in the binding site of Her2 and were further optimized by means of structure-based drug design utilizing a set of obtained complex crystal structures. In addition, the analysis of binding kinetics and absorption, distribution, metabolism, and excretion parameters as well as mass spectrometry experiments and western blot analysis substantiated our approach.

Cancer metastasis is the most lethal attribute of cancer, frequently caused by insufficient therapies and limited therapy options. Novel compounds able to interfere with metastasis formation are therefore of tremendous interest. Colorectal Cancer (CRC) is the third most prevalent and second most lethal cancer worldwide. In CRC, metastasis formation is linked to poor patient survival and treatment failure. Up to 90% of CRC related deaths are attributed to metastasis formation. Identification of causative drivers of metastasis represents the basis for effective anti-metastatic therapy. Our lab newly identified the gene MACC1 (Metastasis Associated in Colon Cancer 1). MACC1 is a key causal molecule for tumor progression and metastasis formation. It is a stage independent prognostic marker, predicting the onset of metastasis in stages I, II and III, based on tumor tissue analyses or blood-based tests. MACC1 promotes several cancer hallmark capabilities, providing cells with a malignant phenotype. Further, MACC1 has been established as a prognostic and predictive biomarker for metastasis in CRC and more than 20 other solid cancer entities. We therefore searched for novel compounds targeting MACC1 transcription. A high-throughput screen with more than 118,500 compounds (EMBL, Heidelberg), employing CRC cells stably transfected with a MACC1 promoter-luciferase reporter construct, revealed a Tetrazolo-pyridazine based compound as a promising lead for effective inhibition of MACC1 expression. We demonstrated that several SAR and MedChem-generated analogues of our lead compound effectively inhibit MACC1 gene expression and MACC1 driven cancer cell motility in vitro in CRC and cross entity cell lines. Further, they inhibit MACC1-induced tumor progression and metastasis in vivo in CRC xenograft models in mice. Moreover, ADMET studies were conducted, confirming our compounds are likely to be orally active drug with high stability in human plasma, low plasma protein binding and great permeability with neglectable efflux in MDR1-MDCKII assay. Through RNA-sequencing and subsequent gene set enrichment analysis a hypothesis on the mode of action was formed. An immune pathway has been identified as the most promising signaling pathway targeted by these compounds, which is currently explored through knock down and signaling studies. Taken together, this novel class of small molecules represents promising candidates for anti-metastatic therapy in CRC and other solid cancer patients in a personalized medicine setting. Citation Format: Yan Shixian, Paul Schöpe, Joe Lewis, Kerstin Putzker, Ulrike Uhrig, Edgar Specker, Jens von Kries, Hector E. Sanchez-Ibarra, Anke Unger, Mia Zischinsky, Bert Klebl, Peter Lindemann, Wolfgang Walther, Marc Nazaré, Dennis Kobelt, Ulrike Stein. Novel Tetrazolo-pyridazine based MACC1 inhibitors are promising for anti-metastatic therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2471.

The leading cause of cancer related deaths is the formation of metastasis, frequently caused by insufficient therapies and limited therapy options. Novel compounds able to interfere with metastasis formation are therefore of tremendous interest. Colorectal Cancer (CRC) is the third most prevalent and second most lethal cancer worldwide. In CRC, metastasis formation is linked to poor patient survival and treatment failure. Up to 90% of CRC related deaths are attributed to metastasis formation. Identification of causative drivers of metastasis represents the basis for effective anti-metastatic therapy. Our lab newly identified the gene MACC1 (Metastasis Associated in Colon Cancer 1) in 2009. Since then, MACC1 has been established as a key causal molecule for tumor progression and metastasis formation. It was shown that MACC1 can function as a stage independent prognostic marker, predicting the onset of metastasis in stages I, II and III, based on tumor tissue analyses or through a blood based test with an accuracy of up to 85%. MACC1 promotes several cancer hallmark capabilitites, providing cells with a malignant phenotype. Further, MACC1 has been established as a prognostic and predictive biomarker for metastasis in CRC and more than 20 other solid cancer entities. We therefore searched for novel compounds targeting MACC1 transcription. A high-throughput screen employing HCT116 cells stably transfected with a MACC1 promoter-luciferase reporter construct with more than 118,500 compounds was conducted at the EMBL in Heidelberg. The screen revealed a Tetrazolo-pyridazine based compound as a promising lead for effective inhibition of MACC1 expression. We demonstrated that several SAR and Medchem-generated analogues of our lead compound effectively inhibit MACC1 gene expression and MACC1 driven cancer cell motility in vitro in CRC and cross entity cell lines. Further, they inhibit MACC1-induced tumor progression and metastasis in vivo in a CRC xenograft model in mice. Moreover, ADMET studies were conducted, confirming our compounds are likely to be orally active drugs with high stability in human plasma, low plasma protein binding and great permeability with neglectable efflux in MDR1-MDCKII assay. Through RNA-sequencing and subsequent gene set enrichment analysis a first hypothesis on the mode of action was shaped. An immune pathway has been identified as the most promising signaling pathway targeted by these compounds and is currently explored through knock down and signaling studies. Taken together, this novel class of small molecules represents promising candidates for anti-metastatic therapy in CRC and other solid cancer patients in a personalized medicine setting. Funding: This study is adviced and financed by the SPARK BIH Program Citation Format: Paul Curtis Schöpe, Shixian Yan, Dennis Kobelt, Joe Lewis, Kerstin Putzker, Ulrike Uhrig, Edgar Specker, Jens Peter von Kries, Mathias Dahlmann, Hector E Sanchez-Ibarra, Anke Unger, Mia-Lisa Zischinsky, Bert Klebl, Peter Lindemann, Wolfgang Walther, Marc Nazaré, Ulrike Stein. Novel tetrazolo-pyridazine based MACC1 transcriptional inhibitors as promising anti-metastatic therapy [abstract]. In: Proceedings of the AACR Special Conference: Cancer Metastasis; 2022 Nov 14-17; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_2):Abstract nr A039.

The functional role of P2X7 receptor (P2X7R) inhibition in cancer-induced bone pain has been highly contradictory. Whereas knockout studies have suggested pro-nociceptive effects, pharmacological studies suggest anti-nociceptive or no effect. The discrepancy is likely linked to the highly polymorphic nature of the P2X7R and the related functional differences in different tissue and conditions. In this study we tested the analgesic potential of AFC5261, a selective P2X7R antagonist, in a rat model of cancer-induced bone pain to evaluate if the opposing pro- and anti-nociceptive effects could be a consequence of long vs. short term inhibition of the P2X7R. Following intratibial inoculation of MRMT-1 carcinoma cells, movement-evoked and background pain was assessed with the limb use and weight-bearing test, and the effect of acute and chronic AFC5261-treatement evaluated. Bone degradation and tumor progression was in addition evaluated with x-ray densitometry and bioluminescence, respectively. In an acute treatment regime, a single administration of 300 mg/kg AFC5261 had no effect on either weight-bearing or limb use deficits. In contrast, morphine significantly increased both the limb use and weight-bearing ratio. In a chronic treatment study, BID administration of 300 mg/kg AFC5261 exacerbated the pain-related behavior, demonstrated by an earlier onset of both limb use and weight-bearing deficits without affecting the overall bone degradation or tumor progression. In contrast, 50 mg/kg and 100 mg/kg AFC5261 had no effect on the pain-related behavior. Overall, the data suggest that whereas acute P2X7R inhibition has no effect on the pain-related behavior, chronic inhibition exacerbate the cancer-induced bone pain.

We present inhibitors of drug resistant mutants of EGFR including T790M and C797S. In addition, we present the first X-ray crystal structures of covalent inhibitors in complex with C797S-mutated EGFR to gain insight into their binding mode., Precision medicine has revolutionized the treatment of patients in EGFR driven non-small cell lung cancer (NSCLC). Targeted drugs show high response rates in genetically defined subsets of cancer patients and markedly increase their progression-free survival as compared to conventional chemotherapy. However, recurrent acquired drug resistance limits the success of targeted drugs in long-term treatment and requires the constant development of novel efficient inhibitors of drug resistant cancer subtypes. Herein, we present covalent inhibitors of the drug resistant gatekeeper mutant EGFR-L858R/T790M based on the pyrrolopyrimidine scaffold. Biochemical and cellular characterization, as well as kinase selectivity profiling and western blot analysis, substantiate our approach. Moreover, the developed compounds possess high activity against multi drug resistant EGFR-L858R/T790M/C797S in biochemical assays due to their highly reversible binding character, that was revealed by characterization of the binding kinetics. In addition, we present the first X-ray crystal structures of covalent inhibitors in complex with C797S-mutated EGFR which provide detailed insight into their binding mode.

Onset of progression even during therapy with novel drugs remains an issue in chronic lymphocytic leukemia (CLL). Thus, there is ongoing demand for novel agents. Approaches targeting cyclin-dependent kinases (CDK) have reached the clinical trial stage. CDK9 mediating RNA transcriptional elongation is the evolving pivotal CLL CDK inhibitor target. However, more CDK9 selective compounds are desirable. Here, we describe the CDK9 inhibitor LDC526 displaying a low nanomolar biochemical activity against CDK9 and an at least 50-fold selectivity against other CDKs. After demonstrating in vitro MEC-1 cell line and primary human CLL cell cytotoxicity we evaluated the LDC526 in vivo effect on human CLL cells transplanted into NOD/scid/ γcⁿull (NSG) mice. LDC526 administration (75 mg/kg) for 5 days resulted in a 77% reduction of human CLL cells in NSG spleens compared to carrier control treatment. Next, we longitudinally studied the LDC526 impact on circulating CLL cells in the TCL1 transgenic mouse model. LDC526 (50 mg/kg) administration for two days led to a 16-fold reduction of blood CLL cell numbers. Remarkably, residual CLL cells exhibited significantly increased intracellular BCL-2 levels. However, the LDC526 cytotoxic effect was not restricted to CLL cells as also declining numbers of normal B and T lymphocytes were observed in LDC526 treated TCL1 mice. Taken together, our in vivo data provide a strong rational for continued LDC526 development in CLL therapy and argue for the combination with BCL-2 inhibitors. CA Göthert

Reversible epidermal growth factor receptor (EGFR) inhibitors prompt a beneficial clinical response in non-small cell lung cancer patients who harbor activating mutations in EGFR. However, resistance mutations, particularly the gatekeeper mutation T790M, limit this efficacy. Here, we describe a structure-guided development of a series of covalent and mutant-selective EGFR inhibitors that effectively target the T790M mutant. The pyrazolopyrimidine-based core differs structurally from that of aminopyrimidine-based third-generation EGFR inhibitors and therefore constitutes a new set of inhibitors that target this mechanism of drug resistance. These inhibitors exhibited strong inhibitory effects toward EGFR kinase activity and excellent inhibition of cell growth in the drug-resistant cell line H1975, without significantly affecting EGFR wild-type cell lines. Additionally, we present the in vitro ADME/DMPK parameters for a subset of the inhibitors as well as in vivo pharmacokinetics in mice for a candidate with promising activity profile.

The anti-inflammatory potential of p38 mitogen-activated protein kinase (MAPK) inhibitors was coincidentally expanded to a dual inhibition of p38α MAPK and phosphodiesterase 4 (PDE4), and the potential benefits arising from the blockage of both inflammation-related enzymes were thoroughly investigated. The most promising compound, CBS-3595 (1), was successively evaluated in in vitro experiments as well as in ex vivo and in vivo preclinical studies after administration of 1 to rodents, dogs, and monkeys. The resulting data clearly indicated a potent suppression of tumor necrosis factor alpha release. For reconfirming the findings of the animal studies when administering 1 to healthy human volunteers, a phase I clinical trial was conducted. Apart from further information regarding the pharmacokinetic and pharmacodynamic characteristics of 1, it was demonstrated that dual inhibition of p38α MAPK and PDE4 is able to synergistically attenuate the excessive anti-inflammatory response.

Aberrations within the PI3K/AKT signaling axis are frequently observed in numerous cancer types, highlighting the relevance of these pathways in cancer physiology and pathology. However, therapeutic interventions employing AKT inhibitors often suffer from limitations associated with target selectivity, efficacy, or dose-limiting effects. Here we present the first crystal structure of autoinhibited AKT1 in complex with the covalent-allosteric inhibitor borussertib, providing critical insights into the structural basis of AKT1 inhibition by this unique class of compounds. Comprehensive biological and preclinical evaluation of borussertib in cancer-related model systems demonstrated a strong antiproliferative activity in cancer cell lines harboring genetic alterations within the PTEN, PI3K, and RAS signaling pathways. Furthermore, borussertib displayed antitumor activity in combination with the MEK inhibitor trametinib in patient-derived xenograft models of mutant KRAS pancreatic and colon cancer. Significance: Borussertib, a first-in-class covalent-allosteric AKT inhibitor, displays antitumor activity in combination with the MEK inhibitor trametinib in patient-derived xenograft models and provides a starting point for further pharmacokinetic/dynamic optimization.

Aberrations within the PI3K/AKT signaling axis are frequently observed in numerous cancer types, highlighting the relevance of these pathways in cancer physiology and pathology. However, therapeutic interventions employing AKT inhibitors often suffer from limitations associated with target selectivity, efficacy, or dose-limiting effects. Here we present the first crystal structure of autoinhibited AKT1 in complex with the covalent-allosteric inhibitor borussertib, providing critical insights into the structural basis of AKT1 inhibition by this unique class of compounds. Comprehensive biological and preclinical evaluation of borussertib in cancer-related model systems demonstrated a strong antiproliferative activity in cancer cell lines harboring genetic alterations within the PTEN, PI3K, and RAS signaling pathways. Furthermore, borussertib displayed antitumor activity in combination with the MEK inhibitor trametinib in patient-derived xenograft models of mutant

Protein kinases represent central and multifunctional regulators of a balanced virus-host interaction. Cyclin-dependent protein kinase 7 (CDK7) plays crucial regulatory roles in cell cycle and transcription, both connected with the replication of many viruses. Previously, we developed a CDK7 inhibitor, LDC4297, that inhibits CDK7 in vitro in the nano-picomolar range. Novel data from a kinome-wide evaluation (>330 kinases profiled in vitro ) demonstrate a kinase selectivity. Importantly, we provide first evidence for the antiviral potential of the CDK7 inhibitor LDC4297, i.e., in exerting a block of the replication of human cytomegalovirus (HCMV) in primary human fibroblasts at nanomolar concentrations (50% effective concentration, 24.5 ± 1.3 nM). As a unique feature compared to approved antiherpesviral drugs, inhibition occurred already at the immediate-early level of HCMV gene expression. The mode of antiviral action was considered multifaceted since CDK7-regulated cellular factors that are supportive of HCMV replication were substantially affected by the inhibitors. An effect of LDC4297 was identified in the interference with HCMV-driven inactivation of retinoblastoma protein (Rb), a regulatory step generally considered a hallmark of herpesviral replication. In line with this finding, a broad inhibitory activity of the drug could be demonstrated against a selection of human and animal herpesviruses and adenoviruses, whereas other viruses only showed intermediate drug sensitivity. Summarized, the CDK7 inhibitor LDC4297 is a promising candidate for further antiviral drug development, possibly offering new options for a comprehensive approach to antiviral therapy.

Chlamydia trachomatis (Ctr) accounts for >130 million human infections annually. Since chronic Ctr infections are extremely difficult to treat, there is an urgent need for more effective therapeutics. As an obligate intracellular bacterium, Ctr strictly depends on the functional contribution of the host cell. Here, we combined a human genome-wide RNA interference screen with metabolic profiling to obtain detailed understanding of changes in the infected cell and identify druggable pathways essential for Ctr growth. We demonstrate that Ctr shifts the host metabolism toward aerobic glycolysis, consistent with increased biomass requirement. We identify key regulator complexes of glucose and nucleotide metabolism that govern Ctr infection processes. Pharmacological targeting of inosine-5'-monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in guanine nucleotide biosynthesis, efficiently inhibits Ctr growth both in vitro and in vivo. These results highlight the potency of genome-scale functional screening for the discovery of drug targets against bacterial infections.

Targeting cytokines has become an important focus in the treatment of many inflammatory disorders. p38 MAP kinase (MAPK) is the key enzyme in regulating the biosynthesis and release of pro-inflammatory cytokines such as IL-1beta and TNFalpha. Inhibition of p38 MAPK results in decreased expression of these cytokines. Tri- and tetrasubstituted pyridinylimidazoles are potent inhibitors of p38 MAPK. Substitution on the pyridinyl moiety allows the design of inhibitors that show increased selectivity and activity by targeting the enzyme's hydrophobic region II. The objective of this study was to synthesize novel 1,2,4,5-tetrasubstituted imidazole derivates and to characterize them not only for their ability to inhibit p38 MAPK and modulate cytokine release in human whole blood, but also to evaluate their metabolic stability. Biological data and metabolic studies demonstrate that the introduction of a 2-acylamino function at C2 of the pyridine results in highly efficient and metabolically stable inhibitors relative to C2-alkylamino derivatives. A series of novel candidates was investigated for metabolic stability in human liver microsomes and in human whole blood. Additionally, metabolic S-oxidation was investigated, and possible metabolites were synthesized.

2-[6-(4-Chlorophenyl)-2,2-dimethyl-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl] acetic acid (licofelone) is a dual inhibitor of both cyclooxygenase isoforms and 5-lipoxygenase and under development for treatment of osteoarthritis. In conventional in vitro assays using liver microsomes and NADPH as cosubstrate, a high metabolic stability of licofelone was observed. In the presence of UDP-glucuronic acid, licofelone is rapidly converted into the corresponding acyl glucuronide, M1. These results are in conflict with data from clinical studies. After administration of licofelone to humans, M1 plasma concentrations were negligibly low, whereas the exposure of the hydroxy-metabolite M2 achieved values of approximately 20% compared with that of the parent drug. Metabolism studies with human hepatocytes and dual-activity assays with microsomes, which allowed the simultaneous monitoring of hydroxylation and glucuronidation reactions, were performed, and the metabolic pathway of licofelone was elucidated. After glucuronidation, predominantly catalyzed by UDP glucuronosyltransferase (UGT) isoforms UGT2B7, UGT1A9, and UGT1A3, M1 is converted into the hydroxy-glucuronide M3 in a CYP2C8-dependent reaction. The enzyme specificities were investigated using recombinant human cytochrome P450 and UGT isoforms as test systems. In vitro drug-interaction studies using the 6alpha-hydroxylation of paclitaxel as control reaction confirmed that neither licofelone nor M1 is a relevant inhibitor of CYP2C8. The formation of M3 was also observed with liver microsomes from cynomolgus monkeys, but in incubations with mouse and rat liver microsomes, M1 remained unchanged. The clinical relevance of these findings is discussed.

Background/Aims: Inhibition of p38 mitogen-activated protein kinase (p38 MAPK) is promising for the treatment of inflammatory disorders, however, the efficacy of p38 MAPK inhibitors in clinical trials is limited so far. Since functional sensitivity of p38 MAPK is commonly predicted by preclinical species, we systematically investigated interspecies differences including human tissue. Methods: Ex vivo test models were established using whole blood and primary cells from different species such as mice, rats, pigs and humans to compare LPS-induced TNF-α inhibition of four different p38 MAPK reference inhibitors SB 203580, BIRB-796, Pamapimod, and a Losmapimod analogue as well as a proprietary imidazole-based p38 MAPK Inhibitor. Results: All analysed p38 MAPK inhibitors resulted in significant inhibition of LPS-induced TNF-α release but with high interspecies differences for dose sensitivity. IC50 values from human whole blood and PBMC showed significant higher sensitivity towards p38 MAPK inhibition compared with data from pig and rat. Conclusion: Inhibition of TNF-α release by p38 MAPK inhibitors can be reliably identified in well-established laboratory species such as rat or mouse. However, our data indicate that animal models appear to be limited for valid prediction of the inhibitory potential for TNF-α release in humans. Thus, human tissues should be considered early in the drug development process of p38 MAPK inhibitors.

Mutations in the catalytic domain at the gatekeeper position represent the most prominent drug-resistant variants of kinases and significantly impair the efficacy of targeted cancer therapies. Understanding the mechanisms of drug resistance at the molecular and atomic levels will aid in the design and development of inhibitors that have the potential to overcome these resistance mutations. Herein, by introducing adaptive elements into the inhibitor core structure, we undertake the structure-based development of type II hybrid inhibitors to overcome gatekeeper drug-resistant mutations in cSrc-T338M, as well as clinically relevant tyrosine kinase KIT-T670I and Abl-T315I variants, as essential targets in gastrointestinal stromal tumors (GISTs) and chronic myelogenous leukemia (CML). Using protein X-ray crystallography, we confirm the anticipated binding mode in cSrc, which proved to be essential for overcoming the respective resistances. More importantly, the novel compounds effectively inhibit clinically relevant gatekeeper mutants of KIT and Abl in biochemical and cellular studies. © 2013 American Chemical Society.

Mitochondria contain a unique DNA genome (mtDNA) that encodes a number of key components of the respiratory chain. Levels of mtDNA gene expression correlate with the metabolic requirements of mammalian cells. Recently, the role of mitochondrial function for the development and progression of cancer has been highlighted. Oncogenes have been identified to redirect mitochondrial functions to increase cancer cell survival. Increased levels of oxidative phosphorylation have also been implicated in cancer cell resistance towards drugs. In agreement with this notion, compounds that inhibit respiration may specifically target such resistant cells. Finally, it was demonstrated that inhibition of mitochondrial gene expression leads to apoptosis in rapidly dividing cells. Based on these observations, we present a completely novel principle different from known electron transfer chain blockers to treat cancer by inhibiting mtDNA transcription. To this end a study to identify and characterize inhibitors of mitochondrial transcription (IMTs) with lead-like properties was initiated. A high throughput biochemical screening campaign was performed identifying small molecular weight inhibitors of PolRMT, the mitochondrial RNA polymerase, which controls mtDNA transcription. Upon hit optimization, potent compounds with biochemical and cellular IC50s in the low nanomolar range have been identified. IMTs displayed good physicochemical and pharmacological properties. They have been shown to be inactive on other RNA polymerases proving their excellent specificity. Testing IMTs in assays for cancer cell proliferation revealed potent inhibition of sensitive cell lines (double digit nanomolar range). Interestingly, none of the tested primary non-cancer cell lines was affected by the IMTs, indicating a good therapeutic window. Testing selected IMTs in pharmacokinetic studies in vivo revealed high exposures and no detectable adverse effects (single and repeated dosing). Medicinal chemistry optimization will help to identify candidate compounds for efficacy testing in xenograft models. Citation Format: Tim Bergbrede, Axel Choidas, Raffaela Di Lucrezia, Sascha Menninger, Anke Unger, Koch Uwe, Peter Nussbaumer, Nina Bonekamp, Emily Hoberg, Victor Posse, Andrea Felser, Maria Falkenberg, Nils Göran Larsson, Claes M. Gustafsson, Bert M. Klebl. Inhibitors of mitochondrial transcription (IMT) specifically affect cancer cell proliferation. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 222.

Tumour metastasis is the primary cause of mortality in cancer patients and remains the key challenge for cancer therapy. New therapeutic approaches to block inhibitory pathways of the immune system have renewed hopes for the utility of such therapies2. Here we show that genetic deletion of the E3 ubiquitin ligase Cbl-b (casitas B-lineage lymphoma-b) or targeted inactivation of its E3 ligase activity licenses natural killer (NK) cells to spontaneously reject metastatic tumours. The TAM tyrosine kinase receptors Tyro3, Axl and Mer (also known as Mertk) were identified as ubiquitylation substrates for Cbl-b. Treatment of wild-type NK cells with a newly developed small molecule TAM kinase inhibitor conferred therapeutic potential, efficiently enhancing anti-metastatic NK cell activity in vivo. Oral or intraperitoneal administration using this TAM inhibitor markedly reduced murine mammary cancer and melanoma metastases dependent on NK cells. We further report that the anticoagulant warfarin exerts anti-metastatic activity in mice via Cbl-b/TAM receptors in NK cells, providing a molecular explanation for a 50-year-old puzzle in cancer biology3. This novel TAM/Cbl-b inhibitory pathway shows that it might be possible to develop a a 'pill' that awakens the innate immune system to kill cancer metastases. © 2014 Macmillan Publishers Limited. Fil: Paolino, Magdalena. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Choidas, Axel. Lead Discovery Center GmbH; Alemania Fil: Wallner, Stephanie. Medizinische Universitat Innsbruck; Austria Fil: Pranjic, Blanka. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Uribesalgo, Iris. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Loeser, Stefanie. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Jamieson, Amanda M.. University Brown; Estados Unidos Fil: Langdon, Wallace Y.. University of Western Australia; Australia Fil: Ikeda, Fumiyo. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Fededa, Juan Pablo. Institute Of Molecular Biotechnology, Vienna; Austria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina Fil: Cronin, Shane J.. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Nitsch, Roberto. Institute Of Molecular Biotechnology, Vienna; Austria Fil: Schultz-Fademrecht, Carsten. Lead Discovery Center GmbH; Alemania Fil: Eickhoff, Jan. Lead Discovery Center GmbH; Alemania Fil: Menninger, Sascha. Lead Discovery Center GmbH; Alemania Fil: Unger, Anke. Lead Discovery Center GmbH; Alemania Fil: Torka, Robert. Institute for Biochemistry Max-Planck; Alemania Fil: Gruber, Thomas. Medizinische Universitat Innsbruck; Austria Fil: Hinterleitner, Reinhard. Medizinische Universitat Innsbruck; Austria Fil: Baier, Gottfried. Medizinische Universitat Innsbruck; Austria Fil: Wolf, Dominik. University Hospital Bonn; Alemania. Medical University Innsbruck; Austria Fil: Ullrich, Axel. Institute for Biochemistry Max-Planck; Alemania Fil: Klebl, Bert M.. Lead Discovery Center GmbH; Alemania Fil: Penninger, Josef M.. Institute Of Molecular Biotechnology, Vienna; Austria

While the Maillard reaction of amino acids and proteins as well as its consequences in vivo has been thoroughly investigated, little attention has so far been paid to the glycation of aminophospholipids such as phosphatidylethanolamine (PE) or phosphatidylserine (PS), which are essential for structure and functionality of biological membranes. PE-derived glucosylamines (Schiff-PEs) and aminoketoses (Amadori-PEs) have now for the first time been simultaneously identified and quantified in erythrocytes from diabetics and healthy individuals by liquid chromatography–electrospray mass spectrometry (LC-(ESI)MS). The amounts of glycated PE ( g PE) were significantly higher in diabetics (0.18–34.2 mol% Schiff-PE and 0.047–0.375 mol% Amadori-PE) than in controls (0.12–3.99 mol% Schiff-PE and 0.018–0.055 mol% Amadori-PE). A positive correlation between fructosylated hemoglobin (HbA 1c ) and the g PE levels was established. No advanced glycation endproducts (AGEs) like 5-hydroxymethylpyrrole-2-carbaldehyde (pyrrole-PE), carboxymethyl (CM-PE), or carboxyethyl (CE-PE) derivatives were detected. To investigate the influence of g PE on lipid peroxidation of biological membranes, liposomes consisting of soy-PE and synthetically prepared Amadori-PE (16:0–16:0) were incubated for several days and the formation of oxidation products was monitored. It could be shown that Amadori-PE extensively promotes lipid peroxidation even in the absence of transition metal ions like Cu 2+ and Fe 3+ . Oxidative damage to membrane lipids therefore is supposed to be at least partially caused by the glycation of aminophospholipids.

The receptor tyrosine kinase Axl belongs to the TAM (Tyro-3, Axl and Mer) family and is involved in the progression of several human malignancies including chronic lymphocytic leukemia (CLL), where it is has been found to be overexpressed in comparison to normal B-cells. An increasing body of evidence suggests that Axl acts as an oncogene which increases the survival, proliferation, metastatic potential and chemotherapy resistance of tumor cells. Hence, it has been recently identified as a potential therapeutic target in a wide range of tumor entities with deregulated Axl expression including prostate cancer, glioma, lung cancer and CLL. Here, we investigated two different Axl inhibitors for their ability to inhibit the migratory capacity and survival of leukemic cells in preclinical CLL models. In vitro studies: We measured soluble Axl plasma concentrations by enzyme-linked immunosorbent assay (ELISA) in 71 CLL patients and 24 healthy donors. Soluble Axl levels were not significantly higher in CLL patients compared to healthy donors (p=0. 11). However, in CLL patients high sAxl plasma concentrations were differentially expressed with some patients exhibiting normal and others elevated plasma concentrations. The latter showed an association with shorter time to first treatment (p=0.0005) and several poor prognostic markers (e.g. CD38, FISH cytogentics, Binet stage). Freshly isolated PBMC (>90% CD5+CD19+) from CLL patients were incubated in serum free medium for 48h containing concentrations series of 2 different Axl inhibitors: BMS777607, a previously published inhibitor of the MET kinase family, and LDC2636, a novel inhibitor of the TAM receptor tyrosine kinase (RTK) family with high affinity to Axl. Viability of CLL cells was assessed by trypan blue staining and flow cytometry employing annexin V staining. Cellular polarization was analyzed by time-lapse microscopy. We detected cytotoxic effects in a patient-dependent manner that were more prevalent in LDC2636 as compared to BMS777607 treated cells (IC50= 0.21 µM vs. 2.88 µM, p In vivo studies To verify our hypothesis that reduced cell polarization results in decreased homing of leukemic cells in vivo we employed a recently developed adoptive transfer model of CLL. In this model NOD/SCID/IL2Rgcnull(NSG) mice were pre-treated with a single intraperitoneal (i.p.) bolus of LDC2636 or BMS777607 (20 mg/kg) and subsequently transplanted with primary CLL cells. Both Axl inhibitors significantly reduced the homing capacity of CLL cells to the BM of NSG mice by 46% and 59%, respectively, compared to vehicle treated controls (LDC2636: p=0.0063, BMS777607 p=0.0007; n=4). To evaluate if LDC2636 also exhibits effects in a disease-relevant CLL model, we applied a MEC-1 xenograft model which causes a lethal leukemia in NSG mice. We pretreated the mice with 40mg/kg Axl inhibitor or vehicle-only control i.p. and subsequently transplanted the CLL cell line MEC-1 intravenously. The following four days the mice were injected again with 40mg/kg LDC2636 or vehicle-only i.p. We evaluated the survival time and found that mice treated with LDC2636 lived significantly longer than vehicle-only controls (24 vs. 18 days median survival, p=0.0016, n=15). Mice that received only LDC2636 and no Mec-1 cells did not show any effect. These data demonstrate that Axl inhibitors exert potent in vitro and in vivo activity against human CLL cells, which is caused at least in part by the suppression of CLL homing to their supportive stromal niches. Disclosures: Schultz-Fademrecht: Lead Discovery Center GmbH: Employment. Unger:Lead Discovery Center GmbH: Employment. Klebl:Lead Discovery Center GmbH: Employment. Choidas:Lead Discovery Center GmbH: Employment.

The receptor tyrosine kinase Axl belongs to the TAM (Tyro-3, Axl and Mer) family and is involved in the progression of several human malignancies including chronic lymphocytic leukemia (CLL), where it is has been found to be overexpressed in comparison to normal B-cells. An increasing body of evidence suggests that Axl acts as an oncogene which increases the survival, proliferation, metastatic potential and chemotherapy resistance of tumor cells. Hence, it has been recently identified as a potential therapeutic target in a wide range of tumor entities with deregulated Axl expression including prostate cancer, glioma, lung cancer and CLL. Here, we investigated two different Axl inhibitors for their ability to inhibit the migratory capacity and survival of leukemic cells in preclinical CLL models. In vitro studies: We measured soluble Axl plasma concentrations by enzyme-linked immunosorbent assay (ELISA) in 71 CLL patients and 24 healthy donors. Soluble Axl levels were not significantly higher in CLL patients compared to healthy donors (p=0. 11). However, in CLL patients high sAxl plasma concentrations were differentially expressed with some patients exhibiting normal and others elevated plasma concentrations. The latter showed an association with shorter time to first treatment (p=0.0005) and several poor prognostic markers (e.g. CD38, FISH cytogentics, Binet stage). Freshly isolated PBMC (>90% CD5+CD19+) from CLL patients were incubated in serum free medium for 48h containing concentrations series of 2 different Axl inhibitors: BMS777607, a previously published inhibitor of the MET kinase family, and LDC2636, a novel inhibitor of the TAM receptor tyrosine kinase (RTK) family with high affinity to Axl. Viability of CLL cells was assessed by trypan blue staining and flow cytometry employing annexin V staining. Cellular polarization was analyzed by time-lapse microscopy. We detected cytotoxic effects in a patient-dependent manner that were more prevalent in LDC2636 as compared to BMS777607 treated cells (IC50= 0.21 µM vs. 2.88 µM, p

Abstract 1789 Active agents for the treatment of CLL are available. However, CLL eventually progresses to refractory disease. Defects in apoptosis, cytogenetic abnormalities and alterations in non-malignant cells of the micro-environment are likely to be the major causes of therapeutic resistance. Therefore, novel agents are required to abrogate apoptosis blocks and to alter the micro-environment of CLL. One approach targets cyclin-dependent kinases (Cdk). Specifically, Cdk9 promotes initiation and elongation steps in transcription maintaining expression levels of anti-apoptotic proteins with inherently rapid turnover rates. Inhibitors of cyclin-dependent kinases (Cdks) have been previously shown to exert cytotoxic effects on CLL cells by inhibiting Cdk7 and Cdk9. However, inhibitors used in these studies suffer from lack of selectivity, making unambiguous interpretation of results difficult, and leading to unspecific toxicity. Here, we studied the novel Cdk inhibitor LDC-9-A, which exhibits potent and selective inhibitory activity against Cdk9. The in vitro cytotoxicity of LDC-9-A was evaluated after 24 and 48 hours in CLL cases (n=8) and the CLL derived prolymphocytic cell line MEC-1. After a culture period of 48 hours LD50 values ranged between 0.1 and 1.9 μM for primary CLL cells and MEC-1 cells, respectively. Western blot analysis of protein extracts from MEC-1 cells showed that LDC-9-A down-modulates the anti-apoptotic proteins Bcl-2 and Mcl-1 in a dose- and time-dependent manner. In order to study the in vivo anti-CLL activity of LDC-9-A 9–12 month-old transgenic TCL1 mice (n=4) were treated for two consecutive days with an orally bioavailable LDC-9-A formulation (50 mg/kg body weight). Control groups consisted of TCL1 mice receiving vehicle only (n=3) and wild-type control littermates (n=4) receiving LDC-9-A. Numbers of peripheral blood leukemic cells (CD19+CD5+CD3−) and non-malignant T-cells (CD19−CD5+CD3+) were longitudinally evaluated by flow cytometry. Remarkably, LDC-9-A treatment of TCL1 transgenic mice led to a decrease of blood leukemic cells to 6.3±2.0% (mean±SEM) of baseline levels (p Finally, the anti-CLL activity of LDC-9-A was further validated by employing a recently developed adoptive transfer model of primary human CLL cells. In this model NOD/SCID/γcnull (NSG) mice were transplanted with CLL cells and treated with different doses of LDC-9-A for 3–5 sequential days. In line with the data generated with the TCL1 murine CLL model the LDC-9-A treatment of xenografted animals with 60 and 90 mg/kg body weight resulted in an 80–90% reduction of human CLL cell recovery from murine spleens as compared to vehicle treated controls. In summary, we demonstrated effective anti-CLL activity of the novel Cdk9 inhibitor LDC-9-A in two independent preclinical mouse models. The activity of LDC-9-A against CLL cells was achieved at least in part by modulating cellular anti-apoptotic protein levels. Furthermore, LDC-9-A interfered with non-malignant T-cells, which represent an important component of the CLL micro-environment. Disclosures: Eickhoff: Lead Discovery Center GmbH (LDC): Employment. Baumann:Lead Discovery Center GmbH (LDC): Employment. Unger:Lead Discovery Center GmbH (LDC): Employment. Schultz-Fademrecht:Lead Discovery Center GmbH (LDC): Employment. Dürig:Roche: Speakers Bureau; GSK: Speakers Bureau; Santaris Pharma: Consultancy, Research Funding; Celgene: Research Funding.

Altered expression of mitochondrial DNA (mtDNA) occurs in ageing and a range of human pathologies (for example, inborn errors of metabolism, neurodegeneration and cancer). Here we describe first-in-class specific inhibitors of mitochondrial transcription (IMTs) that target the human mitochondrial RNA polymerase (POLRMT), which is essential for biogenesis of the oxidative phosphorylation (OXPHOS) system1–6. The IMTs efficiently impair mtDNA transcription in a reconstituted recombinant system and cause a dose-dependent inhibition of mtDNA expression and OXPHOS in cell lines. To verify the cellular target, we performed exome sequencing of mutagenized cells and identified a cluster of amino acid substitutions in POLRMT that cause resistance to IMTs. We obtained a cryo-electron microscopy (cryo-EM) structure of POLRMT bound to an IMT, which further defined the allosteric binding site near the active centre cleft of POLRMT. The growth of cancer cells and the persistence of therapy-resistant cancer stem cells has previously been reported to depend on OXPHOS7–17, and we therefore investigated whether IMTs have anti-tumour effects. Four weeks of oral treatment with an IMT is well-tolerated in mice and does not cause OXPHOS dysfunction or toxicity in normal tissues, despite inducing a strong anti-tumour response in xenografts of human cancer cells. In summary, IMTs provide a potent and specific chemical biology tool to study the role of mtDNA expression in physiology and disease. Inhibitors of mitochondrial transcription that target human mitochondrial RNA polymerase provide a chemical biology tool for studying the role of mitochondrial DNA expression in a wide range of pathologies.