Rolf W Hartmann

Helmholtz Institute for Pharmaceutical Research Saarland, Saarbrücken, Saarland, Germany

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Publications (293)784.45 Total impact

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    ABSTRACT: Dysregulated usage of pre-mRNA splicing sites contributes to the progression of cancer, neurodegenerative diseases, and viral infections. Serine/arginine-rich (SR) proteins play major roles in the splice site recognition and are largely regulated by phosphorylation. This provides an option for the pharmacological correction of aberrant splicing by inhibiting the relevant kinases. Cdc2-like kinases (Clks) and dual specificity tyrosine phosphorylation-regulated kinases (Dyrks) were both reported to phosphorylate numerous SR proteins in vitro and in vivo. In this study, we describe the discovery of new selective dual Clk/Dyrk1A/1B inhibitors, which are able to modulate alternative pre-mRNA splicing of model gene transcripts in cells with submicromolar potencies. The optimization process yielded a dual Clk and Dyrk inhibitor with exceptionally high ligand efficiency. Our results suggested that dual inhibition of both Clk1 and Dyrk1A increased the efficacy of pre-mRNA splicing modulation.
    ACS Medicinal Chemistry Letters 09/2014; 5(9):963-7. · 3.31 Impact Factor
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    ABSTRACT: The bacterial RNA polymerase (RNAP) represents a validated target for the development of broad-spectrum antibiotics. However, the medical value of RNAP inhibitors in clinical use is limited by the prevalence of resistant strains. To overcome this problem, we focused on the exploration of alternative target sites within the RNAP. Previously, we described the discovery of a novel RNAP inhibitor class containing an ureidothiophene-2-carboxylic acid core structure. Herein, we demonstrate that these compounds are potent against a set of methicillin-resistant Staphylococcus aureus (MRSA) strains (MIC: 2-16 μg ml-1) and rifampicin-resistant Escherichia coli TolC strains (MIC: 12.5-50 μg ml-1). Additionally, an abortive transcription assay revealed that these compounds inhibit the bacterial transcription process during the initiation phase. Furthermore, the binding mode of the ureidothiophene-2-carboxylic acids was characterized by mutagenesis studies and ligand-based NMR spectroscopy. Competition saturation transfer difference (STD) NMR experiments with the described RNAP inhibitor myxopyronin A (Myx) suggest that the ureidothiophene-2-carboxylic acids compete with Myx for the same binding site in the RNAP switch region. INPHARMA (Interligand NOE for PHARmacophore MApping) experiments and molecular docking simulations provided a binding model in which the ureidothiophene-2-carboxylic acids occupy the region of the Myx western chain binding site and slightly occlude that of the eastern chain. These results demonstrate that the ureidothiophene-2-carboxylic acids are a highly attractive new class of RNAP inhibitors that can avoid the problem of resistance.
    ACS Chemical Biology 09/2014; · 5.44 Impact Factor
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    ABSTRACT: Topical application of CYP11B1 inhibitors to reduce cutaneous cortisol is a novel strategy to promote healing of chronic wounds. Pyridyl substituted arylsulfonyltetrahydroquinolines were designed and synthesized resulting in a strong inhibitor 34 (IC50 = 5 nM). It showed no inhibition of CYP17 and CYP19 and no mutagenic effects. It exhibited inverse metabolic stability in plasma (t1/2 > 150 min), which is similar to wound fluid in composition, and in liver S9 fractions (t1/2 = 16 min).
    Journal of medicinal chemistry. 08/2014;
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    ABSTRACT: FULL PAPER Martin Empting, Rolf W. Hartmann et al. From in vitro to in cellulo: structure–activity relationship of (2-nitrophenyl)- methanol derivatives as inhibitors of PqsD in Pseudomonas aeruginosa
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    ABSTRACT: There is increasing evidence that the atypical protein kinase C, PKCζ, might be a therapeutic target in pulmonary and hepatic inflammatory diseases. However, targeting the highly conserved ATP-binding pocket in the catalytic domain held little promise to achieve selective inhibition. In the present study, we introduce 1,3,5-trisubstituted pyrazolines as potent and selective allosteric PKCζ inhibitors. The rigid scaffold offered many sites for modification, all acting as hot spots for improving activity, and gave rise to sharp structure-activity relationships. Targeting of PKCζ in cells was confirmed by reporter gene assay, transfection assays, and Western blotting. The strongly reduced cell-free and cellular activities toward a PIF-pocket mutant of PKCζ suggested that the inhibitors most likely bound to the PIF-pocket on the kinase catalytic domain. Thus, using a rigidification strategy and by establishing and optimizing multiple molecular interactions with the binding site, we were able to significantly improve the potency of the previously reported PKCζ inhibitors.
    Journal of medicinal chemistry. 07/2014;
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    ABSTRACT: The inhibition of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1), which catalyzes the conversion of estrone into the potent estrogen receptor agonist estradiol (E2), is discussed as a novel therapeutic approach for the treatment of estrogen-dependent diseases. Because the reduction of E2 would be basically limited to the target tissues, this approach is expected to cause fewer side effects than the currently employed antihormonal therapies. Recently, we reported on 6-hydroxybenzothiazole ketones as a new class of 17β-HSD1 inhibitors with a notable activity/selectivity profile. In an attempt to further optimize these parameters, we modified the benzothiazole core by a systematic bioisosteric replacement. Thus, we were able to identify a new 6-hydroxybenzothiophene derivative that displayed stronger inhibition of 17β-HSD1 (IC50=13 nM) and that was also more selective than a benzothiazole analog. Using ab initio calculations, we found that the higher potency of the 6-hydroxybenzothiophene derivative was probably due to more favorable conformational preorganization of the scaffold for binding to the enzyme.
    ChemMedChem 07/2014; · 2.84 Impact Factor
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    ABSTRACT: Cystic fibrosis (CF) is a genetic disease mainly manifested in the respiratory tract. Pseudomonas aeruginosa (P. aeruginosa) is the most common pathogen identified in cultures of the CF airways, however, its eradication with antibiotics remains challenging as it grows in biofilms that counterwork human immune response and dramatically decrease the susceptibility to antibiotics. P. aeruginosa regulates pathogenicity via a cell-to-cell communication system known as quorum sensing (QS) involving the virulence factor (pyocyanin), thus representing an attractive target for coping bacterial pathogenicity. The first in vivo potent QS inhibitor (QSI) was recently developed. Nevertheless, its lipophilic nature might hamper its penetration of non-cellular barriers such as mucus and bacterial biofilms, which limits its biomedical application. Successful anti-infective inhalation therapy necessitates proper design of a biodegradable nanocarrier allowing: 1) High loading and prolonged release, 2) Mucus penetration, 3) Effective pulmonary delivery, and 4) Maintenance of the anti-virulence activity of the QSI. In this context, various pharmaceutical lipids were used to prepare ultra-small solid lipid nanoparticles (us-SLNs) by hot melt homogenization. Plain and QSI-loaded SLNs were characterized in terms of colloidal properties, drug loading, in vitro release and acute toxicity on Calu-3 cells. Mucus penetration was studied using newly-developed confocal microscopy technique based on 3D-time laps imaging. For pulmonary application, nebulization efficiency of SLNs and lung deposition using next generation impactor (NGI) were performed. The anti-virulence efficacy was investigated by pyocyanin formation in P. aeruginosa cultures. Ultra-small SLNs (<100 nm diameter) provided high encapsulation efficiency (68 - 95 %) according to SLNs composition, high burst in phosphate buffer saline compared to prolonged release of the payload over>8 h in simulated lung fluid with minor burst. All types and concentrations of plain and QSI-loaded SLNs maintained the viability of Calu-3 cells. 3D-time laps confocal imaging proved the ability of SLNs to penetrate into artificial sputum model. SLNs were efficiently nebulized; NGI experiments revealed their deposition in the bronchial region. Overall, nanoencapsulated QSI showed up to sevenfold superior anti-virulence activity to the free compound. Most interestingly, the plain SLNs exhibited anti-virulence properties themselves, which was shown to be related to anti-virulence effects of the emulsifiers used. These startling findings represent a new perspective of ultimate significance in the area of the nano-based delivery of novel anti-infectives.
    Journal of controlled release : official journal of the Controlled Release Society. 07/2014;
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    ABSTRACT: 17β-Hydroxysteroid dehydrogenase type 2 (17β-HSD2) is responsible for the oxidation of the highly active estradiol (E2) and testosterone (T) into the less potent estrone (E1) and Δ4-androstene-3,17-dione (Δ4-AD), respectively. As 17β-HSD2 is present in bones and as estradiol and testosterone are able to induce bone formation and repress bone resorption, inhibition of this enzyme could be a new promising approach for the treatment of osteoporosis. Herein, we describe the design, the synthesis and the biological evaluation of 24 new 17β-HSD2 inhibitors in the 5-substituted thiophene-2-carboxamide class. Structure-activity and structure-selectivity relationships have been explored by variation of the sulfur atom position in the central core, exchange of the thiophene by a thiazole, substitution of the amide group with a larger moiety, exchange of the N-methylamide group with bioisosteres like N-methylsulfonamide, N-methylthioamide and ketone, and substitutions at positions 2 and 3 of the thiophene core with alkyl and phenyl groups leading to 2,3,5-trisubstituted thiophene derivatives. The compounds were evaluated on human and mouse enzymes. From this study, a novel highly potent and selective compound in both human and mouse 17β-HSD2 enzymes was identified, compound 21 (IC50(h17β-HSD2) = 235 nM, Selectivity Factor toward h17β-HSD1 = 95, IC50 (m17β-HSD2) = 54 nM). This new compound 21 could be used for an in vivo proof of principle to demonstrate the true therapeutic efficacy of 17β-HSD2 inhibitors in osteoporosis. New structural insights into the active sites of the human and mouse enzymes were gained.
    European Journal of Medicinal Chemistry 06/2014; 83:317-337. · 3.50 Impact Factor
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    ABSTRACT: Recent studies have shown that compounds based on a (2-nitrophenyl)methanol scaffold are promising inhibitors of PqsD, a key enzyme of signal molecule biosynthesis in the cell-to-cell communication of Pseudomonas aeruginosa. The most promising molecule displayed anti-biofilm activity and a tight-binding mode of action. Herein, we report on the convenient synthesis and biochemical evaluation of a comprehensive series of (2-nitrophenyl)methanol derivatives. The in vitro potency of these inhibitors against recombinant PqsD as well as the effect of selected compounds on the production of the signal molecules HHQ and PQS in P. aeruginosa were examined. The gathered data allowed the establishment of a structure-activity relationship, which was used to design fluorescent inhibitors, and finally, led to the discovery of (2-nitrophenyl)methanol derivatives with improved in cellulo efficacy providing new perspectives towards the application of PqsD inhibitors as anti-infectives.
    Organic & Biomolecular Chemistry 06/2014; · 3.57 Impact Factor
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    ABSTRACT: Pathologically, high levels of aldosterone are associated with severe cardiovascular diseases such as congestive heart failure, hypertension, and myocardial fibrosis. The inhibition of aldosterone synthase (CYP11B2) to reduce aldosterone levels has been proposed as a promising treatment for diseases related to CYP11B2 because it is the crucial enzyme in the biosynthesis of aldosterone. A series of novel pyridyl- or isoquinolinyl-substituted indolines and indoles was designed via a ligand-based approach. The synthesized compounds were tested and found to be strong CYP11B2 inhibitors. The most potent ones showed IC50 values of less than 3 nM, being similarly potent as fadrozole and LCI699. Among them, compounds 14 and 23 showed good selectivity over the highly homologous CYP11B1, with selectivity factors (SF = IC50 CYP11B1/IC50 CYP11B2) around 170; thus, they are superior to fadrozole and LCI699 (SFs < 15). These potent CYP11B2 inhibitors exhibited no inhibition (IC50 > 50 μM) of a panel of hepatic CYP enzymes including CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 and the crucial steroidogenic enzymes, CYP17 and CYP19. Because of these advantageous profiles, compounds 14 and 23 are considered to be candidates for further in vivo evaluation.
    Journal of medicinal chemistry. 06/2014;
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    ABSTRACT: Estradiol is the most potent estrogen in humans. It is known to be involved in the development and proliferation of estrogen dependent diseases such as breast cancer and endometriosis. The last step of its biosynthesis is catalyzed by 17β-hydroxysteroid dehydrogenase type 1 (17β- HSD1) which consequently is a promising target for the treatment of these diseases. Recently, we reported on bicyclic substituted hydroxyphenylmethanones as potent inhibitors of 17β-HSD1. The present study focuses on rational structural modifications in this compound class with the aim of gaining more insight into its structure-activity relationship (SAR). (4-Hydroxyphenyl)-(5-(3-hydroxyphenylsulfanyl)-thiophen-2-yl)methanone (25) was discovered as a member of a novel potent class of human 17β-HSD1 inhibitors. Computational methods were used to elucidate its interactions with the target protein. The compound showed activity also towards the murine 17β-HSD1 enzyme and thus is a starting point for the design of compounds suitable for evaluation in an animal disease model.
    European journal of medicinal chemistry. 06/2014; 82:394-406.
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    ABSTRACT: PqsD mediates the conversion of anthraniloyl-coenzyme A (ACoA) to 2-heptyl-4-hydroxyquinoline (HHQ), a precursor of the Pseudomonas quinolone signal (PQS) molecule. Due to the role of the quinolone signaling pathway of Pseudomonas aeruginosa in the expression of several virulence factors and biofilm formation, PqsD is a potential target for controlling this nosocomial pathogen, which exhibits a low susceptibility to standard antibiotics. PqsD belongs to the β-ketoacyl-ACP synthase family and is similar in structure to homologous FabH enzymes in E. coli and Mycobacterium tuberculosis. Here, we used molecular dynamics simulations to obtain the structural position of the substrate ACoA in the binding pocket of PqsD, and semiempirical molecular orbital calculations to study the reaction mechanism for the catalytic cleavage of ACoA. Our findings suggest a nucleophilic attack of the deprotonated sulfur of Cys112 at the carbonyl carbon of ACoA and a switch in the protonation pattern of His257 whereby Nδ is protonated and the proton of Nε is shifted to the sulfur of CoA during the reaction. This is in agreement with the experimentally determined decreased catalytic activity of the Cys112Ser mutant, whereas the Cys112Ala, His257Phe, and Asn287Ala mutants are all inactive. ESI mass-spectrometric measurements of the Asn287Ala mutant show that anthraniloyl remains covalently bound to Cys112, thus further supporting the inference from our computed mechanism that Asn287 does not take part in the cleavage of ACoA. Since this mutant is inactive, we suggest instead that Asn287 must play an essential role in the subsequent formation of HHQ in vitro.
    Journal of Molecular Modeling 06/2014; 20(6):2255. · 1.98 Impact Factor
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    ABSTRACT: CBR703 was reported to inhibit bacterial RNA polymerase (RNAP) and biofilm formation, considering it to be a good candidate for further optimization. While synthesized derivatives of CBR703 did not result in more active RNAP inhibitors, we observed promising antibacterial activities. These again correlated with a significant cytotoxicity towards mammalian cells. Furthermore, we suspect the promising effects on biofilm formation to be artifacts. Consequently, this class of compounds can be considered unattractive as antibacterial agents.
    Antimicrobial Agents and Chemotherapy 05/2014; · 4.57 Impact Factor
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    ABSTRACT: Liver-specific overexpression of the insulin-like growth factor 2 (IGF2) mRNA binding protein p62/IGF2BP2-2 induces a fatty liver, which highly expresses IGF2. Since IGF2 expression is elevated in patients with steatohepatitis, the aim of our study was to elucidate the role and interconnection of p62 and IGF2 in lipid metabolism. Expression of p62 and IGF2 highly correlated in human liver disease. p62 induced an elevated ratio of C18:C16 and increased ELOVL fatty acid elongase 6 (ELOVL6) protein, the enzyme catalyzing the elongation of C16 to C18 fatty acids and promoting nonalcoholic steatohepatitis in mice and humans. p62 overexpression induced the activation of the ELOVL6 transcriptional activator SREBF1. Recombinant IGF2 induced the nuclear translocation of sterol regulatory element binding transcription factor 1 (SREBF1) and a neutralizing IGF2 antibody reduced ELOVL6 and mature SREBF1 protein levels. Concordantly, p62 and IGF2 correlated with ELOVL6 in human livers. Decreased palmitoyl-CoA levels as found in p62 tg livers can explain the lipogenic action of ELOVL6. Accordingly, p62 represents an inducer of hepatic C18 fatty acid production via a SREBF1-dependent induction of ELOVL6. These findings underline the detrimental role of p62 in liver disease.
    The Journal of Lipid Research 04/2014; · 4.39 Impact Factor
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    ABSTRACT: Increasing antibiotic resistance urgently requires novel therapeutic options to combat bacterial infections. The anti-virulence therapy selectively intervening with pathogenicity without affecting bacterial viability is such a strategy to overcome resistance. We consider the virulence regulator PqsR as an attractive target in the human pathogen Pseudomonas aeruginosa, and recently discovered the first PqsR antagonists, which, however, suffered from poor aqueous solubility. In this work, the antagonists were structurally modified to become more soluble, and their structure-activity as well as structure-property relationships were studied. A novel promising compound with improved solubility and enhanced anti-virulence activity was discovered (IC50: 3.8 μM, pyocyanin). Our findings emphasize the crucial role of substituents at the 3-position and the carbonyl group at the 4-position for ligand-receptor interactions, and illuminate the way for further optimization of PqsR antagonists as anti-virulence agents.
    European journal of medicinal chemistry 04/2014; 79C:173-183. · 3.27 Impact Factor
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    ABSTRACT: 1-Arylthio-2-naphthols are obtained as an unexpected result of the nucleophilic aromatic substitution reaction of β-naphthyl triflates with thiophenols.
    ChemInform 03/2014; 45(12).
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    ABSTRACT: Targeting PqsD is a promising novel approach to disrupt bacterial cell-to-cell-communication in Pseudomonas aeruginosa. In search of selective PqsD inhibitors, two series of benzamidobenzoic acids - one published as RNAP inhibitors and the other as PqsD inhibitors - were investigated for inhibitory activity toward the respective other enzyme. Additionally, novel derivatives were synthesized and biologically evaluated. By this means, the structural features needed for benzamidobenzoic acids to be potent and, most notably, selective PqsD inhibitors were identified. The most interesting compound of this study was the 3-Cl substituted compound 5 which strongly inhibits PqsD (IC50 6.2 μM) while exhibiting no inhibition of RNAP.
    European journal of medicinal chemistry 02/2014; 76C:343-351. · 3.27 Impact Factor
  • Qingzhong Hu, Lina Yin, Rolf W Hartmann
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    ABSTRACT: Besides the well-known roles of aldosterone as a mineralocorticoid in regulating homeostasis of electrolytes and volume, recent studies revealed that it is also a potent pro-inflammation factor inducing reactive oxygen species and up-regulating a panel of fibrosis related genes. Under pathological circumstances, excessive aldosterone is involved in a lot of chronic diseases, including hypertension, cardiac fibrosis, congestive heart failure, ventricular remodelling and diabetic nephropathy. Therefore, the inhibition of aldosterone synthase (CYP11B2), which is the pivotal enzyme in aldosterone biosynthesis, was proposed as a superior approach. Expected pharmacodynamic effects have been demonstrated in both animal models and clinical trials after the application of CYP11B2 inhibitors. The importance of selectivity over other steroidogenic CYP enzymes, in particular 11β-hydroxylase (CYP11B1), was also revealed. Recently, much more selective CYP11B2 inhibitors have been reported, which could be promising drug candidates for the treatment of aldosterone related diseases.
    Journal of Medicinal Chemistry 01/2014; · 5.61 Impact Factor
  • European Journal of Medicinal Chemistry. 01/2014; 79:173–183.
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    ABSTRACT: The Dyrk family of protein kinases is implicated in the pathogenesis of several diseases, including cancer and neurodegeneration. Pharmacological inhibitors were mainly described for Dyrk1A so far, but in fewer cases for Dyrk1B, Dyrk2 or other isoforms. Herein, we report the development and optimization of 2,4-bisheterocyclic substituted thiophenes as a novel class of Dyrk inhibitors. The optimized hit compounds displayed favorable pharmacokinetic properties and high ligand efficiencies, and inhibited Dyrk1B in intact cells. In a larger selectivity screen, only Clk1 and Clk4 were identified as additional targets of compound 48, but no other kinases frequently reported as off-targets. Interestingly, Dyrk1A is implicated in the regulation of alternative splicing, a function shared with Clk1/Clk4; thus, some of the dual inhibitors might be useful as efficient splicing modulators. A further compound (29) inhibited Dyrk1A and 1B with an IC50 of 130 nM, showing a moderate selectivity over Dyrk2. Since penetration of the central nervous system (CNS) seems possible based on the physicochemical properties, this compound might serve as a lead for the development of potential therapeutic agents against glioblastoma. Furthermore, an inhibitor selective for Dyrk2 (24) was also identified, which might be are suitable as a pharmacological tool to dissect Dyrk2 isoform-mediated functions.
    PLoS ONE 01/2014; 9(3):e87851. · 3.53 Impact Factor

Publication Stats

2k Citations
784.45 Total Impact Points


  • 2010–2014
    • Helmholtz Institute for Pharmaceutical Research Saarland
      Saarbrücken, Saarland, Germany
    • University of Vienna
      Wien, Vienna, Austria
  • 1992–2014
    • Universität des Saarlandes
      • Pharmazeutische und Medizinische Chemie
      Saarbrücken, Saarland, Germany
  • 2013
    • The German University in Cairo
      • Department of Pharmaceutical Chemistry
      Cairo, Muhafazat al Qahirah, Egypt
  • 2011–2012
    • The Maharaja Sayajirao University of Baroda
      • Department of Pharmacy
      Vadodara, State of Gujarat, India
  • 2004–2010
    • Panjab University
      Chandigarh, Chandīgarh, India
    • King Faisal Specialist Hospital and Research Centre
      • Department of Biological and Medical Research
      Jeddah, Mintaqat Makkah, Saudi Arabia
  • 2001–2010
    • University of Bologna
      • Department of Pharmacy and Biotechnology FaBiT
      Bologna, Emilia-Romagna, Italy
  • 2003–2007
    • University of Nantes
      Naoned, Pays de la Loire, France
  • 1987–2007
    • Universität Regensburg
      • Institut für Pharmazie
      Regensburg, Bavaria, Germany
  • 2006
    • Technische Universität Braunschweig
      • Institute of Medicinal and Pharmaceutical Chemistry
      Braunschweig, Lower Saxony, Germany
  • 1999
    • Laboratoire de Chimie de Coordination.
      Tolosa de Llenguadoc, Midi-Pyrénées, France