• Cystobactamid 507: Concise Synthesis, Mode of Action and Optimization toward More Potent Antibiotics.

      Elgaher, Walid A M; Hamed, Mostafa M; Baumann, Sascha; Herrmann, Jennifer; Siebenbürger, Lorenz; Krull, Jana; Cirnski, Katarina; Kirschning, Andreas; Brönstrup, Mark; Müller, Rolf; et al. (Wiley-VCH, 2020-01-26)
      Lack of new antibiotics and increasing antimicrobial resistance are the main concerns of healthcare community nowadays, which necessitate the search for novel antibacterial agents. Recently, we discovered the cystobactamids - a novel natural class of antibiotics with broad-spectrum antibacterial activity. In this work, we describe a concise total synthesis of cystobactamid 507, the identification of the bioactive conformation using non-covalently bonded rigid analogs, the first structure–activity relationship (SAR) study for cystobactamid 507 leading to new analogs with high metabolic stability, superior topoisomerase IIA inhibition, antibacterial activity and, importantly, stability toward the resistant factor AlbD. Deeper insight into the mode of action revealed that the cystobactamids employ DNA minor groove binding as part of the drug–target interaction without showing significant intercalation. By designing a new analog of cystobactamid 919-2 we finally demonstrated that these findings could be further exploited to obtain more potent hexapeptides against Gram-negative bacteria.
    • Discovery and Structure-Based Optimization of 2-Ureidothiophene-3-carboxylic Acids as Dual Bacterial RNA Polymerase and Viral Reverse Transcriptase Inhibitors.

      Elgaher, Walid A M; Sharma, Kamal K; Haupenthal, Jörg; Saladini, Francesco; Pires, Manuel; Real, Eleonore; Mély, Yves; Hartmann, Rolf W; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016-07-07)
      We are concerned with the development of novel anti-infectives with dual antibacterial and antiretroviral activities for MRSA/HIV-1 co-infection. To achieve this goal, we exploited for the first time the mechanistic function similarity between the bacterial RNA polymerase (RNAP) "switch region" and the viral non-nucleoside reverse transcriptase inhibitor (NNRTI) binding site. Starting from our previously discovered RNAP inhibitors, we managed to develop potent RT inhibitors effective against several resistant HIV-1 strains with maintained or enhanced RNAP inhibitory properties following a structure-based design approach. A quantitative structure-activity relationship (QSAR) analysis revealed distinct molecular features necessary for RT inhibition. Furthermore, mode of action (MoA) studies revealed that these compounds inhibit RT noncompetitively, through a new mechanism via closing of the RT clamp. In addition, the novel RNAP/RT inhibitors are characterized by a potent antibacterial activity against S. aureus and in cellulo antiretroviral activity against NNRTI-resistant strains. In HeLa and HEK 293 cells, the compounds showed only marginal cytotoxicity.
    • Discovery of Novel Latency-Associated Nuclear Antigen Inhibitors as Antiviral Agents Against Kaposi's Sarcoma-Associated Herpesvirus.

      Kirsch, Philine; Jakob, Valentin; Elgaher, Walid A M; Walt, Christine; Oberhausen, Kevin; Schulz, Thomas F; Empting, Martin; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany.;HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (American Chemical Society (ACS), 2020-01-24)
      With the aim to develop novel antiviral agents against Kaposi's Sarcoma Herpesvirus (KSHV), we are targeting the latency-associated nuclear antigen (LANA). This protein plays an important role in viral genome maintenance during latent infection. LANA has the ability to tether the viral genome to the host nucleosomes and, thus, ensures latent persistence of the viral genome in the host cells. By inhibition of the LANA-DNA interaction, we seek to eliminate or reduce the load of the viral DNA in the host. To achieve this goal, we screened our in-house library using a dedicated fluorescence polarization (FP)-based competition assay, which allows for the quantification of LANA-DNA-interaction inhibition by small organic molecules. We successfully identified three different compound classes capable of disrupting this protein-nucleic acid interaction. We characterized these compounds by IC50 dose-response evaluation and confirmed the compound-LANA interaction using surface plasmon resonance (SPR) spectroscopy. Furthermore, two of the three hit scaffolds showed only marginal cytotoxicity in two human cell lines. Finally, we conducted STD-NMR competition experiments with our new hit compounds and a previously described fragment-sized inhibitor. Based on these results, future compound linking approaches could serve as a promising strategy for further optimization studies in order to generate highly potent KSHV inhibitors.
    • Spray-drying of inhalable, multifunctional formulations for the treatment of biofilms formed in cystic fibrosis.

      Lababidi, Nashrawan; Ofosu Kissi, Eric; Elgaher, Walid A M; Sigal, Valentin; Haupenthal, Jörg; Schwarz, Bianca C; Hirsch, Anna K H; Rades, Thomas; Schneider, Marc; HIPS, Helmholtz-Institut für Pharmazeutische Forschung Saarland, Universitätscampus E8.1 66123 Saarbrücken, Germany. (Elsevier, 2019-11-28)
      Cystic fibrosis (CF) is a serious lung disease, commonly susceptible to Pseudomonas aeruginosa colonization. The dense mucus together with biofilm formation limit drug permeability and prevent the drug from reaching the site of action, causing treatment failure of the bacterial infection. Besides the use of antibiotics, the mucolytic agent N-acetylcysteine (NAC) is recommended to be co-administered in the treatment of CF. Although several formulations have been developed for inhalation therapy to improve the pulmonary condition in CF patients, there is still no comprehensive study on a combined multifunctional dry powder formulation of antibiotics with NAC. In this work, we developed an innovative multifunctional dry powder inhaler (DPI) formulation based on salt formation between NAC and antibiotics and characterized their solid state properties and physical stability. NAC could be spray dried together with three different antibiotics, azithromycin (Azi), tobramycin (Tobra) and ciprofloxacin (Cipro), without the use of organic solvents to form Azi/NAC, Tobra/NAC and Cipro/NAC DPI formulations. Solid-state characterization of these DPI formulations showed that they were amorphous after spray drying. Azi/NAC and Tobra/NAC form co-amorphous salt systems that were physically stable under storage at stress conditions. For particle characterization, the obtained mass median aerodynamic diameters were in a suitable range for inhalation (< 5.0μm). The multifunctional antibiotic/NAC formulations conserved or improved the antibiotic susceptibility and showed promising results regarding the inhibition of P. aeruginosa PA14 biofilm formation.