Waleed M. Hussein

The identification of new metallo-β-lactamase inhibitor leads from fragment-based screening.

The emergence of metallo-β-lactamases (MBLs) capable of hydrolysing a broad spectrum of β-lactam antibiotics is particularly concerning for the future treatment of bacterial infections. This work describes the discovery of lead compounds for the development of new inhibitors using a competitive colorimetric assay based on the chromogenic cephalosporin CENTA, and a 500 compound Maybridge™ library suitable for fragment-based screening. The interactions between identified inhibitory fragments and the active site of the MBL from Klebsiella pneumoniae and Pseudomonas aeruginosa were probed by in silico docking studies.

3-mercapto-1,2,4-triazoles and N-acylated thiosemicarbazides as metallo-β-lactamase inhibitors.

The production of β-lactamases is an effective strategy by which pathogenic bacteria can develop resistance against β-lactam antibiotics. While inhibitors of serine-β-lactamases are widely used in combination therapy with β-lactam antibiotics, there are no clinically available inhibitors of metallo-β-lactamases (MBLs), and so there is a need for the development of such inhibitors. This work describes the optimisation of a lead inhibitor previously identified by fragment screening of a compound library. We also report that thiosemicarbazide intermediates in the syntheses of these compounds are also moderately potent inhibitors of the IMP-1 MBL from Pseudomonas aeruginosa. The interactions of these inhibitors with the active site of IMP-1 were examined using in silico methods.

Synthesis and kinetic testing of new inhibitors for a metallo-β-lactamase from Klebsiella pneumonia and Pseudomonas aeruginosa

There are currently no clinically useful inhibitors against metallo-β-lactamases (MBLs), enzymes that confer resistance against a broad spectrum of commonly used antibiotics and that are produced by an increasing number of bacterial pathogens. New pyrrole derivatives were synthesized and assayed for their inhibitory effect on the catalytic activity of the IMP-1 MBL from Pseudomonas aeruginosa and Klebsiella pneumoniae. Six compounds tested (3a-3c, 5, 7 and 8) show micromolar inhibition constants (K(i) values range from ∼10 to 30 μM). In silico docking was employed to investigate the binding mode of the strongest inhibitor, 3b, in the active site of IMP-1. Implications for further improvements of binding efficiency and specificity are discussed.

Advances in Peptide-based Human Papillomavirus Therapeutic Vaccines

Cervical cancer is the second leading cause of cancer in women worldwide. Human papillomavirus (HPV) is responsible for all cases of cervical cancer. Commercial prophylactic HPV vaccines are now available, but unfortunately these vaccines have no therapeutic effect against established HPV infections. In order to accelerate the control of cervical cancer and treat established HPV infections, it is necessary to develop therapeutic vaccines to eradicate HPV by generating cell-mediated immunity against HPV infected cells. Two HPV-encoded early proteins, the E6 and E7 oncoproteins, are the preferred targets because they are consistently expressed in virtually all cervical cancer cells and are necessary for the induction and maintenance of HPV-associated disease. A variety of vaccine strategies have been employed targeting immune responses to these proteins. Peptide-based vaccines are a promising strategy for the development of therapeutic HPV vaccines because of their safety, stability, and ease of production. This review summarizes the prospects of peptide-based vaccines for the treatment of established HPV infections. We address the challenges that scientists currently face for developing peptide-based vaccines and explore feasible strategies for improving the potency of the induced immune response with the aim of treating established HPV infections.

Synthesis and kinetic testing of tetrahydropyrimidine-2-thione and pyrrole derivatives as inhibitors of the metallo-β-lactamase from Klebsiella pneumonia and Pseudomonas aeruginosa

Metallo‐β‐lactamases (MBLs), produced by an increasing number of bacterial pathogens, facilitate the hydrolysis of many commonly used β‐lactam antibiotics. There are no clinically useful antagonists against MBLs. Two sets of tetrahydropyrimidine‐2‐thione and pyrrole derivatives were synthesized and assayed for their inhibitory effects on the catalytic activity of the IMP‐1 MBL from Pseudomonas aeruginosa and Klebsiella pneumoniae. Nine compounds tested (1a, 3b, 5c, 6b, 7a, 8a, 11c, 13a, and 16a) showed micromolar inhibition constants (Ki values range from ∼20–80 μm). Compounds 1c, 2b, and 15a showed only weak inhibition. In silico docking was employed to investigate the binding mode of each enantiomer of the strongest inhibitor, 5c (Ki = 19 ± 9 μm), as well as 7a (Ki = 21 ± 10 μm), the strongest inhibitor of the pyrrole series, in the active site of IMP‐1.

Toll-like receptor agonists: a patent review (2011 – 2013)

Introduction: Toll-like receptors (TLRs) are a crucial part of the innate immunity and present the first line of defense against pathogens. In humans, there are ten TLRs, with TLR3, 7, 8 and 9 located in intracellular vesicles and the remaining expressed on the cell surface. These transmembrane protein receptors recognize a wide range of pathogen components. A large number of TLR agonists, either derived from pathogen components or modified synthetic molecules, were developed and investigated for their ability to stimulate an immune response. Areas covered: This review includes an updated summary (2011 – 2013) of TLR agonists that have been published in patent applications and/or progressed to clinical studies, with an emphasis on their chemical structure, immune response, prophylactic and therapeutic outcomes. Expert opinion: A number of factors have contributed to the design and development of TLR agonists such as solving the crystal structures of TLR bound to their ligands, improvements in our understanding of the signaling pathway activated after TLR stimulation and the identification of the native ligands of all human TLRs. Some of the TLR agonists have been approved for human use by the FDA while others have reached clinical studies in Phases I, II and III. Generally, immunotherapy based on TLR agonists is very promising for the prevention and/or treatment of several disorders including cancer, allergy and microbial infections. However, many TLR agonists were withdrawn from further studies as they either lacked efficacy or caused serious side effects.

2-Mercaptobenzothiazole and its derivatives: Syntheses, reactions and applications

2-Mercaptobenzothiazole has found widespread industrial applications for the vulcanisation of rubber and, more recently, as a key component of the modified Julia olefination reaction. This review surveys the chemistry of 2-mercaptobenzothiazole, including its aromatic substitution reactions, redox chemistry and factors governing the regioselectivity of its alkylation reactions. In addition, the emerging synthetic uses of this heterocycle, including its application to the deoxygenation of epoxides, and the preparation of alkynes, are described.

Identification of Purple Acid Phosphatase Inhibitors by Fragment‐Based Screening: Promising New Leads for Osteoporosis Therapeutics

Purple acid phosphatases are metalloenzymes found in animals, plants and fungi. They possess a binuclear metal centre to catalyse the hydrolysis of phosphate esters and anhydrides under acidic conditions. In humans, elevated purple acid phosphatases levels in sera are correlated with the progression of osteoporosis and metabolic bone malignancies, making this enzyme a target for the development of new chemotherapeutics to treat bone‐related illnesses. To date, little progress has been achieved towards the design of specific and potent inhibitors of this enzyme that have drug‐like properties. Here, we have undertaken a fragment‐based screening approach using a 500‐compound library identifying three inhibitors of purple acid phosphatases with Ki values in the 30–60 μm range. Ligand efficiency values are 0.39–0.44 kcal/mol per heavy atom. X‐ray crystal structures of these compounds in complex with a plant purple acid phosphatases (2.3–2.7 Å resolution) have been determined and show that all bind in the active site within contact of the binuclear centre. For one of these compounds, the phenyl ring is positioned within 3.5 Å of the binuclear centre. Docking simulations indicate that the three compounds fit into the active site of human purple acid phosphatases. These studies open the way to the design of more potent and selective inhibitors of purple acid phosphatases that can be tested as anti‐osteoporotic drug leads.

Synthesis, modelling and kinetic assays of potent inhibitors of purple acid phosphatase

Purple acid phosphatases (PAPs) are binuclear metallohydrolases that have been isolated from various mammals, plants, fungi and bacteria. In mammals PAP activity is associated with bone resorption and can lead to bone metabolic disorders such as osteoporosis; thus human PAP is an attractive target to develop anti-osteoporotic drugs. Based on a previous lead compound and rational drug design, acyl derivatives of α-aminonaphthylmethylphosphonic acid were synthesised and tested as PAP inhibitors. Kinetic analysis showed that they are good PAP inhibitors whose potencies improve with increasing acyl chain length. Maximum potency is reached when the number of carbons in the acyl chain is between 12 and 14. The most potent inhibitor of red kidney bean PAP is the dodecyl-derivative with K(ic)=5 μM, while the most potent pig PAP inhibitor is the tetradecyl-derivative with K(ic)=8 μM, the most potent inhibitor of a mammalian PAP yet reported.

Self-Adjuvanting Therapeutic Peptide-Based Vaccine Induce CD8 + Cytotoxic T Lymphocyte Responses in a Murine Human Papillomavirus Tumor Model

Vaccine candidates for the treatment of human papillomavirus (HPV)-associated cancers are aimed to activate T-cells and induce development of cytotoxic anti-tumor specific responses. Peptide epitopes derived from HPV-16 E7 oncogenic protein have been identified as promising antigens for vaccine development. However, peptide-based antigens alone elicit poor cytotoxic T lymphocyte (CTL) responses and need to be formulated with an adjuvant (immunostimulant) to achieve the desired immune responses. We have reported the ability of polyacrylate 4-arm star-polymer (S4) conjugated with HPV-16 E744-57 (8Qmin) epitope to reduce and eradicate TC-1 tumor in the mouse model. Herein, we have studied the mechanism of induction of immune responses by this polymer-peptide conjugate and found prompt uptake of conjugate by antigen presenting cells, stimulating stronger CD8(+) rather than CD4(+) or NK cell responses.