Mechanistic Classes of Antibacterials Benjamin D. Horning Group Meeting November 30, 2011 http://images.agoramedia.com/cs/eh/cs_diarrhea_antibiotics_causing_diarrhea_article.jpg http://www.irishhealth.com/content/image/853/Image1.jpg Walsh, C. T. Antibiotics: Actions, Origins, Resistance, American Society for Microbiology Press, Washington DC, 2003 Antibacterials- A Subclass of Antibiotics An antibiotic is “a chemical substance having the capacity, in dilute solution, to kill or inhibit growth of microorganisms.” This definition includes antifungals and antiprotozoals. Antibiotics travel inside the body to fight microorganisms, antiseptics are used externally, and disinfectants are for non-living surfaces. antimicrobials antibiotics disinfectants antiseptics antibacterials antifungals antiprotozoals applied to non- for external applications for internal or kill fungus kill protozoans living objects to living organisms external use (single-celled eukaryotes) http://www.lysol.com/images/products/no-mess-automatic-toiletbowl-cleaner.png, http://www.couponmamacentral.org/wp-content/uploads/2011/09/purell.jpg, http://www.medexpressrx.com/blog/wp-content/uploads/2010/07/antibiotics4.jpg, http://drugster.info/drug/medicament/22969/, http://modernmedicalguide.com/wp-content/uploads/2010/03/Antiprotozoal-Drugs.jpg Antibacterials- A Subclass of Antibiotics in vitro antibacterials human antibacterials veterinary and feedstock antibacterials S. pyogenes S. pneumoniae S. mutans Streptococcus pyogenes - strep throat, rheumatic fever, scarlet fever, necrotizing fasciitis Streptococcus pneumoniae - (bacterial) pneumonia Streptococcus agalactiae - meningitis, (bacterial) pneumonia Escherichia coli - gastroenteritis, urinary tract infections, sepsis, diarrhea (Methicillin-resistant) Staphylococcus aureus (MRSA) - Imepetigo, Staph infections, toxic shock syndrome Image from: http://inst.bact.wisc.edu/inst/images/book_3/chapter_13/13-3.jpg http://www.webcitation.org/5uJyti0mG http://www.medicinenet.com/sepsis/page4.htm Top-Selling Antibiotics in the USA O Me Me Me Me Me Me 21 54 N N 94 Me OH N F CO2H H H H H OH OH N N NH2 NH2 N O OH OH Me Me OH O OH O O OH O OH O O Levaquin (Levofloxacin) Solodyn (Minocycline) Doryx (Doxycycline) Ortho-McNeil Medicis Medicis $1,355 Million $673 Million $673 Million O O O 97 125 126 F CO2H F CO2H F CO2H H H N N N N N N HN HN OMe HN OMe H H Avelox (Moxifloxacin) Ciprodex otic Vigamox (Moxifloxacin) (Cipro and Dexamethasone) Merck Alcon $353 Million Alcon $255 Million $253 Million HO Me OH Me Me OH 138 O 160 H3N O 166 Me OH N HO O O H H O Cl OH O Me O O O N N H Cl OHMe Me HO O O O NH N Me H O H 2 N N F O H N N N OH N H O H H H NHMe H H OH O OH O O O HO O NH2 O Zyvox (Linezolid) HO OH Oracea (Doxycycline) OH Pfizer Vancocin (Vancomycin) ViroPharma Galderma $223 Million $192 Million $187 Million http://cbc.arizona.edu/njardarson/group/top-pharmaceuticals-poster Antibiotics- Why You Should Care of 57 million annual deaths Vaccinations and antibiotics can cure or prevent the majority of infectious diseases currently afflicting humanity. Antibiotic use introduces evolutionary selection pressure to bacteria; Resistant strains are selected for, and cause antibiotics to become ineffective. Bacterial resistance has been observed for every class of antibiotic introduced, sometimes within one year. New therapies will be needed. Graph from: Morens, D. M.; Folkers, G. K.; Fauci, A. S. Nature 2004, 430, 242-249 Table from: Palumbi, S. R. Science 2001, 293, 1786-1790 Strategies to Slow the Development of Antibiotic Resistance 108 bacteria 1 bacterium 108 bacteria antibiotic bacterial one error per 107 bases selection for completely resistant treatment growth 10 mutants (~0.3% of genes) resistant bacteria Overkill (multiple antibiotics) has worked well for HIV/AIDS, but not always applicable for bacteria (side effects). Direct observation therapy - continue antibiotic dose until no bacteria remain (not practical). Use narrow-spectrum antibiotics when applicable. Withhold the most powerful drugs - prevented vancomycin resistance for >30 years - difficult business model for pharma. Continue to develop new therapies and improve old therapies. Palumbi, S. R. Science 2001, 293, 1786-1790 Bacterial Resistance - Three Flavors Three types of bacterial resistance to antibiotics have been observed, coming either from random mutation under the selection pressure of antibiotics, or from antibiotic-producing NH2 bacteria. Resistance can be spread amongst bacteria via horizontal gene transfer. N N N N O H N O S Ph Me O N Me O OH O CO2H H2O RlmN Cfr !-lactamase Ph NH2 N N O NH Me N O S N Me Me O OH HN Me O CO2H O OH antibiotic modification export pumps enzymatic target (only natural products (efflux) modification and semisynthetics) http://www.sciencephoto.com/image/151999/530wm/C0089313-Active_efflux,_artwork-SPL.jpg Fujimori, D. G. et. al. J. Am. Chem. Soc. 2010, 132, 3953-3964 Paul Ehrlich and Drug Discovery Made seminial contributions in histology, haematology, immunology, oncology, microbiology and pharmacology. Alongside Ilya Mechnikov, won the Nobel Prize in Physiology or Medicine in 1908 “in recognition of their work on immunity.” Most famous for his discovery of Salvarsan (arsphenamine, #606), a compound for the treatment of syphilis, which was discovered during the first screen of a library of compounds for pharmaceutical activity, and later part of the first optimization of a lead, becoming the first blockbuster drug and presaging modern drug discovery. OH HO H2N HO H2N NH2 NH2 Paul Ehrlich and Sahachiro Hata H N As Frankfurt 1910 As 2 As As OH As OH As As As As As HO NH2 HO NH NH2 NH 2 2 Revised structure of Salvarsan OH HO NH2 OH Bosch, F.; Rosich, L. Pharmacology 2008, 82, 171-179 www.nobelprize.org/nobel_prizes/medicine/laureates/1908/ Salvarsan http://pubs.acs.org/cen/coverstory/83/8325/8325salvarsan.html Lloyd, N. C.; Morgan, H. W.; Nicholson, B. K.; Ronimus, R. S. Angew. Chem. Int. Ed. 2005, 44, 941-944 The Four Major Targets of Antibiotics Walsh, C. T. Nature Reviews Microbiology 2003, 1, 65-70 Walsh, C. T. Antibiotics: Actions, Origins, Resistance, American Society for Microbiology Press, Washington DC, 2003 The Four Major Targets of Antibiotics Antibiotics either target processes that are unique to bacteria - cell wall biosynthesis and folate metabolism - or processes that have different enough machinery to allow selective inhibition of bacterial over human versions - protein biosynthesis and DNA and RNA replication and repair. O O O H NH2 NH2 N Me S S S NH2 O O O O N H2N N H2N H N Sulfanilamide - 1936 2 Prontosil - 1932 Sulfacetamide O H N O CO2H S Me O N O O N H H H2N N HN N HO2C H Sulfamethoxazole H2N N N H Tetrahydrofolic acid NH2 OMe N H2N N OMe OMe Trimethoprim - 1940s Walsh, C. T. Nature Reviews Microbiology 2003, 1, 65-70 Walsh, C. T. Antibiotics: Actions, Origins, Resistance, American Society for Microbiology Press, Washington DC, 2003 Antibacterials Inhibiting Bacterial Folate Biosynthesis Prontosil was the first sulfa drug, discovered by O Gerhard Domagk while working for Bayer AG. NH2 S NH Bayer AG hoped to use its expertise in dyes to 2 O develop a Ehrlich-style “magic bullet” dye that could N N be selective for pathogenic bacteria, found Prontosil. Immensely successful as the first broad-spectrum H N 2 Prontosil - 1932 antibiotic. Bayer AG’s revenue stream was undercut when a team of French scientists found that Prontosil is a prodrug, and becomes sulfanilamide in the body, the patent for which had long ago expired. in vivo Gerhard Domagk metabolism Massive product and marketing of sulfanilamide Nobel Prize 1939 followed; One preparation, called Elixir “for the discovery Sulfanilamide, was a solution in ethylene glycol. of the antibacterial This raspberry-flavored concoction caused over effects of prontosil” O NH2 100 deaths in 1937. S O In 1938, the FDA passed the Federal Food, Drug H2N and Cosmetic Act, requiring safety tests for a variety of product. This is why we do clinical trials Sulfanilamide - 1936 for all new medicines today. http://www.nobelprize.org/nobel_prizes/medicine/laureates/1939/domagk.html# http://www.fda.gov/AboutFDA/WhatWeDo/History/ProductRegulation/SulfanilamideDisaster/default.htm for a history of clinical trials, see: http://blogs.scientificamerican.com/guest-blog/2011/10/06/molecules-to-medicine-clinical-trials-for-beginners/ Sulfa Drugs - Tetrahydrofolate Biosynthesis in Bacteria O O O O P P P P O O O OH O O O OH O- O- O- O- N N O H HN HN N CO2H S Me O N H2N N N para-amino H2N N N O H H H2N benzoate H2N 7,8-Dihydropteroate Synthase 7,8-Dihydropteroate Synthase O H N CO2H S O O Me O N O N N HN N HN N H H H2N N N H2N N N H H 7,8-Dihydropteroate 7,8-Dihydropteroate O CO2H O CO2H O N O N H NADPH H H N N HN N HO2C HN N HO2C H H H2N N N H2N N N H H 7,8-Dihydrofolate 5,6,7,8-Tetrahydrofolate Sulfa Drugs - Tetrahydrofolate Biosynthesis in Bacteria O O O O O H P P N P P O O O OH S O O O OH O- O- Me O- O- N O N N O H HN HN O N CO2H S H2N Me O N H2N N N para-amino SulfamethoxazoleH2N N N O H H H2N benzoate H2N combination 7,8-Dihydropteroate Synthase marketed as 7,8-Dihydropteroate Synthase co-trimoxazole O H N CO2H NH2 S O O Me OMe George H.O Hitchings N O N N N Nobel Prize 1988 HN N HN N H H “for their discoveries of H2N N OMe important principles for H2N N N H2N N N H OMe H drug treatment” 7,8-Dihydropteroate Trimethoprim 7,8-Dihydropteroate O CO2H O CO2H O N O N H NADPH H H N N HN N HO2C HN N HO2C H H H2N N N H2N N N H H 7,8-Dihydrofolate 5,6,7,8-Tetrahydrofolate Success and Failure with Bacterial Metabolite Biosynthesis OH O O Me fatty acid biosynthesis O N H OH OH O CO2H O platensymicin Me O N H H N n HN N HO2C OH H n H2N N N O H Me n Folate is an essential nutrient for humans, they cannot synthesize it.