Protein Synthesis Inhibitors Part I Slides PDF

Protein Synthesis Inhibitors/Ribosomal Agents Part I: Tetracyclines, Glycylcyclines, and Oxazolidinones (Course: Phar 5337) Dakshina M. Jandhyala PhD, Email: [email protected] Phone: 713 743‐0475 Office: 6009, Health 2 Learning Objectives • Identify the mechanism of action for Tetracyclines and...

Protein Synthesis Inhibitors/Ribosomal Agents Part I: Tetracyclines, Glycylcyclines, and Oxazolidinones (Course: Phar 5337) Dakshina M. Jandhyala PhD, Email: [email protected] Phone: 713 743‐0475 Office: 6009, Health 2 Learning Objectives • Identify the mechanism of action for Tetracyclines and Oxazolidinones • Identify resistance paradigms employed by bacteria to resist the action of these antibiotics • Identify the spectrum for these antibiotics • Identify the common formulations and routes of administration for these antibiotics • Identify key PK/PD characteristics of these antibiotics • Identify any adverse reactions or key drug‐drug interactions with these antibiotics Protein Synthesis and the Ribosome https://micro.magnet.fsu.edu/cells/ribosomes/ribosomes.html Steps in bacterial protein synthesis and targets of several antibiotics. Amino acids are shown as numbered circles. The 70S ribosomal mRNA complex is shown with its 50S and 30S subunits. In step 1, the charged tRNA unit carrying amino acid 6 binds to the acceptor site on the 70S ribosome. The peptidyl tRNA at the donor site, with amino acids 1 through 5, then binds the growing amino acid chain to amino acid 6 (transpeptidation, step 2). The uncharged tRNA left at the donor site is released (step 3), and the new 6-amino acid chain with its tRNA shifts to the peptidyl site (translocation, step 4). The antibiotic-binding sites are shown schematically as triangles. Chloramphenicol (C) and macrolides (M) bind to the 50S subunit and block transpeptidation (step 2). The tetracyclines (T) bind to the 30S subunit and prevent binding of the incoming charged tRNA unit (step 1). (Reproduced, with permission, from Katzung BG, editor: Basic & Clinical Pharmacology, 12th ed. McGraw-Hill, 2012: Fig. 44–1.) Citation: Chapter 44 Tetracyclines, Macrolides, Clindamycin, Chloramphenicol, Streptogramins, & Oxazolidinones, Katzung BG, Kruidering-Hall M, Trevor AJ. Katzung & Trevor's Pharmacology: Examination & Board Review, 12e; 2019. Available at: https://accesspharmacy.mhmedical.com/content.aspx?sectionid=197945582&bookid=2465&Resultclick=2 Accessed: October 01, 2020 Copyright © 2020 McGraw-Hill Education. All rights reserved Tetracyclines and Glycylcyclines • Large class of antibiotics originally discovered in the 1940s as produced by Streptomyces species but which now include several semisynthetic derivatives with a common 4‐ring backbone • Glycylcyclines are semisynthetic tetracycline “congers” with activity against many tetracycline resistant bacteria Tetracyclines and Glycylcyclines • Key Tetracyclines and Glycylcylines: • Tetracycline • *Doxycyline • *Minocycline • Tigecycline (Tygacil) • Omadacycline (recently approved and not heavily used) • Eravacycline (recently approved and not heavily used) *Most frequently prescribed Tetracycline Doxycycline Minocycline Tigecycline Omadacycline Eravacycline Tetracycline Doxycycline Minocycline Tigecycline Omadacycline Eravacycline Mechanism of Action • Tetracyclines reversibly bind to the A‐site on the 30S ribosomal subunit • Sterically blocking amino‐acyl‐tRNAs from docking in the A‐site during elongation • Results in translational arrest Mechanism of Action • Tetracyclines bind to the A site on ribosome http://www.antibiotics‐info.org Cellular Entry • Gram(‐) bacteria and Mycobacteria – Passive diffusion through Outer Membrane Porins (OMPs) • Cytoplasmic membrane – Mediated by active transporters (energy utilizing pumps) Mechanisms of Resistance • Reduced uptake and/or Efflux • Ribosomal protection • Enzymatic inactivation Mechanisms of Resistance • Reduced uptake and/or Efflux • Ribosomal protection • Enzymatic inactivation Reduced uptake and/or Efflux • Gram negative organisms and mycobacteria – Mutations in outermembrane porins (OMPs) (OmpF and OmpC) • Loss of a particular porin • Decreased gene expression of a porin • Functional/structural mutation in a porin (decreased antibiotic permeability) • Active Efflux – Important for multi‐drug resistance (MDR) OmpF RNAP OmpF Transcription ompF Antibiotic Lipopolysaccharide RNAP Inactivating mutation R Repressor Binding OmpF Antibiotic Lipopolysaccharide Reduced uptake and/or Efflux • Gram negative organisms and mycobacteria – Mutations in outermembrane porins (Omps) • Loss of a particular porin • Decreased gene expression of a porin • Functional mutation in a porin (decreased antibiotic permeability) • Active Efflux – Important for multi‐drug resistance (MDR) but it can also occurs in a tetracycline class specific manner. AcrAB Efflux pump H+ H+ H+ H+ H+ H+ H+ H+ Mechanisms of Resistance • Reduced uptake and/or Efflux • Ribosomal protection • Enzymatic inactivation Mechanisms of Resistance • Reduced uptake and/or Efflux • Ribosomal Protection A) Mutations in ribosomal proteins and/or RNA (e.g. 16S) that effect structure and interactions with tetracycline B) Ribosomal protection proteins (RPPs) • GTPases similar in structure to elongation factors • Associated with transferable genetic elements (e.g. plasmids, transposons) • Catalyze release of tetracyclines from the ribosome • Enzymatic inactivation Mechanisms of Resistance • Reduced uptake and/or Efflux • Ribosomal protection A) Mutations in ribosomal proteins, enzymes, and/or RNA (e.g. 16S) that effect structure and interactions with tetracycline B) Ribosomal protection proteins (RPPs) • GTPases similar in structure to elongation factors • Catalyze release of tetracyclines from the ribosome • Associated with transferable genetic elements (e.g. plasmids, transposons) • Enzymatic inactivation Mechanisms of Resistance • Reduced uptake and/or Efflux • Ribosomal mutations • Ribosomal protection • Enzymatic inactivation Enzymatic inactivation • Tet(X) – Flavin dependent monooxygenase • Can inactivate all tetracyclines • Often associated with plasmids and mobile DNA elements • Other less‐well characterized enzymes Mechanisms of Resistance • Reduced uptake and/or Efflux– OMPs and Efflux Pumps • Ribosomal protection – A) Mutations in ribosome associated RNAs and proteins B) Ribosomal Protection Proteins (RPPs) • Enzymatic inactivation – TetX Categories – Mechanisms of resistance Produces an enzyme that inactivates the drug Efflux pump Changes the drug target site Porin loss Alternative pathway Spectrum • Broad spectrum including Gram (+), Gram (‐), spirochetes, mycoplasma, obligate intracellular bacteria, and protozoan parasites • Bacteriostatic • Doxycycline and Minocycline not reliable for S. pyogenes, but great for non‐resistant S. pneumonia, MRSA, and H. inluenzae as well as atypical pathogens (e.g. Legionella, Chlamydia, and Mycoplasma) • Tigecycline is effective in strains typically resistant by efflux and RPPs. Exceptions Proteus and Pseudomonas species • Omadacylcine – Active against tetracycline resistant S. pneumoniae • Eravacycline is active against organisms producing ESBL and KPC‐producing gram‐negatives • No Activity against Pseudomonas aeruginosa Formulations • Tetracycline – Oral only • Doxycyline, Minocycline,– Available in a variety of oral, topical, and parenteral formulations • Tigecycline (Tygacil) ‐ Parenteral only Pharmacodynamics Tetracyclines • Area under the curve/minimum inhibitory concentration AUC/MIC yields best correlation with efficacy • Post‐antibiotic effect observed up to 3 hours Absorption • Absorption (Oral) • Occurs in the stomach and proximal small intestine (Peak [serum] 1‐3 hours) • Absorption is inhibited by divalent and trivalent cations (chelation) • • • • Dairy (exception Doxycycline) Antacids Aluminum hydroxide gels Supplements (iron, zinc, etc.) • Food decreases absorption up to 50 % (exception Doxycycline) • Absorption (Parenteral) • Rapid with Peak concentrations at 30 and 60 min (Doxycycline and Tigecycline/Tygacil respectively) Distribution Tetracyclines • Distribution – Widely distributed • VOD = 50‐700 liters ~ 0.7‐10L/kg • Highly Protein Bound ~ 90% • Tissue penetrance correlates with lipid solubility minocycline > doxycycline > tetracycline • Cerebral Spinal Fluid (0.2% penetrance) • Amniotic fluid and fetal circulation • High concentrations in breast milk (limited availability to infant) • Tigecycline (Tygacil) – Has poor availability (low concentration) in the blood, but good tissue distribution. Don’t use alone to treat a bloodstream infection/bacteremia. Metabolism and Elimination • Tetracycline – Mostly excreted through the kidney but a major CYP3A4 substrate. Only tetracycline requiring dose reduction with renal impairment • Doxycycline – Eliminated through the intestinal tract, up to 90% through feces and up to 20 % through the kidney • Minocycline – Metabolized in the liver* with less than 10 % eliminated through the kidney. No accumulation during liver failure! • Tigecycline (Tygacil) – Metabolized in the liver, dose reduction required for severe liver disease (Child‐Pugh Class C), also eliminated in feces and urine Adverse Effects • Dental Staining – Tetracyclines should not be used in children under 8 years of age. Doxycycline is an exception (for durations up to 21 days*) *https://www.aappublications.org/news/2020/02/27/idsnapshot022720 Adverse Effects (2) • Photosensitivity | QJM: An International Journal of Medicine, 2018, Vol. 111, No. 4 Adverse Effects (3) • GI distress – Most common symptom associated with tetracyclines • Increased frequency with tigecycline (Tygacil) • Food may decrease symptoms but also absorption • Esophagal ulcerations are preventable with increased water intake during administration of drug (oral) • Hypersensitivity reactions – Rare • Hepatotoxicty – Rare but can be fatal. More common with tetracycline and minocycline Adverse Effects (4) • Mortality (Tigecycline/Tygacil) – Tigecycline is associated with increased mortality compared with other antibiotics • Jarisch‐Herxheimer type reaction (JHR) – Associated with spirochetal infections (e.g. syphilis, tick‐borne relapsing fever) – Prevention is of limited value • Pretreatment with acetaminophen or meptazinol • Best results using Anti‐TNF and steroids Special Populations • Children – Accumulation in fetal bones (slows growth) and teeth. Short courses (up to 21 days) with doxycylcline. • Pregnancy – Risk of maternal hepatoxicity and accumulation in fetal bones and teeth. • No teratogenic effects associated with doxycycline • Doxycycline may be appropriate for treatment of serious infections with limited alternatives e.g. Rickettsia rickettsia Drug‐Drug Interactions of Note • Divalent/Trivalent Cations – Agents containing these cations should not be administered with tetracyclines. Patients should be counselled to take Tetracyclines either 2 hours before or 4 hours after a meal • Isotretinoin (Accutane) – Tetracyclines enhances the toxic effects, so do not use these in combination • CYP3A4 interactions – Caution when using tetracyclines (mainly tetracycline but also eravacycline) with drugs that interact with CYP3A4 Tetracycline Summary • Key compounds – Tetracycline, Doxycycline, Minocycline, Tigecycline, Omadacycline, and Eravacycline • MOA – Inhibits protein synthesis by binding the A‐site on 30S ubunit of the bacterial ribosome • Spectrum – Broad and mostly bacteriostatic • Resistance – • Prevent uptake and/or increase efflux (MDR, efflux pumps) • Ribosomal protection – GTPase RPPs that catalyze the release of tetracycline from the ribosomes. Mutations to the ribosome are less frequent • Enzymatic inactivation/modification of drug ex. Tet(X) Tetracycline Summary (2) • Formulations: • • • • Oral only – Tetracycline Oral and Parenteral – Doxycycline and Minocycline Parenteral only – Tigecycline Topical – Doxycycline, and Minocycline Tetracycline Summary (3) • Efficacy – AUC/MIC • Postantibiotic Effect • Absorption (Oral) ‐ inhibited by cations, food, and dairy exception doxycycline • Distribution – Wide distribution • Metabolism and Elimination: • Tetracycline – Renal and major CYP3A4 substrate • Dose reduction for patients with impaired renal function (Only tetracycline) • Doxycycline – Feces and urine • Minocycline – Mainly Liver, < 10% through the kidney • Tigecycline – Metabolized in the liver, eliminated also in feces, and urine. • Dose reduction required for Child‐Pugh Class C Tetracycline Summary (4) • Common Adverse Effects: • • • • • Dental Staining Photosensitivity Gastrointestinal upset Hepatoxicity Jarisch‐Herxheimer (spirochetal infections) • Drug‐drug interactions: • Divalent/trivalent cations (antacids, supplements) • Isotretinoin (Accutane) • Cyp3A4 interacting drugs (mostly tetracycline and eravacycline) Tetracyclines General • Tetracycline ‐ Rarely used except for H. pylori (requires dosing every 6 hours and has lots of drug‐drug interactions • Doxycycline and Minocycline – Prescribed for various infections, only requires dosing every 12 hours and has fewer drug‐drug interactions • Tigecycline ‐ Data suggests increased mortality, nausea, vomiting. It is used rarely as part of combination therapy for multidrug resistant (MDR) organism. Oxazolidinones: Structure Tedizolid Phosphate Linezolid P T. 2014 Aug; 39(8): 555‐558, 579. Oxazolidinones: Mechanism of Action • Oxazolidinones bind the 50S subunit in the P‐site on the 23S rRNA http://www.chm.bris.ac.uk/motm/li nezolid/linezolid.htm Oxazolidinones: Resistance • Target modifications: • Point mutations to the 23S rRNA • Mutations to ribosomal proteins near the binding site • Transferable cfr encodes a rRNA methyltransferase • Confers cross‐resistance with lincosamides, pleuromutilins, and Streptogramins • A‐2503 of 23S rRNA • cfr strains are susceptible to Tedizolid • Tedizolid may be active against some linezolid resistant strains (Example: cfr strains) Oxazolidinones: Spectrum • Narrow Spectrum – Both drugs are used to target antibiotic resistant Gram‐positive organisms such as MRSA, VRSA, VRE, and penicillin resistant strains of S. pneumonia • Mostly bacteriostatic Categories – Mechanisms of resistance Produces an enzyme that inactivates the drug Efflux pump Changes the drug target site Porin loss Alternative pathway Oxazolidinones : Formulations and dosing Both Linezolid and Tedizolid are available in oral and parenteral formulations. Tedizolid is formulated in its prodrug phosphate form. Linezolid is typically given at 600 mg 2X/day Tedizolid has a longer ½‐life than Linezolid, (12 hours vs 4‐6 hours) so it can be dosed at 200 mg 1X/day. Oxazolidinones: ADME • Absorption and Distribution– Both Oxazolidinones are well‐absorbed orally and widely bioavailable 100% and 80% respectively for Linezolid and Tedizolid • Linezolid CSF concentrations are 60‐70% of serum levels • Linezolid and Tedizolid are protein bound at ~ 30% and 70‐90% respectively • Metabolism • Linezolid – non‐enzymatically oxidized in the liver • Tedizolid – undergoes sulfation in the liver • Elimination • Linezolid – 90% eliminated in urine, 10% in feces • Tedizolid ‐ Mainly eliminated in the feces Oxazolidinones : Adverse Reactions • Myelosuppression (Linezolid) – Thrombocytopenia (most common), neutropenia, and anemia with onset between days 7 and 10 • Mitochondrial Toxicities (Linezolid) – Peripheral neuropathies, optic neuritis, and lactic acidosis associated with long‐term treatments > 6 weeks • Nausea Oxazolidinones: Drug‐Drug Interactions • Serotonin Syndrome – Monoamine Oxidase is inhibited by Linezolid as a result people on SSRIs and SNRIs (e.g. tramadol, fentanyl, Effexor) can develop serotonergic symptoms • Avoid this combination especially if the patient is on multiple serotoninergic drugs. • If you must use these together, patient should be in a monitored setting. Summary: Oxazolidinones (Linezolid and Tedizolid) • Mechanism of action – Bind the 23S rRNA on the 50S Ribosome preventing 70S ribosome formation and initiation • Spectrum ‐ Narrow spectrum used mainly for the treatment of drug‐ resistant Gram (+) bacteria • Resistance – Target modification associated with specific point mutations on the 23S rRNA that perturb drug binding or methylation • Formulations – Available in both oral and parenteral formulations • Tedizolid is formulated as a prodrug, tedizolid phosphate Summary: Oxazolidinones (Linezolid and Tedizolid) (2) • ADME – • • • • Well absorbed orally highly bioavailable including CSF metabolized in the liver Linezolid is eliminated mostly in the urine and Tedizolid in the Feces • Adverse reactions – Myelosuppression, and mitochondrial toxicity (Linezolid) • Drug‐Drug interactions – SSRIs and SNRIs Usually used for Ineffective or poor activity Formulations Factoid(s) of note Tetracycline H. pylori P. aeruginosa Oral Doxycycline and Minocycline MRSA H. influenzae Penicillin‐susceptible S. pneumoniae Atypicals – e.g. Legionella Strains with Efflux or RPP resistance Tetracycline resistant S. pneumoniae P. aeruginosa S. pyogenes Oral Topical Parenteral Fewest Drug‐Drug interactions, Dairy and Doxy are OK P. aeruginosa Proteus sp. P. aeruginosa Parenteral only Effective against many strains with RPPs or Efflux resistance Relatively new (2018) P. aeruginosa Parenteral only Linezolid ESBL and KPC expressing Gram (‐) Antibiotic resistant Gram (+) Gram (‐) Tedizolid Antibiotic resistant Gram (+) Gram (‐) Oral and Parenteral Oral and Parenteral Tigecycline Omadacyclin e Eravacycline Oral Intravenous Used rarely except H. pylori Effective against ESBL and KPC producing Gram(‐) Longer ½‐life 1X/day and effective against some linezolid resistant cfr strains Formulations *Tetracycline Doxycycline Minocycline **Tigecycline Distribution Metabolism and Elimination Oral Wide *Urine but also major CYP3A4 substrate Oral, topical, and parenteral Oral, topical, and parenteral Parenteral only Wide Up to 90% through feces and up to 20% via the kidney Mostly metabolized in the liver **Eravacycline Oral and parenteral Parenteral only Linezolid Oral and parenteral Tedizolid phosphorylated prodrug available for oral and parenteral administration Omadacycline Wide Good in Tissue Poor in Blood Wide Mostly through the Liver ** Wide ~34% via urine and 47% via feces, minor CYP3A4 substrate ** Non‐ezymatic oxidation in the liver mostly eliminated in the urine Sulfation in the liver mostly eliminated in the feces CSF = 70% serum, 30% protein bound 70‐90% protein bound Urine and Feces *Only one in the class that requires dose reduction for patients with renal insufficiency ** Dose reduction required for liver disease Child‐Pugh Class C