AntifungalAntifungal PharmacologyPharmacology Deborah Fox, Ph.D. Children’s Hospital 3219 RIC 504-896-2766 [email protected] Special thanks to: John Perfect, MD Andy Alspaugh, MD Sevtap Arikan, MD John Rex, MD www.doctorfungus.org Objectives • To recognize the clinical significance of fungal infections • To identify the antifungal agents and their mechanisms of action • To evaluate potential antifungal drug interactions and toxicities • To differentiate the mechanisms of antifungal drug resistance LectureLecture outlineoutline • Clinical significance of fungal infection • Fungal cell structure and targets • Antifungal agents and mechanism of action • Antifungal drug interactions & nephrotoxicity • Mechanisms of antifungal resistance • Summary MycologyMycology ResourcesResources • http://www.doctorfungus.org • http://mycology.adelaide.edu.au/mycoses • http://mycology.cornell.edu/ • http://www.mycology.net/ LectureLecture outlineoutline • Clinical significance of fungal infection • Fungal cell structure and targets • Antifungal agents and mechanism of action • Antifungal drug interactions & nephrotoxicity • Mechanisms of antifungal resistance • Summary MedicalMedical ProblemsProblems CausedCaused byby FungiFungi 1) Allergic disease 2) “Mushroom” poisoning 3) Mycotoxins Secondary metabolites --many have industrial uses --Fusarium mycotoxin -- USSR after WWII --A. flavus “aflatoxin” 4) Mycoses -- infection and resulting disease cause by fungi TheThe FungiFungi 150 primary human fungal pathogens 100,000 Validly described species of fungi Fungi yet to be discovered -Kwon-Chung and Bennett, 1992 TheThe FungiFungi 150 primary human fungal pathogens 100,000 Validly described species of fungi Fungi yet to be discovered -Kwon-Chung and Bennett, 1992 TheThe FungiFungi Candida, 150 Aspergillus, primary human Crypto, Blasto, Histo, Cocci, Dermatophytes fungal pathogens 100,000 Validly described species of fungi Fungi yet to be discovered -Kwon-Chung and Bennett, 1992 RecentRecent eventsevents inin fungalfungal diseasesdiseases Problems of today: a. Growing population of immunocompromised i. Modern medical practices: transplantations, indwelling catheters, surgeries, anti-cancer therapies, broad-spectrum antibacterials, immunosuppressants; mycoses: especially candidiasis and aspergillosis ii. Natural diseases: AIDS; mycoses: especially candidiasis and cryptococcosis iii. Mean age of population is increasing; mycoses: especially candidiasis b. Special problems associated with immunocompromised. Candida, Aspergillus, i. Mycoses often are more severe, difficult to treat and diagnose. Crypto, Blasto, Histo, ii. Number of disease-causing fungi has increased. Cocci, Dermatophytes c. Mobile population. i. People commonly travel through areas of endemic mycoses, which presents diagnostic challenges. Advances in research: a. New antifungal agents and treatment options b. Tremendous increase in understanding of molecular basis of pathogenesis LectureLecture outlineoutline • Clinical significance of fungal infection • Fungal cell structure and targets • Antifungal agents and mechanism of action • Antifungal drug interactions & nephrotoxicity • Mechanisms of antifungal resistance • Summary 001 002 Fungal cell Cell membrane and cell wall Mannoproteins β-(1,6)-glucan β-(1,3)-glucan Chitin Phospholipid bilayer of cell membrane β-(1,3)-glucan synthase Ergosterol Ergosterol Synthesis DNA/RNA Synthesis Pathway Squalene ANTIFUNGAL DRUGS targets • Membrane disrupting agents • Glucan synthesis Amphotericin B, nystatin inhibitors • Ergosterol synthesis inhibitors Echinocandins Azoles, allylamines, morpholine • Nucleic acid inhibitor • Chitin synthesis Flucytosine inhibitor • Anti-mitotic (spindle disruption) Nikkomycin Griseofulvin • Protein synthesis inhibitors Sordarins, azasordarins LectureLecture outlineoutline • Clinical significance of fungal infection • Fungal cell structure and targets • Antifungal agents and mechanism of action • Antifungal drug interactions & nephrotoxicity • Mechanisms of antifungal resistance • Summary ANTIFUNGAL DRUGS classes • POLYENES • ECHINOCANDINS Amphotericin B, nystatin Caspofungin, • AZOLES anidulafungin, Imidazoles: Ketoconazole.. micafungin Triazoles: Fluconazole, itraconazole, voriconazole, • PEPTIDE-NUCLEOSIDE posaconazole, Nikkomycin Z ravuconazole • ALLYLAMINES • TETRAHYDROFURAN Terbinafine, butenafine DERIVATIVES • MORPHOLINE Sordarins, azasordarins Amorolfine • FLUORINATED PYRIMIDINE • OTHER Flucytosine Griseofulvin PolyenesPolyenes OH OH H3C O OH HO O OH OH OH OH O CH3 COOH H H3C O O CH3 amphotericin B OH NH2 OH OH OH H3C O OH HO O OH OH OH OH O CH3 COOH H3C O Nystatin A 1 O CH3 OH OH NH2 Amphotericin B Ergosterol Cell membrane ++++ Binding to ergosterol, CaCa++++ CaCa Intercalation of cell membrane Na++ ++ Na NaNa KK++ KK++ Leakage of intracellular cations and proteins AmphotericinAmphotericin BB • Mechanism: binds sterols, preferentially ergosterol, and disrupts osmotic integrity of cell membrane • Complications: fever, chills, myalgia, nephrotoxicity, thrombophlebitis • Pharmacokinetics: poorly soluble in water •rapid uptake by RES, then redistributed •four formulations • ampho B colloidal dispersion (ABCD; Amphotec) • amphotericin B lipid complex (ABLC; Abelcet) • liposomal amphotericin B (L-AMB; Ambisome) • oral amphotericin B (poor absorption) • Indications: broad range of activity, ABCD is mainstay of antifungal therapy Azoles,Azoles, allylaminesallylamines && morpholinesmorpholines ergosterol synthesis inhibitors Clin Microbiol Rev 1998; 11: 382 AzolesAzoles N N N O N F O N N N O O H C N 3 H Cl Cl N N ketoconazole OH F fluconazole N N N CH N 3 O O H3C N N N N O O N N N H Cl Cl N N F OH itraconazole N F CH 3 N H C F 3 N O O H3C voriconazole N N N N O HO N H F F posaconazole Azole Cell membrane Ergosterol Ergosterol Synthesis Pathway Squalene Accumulation of toxic sterols in cell membrane Toxic sterols Inhibition of 14-alpha-demethylase AzolesAzoles • Mechanism: block ergosterol synthesis via inhibition of cytochrome P450 dependent 14α-demethylase (Erg11) • Complications: well-tolerated, hepatotoxicity, hypertension, headache, visual disturbances, resistance • Formulations: poorly soluble in water, fungistatic • Fluconazole (Diflucan) • Voriconazole (Vfend) • Ravuconazole • Itraconazole (Sporanox) • Posaconazole • Ketoconazole (Nizoral) • Indications: Candida, Cryptococcus, Coccidioides, Histoplasma, Blastomyces, some Aspergillus spp. Azoles,Azoles, allylaminesallylamines && morpholinesmorpholines ergosterol synthesis inhibitors Clin Microbiol Rev 1998; 11: 382 Allylamines,Allylamines, morpholinesmorpholines CH3 C(CH3)3 N terbinafine CH 3 H3C CH3 CH3 O CH3 N H3C butenafine Allylamines,Allylamines, morpholinesmorpholines • Mechanism: block ergosterol synthesis via inhibition of squalene epoxidase (allylamines), sterol reductase and isomerase activity (morpholines) • Complications: mild gastrointestinal and skin reactions • Formulations: poorly soluble in water, oral and topical, fungicidal • Terbinafine (Lamisil) • Amorolfine (Loceryl) • Butenafine (Mentax) • Indications: dermatophytes, Candida (Mentax) HO OH O HO O EchinocandinsEchinocandins NH H3C NH H2N N O N O HN OH O O HO NH O CH3 H2N O N H HO N NH OH OH O OH O S OH O O HO O NH O O H N HO micafungin O H H2N N OH O HN H3C H3C H H CH3 CH3 CH3 HO OH HO NH O H H O O H HO O N OH OH NH H3C NH O OH N O H3C O HN OH HO NH O CH3 HO caspofungin O N O H HO N H3C OH O OH anidulafungin HO Mannoproteins ß(1,6)-glucan ß(1,3)-glucan Chitin Phospholipid bilayer of cell membrane ß(1,3) glucan synthase glucan synthase inhibitor Depletion of ß(1,3) glucans in cell wall Inhibition of ß(1,3) glucan synthase EchinocandinsEchinocandins • Mechanism: block cell wall synthesis via β-1,3 glucan synthesis inhibition • Complications: well-tolerated, histamine release, no activity against Cryptococcus, Fusarium spp. • Formulations: poorly soluble in water, fungicidal • Caspofungin (Cancidas) • Micafungin • Anidulafungin (Eraxis) • Indications: Candida, Aspergillus spp. AntimetabolitesAntimetabolites OCH 3 OCH H O 3 N O O N O F H3CO H3C Cl NH2 flucytosine griseofulvin CytosineCytosine permeasepermease 5-FC 5-FC CytosineCytosine deaminasedeaminase 5-FC 5-FU PhosphorylationPhosphorylation FdUMP FdUMP FUTP ConversionConversion toto dUMP deoxynucleosidesdeoxynucleosides dTMP SubstitutionSubstitution forfor uraciluracil InhibitionInhibition ofof ProteinProtein SynthesisSynthesis InhibitionInhibition ofof thymidylatethymidylate synthasesynthase InhibitionInhibition ofof DNADNA synthesissynthesis 5-FC, 5-fluorocytosine; 5-FU, 5-fluorouracil; FdUMP, 5-fluorodeoxyuridine; FUMP, 5-fluorouridine monophosphate; FUDP, 5-fluorouridine diphosphate; FUTP, 5-fluorouridine triphosphate; dUMP, deoxyuridine monophosphate; dTMP, deoxythymidine monophosphate AntimetabolitesAntimetabolites • Mechanism: block fungal DNA and protein synthesis (Flucytosine), fungal mitosis (Griseofulvin) • Complications: GI intolerance, bone marrow suppression, hepatotoxicity, headache, hallucinations, sedation, nausea • Formulations: poorly soluble in water • Flucytosine (Ancobon) • Griseofulvin (Grifulvin V, Fulvicin U/F, Grisactin, Peninol) • Indications: (Flucytosine): for resistant Candida, Aspergillus spp. and in combination with Ampho B for Cryptococcus; (Griseofulvin): dermatophytes LectureLecture outlineoutline • Clinical significance of fungal infection • Fungal cell structure and targets • Antifungal agents and mechanism of action • Antifungal drug interactions & nephrotoxicity • Mechanisms of antifungal