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Chemotherapy > Mechanism of Action > Flashcards

Mechanism of Action Flashcards

1
Q

Penicillins

A

Interacts with cytoplasmic binding proteins (PBPs) to inhibit transpeptidation reactions involved in cross-linking (the final steps in cell wall synthesis)

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2
Q

Cephalosporins

A

Interacts with cytoplasmic binding proteins (PBPs) to inhibit transpeptidation reactions involved in cross-linking (the final steps in cell wall synthesis)

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3
Q

Carbapenems

A

Interacts with cytoplasmic binding proteins (PBPs) to inhibit transpeptidation reactions involved in cross-linking (the final steps in cell wall synthesis)

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4
Q

Monobactams

A

Interacts with cytoplasmic binding proteins (PBPs) to inhibit transpeptidation reactions involved in cross-linking (the final steps in cell wall synthesis)

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5
Q

Vancomycin

A

Binds at D-ala D-ala muramyl pentapeptide to sterically hinder transglycosylation reactions involved in elongation of peptidoglycan chains (and indirectly preventing transpeptidation)

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6
Q

Daptomycin

A

Inserts itself and aggregates in cell membrane causing change in membrane shape which creates holes that leak ions leading to rapid depolarization and loss of membrane potential which leads to inhibition of protein, DNA, and RNA synthesis

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7
Q

Telavancin

A

Binds at D-ala D-ala muramyl pentapeptide to sterically hinder transglycosylation reactions involved in elongation of peptidoglycan chains (and indirectly preventing transpeptidation)

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8
Q

Fosfomycin

A

Phosphoenolpyruvate (PEP) analog that inhibits MurA enzyme which leads to inhibition of linking the glycan and peptide portions of peptidoglycan

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9
Q

Polymyxins

A

Binds to the lipopolysaccharide (LPS) in outer membrane of gram -ve bacteria and disrupts both outer and inner membranes (detergent-like action)

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10
Q

Tetracyclines

A

Enter organisms via passive diffusion and energy-dependent transport protein unique to bacterial inner membrane and concentrate intracellularly. Bind reversibly to 30S subunit of ribosome preventing binding tRNA to mRNA-ribosome complex, thereby inhibiting bacterial protein synthesis

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11
Q

Glycylcyclines

A

Bind reversibly to 30S subunit of ribosome preventing binding tRNA to mRNA-ribosome complex, thereby inhibiting bacterial protein

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12
Q

Aminoglycosides

A

Enter organisms through porin channels and oxygen-dependent system (anaerobes intrinsically resistant). Bind 30S ribosomal subunit and interfere with assembly of functional ribosomal apparatus and/or cause the 30S subunit of the completed ribosome to misread the genetic code, thereby inhibition bacterial protein synthesis

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13
Q

Macrolides and Ketolides

A

Bind irreversibly to a site on 50S subunit of bacterial ribosome, thus inhibiting translocation steps of protein synthesis. Also they may interfere with other steps such as transpeptidation.

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14
Q

Fidaxomicin

A

Acts on sigma subunit of RNA polymerase, thereby disrupting bacterial transcription, terminating protein synthesis.

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15
Q

Chloramphenicol

A

Binds reversibly to bacterial 50S ribosomal subunit and inhibits protein synthesis at the peptidyl transferase reaction.

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16
Q

Clindamycin

A

Bind irreversibly to a site on 50S subunit of bacterial ribosome, thus inhibiting translocation steps of protein synthesis. Also they may interfere with other steps such as transpeptidation.

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17
Q

Quinupristin/Dalfopristin

A

Each component binds to a separate site on 50S bacterial ribosome. Dalfopristin disrupts elongation by interfering with addition of new amino acids to the peptide chain. Quinupristin prevents elongation similar to Macrolides and causes release of incomplete peptide chain.

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18
Q

Linezolid

A

Binds to the bacterial 23S rRNA of the 50S subunit, thereby inhibiting the formation of the 70S initiation complex.

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19
Q

Fluoroquinolones

A

Enter bacteria through porin channels and inhibit DNA gyrase (bacterial topoisomerase II) and bacterial topoisomerase IV. DNA gyrase inhibition will result in relaxation of supercoiled DNA, promoting DNA strand breakage. Topoisomerase IV inhibition impacts chromosomal stabilization during cell division, thus interfering with separation of newly replicated DNA.

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20
Q

Sulfonamides

A

Synthetic analogs of p-aminobenzoic acid (PABA) that will inhibit bacterial dihydrofolic acid synthesis by inhibiting dihydropteroate synthase

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21
Q

Trimethoprim and pyrimethamine

A

Inhibition of dihydrofolate reductase which lead to decrease availability of tetrahydrofolate which is a cofactor required for purine, pyramidine, and amino acid synthesis

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22
Q

Methenamine

A

A urinary tract antiseptic that decomposes at an acidic pH of 5.5 or less in the urine, thus producing formaldehyde, which acts locally and is toxic to most bacteria

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23
Q

Nitrofurantoin

A

Sensitive bacteria reduce the drug to a highly active intermediate that inhibits various enzymes and damages bacterial DNA

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24
Q

Isoniazid

A

Prodrug that is activated by mycobacterial catalase-peroxidase (KatG). It targets acyl carrier protein reductase (InhA) and beta-ketoacyl-ACP synthase (KasA), which are essential for mycolic acid synthesis

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25
Q

Rifamycins

A

Blocks RNA transcription by interacting with the beta subunit of mycobacterial DNA-dependent RNA polymerase

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26
Q

Pyrazinamide

A

Unclear

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27
Q

Ethambutol

A

Inhibits arabinosyl transferase (an important enzyme in the synthesis of mycobacterial cell wall)

28
Q

Para-aminosalicylic acid (4-Aminosalicylic acid)

A

Prodrug that converted by dihydropteroate synthase and dihydrofolare synthase to hydroxyl dihydrofolate which is an anti-metabolite that inhibits dihydrofolate reductase

29
Q

Capreomycin and Viomycin

A

Inhibition of protein synthesis by binding to the 70S ribosome. Also they bind to components in mycobacterial cell wall which result in production of abnormal proteins (that are fatal to the bacteria)

30
Q

Cycloserine

A

Inhibits cell wall synthesis by inhibiting alanine racemase (converting L-alanine to D-alanine) and D-alanine:D-alanine ligase which are important in peptidoglycan synthesis

31
Q

Ethionamide

A

A structural analog of Isoniazid that inhibits acyl carrier protein reductase (InhA) which is an essential enzyme in mycolic acid synthesis

32
Q

Dapsone

A

Inhibits dihydropteroate synthase in the folate syntheis pathway

33
Q

Clofazimine

A

Inhibits bacterial proliferation by binding guanine bases on bacterial DNA, blocking template function of DNA. Also increase the activity of bacterial phospholipase A2, leading to release and accumulation of toxic lysophospholipids.

34
Q

Bedaquiline

A

ATP synthase inhibitor (proton pump)

35
Q

Polyenes

A

Bind ergosterol in plasma membrane of sensitive fungal cells forming pores that disrupt membrane function resulting in cell death

36
Q

Flucytosine

A

Pyrimidine antimetabolite, bioactivated to 5F-dUMP which binds folic acid & this complex will inhibit thymidylate synthase

37
Q

Azoles

A

Disrupt membrane structure and function by inhibition of ergosterol biosynthesis through inhibition of C-14 alpha-demethylase (a CYP450 enzyme that demethylate lanosterol to ergosterol)

38
Q

Echinocandins

A

Interfere with the synthesis of fungal wall by inhibiting the synthesis of beta(1,3)-D-glucan, leading to lysis and cell death

39
Q

Squalene epoxidase Inhibitors

A

Inhibit squalene epoxidase, thereby blocking the biosynthesis of ergosterol which is the essential component of fungal cell membrane

40
Q

Griseofulvin

A

Causes disruption of the mitotic spindle and inhibition of fungal mitosis

41
Q

Ciclopirox

A

Inhibits transport of essential elements in the fungal cell, disrupting the synthesis of DNA, RNA, and proteins

42
Q

Nitroimidazoles

A

The nitro group serves as an electron acceptor, forming reduced cytotoxic compounds that bind protein and DNA, resulting in protozoal death (in Helminthes they inhibit the assembly of microtubules and irreversibly blocking glucose uptake)

43
Q

Aminoquinolines

A

Prevent heme biocrystallization, leading to heme build-up. Also associate with heme forming aminoquinolines-heme complex, both of these molecules are highly toxic and will lead to parasite autodigestion

44
Q

Dehydroemetine

A

Unknown

45
Q

Artemisinin

A

Unknown

46
Q

Pentamidine

A

Unknown

47
Q

Suramin

A

Unknown

48
Q

Melarsoprol

A

It will be metabolized to Melarsen oxide which is an arsen-oxide that will bind irreversibly to sulfhydryl groups causing inactivation of many enzymes

49
Q

Eflornithine

A

Irreversible inhibitor of ornithine decarboxylase, thereby inhibit the production of polyamines leading to cessation of cell division

50
Q

Nifurtimox

A

Undergoes reduction and eventually generates intracellular oxygen radicals which are highly toxic

51
Q

Sodium stibogluconate

A

Unknown

52
Q

Miltefosine

A

Unknown

53
Q

Atovaquone-proguanil

A

Atovaquone inhibits mitochondrial processes like electron transport as well as ATP and pyrimidine biosynthesis. Proguanil inhibits dihydrofolate reductase, thereby preventing DNA synthesis

54
Q

Pyrantel Pamoate

A

It acts as a depolarizing, neuromuscular blocking agent, causing release of Ach and inhibit Ach esterase, leading to paralysis of the worm which will release its hold on the intestinal tract and expelled

55
Q

Ivermectin

A

Targets the glutamate-gated chloride channel receptors, enhancing chloride influx causing hyperpolarization which results in paralysis and death of the worm

56
Q

Diethylcarbamazine

A

Inhibits arachidonic acid metabolism in filarial microfilaria making them more susceptible to innate immunity attack

57
Q

Praziquantel

A

Increasing membrane permeability to calcium ion resulting in spastic paralysis of worms

58
Q

Niclosamide

A

It inhibits mitochondrial phosphorylation of ADP which lead to death of worm but not ova

59
Q

Neuroaminidase Inhibitors

A

Inhibit neuroaminidase, thereby preventing release of new virions and their spread from cell to cell

60
Q

Adamantane antivirals

A

Interfere with the function of viral M2 protein, possibly blocking uncoating of the virus particle and preventing viral release within infected cells

61
Q

Nucleotide analogs

A

Act either by inhibiting respective nucleotide formation, thereby blocking RNA or DNA polymerases. Or by being incorporated into viral DNA which leads to termination of chain elongation, thereby preventing replication

62
Q

Protease Inhibitors

A

Reversible inhibitors of proteases (such as HIV aspartyl protease [Retropepsin]), thereby inhibiting the formation of important enzymes and structural proteins, which prevent maturation of viral particles and results in production of noninfectious virions

63
Q

Nucleoside or Nucleotide Reverse Transcriptase Inhibitors (NTRIs)

A

They are phosphorylated by cellular enzymes to corresponding triphosphate analogs, which are preferentially incorporated into viral DNA by RT. and because the 3’-hydroxyl group is not present, a 3’,5’-phosphodiester bond between an incoming nucleoside triphosphate and the growing DNA chain cannot be formed, and DNA chain elongation is terminated (Host mitochondrial DNA polymerase gamma is susceptible at therapeutic concentrations)

64
Q

Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)

A

Highly selective, non-competitive inhibitors of HIV-1 RT. They bind to RT at an allosteric hydrophobic site adjacent to the active site, inducing conformational change that results in enzyme inhibition (they do not require activation by cellular enzymes)

65
Q

Entry Inhibitors

A

act either by preventing conformational changes in viral transmembrane glycoprotein gp41 required for entry (Enfuvirtide) or by blocking CCR5 coreceptor (Maraviroc)

66
Q

Integrase Inhibitors

A

They occupy the active sites in host DNA that integrase acts on, thereby halting the integration process

67
Q

Interferons

A

Incompletely understood

Chemotherapy (4 decks)

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