Antifungal agents.pptx by Dr. Rakam Gopi Krishna MLRIP

Infectious diseases caused by fungi are called mycoses, and they are often chronic in nature.
Fungi have rigid cell walls composed of chitin.
The fungal cell membrane contains ergosterol rather than the cholesterol found in mammalian membranes.
These chemical characteristics are useful in targeting chemotherapeutic agents against fungal infections
In comparison with bacteria or viruses, fungi are more complex organisms.
They have ribosomes, cellular membrane components, and a nuclear membrane.
Therefore, antibacterial antibiotics are, as a rule, ineffective against pathogenic fungi.
Fungal infections (mycoses) occur less than bacterial or viral infections

1. Antifungal agents Unit-IV MC-III Dr Rakam Gopi Krishna Marri Laxman Reddy Institute of Pharmacy Hyderabad

2. Introduction I n f e c tio u s d i s ea s e s c au s e d b y f ung i a r e c a ll e d mycoses, and they are often chronic in nature. Fungi have rigid cell walls composed of chitin. T h e f unga l c e ll m e m b r an e c o n t a ins e r go s t e r o l r a t he r than the cholesterol found in mammalian membranes. These chemical characteristics are useful in targeting chemotherapeutic agents against fungal infections Department of Pharmaceutical Chemistry

3. Introduction In comparison with bacteria or viruses, fungi are more complex organisms. They have ribosomes, cellular membrane components, and a nuclear membrane. Therefore, antibacterial antibiotics are, as a rule, ineffective against pathogenic fungi. Fungal infections (mycoses) occur less than bacterial or viral infections

4. Fungi.. Fungi are small filamentous organisms. They live either as saprophytes or as parasites on plants and in human beings. They are classified as superficial and systemic infections. Superficial:- Hair, skin, nails and mucous membrane. Systemic:- entire body, deeper tissues and internal organs.

5. Fungal infections are usually more difficult to treat than bacterial infections, because fungal organisms grow slowly and fungal infections often occur in tissues that are poorly penetrated by antimicrobial agents (e.g., devitalized or avascular tissues). Therapy of fungal infections usually requires prolonged treatment.

6. I. Antif ungal s damaging permeability of the cell membrane Imidazoles: Clotrimazole, Ketoconazole, Miconazole Triazoles: Fluconazole, Itraconazole, Voriconazole A llylamine s : Terbinafine, Naftifine Thiocarbamates: Tolnaftate P olyene antibiotics: Amphotericin B, Nystatin II. Antifungals inhibiting chitin synthesis in the cell wall Caspofungin, Griseofulvin III. Antifungals inhibiting synthesis of nucleic acids Flucytosine

7. Classification based on MOA Fungal cell wall synthesis inhibition: Caspofungin. B i n d t o f u ng a l c e ll m e m b r an e e r g o s t e ro l: A m pho t e rc i n– B , Nystatin, Natamycin. Inhibition of ergosterol + lanosterol synthesis: Terbinafine, Naftifine, Tolanftite, Butenafine. I nh ibi tion o f e r go s t e r o l s y n t he s i s : A z o les Inhibition of nucleic acid synthesis: 5–Flucytosine . Disruption of mitotic spindle and inhibition of fungal mitosis: Griseofulvin . Miscellaneous: Ciclopirox, Haloprogin, Undecylenic acid, Topical azoles . Department of Pharmaceutical Chemistry

8. Various types of Drugs Antifungal drugs can be divided into Polyenes :- Amphotericin-B, Nystatin & Natamycin . Heterocyclic benzofuran :- Griseofulvin Imidazoles ( Triazoles ) :- Clotrimazole , Ketoconazole & Miconazole. Allylamines :- Naftifine & Terbinafine.

9. Few points on Drugs These compounds have broad spectrum of antifungal activity They possess fungicidal and fungistatic activity Antifungal agents act by various mechanisms

10. Amphotericin B CLASS: Amphotericin B is a polyene, fungistatic or fungicidal antibiotic depending on the concentration obtained in body fluids and the susceptibility of the fungus. BIOLOGICAL SOURCE: It is produced by Streptomyces nodosus . Antifungal Antibiotics

11. MOA: The drug acts by binding to sterols (ergosterol) in the cell membrane of susceptible fungi and creates a t r a n s m em b r a n e c h a n n e l, w h ich a llo w s l e a k a g e of to i n t r ac e llul a r c omp on e n t s . It b i nd s ir r e v e r s i b ly ergosterol, resulting in disruption of mem b r a n e integrity and ultimately cell death. THERAPEUTIC USES: Us e d t o t r e a t p o t e n t i a ll y li f e t h r e a t e nin g fu n g a l infections and leishmaniasis. I t i s u s e d t o t r e a t a s p e r g i ll o s i s , b l a st o m y c o s i s, candidiasis, coccidioidomycosis, and cryptococcosis.

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13. TOXICITY: Due to its extensive side effects, it is often reserved for severe infections in critically ill, or immunocompromised patients. I n t r a v e n ou s a d mi n i s t r a t i o n i s a ss o c i a t ed w i th m u l t i p l e o r g a n damage. It causes a serious reaction soon after infusion (within 1 to 3 h o u r s) , c o n s i s t i ng o f h i gh f e v e r , s h a k i ng c h ill s , h y po t e n s i on, anorexia, nausea, vomiting, headache, dyspnea and tachypnea, drowsiness, and generalized weakness. Amphotericin B overdoses can result in cardio-respiratory arrest. E l e c t r o ly t e im b a l a n c es su c h a s h y po k a l a e m i a a nd hypomagnesemia are also common. Department of Pharmaceutical Chemistry

14. NYSTATIN CLASS: Nystatin is a polyene antifungal drug that has broad-spectrum f un g ici d al a n d f u n g i s t a t i c a ctivi t y . It i s a n e ff ect i v e a n t if u n g al a g e n t synthesized by Streptomyces noursei . It is closely related to Amphotericin B, differing only slightly in structure and has a greater antifungal activity than Amphotericin B. It is a 38-membered macrolide ring containing single tetracene and diene moieties seperated by two methylene groups. Department of Pharmaceutical Chemistry

15. MOA: Nystatin is a channel-forming ionophore. The formation of this pore results in a change in membrane permeability that allows for leakage of intracellular contents and the subsequent disruption of electrochemical gradients necessary for proper cell function. Department of Pharmaceutical Chemistry

16. T HE R AP E U T IC U S E S : Nystatin is an antifungal that is both fungistatic and fungicidal. Nystatin is used orally for the treatment and/or prevention of oral candidiasis (thrush), intestinal candidiasis, and anal candidiasis. It is indicated topically for the treatment of vulvovaginal candidiasis and other cutaneous candida infections. In combination with metronidazole, it is used for the treatment of mixed infections due to Trichomonas vaginalis and Candida albicans . TOXICITY: No serious toxic effects except nausea and GI upset.

17. Vulvovaginal Candidiasis (VVC) Vulvovaginal Candidiasis (VVC) VVC  usually is caused by Candida albicans but can occasionally be caused by other Candida species or yeasts . Typical symptoms of VVC include pruritus (itching), vaginal soreness, dyspareunia, external dysuria, and abnormal vaginal discharge.

18. NATAMYCIN (Pimaricin) CLASS: Amphoteric macrolide antifungal antibiotic BIOLOGICAL SOURCE: It is a tetraene polyene antibiotic derived from Streptomyces natalensis .

19. MOA: Like other polyene antibiotics, Natamycin inhibits fungal growth by binding to ergosterol in the plasma membrane, preventing ergosterol- dependent fusion of vacuoles, as well as membrane fusion. A space or  vesicle  within the  cytoplasm  of a cell, enclosed by a membrane and typically containing fluid. THERAPEUTIC USES: Natamycin is p redominantly fungicidal. Natamycin is an antifungal drug for topical ophthalmic administration. It is used for the treatment of conjunctivitis and keratitis. It possesses invivo activity against a variety of yeast and filamentous fungi, including Candida , Aspergillus , Cephalosporium , Fusarium and Penicillium . Natamycin is not effective in vitro against gram-positive or gram-negative bacteria.

20. Natamycin- Adverse effects A llergic reactions like skin rash, itching or swelling of the face, lips or tongue .  changes in vision ,   severe burning or swelling of the eyelids

21. Synthetic Antifungal Antibiotics Griseofulvin Griseofulvin belongs to the class of organic compounds known as benzofurans. It is fungistatic with in vitro activity against various species of Microsporum, Epidermophyton, and Trichophyton. It has no effect on bacteria or on other genera of fungi. It was the first available oral agent for the treatment of dermatophytoses. BIOLOGICAL SOURCE: Griseofulvin is a mycotoxic metabolic product of Penicillium spp.

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23. THERAPEUTIC USES: It may be given orally for the treatment of ringworm infections of the skin, hair, and nails, namely: tinea corporis, tinea pedis, tinea cruris, tinea barbae, cradle cap or other conditions caused by Trichophyton or Microsporum fungi. TOXICITY: May cause headaches, gastrointestinal reactions and cutaneous eruptions. Department of Pharmaceutical Chemistry

24. Synthetic Antifungal Agents - Imidazoles & Triazoles (Azoles) Some imidazole derivatives are extremely beneficial for treating fungal infections. Clotrimazole Ketoconazole Miconazole Econazole Butaconazole Fluconazole

25. Azoles contn .. Azoles are synthetic antifungal agents. Azoles are 5-membered ring structures with nitrogen groups. Based on number of nitrogen atoms present in the ring, azoles are grouped as i ) Imidazoles – 2 Nitrogens ii) Triazoles - 3 Nitrogens Both have similar antifungal spectrum and mechanism of action.

26. Imidazole & 1,2,4-triazole

27. A Z OL E S Azoles are a class of five-membered heterocyclic compounds containing a nitrogen atom and at least one other non-carbon atom. Azole antifungals are a group of medicines that contain an azole ring and inhibit the growth of a wide range of fungi. They are classified into two groups: Imidazoles -Those with two nitrogens in the azole ring Triazoles-Those with three nitrogens in the azole ring Department of Pharmaceutical Chemistry

28. SAR- Imidazole & 1,2,4-triazole 1 2 3 4 5 1 2 3 4 5

29. Structure Activity Relationship Imidazole or triazole rings are essential for antifungal activity. Nitrogen present at 3 rd position in imidazole & 4 th position in triazole is termed as Amidine nitrogen. This nitrogen impairs the functioning ability of P-450 enzymes by binding to the heme portion of the enzymes. Substitution of halogen atom at 2 nd position or at both 2 nd & 4 th positions results in potent antifungal drugs. 1 1 2 2 3 3 4 4 5 5

30. SAR of Azoles contn .. Substitution of halogen atom apart from 2 nd & 4 th positions on the azole ring gives rise to compounds devoid of Antifungal activity . Substitution of both flourine and sulphonic acids at 2 nd and or 2,4 positions have yielded potent drugs.

31. Synthetic Antifungal Agents- CLOTRIMAZOLE Broad-spectrum antimycotic or antifungal agent May also be used to treat sickle cell disease, malaria and some cancers. Department of Pharmaceutical Chemistry

32. Synthesis of Clotrimazole 2-chlorotriphenyl Methyl chloride imidazole triethylamine Clotrimazole 1 2 3 4 5 6

33. Triethylamine is commonly employed as a base in organic synthesis. It is employed as a base during the preparation of esters, amides and other compounds from acyl chlorides or chlorides. Such reactions lead to the production of hydrochloric acid which combines with triethyl amine to form the salt. i.e , triethyl amine hydrochloride commonly called as Triethyl ammonium chloride. This reaction removes the hydrogen chloride from the reaction mixture & proceed to completion of reaction.

34. Synthesis of clotrimazole Clotrimazole is synthesized by reacting 2-chlorotriphenyl methylchloride with Imidazole In the presence of Triethylamine . Synonym- Canesten, Lotrimin MOA :- it inhibits the biosynthesis of ergosterin in cytoplasmic membrane of fungi.

35. Mechanism of action Lanosterol Demethylation Ergosterol Azoles 14- α -demethylase The cell membrane without ergosterol is defective and results in the leakage of various ions and other useful substances leading to death of the fungus.

36. MOA of Azoles Azoles control the fungal infections by different mechanisms. Azoles bind to cytochrome P-450 class enzyme, i.e., 14 α -demethylase . lanosterol on demethylation produces ergosterol , by 14 α -demethylase and is required in fungal cell-wall synthesis.

37. Mechanism of action of Azoles Reduction of ergosterol synthesis by inhibition of fungal cytochrome P450 enzymes. Greater affinity for fungal than for human cytochrome P450 enzymes. Imidazoles exhibit a lesser degree of specificity than the triazoles, accounting for their higher incidence of drug interactions and side effects.

38. Clotrimazole cont.. Uses :- It is used for candidiasis and vaginal infections. It is used for tinea infections. Available in lotion and cream It is extensively protein bound and hence is not considered optimally bioavailable Adv effs: B urning, itching, redness, swelling, pain, or other signs of skin irritation.

39. ECONAZOLE Broad spectrum antimycotic Active against Gram-positive bacteria. It is used topically in dermatomycoses and also orally and parenterally. Moa:- Econazole interacts with 14- α demethylase, a cytochrome P-450 enzyme necessary to convert Lanosterol to Ergosterol. As ergosterol is an essential component of the fungal cell membrane, inhibition of its synthesis results in increased cellular permeability causing leakage of cellular contents

40. Therapeutic Uses:- Treatment of tinea pedis, tinea cruris, and tinea corporis caused by T richophyton . rubrum , Trichophyton . mentagrophytes , Trichophyton. tonsurans , M icrosporum . canis , M.audouini and E pidermophyton . floccosum , in the treatment of cutaneous candidiasis . It may be used in combination with Fluconazole, Ketoconazole, Itraconazole and Clotrimazole. Adv effs:- S kin rash, burning, swelling, redness, or irritation on the skin .

41. Candidiasis in the mouth and throat can have many different symptoms, including:  White patches on inner cheeks, tongue, roof of the mouth, and throat.

42. Butoconazole Imidazole antifungal used in gynecology. T h e r ape u ti c U s e s:- It has fungicidal activity in vitro against Candida spp. and is clinically effective against vaginal infections due to Candida albicans . It is widely used for the local treatment of vulvovaginal candidiasis Toxicity No report of serious toxic effects. Moa:- The exact mechanism of the antifungal action of butoconazole is unknown, however, it is presumed to function as other imidazole derivatives via  inhibition of steroid synthesis

43. Oxiconazole-Moa An antifungal agent is commonly found in topical formulations. Oxiconazole  inhibits ergosterol biosynthesis , which is required for cytoplasmic membrane integrity of fungi. It acts to destabilize the fungal cyctochrome P450 enzyme (also known as Lanosterol 14-alpha demethylase). This is vital in the cell membrane structure of the fungus. Its inhibition leads to cell lysis.

44. Oxiconazole THERAPEUTIC USES: It has fungicidal or fungistatic activity in vitro against dermatophytes, and yeast infections. ADVERSE EFFECTS : Pruritus, burning, irritation and allergic dermatitis .

45. Tio c on a z ole Imidazole antifungal used to treat fungal and yeast infections. Department of Pharmaceutical Chemistry

46. Therapeutic Uses It is a broad-spectrum imidazole antifungal agent that inhibits the growth of human pathogenic yeasts. Topical formulations are used for ringworm, jock itch, athlete's foot, and tinea versicolor or "sun fungus". Indicated for local treatment of vulvovaginal candidiasis (moniliasis). It exhibits fungicidal activity in vitro against Candida albicans , other species of the genus Candida, and against Torulopsis glabrata . Toxicity: Symptoms of overdose include erythema, stinging, blistering, peeling, edema, pruritus, urticaria, burning, and general irritation of the skin, and cramps . Department of Pharmaceutical Chemistry

47. Miconazole It is used topically and by intravenous infusion. It cannot be used for bacterial or viral infections MOA: Apart from inhibition of ergosterol biosynthesis, it may also inhibit endogenous respiration interact with membrane phospholipids inhibit the transformation of yeasts to mycelial forms inhibit purine uptake, and impair triglyceride and/or phospholipid biosynthesis. THERAPEUTIC USES: It is used either on the skin or in the vagina for fungal infections. Treatment of tinea pedis (athlete’s foot), tinea cruris, and tinea corporis caused by T. rubrum , T. mentagrophytes , and E. floccosum , in the treatment of cutaneous candidiasis (moniliasis), and in the treatment of tinea versicolor. It may be used in combination with Fluconazole, Ketoconazole, Itraconazole and Clotrimazole. Department of Pharmaceutical Chemistry

48. Department of Pharmaceutical Chemistry SYNTHESIS

49. b). Triazoles . Fluconazole & Ketoconazole Itraconazole Voriconazole Voriconazole is under clinical trials. They damage the fungal cell membrane by inhibiting enzyme desmethylase . They are selective Resistant to degradation

50. glycerol 2,4-dichloro phenacyl bromide cis-(2,4dichlorophenyl)-2-bromoethyl-4-hydroxymethyl-1,3-dioxolane Methane sulfonyl chloride Mesylate 1-acetyl-4-(4-hydroxy phenyl) piperazine benzoyl chloride Imidazole Ketoconazole 1 2 3 4 5 1 2 3 4 5 6 2 4 Intermediate 2 3 4 5 4 3 2 5 1 6 6 Synthesis of ketoconazole - HBr ketalisation

51. Synthesis of ketoconazole Ketoconazole: is synthesized from 2,4-dichlorophenacyl bromide, the ketalization of which using glycerol gives cis-2-(2,4-dichlorophenyl)-2-bromoethyl-4-hydroxymethyl-1,3-dioxolane (35.2.1). Acylating the hydroxyl group of this compound with benzoyl chloride, and then alkylating the resulting compound with imidazole gives the derivative (35.2.2)

52. Synthesis of ketoconazole Next, alkaline hydrolysis removes the benzoyl group, and a reaction with methanesulfonyl chloride gives a mesylate (35.2.3). Finally, alkylating the resulting 1-acetyl-4-(4-hydroxyphenyl) piperazine gives ketoconazole (35.2.4).

53. Ketoconazole Ketoconazole was the first drug used for azole-based oral treatment of systemic fungal infections, in the early 1980s. It is an imidazole antifungal agent used in the prevention and treatment of a variety of fungal infections. It is significant due to its broad spectrum and good absorption. It produces frequent gastrointestinal side effects and dose-related hepatitis. These effects combined with waning efficacy led to its eventual replacement by triazole agents. Department of Pharmaceutical Chemistry

54. Ketoconazole Is the first imidazole used orally for systemic infections MOA :- Ketoconazole is known to inhibit cholesterol biosynthesis. It possess higher affinity towards mammalian cytochrome P-450 enzymes. Which causes toxic effects.

55. Mechanism of action of ketoconazole

56. Mechanism of Action Department of Pharmaceutical Chemistry

57. Moa Contn … MOA :-it inhibits cytochrome P-450 dependent enzymes, blocking the synthesis of ergosterol. It possess fungicidal and fungistatic activity. Uses It has a broad spectrum of antifungal activity including many candida infections. Adverse effects :- Anorexia, nausea and vomiting.

58. Itraconazole Imidazole /triazole type antifungal agent T H E R APE U TI C U S E S It has been used against pulmonary and extra pulmonary blastomycosis, Histoplasmosis, onychomycosis, cryptococcal meningitis and aspergillosis. Adv effs:- Decreased urine output, dry mouth, fever, increased thirst, irregular heartbeat Mechanism: Itraconazole acts by  inhibiting the fungal cytochrome P-450 dependent enzyme lanosterol 14- α- demethylase . When this enzyme is inhibited it blocks the conversion of lanosterol to ergosterol, which disrupts fungal cell membrane synthesis

59. Fluconazole Commonly known as Diflucan. Used for the treatment of both systemic and superficial fungal infections in a variety of tissues. It was initially approved by the FDA in 1990. Advantages: option of oral administration. Side effect profile is minimal. It is an efficacious treatment for vaginal yeast infections in one single dose.

60. M O A It is a very selective inhibitor of L anosterol 14-α-demethylase . The free nitrogen atom on the azole ring binds with a single iron atom located in the heme group of lanosterol 14-α-demethylase, prevents oxygen activation, and results in inhibition the demethylation of lanosterol, halting the process of ergosterol biosynthesis. Methylated sterols are then found to accumulate in the fungal cellular membrane, leading to an arrest of fungal growth. Department of Pharmaceutical Chemistry

61. Therapeutic Uses:- Treatment of the following fungal infections: Vaginal yeast infections caused by Candida Systemic Candida infections Both esophageal and Oropharyngeal candidiasis Cryptococcal meningitis UTI caused by Candida Peritonitis caused by Candida Department of Pharmaceutical Chemistry

62. ALLYL AMINES: NAFTIFINE: Naftifine is a synthetic, broad spectrum, antifungal agent and allyl amine derivative used topically. Department of Pharmaceutical Chemistry

63. with s t e ro l MOA : Interferes bio s y n th e s i s by inhi b iti n g t h e enzyme squalene 2,3-epoxidase. This inhibition of enzyme activity results in decreased amounts of sterols, especially ergosterol, a n d a c o r r e s ponding accumulation of squalene in the cells. Department of Pharmaceutical Chemistry

64. T H E R APE U TI C U S E S : Naftifine has triple action: antifungal, antibacterial and anti- inflammatory. It is used for the topical treatment of tinea pedis, tinea cruris, and tinea corporis caused by the organisms Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton tonsurans and Epidermophyton floccosum. ADVERSE EFFECTS : Transient burning/stinging (5-6%) Skin tenderness (0.5-3%) Dryness E ryt h e m a Pruritus Local irritation Rash Department of Pharmaceutical Chemistry

65. TOLNAFTATE Tolnaftate is a synthetic over-the-counter anti-fungal agent. T H E R A P E U TI C U S E S : Tolnaftate is used to treat skin infections such as athlete's foot, jock itch, and ringworm infections. Tolnaftate is also used, along with other antifungals, to treat infections of the nails, scalp, palms, and soles of the feet. It is ineffective against candida. ADVERSE EFFECTS : Rarely causes irritation or allergic contact sensitisation. Moa:- Though its exact mechanism unknown, it is believed to prevent ergosterol biosynthesis by inhibiting squalene epoxidase

66. S YN T H E S I S Department of Pharmaceutical Chemistry

67. New Antifungal drugs Voriconazole a new azole is presently in clinical trials in the United states It has potent activity against a broad variety of fungi Posaconazole is now in phase III clinical trials

68. Other drugs Tolnaftate Synonyms of the drug are Tinatox , Tinactin and Tonoftal Uses:- for dermatophyte infections