Michał Karbownik Department of Pharmacology Medical University of Łódź

Transcription

1 Antiviral drugs Michał Karbownik Department of Pharmacology Medical University of Łódź Virus structure Virus life cycle 1. Attachment and penetration 2. Uncoating (amantadine) 3. Replication (nucleoside analogues) 4. Translation (interferon) 5. Post-translational modification 6. Assembly (protease inhibitors) 7. Releasing (neuraminidase inhibitors) 1

2 Bacteria vs viruses Bacteria Viruses Size: Larger (1000nm) Smaller (20-400nm) Beneficial?: Some beneficial bacteria (e.g. certain bacteria required in the gut) Viruses are not beneficial. However, a particular virus may be able to destroy brain tumors. Viruses can be useful in genetic engineering. Can cause disease?: Yes Yes Ribosomes: Present Absent Outermost structure: Nucleic acid: Living attributes: Peptidoglycan cell wall or capsule/slime layer in some. Protein coat or viral envelope DNA and RNA. Exists as DNA or RNA. can be doublestranded or single-stranded, double-stranded and circular in shape. circular or linear. Living organism Enzymes: Yes Yes, in some Considered living and nonliving Bacterium Drugs affect typical bacteria cell targets Virus Drugs affect viral replication processes in host cell: Inhibit penetration Inhibit replication Inhibit releasing Why is the antiviral therapy difficult? 1. Difficult to find speciffic targets for antiviral drugs 2. Viruses easily develop resistance: In 2009 H1N1 influenza swine flu neuraminidase (N) were to acquire the tamiflu-resistance (His274Tyr) mutation which is currently widespread in seasonal H1N1 strains Altered or defficient thymidine kinase and DNA polimerases have been found in some viral strains of Herpesviridae 3. Clinical symptoms appear late in the course of the disease, at the time when most of the virus particles have replicated 2

3 Influenza Influenza Influenza Common cold Influenza virus Type A, B, C Rhinovirus Parainfluenzaviruses The most virulent Less common and less genetically diverse Less common, usually causes mild infections in children Influenza A virus 3

4 Influenza Prophylaxis preferred approach active immunization Treatment antiviral agents M2 protein membrane matrix Influenza virus protein (ion channel) important role in uncoating of the virus Hemagglutinin glycoprotein responsible for binding the virus to the cell Neuraminidase (sialidase) enzyme that cleave the sialic acid groups from host glycoproteins and enables the virus to be released Helical RNA Influenzavirus A subtypes H1N1, which caused Spanish flu in 1918, and the 2009 flu pandemic (swine flu) H2N2, which caused Asian Flu in 1957 H3N2, which caused Hong Kong Flu in 1968 H5N1, a current pandemic threat H7N7, which has unusual zoonotic potential H1N2, endemic in humans and pigs H9N2 H7N2 H7N3 H10N7 H1N1 4

5 Drugs classes 1. Neuraminidase inhibitors 2. Inhibitors of viral uncoating 3. Ribavirin 1. Neuraminidase inhibitors Prevent the release of new virons and their spread from the cell to cell. Active against influenza A and B. Should be administered prior to exposure or within the first houres Oseltamivir (Tamiflu) Zanamivir (Relenza) Neuraminidase inhibitors Oseltamivir Zanamivir Route of administration P.O. Inhaled intranasally Active substance Prodrug Active substance Biotransformation No No Excretion Adverse effects Gastrointestinal Psychiatric halucynations, mood changes Irritation of the respiratory tract Drug resistance: mutation in neuraminidase. These mutants are fortunatelly less infective and virulent. 5

6 Peramivir Experimental antiviral drug Authorised for critically ill 2009 A(H1N1) subtype patients: Tamiflu-resistant patients unable to take Relenza inhalations peramivir I.V. administration 2. Inhibitors of viral uncoating Block the viral membrane matrix proteine M2, and inhibit internalization of the virus. Active against influenza A (prvention: effective in 70-90% and treatment) Should be administered within first 48 houres of infection amantadine rimantadine Inhibitors of viral uncoating Amantadine Route of administration P.O. P.O. Rimantadine Distribution Crosses BBB Does not cross BBB Biotransformation No Yes Excretion Adverse effects CNS problems: insomnia, dizziness, ataxia, seizures Gastrointestinal Embriotoxic, teratogenic Gastrointestinal Embriotoxic, teratogenic Resistance can be developed among 50% of treated individuals, and resistant strains can be transmitted to close contacts! 6

7 3. Ribavirin Active against broad spectrum of RNA and DNA viruses: 1. Infants and young children infected with Respiratory Syncytial Virus (RSV) 2. Chronic hepatitis C infections (in combination with interferon-α-2b) 3. Reduces the mortality and viremia of Lassa fever Ribavirin nucleozide analog Mode of action: blocks RNA-dependent RNA polimerase preventing replication Administration: P.O., I.V., aerosol anemia, elevated bilirubin (aerosol can be a bit safer) Contraindicated in pregnancy Hepatic viral infections HAV HEV HBV HCV HDV Transmission Enteric Enteric Parenteral Parenteral Parenteral Classification Picornavirus Hepevirus Hepadnavirus Hepacivirus Deltavirus Genome +ssrna +ssrna +dsdna +ssrna -ssrna Antigens HBsAg,HBeAg Core antigen Delta antigen Incubation period days days days days days Chronicity No No Yes (uncommon) Yes (common) Yes - with hepatitis B Acute viral hepatitis require symptomatic treatment Hepatitis B Remission (anti-hbe) Infection 1-6 months Acute hepatitis (HBsAg HBeAg anti-hbc) 5-10% Chronic hepatitis (HBsAg HBeAg) Cirrhosis Hepatocelular carcinoma A simplified drawing of the HBV particle and surface antigen 7

8 Drugs classes 1. Interferon 2. Nucleotide and nucleoside analoges Hepatic viral infections Treatment: Chronic hepatitis B: Interferon-α + lamivudine Chronic hepatitis C: Interferon-α + ribavirin Avoid drinking alcohol!!! 1. Interferon Family of naturally occuring glicoproteins cytokines: Interfere with viral replication (in vivo active only against hepatitis viruses and Papillomaviruses) Activate immune cells (NK, macrophages) Up-regulate antigen presentation to Human interferon-α structure T-lymphocytes (increase recognition of infection or tumor cells) During the infection: Certain host symptoms, such as aching muscles and fever, are related to the production of IFNs 8

9 Indications: 1. Hepatitis B and C Interferon 2. Condylomata acuminata (Papillomavirus HPV) 3. Cancers Hairy-cell leukemia Kaposi sarcoma Administration: Intralesionally I.V. S.C. Biochemical modification: PEG-chain attached: prolonged action (once-a-week dosing) Interferon Flu-like symptoms (fever, chills, myalgias, arthralgias, GI disturbances) Bone marrow suppresions (can potentiate the myelosuppresion caused by other bonemarrowdepressing agents zidovudine) Autoimmune disorders 2. Nucleotide and nucleoside analoges 9

10 5 3 replication 3 5 -OH HO- Must be phosphorylated to triphosphate 3 nucleoside nucleotide 10

11 Lamivudine Nucleoside analog (must be phosphorylated by host cellular enzymes) Stops HBV DNA-polymerase HIV reverse transcriptase P-lamivudine Administration: P.O. Well tolerated (headache, dizziness) Lamivudine alternatives 1. Adefovir nucleotide analog Well tolerated 2. Entecavir nucleoside analog (against lamivudine-resistant strains of HBV) Adverse effect: Renal, liver toxicity (even several months after discontinuation of therapy) Human Herpes Viruses Herpes Simplex Viruses (HSV-1, HSV-2) Varicellovirus (varicella-zoster virus VZV) Epstein-Barr Virus (EPV) Cytomegalovirus (CMV) HHV-1, HHV-2 HHV-3 HHV-4 HHV-5 dsdna 11

12 Overview of herpesvirus infections 1. Gingivostomatitis (HSV-1) oral herpes, cold sores 2. Sexually transmitted diseases (HSV-2) genital herpes Overview of herpesvirus infections 3. Skin infections (VZV) Varicella (chicken-pox) Zoster (shingles) Overview of herpesvirus infections 4. Pharyngitis (EBV) Mononucleosis ANTIVIRAL TREATMENT IS INEFFECTIVE 5. Eye infections (CMV) CMV retinitis Immunocompromised patients 12

13 Treatment of herpesvirus infections Acute phase Latent phase antiviral medications can only reduce the frequency, duration, and severity of outbreaks Treatment of herpesvirus infections 1. Nucleotides and nucleosides analoges 2. Antisense oligonucleotide 3. Foscarnet 4. Hyperimmune globulins Treatment of herpesvirus infections 1. Acyclovir Penciclovir Famciclovir Vidarabine Ganciclovir Cidofovir 2. Fomivirsen HSV, VZV CMV 3. Foscarnet 13

14 1. Nucleotides and nucleosides analoges Acyclovir guanosine analog Active against: HSV-1 HSV-2 VZV, some EBVs CMV resistant lack of specific thymidine kinase Acyclovir Thymidine kinase herpesvirus-encoded enzyme triphosphate (nucleotide) Host cell enzymes monophosphate Clinical application: Acyclovir 1. HSV encephalitis (drug of choice) 2. Genital herpes infections 3. Prophylaxis among immunocompromised patients after organ transplantation before bone marrow transplant during anticancer chemotherapy Pharmacokinetics: Acyclovir Administration: PO, IV, topical Valacyclovir valyl ester greater oral bioavailability doubtful efficiacy Distribution: well, including CSF 14

15 Adverse efects: PO IV Acyclovir Well tolerated headache, GI disturbances transient renal dysfunction Topical local skin irritation Resistance: due to altered thymidine kinase DNA polimerase Guanosine analog Active against: HSV, VZV Administered topically Well tolerated Penciclovir Famciclovir Guanosine analog Active against: VZV (acute herpes zoster infections) Administered orally headaches, GI problems Prodrug metabolised to penciclovir Natural adenosine analog Vidarabine Antiviral activity described in 1964 Active against: HSV, VZV Clinical application limited to: herpetic keratitis and keratoconjunctivitis However, inhibits DNA synthesis Available as an ophtalmic ointment 15

16 Ganciclovir Aciclovir derivative Lack of thymidine kinase OTHER VIRAL ENZYMES Triphosphate active form DNA polymerisation Clinical application: CMV retinistis in immunocompromised patients CMV prophylaxis in transplant patients Pharmacokinetics: Administration: IV Ganciclovir Valgancyclovir valyl ester PO administrated Distribution: well, including CSF 1. Severe dose-dependent neutropenia (zidovudine, immunosupresives can increase the risk of neutropenia) 2. Carcinogenic, teratogenic, embryotoxic Cytosine analog (nucleotide) Clinical application: Cidofovir CMV-induced retinitis in AIDS patients Do not need enzymatic activation Administration: IV, intravitreal injection Nefrotoxicity contarindicated in renallycompromised patients or taking nephrotoxic drugs Neutropenia, metabolic acidosis, ocular hipotony 16

17 2. Antisense oligonucleotide Fomivirsen against CMV mrna Clinical application: CMV retinitis in patients Fomivirsen who cannot tolerate or have failed other therapies Administration: Intravitreally Iritis, vitritis, changes in vision Clinical application: 3. Foscarnet CMV retinitis in immunocompromised patients Acyclovir-resistant HSV infections Herpes zoster infections No cross-resistance with acyclovir and gancyclovir phosphonophormate Inhibits viral DNApolimaerase 17

18 3. Foscarnet Administration: IV Asverse effects: Nephrotoxicity Anemia, GI problems Hipokaliemia, hipomagnesemia, hipocalcemia (seizures, arrhythmias) K +, Mg 2+, Ca Hyperimmune globulines Passive immunization VZV Administered for: immunocompromised patients random exposure to VZV in the last week of pregnancy One single dose Hyperimmune globulines available: anti-vzv (Varitect) anti-hbv anti-hcv AIDS Acquired Immune Deficiency Syndrome HIV Human Immunodeficiency Virus AIDS HIV-1 More virulent, infective Globally occuring HIV-2 Less virulent, infective West Africa 18

19 HIV - retrovirus Viral RNA Reverse transcriptase (RT) Viral DNA 2-4 weeks of asymptomatic incubation period Infection of HIV Acute infection (fever, swollen lymph nodes,pharyngitis, rash) 1. Blood, tissue fluids 2. Intensive sexual contact 3. Perinatal infection Without treatment 10 years With treatment > 30 years 2 weeks 20 years Latency stage CD4+ cells 350/ul AIDS (opportunistic infections) 19

20 CD4+ cells/ul AIDS A Asymptomatic B Neither A nor C C AIDS symptoms >500 A1 B1 C A2 B2 C2 <200 A3 B3 C3 According to Center for Disease Control, Atlanta, Georgia, USA, 1993 AIDS: USA: C1, C2, C3 Europe: C1, C2, C3, A3, B3 20

21 AIDS treatment NRTIs NNRTIs PIs 3 AIDS treatment AIDS treatment 1987 years Decreasing the occurence of opportunistic infections Highly HAART Active AntiRetroviral Therapy 21

22 Diagnostic methods assesing the efficiency of therapy: CD4+ cells/ul Virus load HAART 1. NRTI NRTI NNRTI 2. NRTI NRTI PI 3. NRTI NRTI NNRTI or PI EI and/or II I. NRTIs inhibit RT host cell mitochondrial DNA-polimerase DNA-polimerase Bone marrow supression Peripheral neutropathy Potentially fatal liver toxicity: Except for: Lamivudine Abacavir 22

23 1. Zidovudine (AZT) The first drug active against HIV (1987) Clinical application: Children Adults Prevention: prenatal infection individuals exposed to HIV Contraindication: co-administration of drugs being glucuronylated: Pharmacokinetics: acetaminophen Administration: PO (paracetamol), Distribution: into CSF lorazepam, cimetidine Bone marrow suppression, anemia, leukopenia seizures 2. Didanosine (ddi) The second approved drug Clinical application: Children Adults Pharmacokinetics: Administration: PO (buffered tablets or solutions), without food Distribution: into CSF Pancreatitis Peripheral neutropathy Contain sodium, phenylalanine Contraindication: Phenylketonuria Sodium-restricted diet 23

24 Pharmacokinetics: Administration: PO, without food and Al, Mg-containing antacids Distribution: not into CSF 3. Zalcitabine (ddc) As those of didanosine Pharmacokinetics: Administration: PO, not affected by food Distribution: into CSF 4. Stavudine (d4t) Peripheral neuropathy Clinical application: HIV 5. Lamivudine (3TC) often used with HBV zidovudine (Combiwir ) Pharmacokinetics: Administration: PO Does not affect mitochondrial DNA-polimerase Well-tolerated 24

25 Clinical application: 6. Abacavir For patients who cannot tolerate or have failed current regimens Only some cross-resistance with other NRTIs Pharmacokinetics: Administration: PO Quite well tolerated GI problems, headache, rash 7.Tenofovir Nucleotide analog but needs to be converted to active form Clinical application: For patients who cannot tolerate or have failed current regimens Only some cross-resistance with other NRTIs (as abacavir) Pharmacokinetics: Administration: PO, should be taken with a meal to increase its bioavailability GI problems 8. Emtricitabine Clinical application: HIV Pharmacokinetics: Administration: PO lamivudine fluoro-derivative active against HBV, but not used Hyperpigmentation of soles and palms 25

26 II. NNRTIs Non-Nucleoside Reverse Transcriptase Inhibitors Nevirapine Delavirdine Efavirenz NNRTIs Non-nucleoside reverse transcriptase inhibitors 1. Inhibit RT inducing conformational change of the enzyme (not competiting with nucleosides and terminating DNA synthesis) 2. Do not require activation by cellular enzymes 3. Do not inhibit mitochondrial DNA-polimerase lack of bone marrow suppression 4. No cross-resistance with NRTIs 1. Nevirapine Clinical application: Children Adults Prevention prenatal infection (zidovudine alternative) Pharmacokinetics: Administration: PO well absorbed Distribution: into CSF Severe dermatologic effects (Stevens-Johnson syndrome, toxic epidermal necrolysis) hepatotoxicity CYP450 inducer Increases metabolism of PIs Should not be administrated with saquinavir (PI) 26

27 Pharmacokinetics: 2. Delavirdine Administration: PO well absorbed Distribution: into CSF extensively bound to plasma proteins Rash GI problems CYP450 inhibitor Decreased metabolism of PIs 3. Efavirenz Pharmacokinetics: Administration: PO well absorbed with a high fat meal once-a-day dosing Distribution: into CSF extensively bound to plasma proteins Transient CNS problems in 50% of patients: headache, dizziness, vivid dreams, loss of concentration Rash Modest inducer of CYP450 Increases metabolism of Pis III. PIs Protease Inhibitors Introduced in 1995 active in 60-95% of HAART taking patients decreased number of active deaths due to AIDS 27

28 RNA Reverse transcription DNA Transcription PIs PIs Selective affinity to viral protease mrna Translation Enzymatic claveage HIV aspartyl protease Viral essential proteins: enzymes, structural, etc. Pharmacokinetics: Administration: PIs Specially formulated capsules of saquinavir PO poor (high fat meals increase bioavailability) Distribution: Substrates of gp-p bound to plasma proteins (α 1 -acid glicoprotein) Biotransformation: CYP3A4 potent inhibitors of CYP450 sedation from midazolam bleeding from warfarin respiratory depression from fentanyl the concentration of α 1 -acid glicoprotein increases in response to trauma and surgery PIs GI problems paresthesias disturbances in glucose and lipid metabolism: hypertriglyceridemia hypercholesterolemia hyperglycemia fat redistribution: buffalo hump 28

29 Saquinavir Oral absorption: 12% Should be given with other antiretroviral drugs that inhibits CYP450: saquinavir + delavirdine (NNRTI) ritonavir (PI - the most potent CYP inhibitor) drugs inducing CYP450 should be avoided: rifampin nevirapine efavirenz Ritonavir Oral absorption: ~60% (unaffected by food) Ritonavir pharmacokinetic enhancer (concominant administration): increases other PIs bioavailability diminishes the impact of the meal Other PIs Indinavir quite well tolerated, SE: nephrolithiasis Nelfinavir - SE: diarrhea (can be controlled by loperamide) Amprenavir Lopinavir for patients who are not responding to others Pis Atazanavir composed with ritonavir (Kaletra ) 29

30 IV. Other novel agents salvage therapy can be combined with HAART extremally expensive (>25,000 USD/year) Entry Inhibitors (EIs) Enfuvirtide (2003) Maraviroc (2007) Integrase Inhibitors (EIs) Raltegravir (2007) 30