Agentes quimioterápicos das infecções virais · Agentes Virucidas • Usados principalmente na prevenção da transmissão • Detergentes, solventes orgânicos (éter e clorofórmio),

Agentes quimioterápicos das infecções virais

• Agentes inactivantes das partículas virais -VIRUCIDAS• Agentes inibidores da replicação viral a nível celular - ANTIVÍRICOS• Agentes que modificam ou aumentam a resposta do hospedeiro à infecção -IMUNOMODULADORES

J Miguel Azevedo Pereira FFUL

Agentes Virucidas

• Usados principalmente na prevenção da transmissão• Detergentes, solventes orgânicos (éter e clorofórmio), radiações• Usados no tratamento de lesões mucocutâneas discretas (verrugas, p. exº.)• Crioterapia, laser, podofilina


Problemas da terapêutica antiviral

• Infecções detectadas em fases avançadas e/ou são infecções de curta duração - Grande proliferação viral

Diagnóstico precoce; Intervenção rápida e poderosa

• Vírus “apodera-se” da célula-alvoDifícil de atingir especificamente o vírus

Efeitos secundários - citotoxicidade

• Rápida evolução viralEstirpes resistentes aos antivirais

• Número restrito de proteínas virais

• Dificuldade em testar os antivirais (ausência de modelo animal; alguns vírus não cultiváveis em laboratório)


Alvos da terapêutica antiviral

Ligação aos receptores celulares

Penetração e descapsidação

Síntese dos ácidos nucleicos

Transcrição

Síntese das proteínas

Processamento das proteínas

Formação e saída das novas partículas virais


Vírus Herpes Simplex (HSV)Vírus Varicela-Zona (VZV)

Citomegalovirus (CMV)Vírus da Imunodeficiência Humana (HIV)

Vírus Influenza AVírus Respiratório Sincicial (RSV)

Vírus das Hepatites B e C (HBV, HCV)Papilomavirus Humano (HPV)

Infecções virais tratáveis com anti-víricos



cell prior to its competitive inhibition of the viral DNApolymerase [7]. Within an infected cell, the first phosphor-ylation of ACV occurs through the virally encoded thymi-dine kinase (TK), while the second and thirdphosphorylation steps are carried out by cellular kinases.ACV-triphosphate competes with naturally occurringnucleoside triphosphates and is incorporated into theelongating DNA chain as it replicates, resulting in chaintermination. Valacyclovir is the L-valyl ester oral prodrugof ACV that offers improved bioavailability. Penciclovir issimilar to ACV in that it is an acyclic guanosine analog thatacts through a TK dependent phosphorylation pathway.The active form of the agent, penciclovir-triphosphate,also competitively inhibits the replicative function of theviral DNA polymerase, but unlike ACV, penciclovir is notconsidered an obligate DNA chain terminator, owing to thepresence of a 30 hydroxyl group on its acyclic side chain,which can allow for a limited amount of continued chainelongation [2]. Penciclovir has very poor oral bioavailability

and so famciclovir was designed as its diacetylesterprodrug.

In patients with HSV infections that are failing first-linetherapy, alternative therapy with foscarnet or cidofovircan be considered. The clinical utility of foscarnet andcidofovir is somewhat limited by their toxicity profiles,however. Foscarnet is a pyrophosphate analog that rever-sibly inhibits DNA polymerase in many herpesviruses bybinding to and blocking the viral polymerase’s pyropho-sphate binding site, which interferes with pyrophosphatecleavage from incoming deoxynucleoside triphosphatesand impedes viral replication [8]. Foscarnet acts directlyon viral DNA polymerase without requiring activationvia either viral or host phosphorylation. Cidofovir is adeoxycytidine acyclic nucleotide phosphonate analogwith antiviral activity against a broad range of DNAviruses, including herpesviruses [9]. Because it is amonophosphate analog, cidofovir does not require initial

New HSV antivirals: mechanisms and resistance James and Prichard 55

Figure 1

O

HNHN

HO

HO

HO

OH

HO

OH OH

P

O

O

O

O

O

O

O

O

O

O

O

O

S O

O

NH

pritelivivir

cidofovir

acyclovir famciclovir foscarnet valomaciclovir

brincidofovir

amenamevir N methanocarbathymidine

HO

HO

HN

O

OO O

P

N

N

N

N

N

NN

H

N

N

NO O

OSS NH2

N

N

O

O

O

O

O

OH

OH

O OH2N

NH2

H2N

H2N

N N

N N

NN

N NNN

Current Opinion in Virology

P

Inhibitors of herpes simplex virus replication. Most drugs used to treat herpes simplex virus infections target the viral DNA polymerase. Two newmolecules in clinical development target the helicase–primase complex (pritelivir and amenamevir).

www.sciencedirect.com Current Opinion in Virology 2014, 8:54–61

Terapia da infecção por HSV

Inibidores da helicase-primase

Pró-fármaco do cidofovir

Tratamento da infecção pelo HSV Análogos dos nucleótidos

ALVO: DNA polimerase viral

OHO

OH

H2N

O

N

N

N

HN

OHO

OH

N

N

N

N

NH2

OHO

OH

N

N

NH2

O

OHO

OH

O

N

HN

O

Deoxiguanosina Deoxiadenosina Deoxicytidina Deoxitimidina


Aciclovir (Zovirax) e Valaciclovir

R = H Aciclovir

R = L-valina Valaciclovir


TK viral

Quinases Celulares

OOP

H2N

O

N

N

N

HN

OHO

H2N

O

N

N

N

HN

Mecanismo de acção

Usos terapêuticos: Infecções pelo HSV-1, HSV-2 e VZV

Actividade: HSV-1>HSV-2>VZV


Mecanismo de acção



Tratamento de estirpes HSV resistentes ao Aciclovir

Predominantemente aparecem em indivíduosimunodeficientes e com infecções recorrentes por HSV

Maioritariamente devidas a mutações no gene que codifica para a enzima timidina cinase viral (UL23); em alguns casos as mutações

de resistência ocorrem no gene que codifica para a DNA-polimerase (UL30)

Fármacos alternativos:

cell prior to its competitive inhibition of the viral DNApolymerase [7]. Within an infected cell, the first phosphor-ylation of ACV occurs through the virally encoded thymi-dine kinase (TK), while the second and thirdphosphorylation steps are carried out by cellular kinases.ACV-triphosphate competes with naturally occurringnucleoside triphosphates and is incorporated into theelongating DNA chain as it replicates, resulting in chaintermination. Valacyclovir is the L-valyl ester oral prodrugof ACV that offers improved bioavailability. Penciclovir issimilar to ACV in that it is an acyclic guanosine analog thatacts through a TK dependent phosphorylation pathway.The active form of the agent, penciclovir-triphosphate,also competitively inhibits the replicative function of theviral DNA polymerase, but unlike ACV, penciclovir is notconsidered an obligate DNA chain terminator, owing to thepresence of a 30 hydroxyl group on its acyclic side chain,which can allow for a limited amount of continued chainelongation [2]. Penciclovir has very poor oral bioavailability

and so famciclovir was designed as its diacetylesterprodrug.

In patients with HSV infections that are failing first-linetherapy, alternative therapy with foscarnet or cidofovircan be considered. The clinical utility of foscarnet andcidofovir is somewhat limited by their toxicity profiles,however. Foscarnet is a pyrophosphate analog that rever-sibly inhibits DNA polymerase in many herpesviruses bybinding to and blocking the viral polymerase’s pyropho-sphate binding site, which interferes with pyrophosphatecleavage from incoming deoxynucleoside triphosphatesand impedes viral replication [8]. Foscarnet acts directlyon viral DNA polymerase without requiring activationvia either viral or host phosphorylation. Cidofovir is adeoxycytidine acyclic nucleotide phosphonate analogwith antiviral activity against a broad range of DNAviruses, including herpesviruses [9]. Because it is amonophosphate analog, cidofovir does not require initial

New HSV antivirals: mechanisms and resistance James and Prichard 55

Figure 1

O

HNHN

HO

HO

HO

OH

HO

OH OH

P

O

O

O

O

O

O

O

O

O

O

O

O

S O

O

NH

pritelivivir

cidofovir

acyclovir famciclovir foscarnet valomaciclovir

brincidofovir

amenamevir N methanocarbathymidine

HO

HO

HN

O

OO O

P

N

N

N

N

N

NN

H

N

N

NO O

OSS NH2

N

N

O

O

O

O

O

OH

OH

O OH2N

NH2

H2N

H2N

N N

N N

NN

N NNN

Current Opinion in Virology

P

Inhibitors of herpes simplex virus replication. Most drugs used to treat herpes simplex virus infections target the viral DNA polymerase. Two newmolecules in clinical development target the helicase–primase complex (pritelivir and amenamevir).

www.sciencedirect.com Current Opinion in Virology 2014, 8:54–61

Ganciclovir (Cytovene)

Activo sobre HSV-1, HSV-2, VZV, EBV, HHV-6, HHV-8, e principalmente

CMV

Administrado profilaticamente parece reduzir a incidência de

CMV nos indivíduos com SIDA



Cidofovir

Análogo do nucleótido desoxicitidina (fosforilado)

Espectro de acção alargado: HSV, VZV, CMV (tratamento e

profilaxia), e papilomavirus, poliomavirus, adenovirus e

poxvirus

Usado em infecções por HSV devidas a mutantes resistentes

ao aciclovir (UL23)

128 E. De Clercq / Journal of Clinical Virology 30 (2004) 115–133

O

OH

N

N

N

HN

H2 N

O

O

C

OHCH2N

CHH3C CH3

Valganciclovir

Fig. 29.

◦ Administered: orally at 900mg per day (two 450mgtablets daily) for maintenance therapy (900mg twicedaily for induction therapy).

• Foscarnet◦ Structure (Fig. 30): trisodium phosphonoformate, fos-carnet sodium, Foscavir®.

◦ Activity spectrum: herpesviruses (HSV-1, HSV-2, VZV,CMV, etc.) and also HIV.

◦ Mechanism of action: pyrophosphate analogue, inter-feres with the binding of the pyrophosphate (diphos-phate) to its binding site of the viral DNA polymerase,during the DNA polymerization process.

◦ Principal indication(s): CMV retinitis in AIDS pa-tients, and mucocutaneous acyclovir-resistant (viralTK-deficient) HSV and VZV infections in immuno-compromised patients.

◦ Administered: intravenously at 180mg/kg per day(3 × 60mg/kg, every 8 h) for induction therapy ofCMV retinitis; intravenously at 120mg/kg per day(3 × 40mg/kg, every 8 h) for maintenance therapy ofCMV retinitis and for therapy of acyclovir-resistantmucocutaneous HSV or VZV infections in immuno-compromised patients. Dose adjustments for changesin renal function are imperative.

• Cidofovir◦ Structure (Fig. 31): (S)-1-(3-hydroxy-2-phosphonyl-methoxypropyl)cytosine (HPMPC), (CDV), Vistide®,ForvadeTM.

◦ Activity spectrum: herpesviruses (HSV-1, HSV-2,VZV, CMV, etc.), papilloma-, polyoma-, adeno- andpoxviruses.

3 Na+P-O

O

O-

CO

O-

Foscarnet

Fig. 30.

N

N

O

NH2

P O

OH

O

HO

HO

Cidofovir

Fig. 31.

◦ Mechanism of action: targeted at the viral DNA poly-merase, acts as chain terminator, following intracellu-lar phosphorylation to the diphosphate form, and in-corporation at the 3′-end of the viral DNA chain (twosequential incorporations needed for chain terminationin the case of CMV DNA synthesis) (Scheme 9).

◦ Principal indications(s): officially licensed for the treat-ment of CMV retinitis in AIDS patients. Also shownto be effective in the treatment of acyclovir-resistant(viral TK-deficient) HSV infections, recurrent genitalherpes, genital warts, CIN-III (cervical intraepithelialneoplasia grade III), laryngeal and cutaneous papillo-matous lesions, molluscum contagiosum lesions, orf le-sions, adenovirus infections and progressive multifocalleukoencephalopathy (PML).

◦ Administered: intravenously (Vistide®) at 5mg/kg perweek during the first 2 weeks, then 5mg/kg everyother week, with sufficient hydration and under coverof probenecid to prevent nephrotoxicity. Can also beadministered topically as a 1% gel or cream.

• Fomivirsen◦ Structure (Fig. 32): antisense oligodeoxynucleotidecomposed of 21 phosphorothioate-linked nucleosides,ISIS 2922, Vitravene®.

◦ Activity spectrum: CMV.◦ Mechanism of action: being complementary in basesequence, it hybridizes with, and thus blocks expres-sion (translation) of, the CMV immediate early 2 (IE2)mRNA.

◦ Principal indication(s): CMV retinitis (in AIDS pa-tients).

◦ Administered : intraocularly (intravitreally).

5'-d-[G*C*G*T*T*T*G*C*T*C*T*T*C*T*T*C*T*T*G*C*G]_3'sodium salt

* = racemic phosphorothioate

Fomivirsen

Fig. 32.

Treatment of chronic HBV infection

• Interferon-alpha pegylated interferon-alpha (48 weeks)

• Nucleoside analogs:

‣ lamivudine

‣ entecavir

‣ telbivudine

‣ Emtricitabine

• Nucleotide analogs

‣ Adefovir

‣ Tenofovir

➡ long duration >1 y; probably lifetime


Terapêutica anti-HBV

Hepatology - A clinical textbook

108

Pregnancy is usually a contraindication for all available drugs. Therapy with • nucleos(t)ide analogues during pregnancy may be considered if the benefit out-weighs the risk.

Occupational and social aspects and extrahepatic complications may justify • therapy in individual cases (Cornberg 2007).

Treatment options for chronic HBV infectionThere are two classes available for the treatment of chronic HBV infection: interferon

(standard or pegylated (PEG)-IFN ) and inhibitors of the HBV polymerase, the nucleoside and acyclic nucleotide analogues.

While IFN has been a mainstay in the treatment of chronic HBV infection for many years it is limited by its tolerability and side effect profile allowing administra-tion for only a limited period of time (6-12 months, maximum 24 months). Nucleo-side and nucleotide analogues have a better tolerability and are therefore applied in the long-term treatment of chronic hepatitis B. However, the efficacy of these oral agents can be hampered by the risk of the emergence of resistance. Two interferons and five oral antivirals are currently approved for the treatment of chronic HBV infec-tions: standard IFN -2b and PEG-IFN -2a, lamivudine (LAM), adefovir dipivoxil (ADV), telbivudine (LdT), entecavir (ETV) and tenofovir disoproxil fumarate (TDF) (Table 2). The efficacy of the available drugs after one year of treatment, assessed by the proportion of individuals with HBV DNA below the limit of detection, normalized transaminases and HBeAg seroconversion is shown in Figure 4.

Agent Name Dose Duration

Interferon Standard Interferon -2a Roferon® 2.5-5 mi. IU per 4-6 months m2 body surface 3x/week

Standard Interferon -2b Intron A® 5-10 mi. IU 3x/week 4-6 months

Pegylated Interferon -2a Pegasys® 180 µg/week 48 weeks

Nucleoside analoguesLamivudine Zeffix® 100 mg/day long-term*

Telbivudine Sebivo® 600 mg/day long-term*

Entecavir Baraclude® 0.5 mg/day long-term* 1 mg/day for patients with long-term* lamivudine resistance

Nucleotide analogues Adefovir dipivoxil Hepsera® 10 mg/day long-term*

Tenofovir disoproxil fumarate Viread® 300 mg/day long-term*

* see Figure 7

Table 2. Overview of interferons and oral antiviral drugs currently approved for the treatment of HBV infection.



T h e n e w e ng l a nd j o u r na l o f m e dic i n e

n engl j med 355;23 www.nejm.org december 7, 20062446

Interferonalfa

Interferonreceptors

Tyrosinekinase

Janus-activatedkinase

STAT

STAT

ViralRNA

P

P

P

HCV

STAT1

STAT2

IRF9

ISGF3

ISRE

ISG mRNAs

OtherISGs

Proteinkinase R

HCV replicativecomplex

Assembly

HCV virions

Adenosinedeaminase

Host DNA

2',5'oligoadenylatesynthetase

Figure 1. Proposed Mechanisms of Action of Interferon Alfa against HCV.

Interferon alfa engages receptors on the hepatocyte cell-surface membrane, causing them to dimerize and to activate Janus-activated and tyrosine kinases that phosporylate the cytoplasmic signal transducers and activators of transcription (STAT) proteins. STAT1 and STAT2 dimerize and bind interferon regulatory factor 9 (IRF9), creating a large complex (interferon-stimulated gene factor 3, or ISGF3) that is translocated into the nucleus, where it binds to interferon-stimulated response elements (ISREs) on DNA. This engagement causes transcription of multiple (>100) interferon-stimulated gene (ISG) mRNAs, which exit the nucleus and encode proteins that alter cell metabolism and interfere with virus replication, protein synthesis, and assembly. Major ISGs thought to be important in inhibiting HCV replication include 2',5' oligoadenylate synthetase, which activates antiviral RNases; RNA-specific adenosine deaminase, which edits viral RNA; and protein kinase R, which inactivates protein translation from viral mRNA. The HCV replicative complex is associated with the cytoplasmic membranes of hepatocytes and comprises RNA replicative intermediates, viral mRNA, structural and nonstructural viral proteins, and assembling virions.

The New England Journal of Medicine

Downloaded from nejm.org at FACULDADE MEDICINA UNIV DE LISBOA on November 25, 2011. For personal use only. No other uses without permission.

Copyright © 2006 Massachusetts Medical Society. All rights reserved.

2’,5’-oligoadenilato sintetase: activação de RNAses virais

Proteína cinase R: inactiva a tradução

RNA-specific adenosine deaminase: edição do RNA viral

Hoofnagle. NEJM 2006, 355:23


Terapêutica anti-HBV (NA ou NtA)

• Alvo: DNA-polimerase viral (RT)

• Inibe a conversão de pgRNA em DNA genómico

• Cura = desaparecimento do cccDNA…

Standard therapy for hepatitis B virus infection

121

HBV DNA as a parameter of response to antiviral therapyDuring antiviral therapy, the decrease of HBV DNA levels from baseline is the most important tool in monitoring treatment efficacy. Complete response to antiviral thera-py is defined as suppression of HBV DNA to below the limit of detection as measured by a sensitive real time PCR assay (Figure 7). Incomplete suppression is characterized by persistent HBV replication despite antiviral therapy. Ongoing HBV replication should be avoided to prevent the selection of resistant HBV strains by replication of the virus in the presence of drug in the so called “plateau phases”. An HBV DNA breakthrough despite continuous antiviral therapy is often caused by viral resistance. Measuring of HBV DNA kinetics early during therapy will help to guide antiviral treatment and to establish early stopping rules or add-on strategies to avoid antiviral failure (Figure 7).

Figure 7. Possible courses of antiviral treatment with nucleoside/nucleotide analogues. Incomplete suppression of HBV DNA results in either a “plateau phase” or in a continuous slow decline. A plateau phase represents a high risk for selection of resistant HBV variants, therefore treatment should be changed to a more effective agent or combination therapy. A continuous slow decline should induce a treatment change after 6 months if drugs with a low genetic barrier like LAM or LdT are used. If drugs with a high genetic barrier like ETV or TDF are applied, a continuous slow decline can be monitored for at least 12 months without increased risk of consecutive HBV resistance.

Incomplete or partial virologic response to oral nucleoside or nucleotide analogues is defined as a decrease of HBV DNA >1 log but remaining measurable (Lavanchy 2004) (Figure 7). The definition of partial response depends on the type of treatment; thus, for agents with a high genetic barrier against resistance like ETV, ADV or TDF partial response is defined after 12 months and for substances with a low genetic bar-rier against HBV resistance like LAM or LdT, after 6 months of monotherapy. In case


Viruses 2010, 2

1284

Figure 2. Cumulative incidence of HBV resistance to lamivudine (LAM), adefovir (ADV), entecavir (ETV), telbivudine (LdT) and tenofovir (TDF) in published pivotal trials in NUC-naive patients. For method of calculation, see [61]. These trials included different populations, used different exclusion criteria and different follow-up endpoints [151].

3.2. Adefovir dipivoxil

Adefovir (or PMEA [9-(2-phosphonylmethoxyethyl)adenine]) is an acyclic nucleoside phosphonate [66]. To increase its oral availability, PMEA has been esterified to its prodrug bis(POM)PMEA (Figure 1B). Adefovir dipivoxil was licensed as Hepsera® in September 2002 for the treatment of CHB. It is administered orally at a dose of 10 mg daily.

When PMEA enters the cell, it is phosphorylated twice by AMP kinase [67] to its active form PMEApp, which is incorporated into the growing HBV DNA chain, where it acts as (i) an obligatory chain terminator [68] and/or (ii) a competitive inhibitor of the natural substrate dATP. In addition to its anti-HBV activity, PMEApp has also demonstrated activity against other viruses, i.e., herpesviruses and retroviruses as well as bacteria producing adenylate cyclase toxins (e.g., B. anthracis, B. pertussis, P. aeruginosa) [69]. Treatment for 48 weeks with adefovir dipivoxil led to a decrease of both cccDNA and HBsAg levels in HBeAg-positive CHB patients; it has been estimated that it may take approximately 14.5 years to clear infected cells from cccDNA [70].

Evolução virológica

após terapêutica

Fármacos antivirais (SOC - standard of care)Interferão alfa

15-20% de resultados satisfatórios após 6 meses de tratamento; 25-30% após 12-18 meses de tratamentogenótipos virais 1 e 4 menos susceptíveisTempo de semi-vida superior no caso de interferão alfa pegilado (PEG-Intron®)

Ribavirina

HCV - Tratamento


Análogo da guanosina

Fosforilado intracelularmente a

mono-, di-, e trifosfato por acção de quinases

celulares

Ribavirina

OHO

OH

H2N

O

N

N

N

HN

OH


IMP-desidrogenase

Inosina monofosfatoIMP

Xantosina monofosfato

Guanosina monofosfatoGMP

Ribavirina monofosfato

Consequência: Diminuição dos níveis intracelulares de GTP

Ribavirina - Mecanismo de acção


Outros mecanismos

Inibição da enzima guanilil-transferase (GTP-dependente) que leva à síntese de RNAm com

extremidades anormais provocando uma tradução ineficaz

Efeitos inibitórios directos sobre a RNA-polimerase RNA-dependente de origem viral

Ribavirina - Mecanismo de acção


Ribavirina - Usos terapêuticos

Activo sobre HCV

Vírus Respiratório Sincícial (RSV) (aerossol) Vírus da Febre de Lassa (IV)

Vírus Hantaan (IV) Vírus Influenza (aerossol)

Efeitos secundários Anemia

Linfopénia Potencialmente oncogénico e teratogénico


Esquema terapêutico

26 | Hepatitis C Treatment

Table 1.2 – First-line treatment recommendations for antiviraltherapy in Hepatitis C*HCV

Genotypes

PegIFN alfa-2a

once per week

PegIFN alfa-2b

once per week

RBV

once per dayPlanned

duration†

1 and 4 180 µg

Flat dose

1.5 µg/kg

weight-based

dose

15 mg/kg weight-

based dose

48 weeks

800 mg daily

flat dose, if BMI<25

2 and 3 180 µg

Flat dose

1.5 µg/kg

weight-based

dose15 mg/kg weight-

based dose, if

BMI>25

24 weeks

*According to data from EASLD 2011

†Treatment duration should be tailored to the on-treatment virological response

at weeks 4 and 12, and eventually, week 24.

For RGT, the following recommendations can be made

(Tsubota 2011):

– Treatment duration can be reduced to 12 weeks for

genotypes 2/3 infected patients who obtain an RVR with

PegIFN and weight-based RBV dosing. This does not

compromise the likelihood of achieving an SVR, but reduce

the AEs and the associated costs.

– Treatment duration can be reduced to 24 weeks for

genotype 1 infected patients with low baseline

(pretreatment) VL who attain a RVR.

– Treatment may be extended to 72 weeks for genotype 1

infected patients who show a slow virological response (with

partial EVR and HCV RNA negative by week 24). However,

for those who do not attain an EVR, the chance of treatment

success is very low (Thomson 2008).

In the clinical trials of the new direct-acting antivirals, a new

marker has been implemented, namely extended RVR (Sherman

2010). Extended RVR (eRVR) is defined as undetectable HCV

RNA at week 4 of therapy, maintained through a later time point

(in some cases over a period of 12 weeks, in others over 24

weeks). eRVR is a good predictor of the ability to shorten triple

therapy with protease inhibitors. Patients with G1 HCV, who


HCV - tratamento

Percentagem de cura (IFN + RBV)

Genótipo 1: 50%

Genótipo 2: 90%

Genótipo 3: 80%

Genótipo 4: 70%


J Miguel Azevedo-Pereira CPM-URIA, FFUL

Direct-acting agents (DAA) Protease and polymerase inhibitors

BoceprevirTelaprevir

SofosbuvirDasabuvir

SimeprevirAsunaprevir

ABT-450

DaclatasvirOmbitasvirLedipasvir

Objective - SVR

T (Years)

NR

SVR


Fármacos anti-Vírus Influenza

Alvos terapêuticosÁcido nucleico: Ribavirina

Proteína M2: Amantadina, RimantadinaNeuraminidase: Zanamivir, Oseltamivir


R = NH2 Amantadina

R = H Adamantano

R = RimantadinaN H 2

C H 3

Amantadina e Rimantadina


Amantadina e Rimantadina Mecanismo de acção

Inibem a descapsidação do vírus devido ao bloqueio da proteína M2 que funciona como canal iónico.

A redução do influxo de H+ resulta na não libertação da NP


Papel da Neuraminidase

Promove a libertação dos viriões

Previne a formação de agregados virais após a sua libertação da célula

Previne a inactivação viral por parte do muco Promove a entrada do vírus na células epiteliais do tracto respiratório

Induz a apoptose celular por activação do TGF β

Induz várias citocinas (IL-1, TNF, etc.)


Inibidores da Neuraminidase

Galactose

Ácido N-acetilneuramínico (Ác. Siálico)

Neuraminidase




Zanamivir

Intranasal

Oseltamivir

Oral


Terapêutica do HIVInibidores da fusão do vírus com a célula

Inibidores da ligação aos co-receptores (CCR5)

Inibidores da transcriptase reversa

Inibidores da integrase viral

Inibidores da transcrição - inibidores da proteína Tat

Inibidores da maturação viral - Inibidores da protease viral


Inibidores da transcriptase reversa

Análogos dos nucleósidos (NRTI)

Não análogos dos nucleósidos (NNRTI)

Análogos dos nucleótidos (NtRTI)


Análogos dos nucleósidos (NRTI)

Fármaco Abreviatura Nome comercial

AZT+3TC CBV Combivir

Emtricitabina FTC Emtriva

Lamivudina 3TC Epivir

Zalcitabina KVX Kivexa

Zidovudina AZT Retrovir

AZT+3TC+ABC TZV Trizivir

FTC+TDF TVD Truvada

Didanosina ddI Videx

Stavudina d4T Zerit

Abacavir ABC Ziagen


NRTI - Zidovudina

Desoxitimidina



Tenofovir TDF Viread

Adefovir ADF Preveon; Hepsera

Inibidores da RT - NtRTI


NtRTI - Tenofovir

Adenosina monofosfato


Mecanismo de acção dos NRTI e NtRTI


Inibidores da RT - NNRTI


Delavirdina DLV Rescriptor

Efavirenz EFV Sustiva

Nevirapina NVP Viramune


NNRTI - DelavirdinaJ Miguel Azevedo Pereira

FFUL

Mecanismo de acção dos NNRTI

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w.H

IVw

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http://www.HIVwebstudy.org


Tipranavir TPV Aptivus

Amprenavir APV Agenerase

Indinavir IDV Crixivan

Saquinavir SQV InviraseLopinavir LPV Kaletra

Ritonavir RTV Norvir

Atazanavir ATV Reyataz

Fosamprenavir FPV TelzirNelfinavir NFV Viracept

Inibidores da Protease


Raltegravir RAL Isentress

Inibidores da Integrase

J Miguel Azevedo Pereira - FFUL

Inibidores da Protease


Mecanismo de acção da protease viral

gag

pol

env

poliproteína gag/pol poliproteína env

poliproteína gag

p17 p24 p9 p6 Protease RT Integrase SU TM

Genes

Proteínas precursoras

Proteínas finais

Proteasescelulares

Protease viral


Inibidor da Integrase - Raltegravir



Enfuvirtida T-20 Fuzeon

Inibidores da fusão

Inibidores dos co-receptores


Maraviroc MRV Celsentri


Inibidores do co-receptor CCR5


Mecanismo de acção do inibidor de fusãoD

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l. 20

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Inibidor da Fusão - Enfuvirtide


Problemas na terapêutica anti-HIV

Variabilidade genética

Alta taxa de erro da DNA-polimerase RNA-dependente (RT)Alta taxa de replicação do HIV (109 partículas virais/dia)

Consequências:

Causas:

Mutações Variabilidade

Estirpes mais virulentas Fuga ao sistema imunológico

Estirpes resistentes





Vírus latente vs. vírus em replicação


J Miguel Azevedo-Pereira FFUL

How to induce replication of latent HIV

LETTERdoi:10.1038/nature11286

Administration of vorinostat disrupts HIV-1 latencyin patients on antiretroviral therapyN. M. Archin1, A. L. Liberty1, A. D. Kashuba1, S. K. Choudhary1, J. D. Kuruc1, A. M. Crooks1, D. C. Parker1, E. M. Anderson2,M. F. Kearney2, M. C. Strain3, D. D. Richman3, M. G. Hudgens1, R. J. Bosch4, J. M. Coffin2, J. J. Eron1, D. J. Hazuda5 & D. M. Margolis1

Despite antiretroviral therapy, proviral latency of humanimmunodeficiency virus type 1 (HIV-1) remains a principalobstacle to curing the infection1. Inducing the expression of latentgenomes within resting CD41 T cells is the primary strategy toclear this reservoir2,3. Although histone deacetylase inhibitors suchas suberoylanilide hydroxamic acid (also known as vorinostat,VOR) can disrupt HIV-1 latency in vitro4–6, the utility of thisapproach has never been directly proven in a translational clinicalstudy of HIV-infected patients. Here we isolated the circulatingresting CD41 T cells of patients in whom viraemia was fullysuppressed by antiretroviral therapy, and directly studied the effectof VOR on this latent reservoir. In each of eight patients, a singledose of VOR increased both biomarkers of cellular acetylation, andsimultaneously induced an increase in HIV RNA expression inresting CD41 cells (mean increase, 4.8-fold). This demonstratesthat a molecular mechanism known to enforce HIV latency canbe therapeutically targeted in humans, provides proof-of-conceptfor histone deacetylase inhibitors as a therapeutic class, and definesa precise approach to test novel strategies to attack and eradicatelatent HIV infection directly.

Among the many important aims of future HIV research is thedevelopment of therapies of finite duration capable of eradicatingHIV infection. The persistence of quiescent HIV infection within asmall population of long-lived CD41 T cells is currently a majorobstacle to this goal1. Histone deacetylases (HDACs) are recruited tothe HIV long terminal repeat (LTR) promoter, establishing one ofseveral restrictions that can limit LTR expression and maintain virallatency2,3. Deacetylated LTR chromatin seems to play a key contributoryrole in regulating HIV expression, and especially in maintaining proviralquiescence and latency. In vitro, HDAC inhibitors have been shown todisrupt latent proviral HIV infection in both cell culture models and exvivo assays using cells from HIV-1-infected patients. Althoughdisrupting latency has been proposed as part of a strategy to eradicateHIV infection, previous studies using the weak HDAC inhibitorvalproic acid did not consistently demonstrate a marked depletion ofresting cell infection7–11 in patients on antiretroviral therapy (ART).However, the effects measured in these studies are significantlydownstream of the molecular site of action of HDAC inhibitors, andthus the proximal pharmacodynamic measures of HDAC inhibitoractivity and HIV-1 expression were not evaluated. Here we show thatHDAC inhibitors disrupt the latency of proviral genomes withinresting CD41 T cells, establishing the first (to our knowledge) classof drugs that could lead to the eradication of HIV infection.

VOR is a potent HDAC inhibitor used to treat human malignancies.At clinically relevant concentrations, VOR inhibits the class I HDACsmost important for repression of HIV expression4,12; it also inducesLTR expression and virus production in vitro from the resting CD41 Tcells of HIV-positive patients on ART with levels of plasma HIV RNAbelow the detection limit (BDL)5,6,13. As the most proximal measure of

effect on latent infection is expression of HIV-1 RNA, we developed asensitive assay to enable a direct measurement of unspliced gag HIVRNA within the resting CD41 T cells of HIV-infected patients.The assay has a limit of detection of 1 copy per million restingCD41 T cells, and a limit of quantification of 10 copies per millionresting CD41 T cells.

To evaluate the effect of VOR on latent infection in vivo, HIV-infected patients receiving stable ART with plasma HIV-1 RNA,50 copies per ml for at least 6 months and a CD4 count .300ml21

were enrolled following informed consent. To demonstrate that it wasethical to expose patients to an experimental agent with potential riskin a study with no proven clinical benefit for the individual, we vali-dated the ability of this assay of HIV RNA within resting CD41 T cellsto measure HIV expression at baseline, and to detect up-regulation ofHIV expression in resting cells from each patient after physiologicalexposure to VOR.

Patients maintained suppressive ART, and purified populations ofresting CD41 T cells were obtained by continuous-flow leukapheresisand negative selection in an immunomagnetic column7. To establish abaseline, we measured the mean quantity of HIV-1 gag RNA in poolsof 1 million resting CD41 T cells immediately after their isolation frompatients. To measure validated biomarkers of VOR effect in peripheralblood mononuclear cells (PBMCs) of patients, we performed parallelassays of total cellular histone acetylation and measured histoneacetylation by chromatin immunoprecipitation (ChIP) at the humanp21 gene promoter, a gene known to upregulate chromatin acetylationafter VOR exposure14. Then to model the effect of a clinical dose ofVOR, multiple replicate pools of 1 million resting CD41 T cells wereincubated in complete media alone, with 335 nM VOR, or with 3mgphytohaemagglutinin (PHA) and 60 U interleukin-2 (IL-2) for 6 h.VOR conditions were selected to mimic the unbound drug exposureexpected after a single 400 mg dose of VOR in vivo5.

Validation assays were performed in resting CD41 T cells isolatedby leukapheresis from 16 patients with plasma HIV RNA BDL(Fig. 1a). In each patient a total of 48–72 million highly purified restingCD41 T cells were studied; that is, 12–48 million cells in each con-dition, depending on cell availability. In 9 patients following 6 h ofculture of 16–24 million cells without stimulation in media alone,HIV gag RNA was quantifiable at a mean level of 52 6 32 copies permillion cells. However, in the other 7 patients in whom 12–24 millioncells were studied (Fig. 1a), HIV RNA was not quantifiable at a limit of10 copies per million cells, although in all but 2 of these patients RNAwas detected but not quantifiable (.0 but ,10 copies per millioncells).

Following in vitro exposure to 335 nM VOR for 6 h, HIV RNAexpression was significantly upregulated in 8 of 9 patients in whomresting CD41 T cell HIV RNA was quantifiable without HDAC inhibitorexposure, and also in 3 of 7 patients in whom cell-associated HIV RNAwas ,10 copies per million cells before HDAC inhibitor exposure. In

1The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA. 2HIV Drug Resistance Program, NCI, NIH, Frederick, Maryland 21702, USA. 3VA San Diego Healthcare System andUniversity of California San Diego, San Diego, California 92093, USA. 4Harvard School of Public Health, Boston, Massachusetts 02115, USA. 5Merck Research Laboratories, White Horse Junction,Pennsylvania 08889, USA.

4 8 2 | N A T U R E | V O L 4 8 7 | 2 6 J U L Y 2 0 1 2

Macmillan Publishers Limited. All rights reserved©2012

Vorinostat - potent histone diacetylases (HDAC) inhibitor

Documents

Agentes quimioterápicos das infecções virais · Agentes Virucidas • Usados principalmente na prevenção da transmissão • Detergentes, solventes orgânicos (éter e clorofórmio),