ID 2 Final: Harrold HIV (p1-22)

3 Key Enzymes for HIV

1. ___ ___

2. ____

3. ___

reverse transcriptase, RNaseH, integrase

Key Parts of HIV Structure

-____ -attaches to the CD4 Receptor on the human T cell

-____-provides conformational flexibility for fusion

gp120, g41

HIV Replication Cycle

Step 1: ___ of virus to CD4+ helper T cells

attachment

Step 1: attachment of virus to CD4+ helper T cells

-this results from a specific interaction between __ and __

gp120, CD4+

Step 1: attachment of virus to CD4+ helper T cells

-additional chemokine ____ located on the CD4+ helper T cells are also involved (CCR5 and CXCR5) that are essential for __ and ___

coreceptors, fusion, penetration

HIV Replication Cycle

Step 2: ___ and ___ to release viral RNA

penetration, uncoating

HIV Replication Cycle

Step 3: ____ of viral RNA to proviral DNA

transcription

Step 3: transcription of viral RNA to proviral RNA

-requires the regulatory protein ___ (Trans-Activator of Transcription) and the enzyme ___ ___

TAT, reverse transcriptase

HIV Replication Cycle

Step 4: digestion of RNA by ____ and the formation of __ ___ DNA

RNase H, double stranded

HIV Replication Cycle

Step 5: integration of double stranded proviral DNA into host cell DNA using __ enzyme

integrase

HIV Replication Cycle

Step 6: ___ and ___ of proviral DNA

transcription, replication

Step 6: transcription and replication of proviral DNA

-transcription produces the __ required to make viral proteins and enzymes

-replication makes __ of viral RNA

mRNA, copies

HIV Replication Cycle

Step 7: translation of viral mRNA into __ ___ ___

viral precursor polyproteins

Step 7: translation of viral mRNA into viral precursor polyproteins

-the main precursors are __, ___, and __

gag, pol, env

HIV Replication Cycle

Step 8: initial __ of viral precursor polyproteins

processing

Step 8: initial processing of viral precursor polyproteins involves:

a) the addition of __ __ to the precursor proteins. This targets them to the __ __ where they can be cleaved into individual proteins and enzymes

fatty acids, cell membrane

Step 8: initial processing of viral precursor polyproteins involves:

b) ____- the addition of sugars to make glycoproteins (ie gp120)

glycosylation

Step 8: initial processing of viral precursor polyproteins involves:

c) NOTE that the intact polyprotein is necessary __ in the lifecycle, when it assembles the immature form of the virus

early

HIV Replication Cycle

Step 9: ___ and ___ of new viral particles

assembly, budding

Step 9: assembly and budding of new viral particles

-assembly involves combining the viral __ (from step 6) with the __/glycoproteins (from step 8)

-budding is the release of new viral particles without __ the host cell

RNA, proteins, damaging

HIV Replication Cycle

Step 10: ____ of precursor polyproteins using the enzyme HIV ___

proteolysis, protease

Step 10: Proteolysis of precursor polyproteins using the enzyme HIV protease

-the last step involves converting inactive polypeptides to specific proteins/enzymes. This is required for __ and __ change

maturation, conformational

NRTIs, NNRTIs, entry

Agents used to treat HIV

1. Nucleoside Reverse Transcriptase Inhibitors (___)

2. Non-Nucleoside Reverse Transcriptase Inhibitors (___)

3. HIV Protease Inhibitors

4. Integrase Inhibitors

5. Agents to prevent viral __ of HIV into human cells

prodrugs, nucleosides

NRTIs

-ALL are ___

-with 1 exception (tenofovir), all are ___

3'-OH

NRTIs

-ALL lack a __-___

zidovudine, emtricitabine, lamivudine, stavudine, tenofovir, abacavir, didanosine

NRTIs (zelstad)

1. ___

2. ___

3. ___

4. ___

5. ___

6. ____

7. ____

NRTIs

-all are converted to their respective ___ that mimic normal substrates for reverse transcriptase

triphosphate

NRTIs

-since tenofovir comes with 1 phosphate, when it is converted to tenofovir diphosphate--this is actually a ___!

triphosphate

When using NRTIs in combination therapy:

-use 2 drugs that mimic 2 different nucleotides (DO NOT use 2 drugs that mimic the __ nucleotide)

same

NRTIs

-all of these drugs inhibit ___ ___; and are therefore selective for __ viruses like HIV

reverse transcriptase, RNA

NRTIs

-the active nucleotides can be ___ into DNA resulting in ___ ___ ___!!!

incorporated, immediate chain termination

NRTIs

-can cause a potentially fatal syndrome of ___ ___ with hepatic steatosis due to mitochondrial toxicity

lactic acidosis

NRTIs

-selective toxicity depends on ability to inhibit reverse transcriptase without inhibiting human ___ ___

DNA polymerase

NRTIs

-problems arise because some reverse transcriptase inhibitors can also inhibit human ___ ____-__, which is the mitochondrial enzyme

DNA polymerase γ

Which 3 NRTIs have lower affinity for DNA polymerase γ and are therefore safer drugs?

lamivudine, emtricitabine, tenofovir

NRTIs

-can be taken without regard with meals and generally do not react with drugs because they are __ soluble and generally do not require __

water, metabolism

Which NRTI requires a genetic test?

Abacavir

Abacavir

-warning: ___ reactions which can be fatal

-therefore, DO NOT ___ patient on abacavir after reaction has occurred

hypersensitivity, restart

Abacavir

-if genetic marker HLA-B*5701 is present, do ___ use abacavir in this patient

not

Emtricitabine/Lamivudine

-both mimic ___ and after often used interchangeably, but should never be used together

-best tolerated NRTIs along with tenofovir

CTP

Tenofovir

-most common ADR is GI disturbances

-can be dosed QD

-used for Hep B infection as well

-2 prodrug forms: tenofovir __ and tenofovir ___

disoproxil, alafenamide

Tenofovir Disoproxil undergoes an initial hydrolysis of 2 ___ to form tenofovir

esters

Tenofovir Disoproxil

-BBW: 1. exacerbations of ___ ___ after discontinuation 2. ___ ___ and severe hepatomegaly with steatosis

hepatitis B, lactic acidosis

Tenofovir Alafenamide

-gets taken up by ___ where it undergoes hydrolysis by ___ ___

cells, cathepsin A

Tenofovir Alafenamide

-Hydrolysis occurs in cells, resulting in lower concentrations in the blood stream, but high concentrations in cells where HIV-1 ___, therefore less ADRs

replicates

Tenofovir Alafenamide

-activation involves cathepsin A (has a ___ function beyond hydrolysis)

deamination

Tenofovir Alafenamide

-Key Point: this prodrug was developed to help reduce ___ __

-BBW are the same as tenofovir disoproxil

adverse events

Why does Tenofovir Alafenamide produce less ADRs?

Tenofovir Disoproxil undergoes hydrolysis in the ___

Tenofovir Alafenamide undergoes hydrolysis in ___

blood, cells

The Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) all have "___" in the middle of their name

vir

1st Gen NNRTIs

1. ____

2 ___

3. ____

efavirenz, nevirapine, delavirdine

The 1st generation Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) were approved under provisions of the accelerated approval process based on ___ ___ changes (ie CD4 Count, plasma HIV-RNA levels)

surrogate marker

NNRTI MOA

-bind to and non-competitively inhibit ___ ___ by causing a conformational change in the enzyme

reverse transcriptase

NNRTIs have the same target as NRTIs. What's different?

the binding site

NNRTIs bind to an ___ ___ and alter the conformation of the active site

auxiliary site

Since the binding site of NNRTIs is different than NRTIs, strains that are resistant to NRTIs are NOT NECESSARILY ___ to NNRTIs

resistant

NNRTIs-1st gen

-Delavirdine is rarely used because it is less ___ than efavirenz and nevirapine

potent

NNRTIs-1st gen

-Nevirapine is rarely used because it can cause severe ____

hepatotoxicity

NNRTIs-1st gen

-Evfavirenz is the ___

DOC

NNRTIs Adverse Effects

-ALL (1st and 2nd gen) can cause a __

rash

NNRTIs Adverse Effects

-the main ADE seen with Evfavirenz (DOC) is ___ effects (dizziness, impaired concentration, abnormal dreams, etc)

CNS

NNRTIs Drug Interactions

-Efavirenz induces CYP___ and CYP___

3A, 2B6

NNRTIs Drug Interactions

-an ___ in gastric pH will decrease ionization, decrease dissolution, and therefore may reduce absorption of Delavirdine

increase

NNRTIs Drug Interactions

-Allow at least 2 hours between administration of Delavirdine with an ___

antacid

NNRTIs Drug Interactions

-Avoid use of Delavirdine with a ___ or ___ ___

PPI, H2 antagonist

Key advantage of 2nd gen NNRTIs = potentially effective in patients who have infection that is ___ to 1st gen NNRTI

resistant

2nd gen NNRTIs

1. ____

2. ____

3. ____

etravirine, rilpivirine, doravirine

2nd gen NNRTIs

-ALL 3 drugs have increased ___ compared to 1st gen drugs

flexibility

2nd gen NNRTIs

-the increased conformational flexibility allows these drugs to have access to ___ binding sites, therefore enhancing their ___

additional, activity

NNRTIs Drug Interactions

-Etravirine induces CYP___ and inhibits CYP___ and CYP___

3A4, 2C9, 2C19

NNRTIs Drug Interactions

-Coadministration of Rilpivirine with drugs that drugs that increase the gastric pH (H2 antagonists, PPIs, antacids) decrease the ___ or rilpirivine

absorption

Why is the absorption of Etravirine not affected by increased gastric pH?

-it has increased ____, therefore increased ionization that is not dependent on gastric pH

basicity

HIV Protease Inhibitors

-___ peptide analogs

stable

HIV Protease Inhibitors

-mimic the ___ state of the reaction that is catalyzed by HIV Protease

transition

HIV Protease Inhibitors

-all have the suffix "-___"

navir

Advantages of HIV Protease Inhibitors

1. Complement the effects of ___ ___ inhibitors

reverse transcriptase

Reverse Transcriptase Inhibitors target ___ events (establishment of infection in host cell)

HIV Protease Inhibitors target ___ events (Production of mature viral particles + spread to infection)

early, late

Advantages of HIV Protease Inhibitors

2. No ___-____ between reverse transcriptase inhibitors and HIV protease inhibitors because they have different mechanisms

cross-resistance

Advantages of HIV Protease Inhibitors

3. HIV Protease catalyzes protein cleavages which are not recognized by __ proteases and peptidases. The HIV Protease Inhibitors have been designed based on this ___

human, selectivity

HIV protease cleaves viral polyproteins at sites that human proteases do not recognize, especially peptide bonds involving ___ residues.

proline

HIV Protease Inhibitors

-inhibit HIV protease, the viral enzyme responsible for cleaving the viral precursor polypeptides (eg gag, gag-pol), therefore preventing viral ___ and the infection of __ cells

replication, new

As part of its mechanism, HIV Protease uses a pair of __ __ residues

aspartic acid

As part of its mechanism, HIV Protease uses a pair of aspartic acid residues to catalyze the cleavage of a peptide bond between ___ and ___

phenylalanine, proline

HIV Protease Mechanism

Step 1: Ionized Asp residue extracts a __ atom from H2O

hydrogen

HIV Protease Mechanism

Step 2: Hydroxide ion attacks ___ of labile peptide bond

carbonyl

HIV Protease Mechanism

Step 3: A second Asp residue stabilizes the ___ ___

transition state

ALL HIV Protease Inhibitors have the following:

1. a ___ ___ to mimic the transition state

2. a ___ side chain adjacent to the 2° OH Group

2° OH Group, Phenyl

ALL HIV Protease Inhibitors have the same __ between the 2 hydrophobic regions

distance

Common Features to All HIV Protease Inhibitors

1. ___ to protease inhibitors can occur

resistance

Resistance to protease inhibitors can occur and primary mutations initially occur near the ___-___ cleft of the enzyme and interfere with the binding of the drug

substrate-binding

Common Features to All HIV Protease Inhibitors

2. Can cause __ disturbances (including stool urgency, diarrhea)

GI

Common Features to All HIV Protease Inhibitors

3. Can cause __

hepatotoxicity

Common Features to All HIV Protease Inhibitors

3. Metabolism by CYP enzymes, especially CYP__ family; Additionally, they inhibit these enzymes resulting in many drug interactions

3A

HIV Protease Inhibitor- Ritonavir

-poorly ____

tolerated

HIV Protease Inhibitor- Ritonavir

-most commonly used to elevate plasma levels of other protease inhibitors due to POTENT inhibition of CYP___

-when used for this purpose, adverse effects are much less common

3A4

HIV Protease Inhibitor- Lopinavir

-generally well tolerated, but can cause pancreatitis and elevations of QT and PR intervals

-When used alone, it has poor ____; Therefore, it is used in combination with ___

bioavailability, ritonavir

HIV Protease Inhibitor- Atazanavir

-requires the presence of ___ and an ___ gastric pH for optimal absorption

food, acidic

HIV Protease Inhibitor- Atazanavir

-H2 antagonists, PPIs, and antacids can decrease the oral ___

-lower effects on plasma lipids

absorption

HIV Protease Inhibitor- Darunavir

-Advantage = HIV strains resistant to other protease inhibitors may show ___ cross-resistance to darunavir

decreased

HIV Protease Inhibitor- Darunavir

-HIV strains resistant to darunavir show cross-resistance to most other protease inhibitors, with the possible exception of ___

tipranavir

HIV Protease Inhibitor- Darunavir

-can cause ___ (potentially more severe than other protease inhibitors)

-use with caution in patients with __ allergies

rash, sulfa