Anti-HIV Therapy CHEM 4470-5470 PDF

Anti-HIV therapy CHEM 4470-5470 Protease inhibitors and others Acquired Immunodeficiency Syndrome (AIDS) History 1950s: Blood samples from Africa have HIV antibodies. 1976: First known AIDS patient died. 1980: First human retrovirus isolated (HTLV-1). 1981: First reports of “Acquired Immuno-deficien...

Anti-HIV therapy CHEM 4470-5470 Protease inhibitors and others Acquired Immunodeficiency Syndrome (AIDS) History 1950s: Blood samples from Africa have HIV antibodies. 1976: First known AIDS patient died. 1980: First human retrovirus isolated (HTLV-1). 1981: First reports of “Acquired Immuno-deficiency Syndrome” in Los Angeles. (Gallo) 1983: Virus first isolated in France (Françoise Barré-Sinoussi, Luc Montagnier). 1985: Development and implementation of antibody test to screen blood donors. 1986: Consensus name Human Immunodeficiency Virus (HIV-1). Related virus (HIV-2) identified. 1991: Magic Johnson announces he is HIV+ (a death sentence at the time) 1992: AIDS becomes the leading cause of death among adults ages 25-44 in the U.S 1997: Mortality rates of AIDS starts to decline due to the introduction of new drug cocktails. 2008: Nobel Prize in Medicine to Françoise Barré-Sinoussi and Luc Montagnier "for their discovery of human immunodeficiency virus". Prevalence Characteristics of the virus Icosahedra (20 sided), enveloped virus of the lentivirus subfamily of retroviruses. Two viral strands of RNA found in core surrounded by protein outer coat. – Outer envelope contains a lipid matrix within which specific viral glycoproteins are imbedded. – These knob-like structures responsible for binding to target cell. HIV invades mainly the helper T cells to replicate itself. No Cure Structure of HIV virus HIV Lifecycle Phases: binding and entry, reverse transcription, replication, budding, and maturation Reverse Transcriptions Act Here Protein Inhibitors Act Here 6. Release 3. Transcription 1. Attachment 7. Maturation 2. Entry 4. Integration 5. Polyprotein Production Classes of drugs Antiretroviral (ARV) drugs are broadly classified by the phase of the retrovirus life-cycle that the drug inhibits. Reverse-transcriptase inhibitor(RTI) Protease inhibitors (PIs) Integrase inhibitors Entry inhibitors (fusion inhibitors) Maturation inhibitors Reverse-transcriptase inhibitor RTIs come in three forms: Nucleoside analog reverse-transcriptase inhibitors (NARTIs or NRTIs) Nucleotide analog reverse-transcriptase inhibitors (NtARTIs or NtRTIs) Non-nucleoside reverse-transcriptase inhibitors (NNRTIs) Mechanism When HIV infects a cell, reverse transcriptase copies the viral single stranded RNA genome into a double-stranded viral DNA. The viral DNA is then integrated into the host chromosomal DNA, which then allows host cellular processes, such as transcription and translation to reproduce the virus. RTIs block reverse transcriptase's enzymatic function and prevent completion of synthesis of the double-stranded viral DNA, thus preventing HIV from multiplying. Reverse transcriptase is unique to HIV Zidovudine (Azidothymidine, AZT) Converted to triphosphate which inhibits viral reverse transcriptase AZT is also a chain terminator AZT was the first approved treatment for HIV, sold under the names Retrovir and Retrovis. AZT use was a major breakthrough in AIDS therapy in the 1990s. AZT slows HIV spread significantly but does not stop it entirely. O O NH NH N N O O HO HO O N N N azido thymidine O OH thymidine Zidovudine/Retrovir Gertrude Elion and George Hitchings: 1988 Nobel Prize in Medicine Other Nucleoside Reverse Transcriptase Inhibitors (NRTI’s) H3C NH2 O N NH HO O N O Stavudine/Zerit (d4T) O HO NH2 N HN N N O S Lamivudine/Epivir (3TC) N N H OH Abacavir/Ziagen (ABC) Tenofovir Tenofovir belongs to a class of antiretroviral drugs known as nucleotide analogue reverse transcriptase inhibitors (NRTIs), which block reverse transcriptase O NH2 N (NaO)2OP N N O N H3C tenofovir NH2 N O O HO2C O O O O O CO2H NH2 N O P N N N O H3C tenofovir disoproxil fumarate N O - O P O N N O - O OH adenosine 5'-nucleotide Viread Recall: nucleosides do not have phosphate group and nucleotides do What is a potential disadvantage to nucleotides as potential drugs? HIV Protease inhibitors (PIs) PIs prevent viral replication by inhibiting the activity of proteases Protease inhibitors were the second class of antiretroviral drugs developed. Rang, H. P., Dale, M. M., Ritter, J. M., & Flower, R. J. (2007). Rang and Dale's Pharmacology (6th Edition ed.). Philadelphia: Churchill Livingstone Elsevier. Proteases All proteases selectively catalyze the hydrolysis of polypeptide bonds by activation of water in the catalytic site. 1) Aspartyl: hydrolysis via two aspartic acids 2) Metallo: hydrolysis via coordinated metal 3) Serine: hydrolysis via serine 4) Cysteine: hydrolysis via cysteine Nomenclature S1 H N O P1 O P2 S2 N H P2' O H N O S2' Scissile bond P1' N H H N O S1' Standard nomenclature for substrate residues and their corresponding binding sites. flaps HIV Protease Binding pocket HIV protease is a 99 amino acid aspartyl protease that functions as a homodimer with one active site. The active sites of protease are hydrophobic. Aspartyl Proteases Catalytic mechanism for substrate hydrolysis by aspartic proteases. O p1 N H P1 ' O H O O N H p1 N H H O O O Asp 25 O H N O O P1' N H H O O Asp 25 Asp 25' OH N H + H2N P1' O HO O O O p1 O H H H O O H N Asp 25' O O O Asp 25 Asp 25' Nucleophilic attack of an activated water molecule on the scissile amide bond. Protonation of the amide nitrogen to give the zwitterionic intermediate. Collapse to the cleavage products. N H Known TSIs for aspartyl proteases O H2N N H CO2H OH Statine (Sta) R1 N H R2 Reduced Amide R1 N H R1 N H OH Phosphonic OH R1 O O O R2 Hydroxyethylene O P N H H N OH O N H O CO2H OH Pepstatin O H N O H N N H R1 N H a-Hydroxy-b-amino acid OH N H O Hydroxyethylamine O OH R1 R2 R1 N H N H OH OH R2 R1 N H Hydroxyethylureas TSI=transition state isostere N O Hydroxyethylhydrazide O N H H N N H OH N H O O S Hydroxyethylsulfonamide HIV Protease Inhibitors O H N N O O CONHtBu N H CONH2 N OH N S N N H O H N O OH N H O S HO N H N OH N N H Saquinavir (Roche) MW = 670 12/6/95 hydroxyethylamine Approved in 97 days Poor and variable BA H O CONHtBu N Ritonavir (Abbott) MW =720 3/1/96 hydroxyethylene Approved in 71 days Potent CYP inhibitor Synthetically challenging Indinavir (Merck) MW = 613 3/13/96 hydroxylamine pentamide Approved in 41 days More potent with better BA Complex synthesis Complicated dosing regimen All suffered from cross-resistance and high pill burden Marketed hydroxyethyl sulfonamides O O N H O H O O O S N OR O O H O N H NH2 O O S N OH R= H, amprenavir (Agenrase) R= P(O3)Ca, fosamprenavir (Lexiva) Darunavir (Prezista) NH2 (these drugs are co-administered with ritonavir ) Source: US Patents 5,834,946 and 6,248,775 Integrase inhibitors Integrase inhibitors are a class of antiretroviral drug designed to block the action of integrase, a viral enzyme that inserts the viral genome into the DNA of the host cell. https://aidsinfo.nih.gov/understanding-hiv-aids/glossary/380/integrase-strand-transfer-inhibitor raltegravir, brand name Isentress FDA approved in 2007 elvitegravir, brand name Vitekta FDA approved in 2012 dolutegravir, brand name Tivicay FDA approved in 2013 Entry inhibitors Entry inhibitors, also known as fusion inhibitors Interfere with the binding, fusion and entry of an HIV virion to a human cell. By blocking this step in HIV's replication cycle, such agents slow the progression from HIV infection to AIDS An HIV virion binds to a CD4+ human cell. The two bottom pictures depict two proposed models of HIV fusion with the cell. Source: Biswas, P.; Tambussi, G.; Lazzarin, A. "Access denied? The status of co-receptor inhibition to counter HIV entry" (abstract page). Expert Opin Pharmacother 2007, 8, 923–933. Proteins involved in the HIV entry process Figure: HIV entry into CD4+ cell via CCR5 co-receptor. CD4, a protein receptor found on the surface of helper T cells in the human immune system, also called CD4+ T cells gp120, a protein on HIV surface that binds to the CD4 receptor CCR5, a second receptor found on the surface of CD4+ cells, called a chemokine co-receptor CXCR4, another chemokine coreceptor found on CD4+ cells gp41, a HIV protein, closely associated with gp120, that penetrates the cell membrane CCR5-receptor antagonists: Maraviroc Brand-named Selzentry Maraviroc is an entry inhibitor. Specifically, maraviroc is a CCR5 receptor antagonist, and binds to the chemokine receptor CCR5 and blocks the HIV gp120 (V3 loop) from associating with the receptor. HIV is then unable to bind and enter human macrophages. Source: Levy, J. A. "HIV pathogenesis: 25 years of progress and persistent challenges". AIDS 2009, 23, 147–160. HIV Drug Summary Reverse-transcriptase inhibitor(RTI) Protease inhibitors (PIs) Integrase inhibitors Entry inhibitors (fusion inhibitors) Maturation inhibitors