Advances and Challenges in HIV Antiretroviral Therapy Camille Angle, Meagan Bardan, Hanna Schimjawicz and Sean Tabarah PHM142 Fall 2018 Instructor: Ms. Maya Latif Coordinator: Dr. J. Henderson

HIV Attachment and Penetration https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3405824/pdf/cshperspectmed-HIV-a006866.pdf Wilen, C. B., Tilton, J. C., & Doms, R. W. D. (2012). HIV: Cell binding and entry. CSH Perspectives.

Genome Replication, Assembly, and Egress •RNA undergoes RT yielding dsDNA •Capsid disassembles and DNA enters the nucleus where it integrates into the host genome •Host cell machinery continues to carry out transcription, transcribing essential viral genes •Two copies of viral RNA, Gag and Env get sent to viral assembly sites •Virus exits the cell, and is now able to infect new host immune cells Adapted from: https://vimeo.com/174706793

Treating HIV: Anti-Retroviral Therapy (ART) Combination of Antiretrovial Drugs (ARVs) 7 classes Reduces viral load to undetectable levels in the blood Immune system can recover Prevents progression to AIDS Improves health outcomes and reduces transmission NOT a cure!

Drug Classes 7 drug classes First drug (NRTI) approved in 1987 Combination of these used in ART

Drug Classes: NRTIs/NNRTIs NRTI = Nucleotide Reverse Trascriptase Inhibitor NNRTI = Non- Nucleotide Reverse Transcriptase Inhibitor

NRTI competes with endogenous nucleosides Missing -OH terminal required for addition of subsequent nucleosides Terminates DNA chain Incomplete DNA fragment is unable to integrate NNRTI are noncompetitive inhibitors of RT Induces conformational change in RT Reduces RT activity

Challenges: Treatment but no cure 2 possible outcomes when virus infects a cell Uses cell machinery to replicate Remains in cell without replicating = latent cells Form latent reservoir of HIV proviruses in resting CD4+ cells Evades immune system and drug therapies Requires lifelong medication Expensive Lifelong toxic side effects Adherence difficulties Fernández, Clara Rodríguez. Labiotech.eu, Labiotech UG, 22 Aug. 2018, labiotech.eu/medical/abivax-hiv- cure-viral-reservoir/.

Challenges: antiretroviral drug resistance Nucleoside reverse transcriptase inhibitors Virus replicates at high rate → ~1 mutation per replication cycle Second type of mutation that increases RT selectivity for regular nucleotides Mutation in RT Chain terminating nucleotide is excised Free 3’OH Elongation Resumes

Challenges: antiretroviral drug resistance Non-nucleoside reverse transcriptase inhibitors 2 mechanisms of drug resistance caused by mutation: Loss/Change of interactions at NNRTI binding pocket Steric hindrance

Dark blue and light blue = residues responsible for NRTI resistance Red = Residues responsible for NNRTI resistance NRTI acts at the dNTP binding pocket NNRTI acts allosterically Nikolenko, G. N., et al. "Mechanisms of HIV-1 drug resistance to nucleoside and nonnucleoside reverse transcriptase inhibitors." Molecular biology 45.1 (2011): 93-109,

Improvements in public health Awareness for at-risk demographics Better compliance PrEP Safe injection sites Perinatal transmission prevention ART during pregnancy Precautions during labor ART for child and mother postpartum

HIV therapy development

Biktarvy: Gilead’s latest regimen Similar to Truvada® Monthly PrEP was 1200$ in 2012, now at 2000$ Huge court decision in the UK last week Smallest integrase-inhibitor based daily tablet FDA approval this year Phase 4 trials started May 2018 Being considered as PrEP Improved cocktail Bictegravir 50 mg – INSTI Emtricitabine 200 mg – NRTI Tenofovir alafenamide 25 mg – NRTI Prodrug, lower dose than Truvada Less bone and renal adverse events

Summary ARVs reduce viral load in HIV positive individuals and significantly improve health outcomes 7 classes of ARVs that exert effects at different stages of the HIV life cycle NRTIs and NNRTIs are most commonly used classes Both act on Reverse Transcriptase to prevent transcription of viral DNA from viral RNA NRTI completes with nt when RT is extending viral DNA chain → missing OH group causes termination of DNA chain→ Incomplete DNA fragment is unable to integrate NNRTIs bind and inhibit the activity of RT directly so no viral DNA is transcribed HIV infection of inactive T-cells leads to latent cells that cannot be targeted by drugs → therefore unable to completely eradicate virus and requires lifelong treatment Mutations in RT confers resistance to antiretrovirals Mutations can decrease selectivity for drug or allow it to excise chain terminating nucleotides (NRTIs) and decrease the affinity between the drug and the enzyme (NNRTI) Resistance mechanisms slowed partially by combination therapy and varying drug targets Some routes of infection can be controlled with the right programs in place PrEP Perinatal care Clean needle distribution

References Wilen CB, Tilton J.C, Doms RWD. HIV: Cell binding and entry. CSH Perspectives. 2012;2:a006866 HIV Egress [Internet]. Vimeo.com [cited 24 September 2018]. Adapted from: https://vimeo.com/174706793 HIV/AIDS: The Basics Understanding HIV/AIDS [Internet]. AIDSinfo. 2018 [cited 23 September 2018]. Available from: https://aidsinfo.nih.gov/understanding-hiv-aids/fact-sheets/19/45/hiv-aids--the-basics HIV treatment [Internet]. Unaids.org. 2018 [cited 23 September 2018]. Available from: http://www.unaids.org/en/topic/treatment Richman D. HIV chemotherapy. Nature. 2001;410(6831):995-1001. Tsibiris A, Hirsch M. 130 - Antiretroviral Therapy for Human Immunodeficiency Virus Infection. In: Mandell G, Douglas R, Bennett J, Dolin R, Blaser M, ed. by. 8th ed. Philadelphia, Pa: Elsevier, Saunders; 2018. Xing S, Siliciano RF. Targeting HIV latency: pharmacologic strategies toward eradication. Drug discovery today. 2013 Jun 1;18(11-12):541- 51. Wilen CB, Tilton J.C, Doms RWD. HIV: Cell binding and entry. CSH Perspectives. 2012;2:a006866 HIV Egress [Internet]. Vimeo.com [cited 24 September 2018]. Adapted from: https://vimeo.com/174706793

References 7. Aguilera LU, Rodríguez-González J. Studying HIV latency by modeling the interaction between HIV proteins and the innate immune response. Journal of theoretical biology. 2014 Nov 7;360:67-77. 8. Nikolenko GN, Kotelkin AT, Oreshkova SF, Ilyichev AA. Mechanisms of HIV-1 drug resistance to nucleoside and nonnucleoside reverse transcriptase inhibitors. Molecular biology. 2011 Feb 1;45(1):93-109. 9. Singh K, Marchand B, Kirby KA, Michailidis E, Sarafianos SG. Structural aspects of drug resistance and inhibition of HIV-1 reverse transcriptase. Viruses. 2010 Feb 11;2(2):606-38. 10. Andrew Hill, A. (2018). Tenofovir alafenamide versus tenofovir disoproxil fumarate: is there a true difference in efficacy and safety?. [online] PubMed Central (PMC). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892670/ [Accessed 24 Sep. 2018]. 11. Fitzaimons T. Following court ruling, generic Truvada could soon be available in U.K. [Internet]. NBC Universal News Group. Available at: https://www.nbcnews.com/feature/nbc-out/following-court-ruling-generic-truvada-could-soon-be-available-u-n911586 [accessed 25 Sep. 2018].

NRTIs/NNRTIs NRTIs Action NRTI Result: NNRTI Action: NNRTI Result: Competes with nucleosides in growing viral DNA chain NRTI Result: Incomplete DNA chain Cannot integrate NNRTI Action: Binds and reduces reverse transcriptase (RT) activity NNRTI Result: No viral DNA is transcribed NRTIs/NNRTIs Removed slide but still relevant information