HAART

HAART
Name	Highly Active Antiretroviral Therapy
Synonyms	Combination Antiretroviral Therapy (cART)
Pronounce	/hɑːrt/
Specialty	Infectious Disease, HIV/AIDS
Uses	Treatment of HIV infection
Contraindications	Varies by specific drug; includes severe liver disease, certain drug interactions
Interactions	Numerous, including with protease inhibitors, CYP3A4 substrates
Onset	Viral load reduction within weeks
Duration	Lifelong
Legal status	Prescription required
Routes of administration	Oral

HAART. Highly Active Antiretroviral Therapy, now more commonly termed Combination Antiretroviral Therapy (cART) or simply Antiretroviral Therapy (ART), is the standard treatment for infection with the Human Immunodeficiency Virus (HIV). It involves the simultaneous use of multiple antiretroviral drugs from at least two different classes to maximally suppress viral replication and halt the progression of HIV/AIDS. This strategy has transformed HIV from a fatal diagnosis into a manageable chronic condition, dramatically reducing AIDS-related mortality and opportunistic infections worldwide.

Definition and Overview

HAART is defined by the use of a combination of three or more antiretroviral medications, a strategy pioneered to overcome the rapid development of drug resistance seen with monotherapy. The foundational principle, established by researchers like David Ho of the Aaron Diamond AIDS Research Center, is to suppress viral load to undetectable levels, thereby preserving immune function and preventing transmission. The global scale-up of this therapy has been coordinated by major entities like the World Health Organization and the President's Emergency Plan for AIDS Relief (PEPFAR). Landmark clinical trials, such as those presented at the International AIDS Conference, have consistently validated its life-saving efficacy, making it the cornerstone of modern HIV management.

Mechanism of Action

The mechanism targets specific stages of the HIV life cycle using drugs from distinct pharmacological classes. Nucleoside Reverse Transcriptase Inhibitors (NRTIs) and Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs) inhibit the action of the viral reverse transcriptase enzyme, blocking the conversion of viral RNA into DNA. Protease inhibitors (PIs) prevent the cleavage of polyproteins into functional units, resulting in the production of immature, non-infectious virions. More recent classes include Integrase Strand Transfer Inhibitors (INSTIs), which block the integration of viral DNA into the host genome, and Entry inhibitors, such as CCR5 antagonists, which interfere with viral entry into CD4+ cells.

Clinical Efficacy and Impact

The clinical impact of HAART has been profound, reducing AIDS-defining illnesses and mortality by over 80% in populations with access to treatment. The landmark Swiss HIV Cohort Study provided early evidence that individuals with sustained undetectable viral loads do not transmit HIV sexually, a concept formalized as Undetectable = Untransmittable (U=U). Widespread implementation, supported by programs like the Global Fund to Fight AIDS, Tuberculosis and Malaria, has significantly altered the epidemiology of opportunistic infections such as Pneumocystis pneumonia and Cytomegalovirus retinitis. Furthermore, it is a critical tool in preventing mother-to-child transmission of HIV, as demonstrated in protocols like the PETRA study.

Drug Classes and Regimens

Modern first-line regimens typically consist of two NRTIs (a "backbone") combined with a drug from a more potent class, such as an INSTI or an NNRTI. Common NRTI backbones include combinations like Tenofovir disoproxil fumarate/Emtricitabine or Abacavir/Lamivudine. These are paired with agents like the INSTI Dolutegravir, the NNRTI Efavirenz, or a boosted PI such as Darunavir co-administered with Ritonavir. The development of single-tablet regimens, like those containing Elvitegravir, has greatly improved adherence. Treatment guidelines are regularly updated by bodies like the U.S. Department of Health and Human Services and the British HIV Association.

Side Effects and Challenges

Despite its efficacy, HAART is associated with a range of side effects and long-term challenges. Early regimens, particularly those containing Zidovudine or Stavudine, were linked to significant mitochondrial toxicity, lipodystrophy, and dyslipidemia. Contemporary drugs still pose risks of renal impairment, osteoporosis, and cardiovascular disease. The phenomenon of immune reconstitution inflammatory syndrome (IRIS) can occur upon initiation. Major ongoing challenges include ensuring lifelong adherence, managing complex drug-drug interactions (especially with tuberculosis treatments), and addressing the global inequities in access highlighted by organizations like the Joint United Nations Programme on HIV/AIDS (UNAIDS).

History and Development

The history of HAART began with the approval of the first antiretroviral, Zidovudine (AZT), by the U.S. Food and Drug Administration in 1987. The failure of monotherapy due to resistance led to the concept of combination therapy, which was validated by pivotal studies like the ACTG 175 trial. The term HAART was coined following the introduction of protease inhibitors in the mid-1990s, a period often called the "Lazarus effect" due to dramatic patient recoveries. Subsequent decades have focused on simplifying regimens and improving tolerability, driven by research from institutions like the National Institute of Allergy and Infectious Diseases and pharmaceutical innovations from companies such as Gilead Sciences and ViiV Healthcare.

Category:HIV/AIDS Category:Antiviral drugs Category:Infectious disease treatments