April 18, 2018
On June 5th, 1981, the United States Centers for Disease Control and Prevention (CDC) published a Morbidity and Mortality Weekly Report (MMWR), describing five cases of a rare lung infection, Pneumocystis carinii pneumonia (PCP), in young, otherwise healthy, gay men.1 This would become the first report of what would later be called the Acquired Immune Deficiency Syndrome (AIDS) epidemic. Clusters of other cases of rare diseases such as Kaposi's Sarcoma continued to be reported.2 In the decades that followed these reports, the detection, diagnosis, and treatment of Human Immunodeficiency Virus (HIV) would evolve in rapid fashion. Clinicians, researchers, and patients constantly look to the future. Vaccine studies and cure research are met with cautious optimism.
This review will summarize the past, present, and future of antiretrovirals (ARVs) for the treatment and prevention of HIV.
Treatment of HIV has a long and rich history. The first decade after the initial report of HIV saw the first immunoassay test and the approval of zidovudine (1987).3 This was followed in the 1990s by many more therapies and the advent of triple drug therapy. Combination tablets and single tablet regimens then followed.
New formulations of existing products also simplified treatment (e.g. ritonavir tablets vs capsules) and improved bioavailability.3 The US President's Emergency Plan for AIDS Relief (PEPFAR) changed the discussion regarding the approach to universal access to treatment and care to accelerate control of the epidemic.4 The US Department of Health and Human Services Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents Living with HIV have been updated over 30 times.5
Early innovations, such as giving medication sequentially and alternating therapies, gave way to triple drug therapy with data provided by a small study with indinavir, zidovudine, and lamivudine.6,7 Initial use of the nucleoside reverse transcriptase inhibitors (NRTIs) also led to the discovery that treatment of HIV led to decreased rates of vertical transmission.8 The use of low-dose ritonavir as a "boosting" agent for saquinavir set the stage for the recommendations currently in use and the need for decreased doses of other protease inhibitors.7,9 Monitoring HIV RNA, or "viral load" was recommended after HIV in the plasma was shown to be predictive of disease progression and death.10 Despite a low quality of life with the older agents, HIV was now a manageable, chronic disease.
Currently there are 40 individual and combination medications approved for the treatment of HIV and one approved for the prevention of HIV infection.11 The life expectancy of a person living with HIV nears that of a person not living with HIV.12 There are enough options that patients may "switch" their therapy to one that requires fewer tablets or frequency of dosing, lesser food requirements, or has lesser side effects. Patients on "salvage" therapy also have options for effective treatment.13,14 "Treatment as prevention" and PrEP have led to a decrease in new infections.15,16 The newly endorsed "undetectable = untransmittable" data provides patients and those at risk of infection with important information about the virus.17 Test and treat is a new strategy to approaching the epidemic.18
However, there are many challenges that remain. While many of the newer agents are tolerable, long term side effects (e.g. metabolic and cardiovascular) and drug-drug interactions remain a concern.19 Patients faced with the need to take "lifelong" therapy for upwards of fifty years require agents with safer long term side effects. The approval of tenofovir alafenamide will likely reduce the incidence of bone and renal toxicity; however, long term data over a lifetime is needed to guide therapy.20 While there are many treatment options available to decrease HIV RNA, an agent to increase CD4 T-lymphocyte count remains elusive.
Safer alternatives may be available to some patients, however, global access to care continues to evolve. Even within the US, access to HIV therapy remains an issue for many patients faced with high deductibles and copayments.21,22 Disparities in treatment continue to exist for specific patient populations.23 Many programs are in place to close the gap between access in developed and non-developed countries.4 The current WHO guidelines recommend that all patients are started on ARV therapy regardless of CD4 T-lymphocyte count.24 The scale up of these programs requires the funding and infrastructure to treat a larger number of patients.
Special patient populations are also in the spotlight. Overall, the available data on treatment of pediatric and adolescent patients falls behind the availability of data for adults. If a drug is approved for use in children, dosage formulations may not be available for all stages of care. Women continue to face many issues surrounding contraception and ARV therapy.25 Disparities in PrEP efficacy for women versus men require more data and evidence for clinicians to be able to provide appropriate patient counseling.26 Management of comorbidities, drug-drug interactions, and polypharmacy in an aging population must be addressed by clinicians.19,27
As tolerability of medications is no longer a main concern, the conversation has shifted to medication adherence and engagement in care.28 The "HIV Cascade" has many steps for which intervention and research are required.29,30 Engagement and continuation of ARV therapy after transitions in care remains an issue. The transitions from adolescent to adult and prison to society each have their own unique challenges.31,32
Given the high efficacy, safety, tolerability, and convenience of contemporary ARV therapy, it can be challenging to identify where and to what extent improvements can be made. However, considering the vast advancements in treatment that have already occurred, it may be naive to think that the current approach to HIV treatment is the best and only way.
New agents under investigation are challenging the current treatment paradigm of three active antiretroviral medications by mouth every day to maintain viral suppression. Several two drug therapy options are emerging that may simplify treatment and reduce cost.33 Long-acting medications dosed every week or every month may be easier for some patients, improve medication adherence, and increase cost effectiveness.34
A few longer acting antiretrovirals in development will provide additional oral therapy options, but the majority will likely be delivered via alternative drug delivery systems.34,35 This includes the potential delivery of agents such as cabotegravir and rilpivirine as long acting injectables, dapivirine within a vaginal ring, and tenofovir alafenamide as a subdermal implant.35-37 These methods of drug delivery may seem foreign to some providers of HIV medicine, but they are common methods for delivering medications in other areas of healthcare and may represent a novel and effective method to ensure medication adherence and effective treatment.38
In addition to challenging the number of medications necessary for HIV treatment and their modes of delivery, new agents with novel drug therapy targets may also challenge the status quo. Capsid assembly, glycoprotein 120 attachment, and Rev-dependent mRNA expression are among the novel drug therapy targets under current investigation.39-41 Agents in these classes along with the recent approval of a novel anti-CD4 monoclonal antibody may provide future therapy options, particularly for those with heavy treatment experience.42
The last component of the treatment paradigm, the consistent need for antiretroviral medications, may be the most challenging of all to change. Will broadly neutralizing antibodies, therapeutic vaccines, latency reversing agents, or CRISPR technology ever become routine methods for inhibiting, suppressing, or eliminating HIV? Evidence for these approaches and others continue to emerge and provide optimism that the future may hold a potential cure.43,44
The remaining articles in this magazine take a deeper dive into the future of HIV medicine, providing more in-depth discussion of emerging treatment and prevention options. From new agents and drug therapy targets, approaches to drug delivery, and novel practice models, these articles demonstrate that the future of HIV treatment and prevention is evolving and the status quo is likely to change again.
Milena Mclaughlin, Pharm.D, M.S.C., BCPS-AQ ID, AAHIVP, is an Assistant Professor in the Department of Pharmacy Practice at Midwestern University's Chicago College of Pharmacy in Downers Grove, IL. She is also an HIV/ID Clinical Pharmacist in the Department of Pharmacy at Northwestern Memorial Hospital in Chicago, IL.
Jason Schafer, Pharm.D., M.P.H., BCPS, AAHIVP, is an Associate Professor in the Department of Pharmacy Practice at Jefferson College of Pharmacy at Thomas Jefferson University in Philadelphia, PA.
|Novel Drugs in the Pipeline for HIV Treatment|
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