Tag: HIV drugs

In-depth: How do Long-acting HIV Treatments Work?

Photo by Miguel Á. Padriñán

By Elri Voigt for Spotlight

Researchers have been trying to develop antiretroviral medicines that can last for weeks, months or even years per dose. It is thought that such long-acting therapies may eventually end up replacing the daily pills taken by most people living with HIV today.

As pointed out by Dr Anushka Naidoo, a Clinical Pharmacologist and Principal Investigator and Scientist at the Centre for AIDS Programme of Research in South Africa (CAPRISA), three such long-acting HIV medicines have made it to market so far. They are the injectables cabotegravir (CAB-LA) and rilpivirine (RPV-LA) and the dapivirine vaginal ring (DPV-VR). Of these only CAB-LA (two-monthly) and DPV-VR (monthly) have so far been approved by the South African Health Products Regulatory Authority (SAHPRA) for HIV prevention. CAB-LA and RPV-LA have been approved for HIV treatment in the United States, but not yet by SAHPRA.

Image: DOH

CAB-LA and DPV-VR are being rolled out as HIV pre-exposure prophylaxis (PrEP) in pilot studies in South Africa. Spotlight earlier this year provided an update on these pilots here.

How do long-acting formulations work?

Dr Sindiswa Maphumulo, a Specialist Virologist and lecturer at the University of the Free State, tells Spotlight that designing long-acting formulations is a very complex and costly process. She explains that when designing any drug, whether it is long-acting or not you need to look at two things – pharmacodynamics and pharmacokinetics. Basically, she says, pharmacokinetics refers to what the body does with the drug in question while pharmacodynamics refers to what the drug does to the body.

“So you’re going to have to know what is the human body going to do to this drug once you’ve administered it and also what is the drug targeting or aiming to do in the human body once it has been given,” she says. For long-acting drugs, studies need to determine what the half-life (how long it lasts in the body) of the drug is so the doses can be timed correctly. It is also essential that different populations are studied to determine how individual’s bodies react to the drug.

“You want to make sure that there is a steady release of that specific drug, which depends on the drug class that you’ve chosen because we target different sites of HIV [with different drug classes],” she adds.

Naidoo tells Spotlight that: “Long-acting drug delivery formulations enable slow drug release after administering a single dose over the course of days, weeks, months or even years, and can maintain a steady pharmacokinetics profile.”

Naidoo says that long-acting drugs are formulated so that they form a “depot” of the drug, either through the way the drug is released into the body or the way device that contains the drug is designed to slowly release it over time. Several ways of achieving this has been investigated, including long-acting injectables, implants, infusion pumps, and patches. Long-acting injections and implants, for example, are already widely used in South Africa as contraceptives.

For HIV this means that ARVs can either be stored in the body and slowly absorbed or be stored in a device that is placed in the body which releases consistent drug levels over time. For example, “long-acting injectables are usually the same medication that is taken in pill form but when injected they allow for the slow release of medication into the blood over a longer period of time,” says Naidoo.

How CAB-LA works

Maphumulo explains that CAB-LA and DPV-VR fall under different drug classes which target different stages of the HIV viral replication cycle inside the human body. Cabotegravir is an Integrase Strand Transfer Inhibitor (INSTI) – which is to say it targets the integrase enzyme that allow HIV to integrate itself into a cell’s DNA.

“Cabotegravir’s unique physiochemical and pharmacokinetic properties have permitted its formulation and delivery both as an oral tablet for daily administration and as a long-acting nanosuspension for monthly to quarterly intramuscular injection,” Naidoo says.

“Cabotegravir LA is made from the free acid form of cabotegravir, which has a low water solubility, a long systemic half-life and high antiviral potency,” says Emmanuella Chinonso Osuala, a Research fellow and PhD student based at CAPRISA.

She explains that the properties of this drug make it suitable for a so-called nanosuspension delivery system and allows for high levels of the drug be contained in a small volume that can be administered through an intramuscular injection. This is achieved by manufacturing cabotegravir, through a process called wet-bead milling, to form nanocrystals – approximately 200nm in size. These have a large surface which allows for “a slower and controlled release of the drug over time”.

“[The] drug is released from the injectable suspension over several months due to the slow dissolution of crystals from the suspension,” Osuala explains.

How DPV-VR works

Naidoo explains that DPV-VR is a ring made of “a flexible silicone polymer” and contains the drug dapivirine, which is slowly released over the course of a month and can be inserted and replaced by the women themselves each month. A three-month ring is also currently in development.

“The ring delivers dapivirine directly at the site of potential infection, with low systemic exposure (it acts at the site of action in the vagina and is not released in significant amounts into the blood circulation), which could minimise side effects…and reduce the risk of developing HIV (drug) resistance,” she says.

Dapivirine, according to Maphumulo is part of a drug class called Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs), which block the reverse transcriptase enzyme on the HIV virus that allows for the transcription of HIV – which is an RNA virus into DNA. It is this transcription which would allow HIV to enter the human cell nucleus and replicate there.

Making current treatments long-acting

While long-acting forms of cabotegravir and dapivirine are clearly useful, these are far from the most widely used ARVs. Most HIV treatment in South Africa today is with a combination of three drugs, with the key one being dolutegravir. Earlier this year we reported on how more than 4.7 million people in the country have started or switched to dolutegravir-based HIV treatment in the last five years.

One group of researchers are trying to develop long-acting formulations of these commonly used ARVs. Using so-called drug combination nanoparticles (DcNP) they have developed a long-acting formulation of the ARVs tenofovir, lamivudine, and dolutegravir (LA-TLD) that shows some promise as a monthly injection. Early findings presented at this year’s International AIDS Society (IAS) conference in Australia and published in the journal AIDS suggest that the formulation achieves sufficient drug concentrations in non-human primates to allow for monthly dosing.

Dr Rodney Ho, an expert in biomedical science and pharmacology based at the University of Washington in the United States who led the research, tells Spotlight the study wanted to address a seemingly impossible question.

“Can we make three incompatible oral antivirals – tenofovir, lamivudine (which are water soluble) and dolutegravir (which is oil soluble and water-insoluble) – compatible and create a long-acting drug combination injectable product? With creativity and hard work, our team finally found a way to make this happen,” he says.

He explains that the three drugs were bound to lipid (fatty) nanoparticles using DcNP technology, which stabilises them so that the combination of drugs do not get released at the injection site immediately. Instead, the drugs are taken up by the body’s lymph and lymph nodes, which allows the drug to be metabolised within the body’s cells, which host the HIV virus, before it is taken up in the blood stream.

“As a result of this intentional design, LA-TLD has now provided data verifying that we are able to provide the necessary long-acting drug profile while achieving targeted drug exposure in cells and tissues of interest for an extended time,” Ho says.

“These results verified that a stable and scalable long-acting product, previously considered impossible, is now proven to be possible. This novel LA-TLD product can be administered via subcutaneous injection and will reach therapeutic drug levels within hours (not days which is needed for CABENUVA – LA-CAB and LA-RPV taken as HIV treatment). Thus, two-month oral leading doses may not be necessary,” he says.

Challenges around long-acting formulations

Osuala says there are several scientific challenges when it comes to long-acting formulations. This includes ensuring that: the drugs remain stable when released over long periods of time; sustained drug release is maintained; and the biocompatibility of the materials used in the product. Other challenges include issues around drug potency, as the amount of drug required for the formulation depends on its potency; as well as the cost and access to the formulations, as it is currently expensive to develop and manufacture which may hinder the accessibility of these products in low-and-middle-income (LMIC) countries.

Further challenges, according to Naidoo include the added complication that if adverse events occur for long-acting injectables, “one cannot simply stop taking the medication like one can with daily pills” since the drug will continue to be released into the body. One way to reduce this risk is through having an oral lead-in period where the drugs, like cabotegravir and rilpivirine that are set to be injected are first taken in pill form for four weeks, which can be stopped if an adverse event like hypersensitivity, an allergy or a severe side effect occurs.

Other challenges include the cold-chain storage requirements that some long-acting formulations and injections have, Naidoo says, “which can be challenging in LMIC settings so formulations without cold chain needs are needed.”

“The development of long-acting injectable formulations are a complex, time-consuming, and costly process. One of the challenges in the development of long-acting injectable formulations is the limited selection of ‘polymers’ and ’excipients’ (materials used to formulate the long-acting injectables that are available). As a result, some innovator companies develop proprietary excipients for use in long-acting injectable formulations, which can delay the development of generic long-acting injectable products,” she adds.

Republished from Spotlight under a Creative Commons Licence.

Source: Spotlight

HIV Infection Found to Accelerate Ageing Process

HIV Infecting a T9 Cell. Credit: NIH

Within just two to three years of infection, HIV causes an “early and substantial” impact on ageing in infected people, accelerating epigenetic changes and telomere shortening associated with normal ageing, according to a study in iScience.

The findings suggest that new HIV infection may act to reduce an individual’s life span by five years compared to an uninfected person.

“Our work demonstrates that even in the early months and years of living with HIV, the virus has already set into motion an accelerated ageing process at the DNA level,” said lead author Elizabeth Crabb Breen, a professor emerita at UCLA. “This emphasises the critical importance of early HIV diagnosis and an awareness of ageing-related problems, as well as the value of preventing HIV infection in the first place.”

In previous studies, HIV and antiretroviral treatment has been observed to accelerate age-related conditions such as cardiovascular and renal disease, grail and cognitive impairment.

Researchers analysed stored blood samples from 102 men collected six months or less before they became infected with HIV and again two to three years after infection. They compared these with matching samples from 102 non-infected age-matched men taken over the same time period. All the men were participants in the Multicenter AIDS Cohort Study, an ongoing US study initiated in 1984.

The study examined how HIV affects epigenetic DNA methylation. Epigenetic changes are those made in response to the influence of outside factors such as disease that affect how genes behave without changing the genes themselves.

Five epigenetic measures of ageing were analysed – four of them are epigenetic ‘ clocks’, each of which uses a slightly different approach to estimate biological age acceleration in years, relative to chronologic age. The fifth measure assessed telomere length, which shorten with age and cell divisions.

Compared to non-infected controls, HIV-infected individuals showed significant age acceleration in each of the four epigenetic clock measurements – ranging from 1.9 to 4.8 years – as well as telomere shortening over the period beginning just before infection and ending two to three years after, in the absence of highly active antiretroviral treatment.

“Our access to rare, well-characterised samples allowed us to design this study in a way that leaves little doubt about the role of HIV in eliciting biological signatures of early ageing,” said senior author Professor Beth Jamieson. “Our long-term goal is to determine whether we can use any of these signatures to predict whether an individual is at increased risk for specific ageing-related disease outcomes, thus exposing new targets for intervention therapeutics.”

Study limitations included having only men as participants, with few non-white participants. The sample size was also too small to take into consideration later effects of highly active antiretroviral treatment or to predict clinical outcomes. Additionally, there presently is no consensus on what is normal ageing or how to define it, the researchers wrote.

Source: UCLA

An Anti-HIV Drug for Memory Recall in Older Adults?

Old man
Photo by Kindel Media on Pexels

The human brain usually stores memories in groups so that the recollection of one significant memory triggers the recall of others connected by time. With ageing, the brain gradually loses this ability to link related memories.

Now, researchers have discovered a key molecular mechanism behind this memory linking, and also identified a way to restore this brain function in middle-aged mice. They also found an anti-HIV drug that can do this.

Published in Nature, the findings suggest a new method for strengthening human memory in middle age and a possible early intervention for dementia.

“Our memories are a huge part of who we are,” explained Professor Alcino Silva. “The ability to link related experiences teaches how to stay safe and operate successfully in the world.”

The team from UCLA focused on a gene called CCR5 that encodes the CCR5 receptor – the same one that HIV hitches a ride on to infect brain cells, resulting in memory loss in AIDS patients.

In previous work, Prof Silva’s lab showed that CCR5 expression reduced memory recall.

In the current study, Prof Silva and his colleagues discovered a central mechanism underlying mice’s ability to link their memories of two different cages. Using a tiny microscope, the researchers observed neurons firing and creating new memories in the brains of the mice.

They found that boosting CCR5 gene expression in the brains of middle-aged mice interfered with memory linking, with animals forgetting the connection between the two cages.

Mice with the CCR5 gene knocked out were able to link memories that normal mice could not.

Proof Silva had previously studied the anti-HIV drug maraviroc, which inhibits the entry of HIV into human cells. His lab discovered that maraviroc also suppressed CCR5 in the brains of mice.

“When we gave maraviroc to older mice, the drug duplicated the effect of genetically deleting CCR5 from their DNA,” said Prof Silva. “The older animals were able to link memories again.”

The finding suggests that maraviroc could be used off-label to help restore middle-aged memory loss, as well as reverse the cognitive deficits caused by HIV infection.

“Our next step will be to organise a clinical trial to test maraviroc’s influence on early memory loss with the goal of early intervention,” said Prof Silva. “Once we fully understand how memory declines, we possess the potential to slow down the process.”

All of this raises a question: what’s the purpose of a gene that interferes with the brain’s ability to link memories?

“Life would be impossible if we remembered everything,” said Prof Silva. “We suspect that CCR5 enables the brain to connect meaningful experiences by filtering out less significant details.”

Source: University of California – Los Angeles Health Sciences

Differences in Drug Onset Explain Development of Resistance

HIV invading a human cell
HIV invading a human cell: Credit NIH

Researchers examining the development of resistance to HIV drugs have uncovered a mechanism of drug resistance development in combination therapy, where ‘windows’ open up for resistance to develop.

In the late 1980s, when HIV treatments were first introduced, patients would often develop resistance to those treatments within six months. The introduction of triple-drug treatment regimens in the 1990s was intended to rectify that. Even if the virus developed resistance to one drug, two others would still knock it out – in theory. Unfortunately, some patients still develop resistance, leaving scientists with a critical question to answer: Why?

“There’s all these things that we still don’t understand, like why do we even get resistance when treating with three drugs,” said San Francisco State University Associate Professor of Biology Pleuni Pennings. “We understand why it is becoming less common, but it should have been zero all along.”

Prof Pennings and her colleagues offer explanations for this phenomenon in a study published in eLife.

Several interesting observations were noted from analysis of HIV patient records. Drug resistance can evolve years after successful therapy, often the result of sequential mutations that occur in a predictable order. Current models could not explain these observations, and while some studies identify mutations that confer drug resistance, they don’t address how and where they arise.

Drawing on two computational models, the researchers suggest that these observations may result from drug heterogeneity over time and throughout the body. While patients receive three HIV therapies simultaneously, drugs have different half-lives and patients do not always adhere to therapy regimens. This could create opportunities for drug resistance evolution, during a window when only one drug is active. Drugs also don’t uniformly penetrate the entire body, meaning that in some locations in a patient’s body, only one of the drugs might be active, creating another evolution and escape opportunity.

“I think one main reason why we should care is actually not because of HIV but because of drug resistance in other situations,” Prof Pennings explained.

Although drug resistance among patients with HIV is fairly low, drug resistance to multidrug therapies is a big problem for diseases such as malaria and tuberculosis. In addition, the COVID pandemic and the rise of variants show how our understanding of evolving pathogens is still lacking.

“In a way, HIV is the poster child of how we solved drug resistance. … [But] if we don’t understand how we did it, then it’s really hard to take these lessons to other situations,” Prof Pennings said.

Source: San Francisco State University

HIV Drugs Could Stop Macular Degeneration

Photo by Victor Freita on Pexels

A new study has found that there is a buildup of damaging DNA in the eyes of patients with geographic atrophy, an untreatable, poorly understood form of age-related macular degeneration that leads to blindness. Based on this, the researchers believe it may be possible to treat the condition with HIV drugs, or even simpler ones.

Dr Jayakrishna Ambati and colleagues had previously discovered that the harmful DNA, known as Alu cDNA, was manufactured in the cytoplasm. This represents the first time toxic Alu cDNA accumulation has been confirmed in patients in any disease.

“Although we’ve known that geographic atrophy expands over time, we didn’t know how or why,” said Dr Ambati, of UVA’s Department of Ophthalmology and Center for Advanced Vision Science. “Our finding in human eyes that the levels of toxic Alu cDNA are highest at the leading edge of the geographic atrophy lesion provides strong evidence that it is responsible for this expansion over time that leads to vision loss.”

Geographic atrophy is an advanced form of age-related macular degeneration, which ultimately destroys vital cells in the retina, resulting in blindness.

Dr Ambati, a leading expert in macular degeneration, and colleagues found that this destruction is brought about by the buildup of Alu DNA. As Alu DNA accumulates in the eye, it triggers harmful inflammation via the inflammasome. The researchers discovered the mechanism involving a previously unknown structural facet of Alu that triggers the immune response that destroys the retinal cells.

HIV drugs called nucleoside reverse transcriptase inhibitors, or NRTIs, could treat this; tests in lab mice suggest these drugs, or safer derivatives known as Kamuvudines, could block the harmful inflammation and protect against retinal cell death.

“Over the last two decades, dozens of clinical trials for geographic atrophy that have targeted other pathways have failed,” Dr Ambati said. “These findings from patient eyes provide a strong impetus for a new direction.”

Dr Ambati says his latest findings support clinical trials testing the drugs in patients with macular degeneration. A prior study of health insurance databases with over 100 million patients found that people taking NRTIs were almost 40% less likely to develop dry macular degeneration.

“Our findings from human eyes show that these toxic molecules, which activate the inflammasome, are most abundant precisely in the area of greatest disease activity,” Dr  Ambati said. “We are very hopeful that a clinical trial of Kamuvudines will be launched soon in geographic atrophy so that we can potentially offer a treatment for this devastating condition.” 

The findings were published in Science Advances.

Source: University of Virginia

Anti-HIV Drugs may Combat Macular Degeneration

New research has shown that anti-HIV drugs may fight macular degeneration – overturning a preconception about DNA in the process.

Macular degeneration is the leading cause of blindness in developed countries. Even though HIV does not cause dry macular degeneration, the drugs prevented the loss of vision.

“We are extremely excited that the reduced risk was reproduced in all the databases, each with millions of patients,” said Jayakrishna Ambati, MD, a leading macular degeneration researcher at the University of Virginia School of Medicine. “This finding provides real hope in developing the first treatment for this blinding disease.”

A Big Data Archeology review of four health insurance databases showed that Nucleoside Reverse Transcriptase Inhibitors (NRTIs), a commonly used HIV treatment, reduced the incidence of dry macular degeneration by 40%. The records spanned two decades and covered over 100 million patients. The drugs had also previously been shown to possibly prevent diabetes.

The finding also comes with the discovery that DNA can be produced inside the cytoplasm. Alu DNA (found exclusively in primates), which makes up 10% of the human genome, is transposable and can insert itself into other places on the genome. It was long considered “junk” DNA, but are now believed to have important functions, such as allowing for multiple expressions of proteins from a single Alu element. Since it cannot replicate itself, Alu DNA requires a transposon called L1 to accomplish this, which was now reported to allow the production of Alu DNA outside the chromosome. The buildup of Alu DNA in cells contributes to macular degeneration, by killing off cells that support the retina.
The researchers are urging further investigation into NRTIs or safer derivatives known as Kamuvudines, both of which block a key inflammatory pathway, can be useful in preventing vision loss from dry macular degeneration.

“A clinical trial of these inflammasome-inhibiting drugs is now warranted,” said Ambati. “It’s also fascinating how uncovering the intricate biology of genetics and combining it with big data archeology can propel insights into new medicines.”

Source: Medical Xpress

Journal Information: Shinichi Fukuda el al., “Cytoplasmic synthesis of endogenous Alu complementary DNA via reverse transcription and implications in age-related macular degeneration,” PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.202275111