Could a quarterly injection prevent HIV infection?

PrEP (pre-exposure prophylaxis) is the term used for methods to prevent disease transmission before contact with the disease occurs, thereby preventing infection.

Vaccinations can be an example of this technique. Getting Yellow Fever is a possibility if someone travels to Africa. To protect the traveler, he gets vaccinated against Yellow Fever weeks before the trip. The vaccination may then protect him from the disease should he be exposed to it.

In HIV, PrEP centers around taking an oral medication daily to prevent infection by HIV in conjunction with condom use.

About two years ago, the FDA approved a combination of two antiretroviral medications that can be given together as PrEP for HIV in sexually-active people. These medications are tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC) [Truvada®], which can be given together as a single dose.

In studies, PrEP seems to be quite effective in decreasing HIV transmission in men who have sex with men (MSMs). However, some trials showed that PrEP wasn’t as effective in some cases. This seemed to be due to non-compliance. That is, the patients were not taking the PrEp medication as they were supposed to on a daily basis.

HIV virus attacking cell. 3D render, via Shutterstock.

HIV virus attacking cell. 3D render, via Shutterstock.

However, PrEP isn’t being used as much as was anticipated. There may be a few different reasons for this. Some people, even in higher risk groups, don’t feel that they are at risk to get HIV and therefore don’t even consider PrEP. Some may feel that HIV is now an easily treatable disease and not a major threat, and therefore don’t consider PrEP. Others may not be aware that PrEP even exists. Some may not want to experience the side effects that these drugs can cause. Still others may not like the thoughts of taking a pill every day (as mentioned previously in the trials showing a lower rate of prevention of HIV transmission.) For whatever reason(s), PrEP as a daily dose, isn’t being used much.

Investigators are working on a technique where PrEP can be injected once monthly, or perhaps once every few months.

To date, this research has only been carried out in a small number of male monkeys using an antiretroviral medication, GSK1265744-LAP. This medication is an integrase inhibitor that is already in human clinical trials. To replicate in a host cell, HIV’s RNA needs to be converted to DNA in the host cell (CD4+). Then it needs to be merged with the cell’s own native DNA. Integrase inhibitors block this merger of the two strands of DNA.

The researchers took this drug, in a special formulation, and injected it into monkeys. They chose this drug because it has a long half-life. That is, the drug will remain in the monkey’s plasma for much longer than a dose of some other antiretrovirals. In humans, the half-life can range from about 3 weeks to about 8 weeks, depending on the dose given. After the drug was injected, the scientists attempted to infect the monkeys with SIV, a virus that is similar to HIV and can infect monkeys. The scientists tried to infect the monkeys several times with SIV over about a 2-month period. Control monkeys, who were not given the antiretroviral injection, were also exposed to SIV multiple times.

The results showed that all of the monkeys exposed to SIV, and who weren’t given the integrase inhibitor, became infected with SIV. None of the monkeys who did get the drug developed an infection with SIV.

These results are promising. The investigators feel that this medication, in this formulation, might be the next generation of PrEP. An injection that people will get monthly, or perhaps, quarterly, could help prevent the acquisition of HIV. However, there is still a lot of work to be done before this antiretroviral and this technique can be considered for use in humans.


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Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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  • docsterx
  • Mighty

    I keep hoping for the best. Make it so people will take it is the best thing. Many people don’t like daily injections of anything. As a diabetic I can understand this feeling.

  • http://www.americablog.com/ Naja pallida

    I so much want a loud alarm, maybe some flashing LEDs, and voice that says “ERECTION DETECTED!”

  • http://www.americablog.com/ Naja pallida

    Not to mention, insurance companies don’t really want to cover it, so generally only give 6 month approvals at a time. And you have to meet very specific criteria of being at risk of HIV infection. Their ultimate belief is that one can avoid being infected with HIV in much more cost effective ways than this medication. I do wonder if they’d make a special exception for the spouse of an HIV infected person though.

    Truvada alone is expensive, plus on top of that you have to factor in extra doctors visits to monitor liver and kidney function. Haggling constantly with your insurance company for approval and the manufacturer for co-pay assistance. Even if it was less of a hassle and affordable, that list of side effects would keep me away from it anyway.

  • docsterx

    Cold pack to groin while listening to yodeling yaks of Tibet and watching videos of Santorum, Pat Robertson and Newt Gingrich.

    Masturbation would be a good way to “prime the pump” and make sure that ARV is primed in tubes. Think wet run v. dry run.

  • Indigo

    Good luck with that. It’s futuristic but the thing is, our bodies keep on moving into the future, regardless of how far into the past our minds are fixating.

  • Indigo

    Common sense is rarely common but your anger at the system is exactly that.

  • Mike_in_the_Tundra

    Is there some way to turn it off externally? Masturbation could use up a lot of the medication. Think what it was like when we were twenty or twenty one. I hate to bring it up, but if one was just getting a hand job, it wouldn’t be necessary unless the other guy had a cut on his hand.

  • docsterx

    Actually, at my lab, we’re already ahead of the curve. We’re working on an implantable device that will dispense the selected ARV drug automatically. The pump is inserted and appropriate sensors and delivery tubing attached. One sensor measures penile blood flow. When ingoing penile blood flow increases as venous outflow decreases, erection is detected. The device then injects a premeasured dose of ARV. So PrEP is done automatically. Then, at the moment of ejaculation, the device user get another dose of the ARV. This is called the During Ejaculation Realtime Prophylaxis (DERP). Then, every two hours post ejaculation for up to three days, more ARV is released. That is called Completed Coital EXposure CoCX.

    A brother-lab is working on a similar device that not only does prophylaxis in the device user, it is programmed to detect ejaculation and release a premeasured dose of ARV into the seminal fluid to help protect the recipient of the orgasmic response. This is called Ejaculation Medication or Outflow Medicated Genital therapy (OMG!)

    We have some rigorous trials planned and will be looking for volunteers soon.

  • wowwww

    Your one of the fools to fall for this… they had cures loooong ago… no money in a cure…instead of giving away a cure and losing money, lets collect medicine money from current chronic sufferers and then get quarterly payments from everyone else who doesn’t have hiv for as long as they live too…this is just common sense… lmaooo wow

  • http://40yrs.blogspot.com Matthew G. Saroff

    I wrote about this 2 months ago, and noted that there are two problems with Truvada: some nasty side effects, and the fact that the company has used evergreening to render it ruinously expensive, to the tune of $1200/month. ( http://40yrs.blogspot.com/2013/12/because-it-is-too-expensive-and-side.html )

  • Indigo

    That sounds like a good thing. Quarterly inoculations are a lot, though. Maybe as time goes on, biomedical research will refine that to a once a year or even a one-time shot. It’s a hopeful development.

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