Real Story behind HAART
Mar 18, 2001
Thank you for your wonderful work. It has positively impacted so many lives for the better. I have 2 questions about the success rates of HAART treatment. Specifically, what percent of HIV patients respond favorably to HAART in terms of viral load and CD4 count? Second, what is the average length of time that HAART remains successful (2 years, 10 years, etc)? Thank you for your invaluable help!
Response from Dr. Cohen
Well, it is fair to say that our current knowledge allows us to contemplate the possibility that if all goes right, an antiviral regimen may be successful for years and years and even decades later. But clearly this is not the story for all. What percent achieve this success varies greatly. What is in the way of success? There are four components that if present, allow these meds to be successful in anyone:
1 - the meds we pick must be active against that person's strain of HIV. For those who have already been on meds, and acquired some drug resistance, this clearly gets harder, since while we have 15 meds available in the US - some of them are "cousins" - if HIV learns resistance to one, it may have learned some tricks allowing it to become at least partially resistant to other meds as well. This issue is also a concern for someone who has never take a pill - since for perhaps 5% or so - the HIV they start with came from someone who had drug resistant HIV - and they start with this resistant strain. Fortunately, we can sometimes measure these resistant strains through testing.
2. Someone needs to take enough of these meds to keep the blood levels active enough to stop HIV. This is the key issue - called adherence. Now, much has been said about this - but key concepts here include that adherence to some meds may be fairly demanding, but progress has been made such that, for some meds, there is flexibility with dosing times. And we have improvements here including having at least a few of our meds that can be taken just once a day, as well as combinations allowing people to take just a few pills total per day - all of which may help make pill taking easier. But we have learned that this issue is among the biggest obstacles to more frequent success. Since it is simply hard to remember to take pills once or twice or more each day every day.
3. The regimen must be potent enough for that person. We have seen evidence that those who have a higher initial viral load (off meds) - higher often defined as somewhere above 100,000 copies - and/or a lower CD4 count - somewhere below 200 cells - may need a more potent regimen than others. The potency can be manipulated - sometimes by using four drugs instead of three, or by "boosting" the potency of our meds in various ways. However, we know a regimen is potent enough if it drives the viral load to below 50 - since when that happens - the response can be durable - perhaps for an indefinite period of time.
However - there is a key fourth issue - Safety. Since if we have ways to create potent combos that people can successfully adhere to - they must then monitor for side effects. These side effects can happen early on like the first month or two, or later on like after a year or more. But this is the current challenge for us - since we ARE more successful - and therefore need to define who can best take which meds - so they can avoid side effects and maintain the benefits.
And we have made substantial progress with each of these points - read on in this forum for more details on each issue.
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