So this is hard to know for sure - but here are some thoughts.
You don't mention any NRTI mutations, so I'll assume there are none, and you don't mention any prior regimens. I also don't know if the viral load here is any better than what this person would have off drugs - is this partial suppression? And finally I don't know how to interpret the level you provided since we don't know the lab nor units - but I'll assume that level is at target for the drug.
So, some drugs do require stomach acid, while some are actually better absorbed without acid. And finally some are more dependent on food effects for absorption. And as you can imagine there are no data about the impact of a gastric bypass on absorption of these agents. However, ddI (videx) should be fine as it requires no stomach acid, and both zerit and kaletra don't need acid - but kaletra is better absorbed with food. T20 is injected so the bypass should make no difference.
So - if someone has a detectable viral load on a regimen of two NRTI, one boosted PI and T20, and there are few or even no primary PI mutations, what is happening? In several studies done, it has become clear that this is often the case, as boosted PIs have a high "genetic barrier" to resistance. This means that even if HIV is growing despite someone taking a boosted PI such as Kaletra, there may not (yet) be resistance to the drug as HIV has trouble creating the mutations (in its genetic structure) that are needed to become resistant to this agent. So then why is HIV growing if it is supposed to be susceptible to the drug?
This is among the mysteries in the field and not completely explained to everyone's satisfaction. However - one hypothesis that can explain this is by thinking about cellular sites that do not have enough drug to create significant drug pressure on HIV - as there is information about cell "pumps" that may, despite good blood levels, pump the drugs out of the cells and prevent the benefits in viral load reduction. This is one reason that the blood levels may appear adequate but the effect is not seen. If there are no resistance mutations to explain why HIV is growing despite good blood levels, it is one of the few explanations we have that makes sense, based on the information learned in the past few years about these cellular pumps.
So what to do? Well, these pumps cannot be measured, and we don't know how to test for this, so it is hard to use this data to make specific recommendations. However, one approach is just to simply try other medications and hope that we can overcome these effects by coming at it with another approach. For example, there is some information that some protease inhibitors accumulate in the cells more than predicted by drug levels - this may be true for saquinavir and nelfinavir for example.
Since I don't know if the values you gave reflect some antiviral benefit or no benefit - the options would include building on the combination listed - for example adding saquinavir at a dose of 1000 mg twice a day in addition to the Kaletra - since the ritonavir in the Kaletra can also boost saquinavir. (Of the two formulations, invirase is far better tolerated than fortovase whenn boosted, so that is another way to improve this outcome.) Another option is to consider additional nucleoside RT inhibitors - for example adding tenofovir and/or lamivudine to this combination since these drugs can add activity to the combination listed.
One more point. These days there is a general recommendation to NOT give both zerit and videx together - since the toxicity of these two drugs does overlap and some will have substantial toxicity over time if these are given together. So for example you might stop the videx, and use zerit with epivir and tenofovir along with the two boosted PIs. And the T20.
Now that's six antivirals. And may be more than needed - or more than the person can tolerate. But if the Cd4 counts are near 100 with this viral load despite the combination listed - one approach is to hit "hard" with a combo that, if it works, can be simplified over time to maintain the control you've established. But you first have got to get that control and get that Cd4 count up there...
Hope that helps. Let us know what happens.
