EARNEST Rifabutin Pharmacokinetics (PK) Substudy

- Background and study aims?

Some of the drugs used to treat HIV (anti-retrovirals, or ARVs) can affect the blood levels of other drugs used to treat TB - called a "drug-drug interaction". The main drug used in second-line therapy, Aluvia (lopinavir/ritonavir), is one of the drugs that has this effect. This is why people on second-line ARVs usually cannot use one of the main TB drugs, "rifampicin", and instead will be prescribed a slightly different drug called "rifabutin", which is less affected by these drug-drug interactions. Although blood levels of rifabutin are not as badly affected by Aluvia as blood levels of rifampicin, rifabutin levels in the blood are still increased a lot by taking Aluvia at the same time. This could lead to higher levels of side-effects because there is more drug in the body. So in the past doctors have suggested that instead of taking rifabutin every day with Aluvia, it should only be taken three times a week, on Mondays, Wednesdays and Fridays. However, in the last 2 years, new studies have suggested that this three times a week regimen might not be enough and that it may not completely cure TB. So the purpose of this study is to find out whether taking rifabutin every day with Aluvia really does lead to more side-effects, and whether taking rifabutin three times a week with Aluvia really does lead to much lower levels of rifabutin in the blood.

- Who can participate?

This substudy is specifically for people who are already taking anti-TB drugs in EARNEST, or who need to start anti-TB drugs whilst they are in the EARNEST trial.

- What does the study involve?

Participants will be selected (by chance, chosen by a computer) to one of the following two rifabutin groups:

Group 1: Rifabutin (150 mg) taken three times a week on Monday/Wednesday/Friday Group 2: Rifabutin (150 mg) taken every day On these days, one capsule of rifabutin (150 mg) should be taken in the morning by mouth.

Participants will be asked to attend clinic 2 and 12 weeks after entering the sub-study then every 6 weeks until the end of their TB treatment, and then return to their usual EARNEST follow-up schedule. This is roughly the same visit schedule for people with TB who are usually seen more frequently than those without TB, whether or not the patients join this sub-study. The 2 week visit is specifically so the investigators can make sure participants are doing OK on rifabutin and to check carefully that they don't have any side-effects. At all these visits (including the day when participants enroll into the substudy) the investigators will take an extra 10 ml (two teaspoons) of blood to do laboratory tests for side-effects of rifabutin, and to measure the levels of rifabutin and other ARVs in the blood - these are called "pharmacokinetic" or "PK" studies. On the day of these visits, participants should not take their dose of rifabutin until after this blood draw, so the investigators can measure the lowest amount of drug likely in their blood. Instead, participants should bring the rifabutin dose to clinic, so that they can take it straight after the blood draw. At the visit 12 weeks after starting rifabutin, participants will need to stay in clinic for a second blood draw of ~3 ml (half a teaspoon) around 4 hours after they take the rifabutin dose immediately after the first blood draw. We use this second sample to see how quickly rifabutin enters the blood. At this special visit the investigators will make sure participants are first seen as early as possible, so they don't have to stay any longer than necessary for the second blood draw to be taken 4 hours later. After participants have completed their TB treatment they will stay in EARNEST until the end of the trial (144 weeks on second-line therapy).

- What are the possible benefits and risks of participating?

If participants are allocated to Group 1 (150 mg rifabutin three times a week), there is a risk that they may have lower levels of rifabutin in your blood and this may be less effective at treating the TB. However, participants should have fewer side-effects. In contrast, if participants are allocated to Group 2 (150 mg rifabutin daily), here is a risk that they may get more side-effects, but the levels of rifabutin in the blood should be more than high enough to have a good chance of curing the TB. Having blood taken may cause some discomfort and/or bruising in some people. It is currently impossible to know which rifabutin regimen would be best and participants may find in years to come that they may or may not have received the best treatment.

• Where is the study run from?

  9 EARNEST sites in Uganda as follows: JCRC Kampala, IDI, San Raphael of St Francis Hospital (Nsambya), JCRC Mbarara, JCRC Mbale, JCRC Kabale, JCRC Kakira, JCRC Gulu

• When is study starting and how long is it expected to run?

Start 05/03/2012 finish on 31/01/2014

- Who is funding the study? Abbott