Dear Dr. Eva,

I read that there’s a new HIV medicine out. How different is it from other HIV medicines? Should I ask my doctor if I can switch?

Treatment Experienced

Dear TE,

A new HIV medicine called fostemsavir (brand name Rukobia) was approved early last month (July 2020).  Fostemsavir is an entry inhibitor, which means it prevents the HIV virus from getting inside the specialized white blood cells (T cells) that HIV infects. Over time, T cells that have already been infected die off and are replaced.  When an entry inhibitor is taken, the HIV virus cannot get inside the new cells. The virus has to be inside T cells in order to make copies of itself and maintain the infection, so the HIV infection cannot continue.

There are three other entry inhibitors, but fostemsavir is likely to be used more often than the others. Fostemsavir is a pill taken twice a day. About one in five people taking it have side effects; the commonest side effect is nausea.

The other three entry inhibitors are:

Enfurvitide (brand name Fuzeon): A twice a day injection which causes hard painful bumps at the injection sites. Few patients continue taking it for long.

Ibalizumab (Trogarzo): Taken as an IV infusion, once every two weeks in a doctor’s office.

Maraviroc (Selzentry): A pill, taken twice a day. The virus easily becomes resistant to Maraviroc, then the drug stops working.

Because each of the four entry inhibitors works in a different way, people can try all of them: resistance to one does not cause resistance to the others.

Fostemsavir is reserved for use by people who have tried multiple HIV medications and who cannot be successfully treated with other therapies either because of resistance to other drugs, severe side effects, or rare safety issues. Fostemsavir was tried out with highly experienced patients, most of whom had HIV for more than 15 years and had been on more than five different combinations of HIV medications.

Like most HIV medicines, fostemsavir was rushed into use. The clinical trials before it was approved included only 371 people, which is a very small number for a new medicine. This means that there may be dangerous side effects which will become apparent only when this medicine is taken by a muchlarger number of people. This is another reason why new HIV medicines used mainly for people who have no other options.

The measure of success of any HIV treatment is whether the person’s HIV virus level is undetectable or very low. If the virus count is undetectable or close to undetectable (less than 20 copies per milliliter) and the person is not having any problems with their current medication, no changes should be made. If the person has an increasing virus level or troubling side effects, changing the medicine should be considered.

There are currently 11 different HIV regimens that are taken as one pill once a day. Each of these 11 is a tablet containing two or three different HIV medicines. The combination of medicines is different in each one. Almost every person with HIV can be treated with one of these ‘one pill once a day’ treatments.

So, should you consider changing your medication? I wouldn’t, not unless your HIV viral load is rising or you’re having side effects. If that’s the case, discuss it with your doctor. There will almost certainly be better options for you than fostemsavir.

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Dr. Eva Hersh, MD
Dr. Eva Hersh, MD
Eva Hersh is a family physician. Send your comments and questions to her by email at