Descovy Courtesy Gilead Sciences The FDA just approved a new treatment for HIV.

Descovy, a combination drug that only has to be taken once a day, is the third in a series of HIV medicine updates to get the FDA's green light.

Developed by Gilead Sciences Inc., it works by interfering with a special protein necessary for the virus to multiply.

Keeping the amount of HIV in the blood low is key for suppressing symptoms of the virus, but it isn't a cure.

Here's what you need to know:

Descovy is a combo of the drugs emtricitabine, and tenofovir alafenamide, or TAF. Only TAF is new, and it's been used in other new HIV medications such as Genvoya and Odefsey. It's an update to Truvada, which has emtricitabine and tenofovir disoproxil fumarate.

The goal with the update from tenofovir disproxil fumarate to TAF is so that the medications are less harsh on the body, and can be used in smaller doses.

In a late-stage trial, a combination using TAF called Genvoya proved just as effective as Stribild, one of Gilead's combination pills that was approved in 2012 and that contained tenofovir disoproxil fumarate.

Compared with Stribild, Genvoya had better long-term safety in trials. It is also less toxic to kidneys and has less of a negative impact on bone density.

In the case of Genvoya, that includes possible lactic acid buildup in the blood and severe liver problems, which can both be life-threatening.

Analysts forecast Descovy to make $2 billion by 2020.

Essentially, the new-and-improved drugs ares set up to be a safer alternatives for HIV treatment. Having new once-daily pills with lessened effects to bones and kidneys could be good news for the estimated 1.2 million people in the US living with HIV.