Although there are two other drugs on the market

Although there are two other drugs on the market, maraviroc and T-20, which also prevent the virus from entering cells, they don't target fusion peptides. That makes this trial the first time that scientists have seen that fusion peptides are a worthwhile target in the fight against HIV/AIDS.

And given that fusion peptides also provide a point of entry for many other viruses, from measles to Ebola and hepatitis B and C, scientists theorize that the strategy could be turned against these illnesses as well.

The 18 patients with HIV in this small phase I/II trial took either 0.5, 1.5 or 5 grams of VIR-576 a day for 10 days via injection.

Those taking the highest dose saw a 95 percent reduction in their average viral load, the amount of HIV in the blood, without developing severe adverse effects.

"They were getting results that are similar to maraviroc and T-20 and certainly comparable to what's seen with intracellular drugs," Horberg said.

But the same factors that have limited the use of maraviroc and T-20 are also likely to get in the way here as well, namely the cost and the fact that they must be given by injection (because of the large size of the molecule), he warned.

The needle-vs-pill hurdle is something patients and doctors have to contend with in many settings, not just HIV, Horberg said. For example, "we all know that insulin works great [in diabetic patients] but the hard part is convincing patients to actually take it."

Hoping to get around the problem, the researchers are now searching for a smaller molecule to do the same job.

"The next big step is to use the structure of VIR-576 and its viral target (the fusion peptide) to generate small molecule inhibitors that act by the same mechanism but are orally available," Kirchhoff said. "We will start to test the first compounds next year, but how long it will take such drugs make it to the market is impossible to say."

"The bottom line is, yes, any time that you can find a new mechanism to attack the virus -- and certainly if you can prevent the virus from getting into the host cells -- that's a really good thing. But this isn't near prime-time," Horberg concluded.