Dr. Anthony Fauci doesn't get too excited about the results of animal studies, and he doesn't make house calls.

But when a drug already taken by thousands of people for intestinal conditions appeared to control the monkey version of HIV, it got the attention of the director of the National Institutes of Allergy and Infectious Diseases.

Fauci hopped on a plane to Cambridge, Massachusetts, to personally tell Japan's Takeda Pharmaceutical Co.'s U.S. representatives that their drug may offer a dramatic advance in the fight against AIDS.