No, this isn't really true. The NIH's budget is 30 billion a year, and that funding is already incredibly competitive. Private universities, other government sources such as NSF, NASA, and DoE, and private institutions then in addition spend an amount that dwarfs that number. On top of all of that, the last 6 years have seen cuts, layoffs, and an enormous amount of work go unfunded in the life sciences.

Only about 16% of proposed NIH grants alone are funded each year- we can immediately see from that data that funding all NIH grants in just one year would probably take well over $100 billion.

The life scientists of the U.S. could find a use for Bill Gate's entire fortune in a few years. Not that dropping $80 billion on across the board medical research wouldn't be incredibly, enormously beneficial, but the infrastructure and manpower in the medical sciences are there to be able to absorb it and put it to use.