Pregelatinized starch gets cooked and dried so it can dissolve and thicken in cold liquids. In supplement tablets, it works as a binder, filler, and disintegrant. That means it holds the tablet together and helps it break apart after you swallow it. The starch provides no nutritional value, only manufacturing support.
This starch has no therapeutic benefits. You don't take it for a health purpose. Its only role is to make the product form correctly.