Every living organism already undergoes biological processes involving the breakdown of proteins, fats, carbs, minerals you get it to repair and grow their cell tissue to form the organs that makeup themselves.

The “cure” for ageing in its most realistic form would most likely just be a simple repair of those biological processes since they naturally breakdown overtime rather than some sort of pseudoscientific bs of reversing the concept of ageing entirely. You would still die, but you’d live a healthier life