No technology has ever extended life. The so-called gains in life expectancy have only come about by reducing the causes of early mortality and slowing down the diseases of ageing.
I'm not the commenter you're replying to, but maybe they meant that we've only reduced early causes of death like disease etc, but not done anything to affect our internal biological processes that cause aging. As an example, reducing skin cancer by staying out of the sun keeps you from prematurely aging, but it doesn't stop your hair from turning white and your wrinkles from forming.
Drugs that change our metabolism can affect how much damage something does to your body, and you die because your body systems fail or degrade. So fixing some causes and symptoms should be able to increase your possible lifespan. Just like we can increase the lifespan of some simple animals, we could increase our lifespan through physical means. There's no magic spirit inside you that can only last 120 years, as far as anyone knows.
