There is no known cure for narcissism as personality disorders are not curable, there are no medication or treatment for them, but narcissistic can change through therapy. If those diagnosed with narcissist personality disorder are willing to dedicate time and energy to overcome their narcissistic tendencies, they can change for better. Narcissistic personality disorder is not easy to change as they are narcissistic to their subconscious level. Some with narcissistic behaviour can change a bit.
With help, narcissistic can learn skills that will help better how they relate with people, grow their self-esteem, have more realistic expectations. It is possible for a narcissistic person to become softer, gentler and also shift into a more flexible form of intimacy.
Technically, there is no cure for narcissism, but therapy can help. The goal is to bring up the person's poor self-esteem and have more realistic expectations of others. There are no medications to treat this disorder, but depression and anxiety sometimes go hand in hand with narcissism.
With help, narcissists can learn how to relate to others in more productive ways, which would depend on how open they are to critical feedback and how willing they are to change. Having a realistic view of others and being more compassionate eliminates the need to bolster the self-esteem or narcissism through comparing ourselves to others. Establishing a self-image that is grounded in truth is the key.