Quote from Keytruda.com"KEYTRUDA can cause your immune system to attack normal organs and tissues in any area of your body and can affect the way they work. These problems can sometimes become severe or life-threatening and can lead to death. These problems may happen any time during treatment or even after your treatment has ended" so...there's that. Far as I know TLD1433 has almost ZERO side effects and anyone can use it to access its superior efficacy. Also probably what people will care about