CTLA4 and pneumonitis: Based on their mechanism of action, these agents destabilize the balance between self-tolerance and autoimmunity, and induce immune-system related adverse events such as hepatitis, pneumonitis, colitis, dermatitis, and myositis.147 The anti-CTLA4 therapy targets the immune system inhibition in a more robust way and also relatively upstream within the immune activation cascade, whereas the anti-PD1 therapies act at a later stage mostly relevant to peripheral tissues.