ALK and hypersensitivity pneumonitis: Lung toxicity is a rare but potentially fatal adverse event also associated with ALK inhibitors, with a reported incidence of 1% to 3%.[17] ALK inhibitor-related pneumonitis is classified as nonspecific interstitial pneumonia, OP, hypersensitivity pneumonitis, and acute interstitial pneumonia, and of these OP is rare.[10]