DLL4 and pulmonary arterial hypertension: Recent clinical trials investigating DLL-4 inhibitors, such as Demcizumab [29,30], Enoticumab [31], ABL001 [32], Navicixizumab [33], and Dipacimab [34], for the treatment of oncologic malignancies, have shown that these drugs induce PAH as an unanticipated, deleterious side effect [30,34,35,36].