Abstract: The present invention pertains to the use of 4-(4-methylpiperazin-1-ylmethyl)-N-[4-methyl-3-(4-pyridin-3-yl)pyrimidin-2-ylamino)phenyl]-benzamide or a pharmaceutically acceptable salt thereof or a pyrimidylaminobenzamide of formula I wherein the radicals and symbols are as defined herein, or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament for treating pulmonary arterial hypertension (PAH), especially in patients who failed prior PAH therapy.

Abstract: We have found that when an antibody binds to (captures) its specific ligand, the antibody-ligand complex is redirected to a route of elimination which is different from that which occurs naturally for the specific ligand that is not bound to an antibody. As a consequence, the amount of antibody-bound ligand in the blood increases over time. The increase in total ligand concentration is a property that is specific to the patient to whom the antibody is administered. Accordingly, the invention provides a method for diagnosing disease in a subject and a method for identifying the most appropriate treatment for a particular patient. Patients who produce more ligand, and thus more antibody-ligand complex, may be more likely to have a disease which is predominantly driven by that ligand. These patients should respond better to a therapy targeted against that ligand.