A compound for use in a method of treating pulmonary arterial hypertension, wherein the compound is 2-(( -4-(((4-chlorophenyl)(phenyl) carbamoyloxy)methyl)cyclohexyl)methoxy) acetic acid (Compound 1), or a pharmaceutically acceptable salt, hydrate, or solvate thereof, wherein the Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof, is administered via a titration scheme that comprises the up-titration of Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof; wherein the titration scheme comprises administering the Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof, at an initial dose for about one week and, provided that the patient tolerates the initial dose, increasing the dose by an amount equal to a first incremental value; wherein the titration scheme further comprises administering the Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof, at the increased dose for about one week and, provided that the patient tolerates the increased dose, further increasing the dose by an amount equal to a second incremental value; wherein the titration scheme comprises a cycle of administering the increased dose and then further increasing the dose by an amount equal to an incremental value, wherein the cycle is repeated so long as the patient tolerates the further increased dose, until an optimized dose is administered; wherein (i): the initial dose is equivalent to 0.01 mg of Compound 1 twice daily; and the first incremental value is equivalent to 0.01 mg of Compound 1 twice daily; or wherein (ii): the initial dose is equivalent to 0.05 mg of Compound 1 once daily; and the first incremental value is equivalent to 0.05 mg of Compound 1 once daily. wherein the compound is 2-(( -4-(((4-chlorophenyl)(phenyl) carbamoyloxy)methyl)cyclohexyl)methoxy) acetic acid (Compound 1), or a pharmaceutically acceptable salt, hydrate, or solvate thereof, wherein the Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof, is administered via a titration scheme that comprises the up-titration of Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof; wherein the titration scheme comprises administering the Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof, at an initial dose for about one week and, provided that the patient tolerates the initial dose, increasing the dose by an amount equal to a first incremental value; wherein the titration scheme further comprises administering the Compound 1, or a pharmaceutically acceptable salt, hydrate, or solvate thereof, at the increased dose for about one week and, provided that the patient tolerates the increased dose, further increasing the dose by an amount equal to a second incremental value; wherein the titration scheme comprises a cycle of administering the increased dose and then further increasing the dose by an amount equal to an incremental value, wherein the cycle is repeated so long as the patient tolerates the further increased dose, until an optimized dose is administered; wherein (i): the initial dose is equivalent to 0.01 mg of Compound 1 twice daily; and the first incremental value is equivalent to 0.01 mg of Compound 1 twice daily; or wherein (ii): the initial dose is equivalent to 0.05 mg of Compound 1 once daily; and the first incremental value is equivalent to 0.05 mg of Compound 1 once daily. the initial dose is equivalent to 0.01 mg of Compound 1 twice daily; and the first incremental value is equivalent to 0.01 mg of Compound 1 twice daily; or wherein (ii): the initial dose is equivalent to 0.05 mg of Compound 1 once daily; and the first incremental value is equivalent to 0.05 mg of Compound 1 once daily. the initial dose is equivalent to 0.05 mg of Compound 1 once daily; and the first incremental value is equivalent to 0.05 mg of Compound 1 once daily. <EOS>