The present invention relates to amide derivatives of Formula (XIIIa) and pharmaceutical compositions thereof that modulate the activity of the PGI2 receptor. Compounds of the present invention and pharmaceutical compositions thereof are directed to methods useful in the treatment of: pulmonary arterial hypertension (PAH); idiopathic PAH; familial PAH; PAH associated with a collagen vascular disease, a congenital heart disease, portal hypertension, HIV infection, ingestion of a drug or toxin, hereditary hemorrhagic telangiectasia, splenectomy, pulmonary veno-occlusive disease (PVOD) or pulmonary capillary hemangiomatosis (PCH); PAH with significant venous or capillary involvement; platelet aggregation; coronary artery disease; myocardial infarction; transient ischemic attack; angina; stroke; ischemia-reperfusion injury; restenosis; atrial fibrillation; blood clot formation in an angioplasty or coronary bypass surgery individual or in an individual suffering from atrial fibrillation; atherosclerosis; atherothrombosis; asthma or a symptom thereof; a diabetic-related disorder such as diabetic peripheral neuropathy, diabetic nephropathy or diabetic retinopathy; glaucoma or other disease of the eye with abnormal intraocular pressure; hypertension; inflammation; psoriasis; psoriatic arthritis; rheumatoid arthritis; Crohn's disease; transplant rejection; multiple sclerosis; systemic lupus erythematosus (SLE); ulcerative colitis; ischemia-reperfusion injury; restenosis; atherosclerosis; acne; type 1 diabetes; type 2 diabetes; sepsis; and chronic obstructive pulmonary disorder (COPD).