HTR4 and gastroparesis: PICO was determined as Population (P): patients with diabetic and/or idiopathic gastroparesis; Intervention (I): highly selective 5-HT4 agonist agents (velusetrag, felcisetrag, prucalopride); Comparison (C): we compared the efficacy and safety of highly selective 5-HT4 agonist agents (velusetrag, felcisetrag, prucalopride) to placebo for diabetic and/or idiopathic gastroparesis; and Outcomes (O): our primary outcome measures were improvement in gastric emptying time (GET), Gastroparesis Cardinal Symptom Index (GCSI), and adverse event rates.