GLP1R and type 2 diabetes mellitus: In September 2019, the first oral GLP-1R agonist for T2D was approved by FDA (Davies et al., 2017; Aroda et al., 2019; Husain et al., 2019; Mosenzon et al., 2019; Pieber et al., 2019; Pratley et al., 2019; Rodbard et al., 2019; Rosenstock et al., 2019; The U.S. Food and Drug administration, 2019; Zinman et al., 2019a; Yabe et al., 2020; Yamada et al., 2020; Khoo and Lin, 2021).