MSA-2

**MSA-2** is a potent, orally available non-nucleotide small molecule agonist of the human stimulator of interferon genes (STING, also known as TMEM173 or STING1)[1][2][4][6]. It promotes antitumor immunity by activating the STING pathway, which triggers type I interferon production and subsequent innate and adaptive immune responses against tumors[2][4][6]. In vivo, MSA-2 demonstrates significant antitumor effects, superior oral bioavailability compared to earlier STING agonists, and enhances efficacy in combination with anti-PD-1 checkpoint inhibitors[2][4][6]. MSA-2 operates via noncovalent dimerization in solution, resulting in strong, selective binding to the closed conformation of the STING protein[2][6]. It is under preclinical development, with no approved clinical use as of 2025[5][6]. Merck & Co. is the original developer[5][6].

Other names

4-(5,6-dimethoxy-1-benzothiophen-2-yl)-4-oxobutanoic acid