A small molecule analogue of cyclic GMP-AMP (cGAMP) that acts as an agonist of the stimulator of interferon genes protein (STING; transmembrane protein 173; TMEM173) with potential immunoactivating and antineoplastic activities. Upon intratumoral administration, STING agonist IMSA101 binds to STING and activates STING-mediated pathways. This activates the immune response through the activation of certain immune cells which induces the expression of pro-inflammatory cytokines and chemokines, promotes tumor-associated antigen (TAA) processing and presentation by dendritic cells (DCs) and leads to an antigen-specific T-cell mediated immune response against cancer cells. STING, a transmembrane protein that activates immune cells in the tumor microenvironment, plays a key role in the activation of the innate immune system.