MSA-1

MSA-1 is a synthetic cyclic dinucleotide (CDN) agonist of the stimulator of interferon genes (STING) pathway, originally developed by Merck & Co.. It is designed to activate both human and murine STING with high potency, triggering the downstream activation of TBK1 and IRF3, which leads to the production of type I interferons (such as IFN-α and IFN-β) and other pro-inflammatory cytokines. In preclinical models of solid tumors, MSA-1 has been evaluated via intratumoral and systemic (intravenous) administration. When combined with Vesselon's sonoporation technology (using the acoustically active microbubble agent Imagent and diagnostic ultrasound), systemic delivery of MSA-1 demonstrated significantly enhanced tumor uptake and robust tumor regression. MSA-1 has also shown synergistic anti-tumor activity when combined with immune checkpoint inhibitors, such as anti-PD-1 antibodies, helping to overcome resistance in cold or unresponsive tumors.