The mechanism of action of Primovist®
Primovist is a combined contrast agent, which means it has properties of an extracellular gadolinium based contrast agent and a liver-specific agent. Similar to an extracellular agent, Primovist is distributed in the vascular system following injection allowing for dynamic phase imaging, including arterial, portal venous and equilibrium phases. About 50% of the injected Primovist is selectively taken up by hepatocytes, while the remaining 50% is eliminated by the kidneys. Primovist is transported into hepatocytes through the OATP1 transporter in the cell membrane, which is same receptor responsible for the uptake of bilirubin into hepatocytes. This uptake of Primovist into the hepatocytes will result in an intracellular concentration of Primovist that is up to 100 times higher than the concentration in the plasma. Maximum enhancement within 20 to 120 minutes after Primovist injection.
Lesions that have minimal or no functioning hepatocytes, such as cysts, hemangiomas, metastases and most hepatocellular carcinomas, will have reduced or no uptake of Primovist. The lack of enhancement in these lesions provides contrast with the surrounding healthy liver parenchyma, which is enhanced by the uptake of Primovist into the hepatocytes.
Primovist and bilirubin are transported out of the hepatocytes through the transport protein cMOAT and excreted into the biliary ducts. This dual elimination of Primovist through the renal and hepatobiliary systems enables Primovist to have the shortest terminal half-life of any approved gadolinium-based contrast agent.
The mechanism of action of Primovist is demonstrated in this video.