Pharmaceutical companies have rolled out a number of MR contrast agents for liver imaging over the past decade. None has fared particularly well financially. One reason is the rapid advance of CT technology, whose 16-slice scanners now deliver images
Pharmaceutical companies have rolled out a number of MR contrast agents for liver imaging over the past decade. None has fared particularly well financially. One reason is the rapid advance of CT technology, whose 16-slice scanners now deliver images that rival those obtained with contrast-enhanced MR imagine. This intermodality competition, however, has not fazed German-based Schering, which is preparing to introduce another MR agent into the liver imaging market.
The new agent (gadoxetic acid disodium), called Primovist, is related chemically to Schering's gadolinium-based Magnevist (Gd-DTPA), and it likewise brightens signal from T1-weighted MRI. But whereas Magnevist is distributed through the bloodstream to all parts of the body, Primovist contains an additional "fat-loving" chemical group that causes it to accumulate in the liver.
Schering claims Primovist will be able to detect, locate, and distinguish various types of liver lesions. Once taken up by hepatocytes, the agent will enhance healthy liver tissue through a process called parenchymal imaging. Lesions containing a few or no hepatocytes, such as cysts, metastases, and the majority of hepatocellular carcinomas (HCC), will remain unenhanced, aiding their detection. Dynamic imaging, the assessment of enhancement changes after contrast administration, is expected to promote lesion characterization.
Primovist works faster than existing MR liver imaging agents that rely on accumulation of iron oxide particles in the liver, according to Johannes Weid, head of MRI and x-ray product development in Schering's strategic marketing team. One competing MR contrast product, for example, requires radiologists to wait 40 minutes before beginning parenchymal liver imaging, Weid said. Primovist not only permits immediate postinjection dynamic phase imaging, but it also allows parenchymal imaging within 10 to 20 minutes.
"We have a considerably shorter, more convenient time window in which to do the patient workup," Weid said.
Schering plans to market Primovist globally once the necessary regulatory steps are complete. The company has gained marketing approval for the MR agent from the Swedish health authority with the goal of using Sweden as the reference member state for a process of "mutual recognition" throughout the European Union. EU-wide registration of the drug is expected to be near completion by the end of this year.
"We will start the European mutual recognition procedure around June in order to have the new EU countries involved, too," Weid said.
He believes the high incidence of liver disease in Asia will make Primovist an important product for this region. Schering plans to submit an approval application to Japan soon, with a view to launching the product in that market by the end of 2005. A number of other Asian countries will also be targeted.
Submission for FDA approval is awaiting the results of ongoing of clinical work in the U.S., Weid said.
The difficulties encountered by Primovist predecessors are not sufficient reason to discount the new medium's chance of success in the global marketplace, according to Weid. Contrast-enhanced MR offers high-resolution liver scans for accurate diagnosis, with the added benefit that no ionizing radiation is involved.
"I firmly believe we will be able to shift part of the liver CT market to MRI, based on this specific contrast medium that we have," he said.