FDA casts doubt on future of Medco's ViaScint radiotracer

Medco intends to get out of the radiotracer business

A radiopharmaceutical designed to light up injured but viable heart muscle has hit a rough patch at the Food and Drug Administration. Unless the problems are easily resolved, ViaScint from Medco Research might be relegated to the drug development scrap heap.

FDA reviewers notified Medco executives in July that its new drug application for ViaScint is not approvable and that further work is needed. If discussions in coming weeks with the FDA indicate that the effort to win approval is not worth the potential gain, the company might turn the license for developing the product over to Canadian radioisotope company MDS Nordion, which owns the rights to the technology.

"We'll just have to evaluate whether it makes economic sense to go forward," said Glenn Andrews, CFO of Medco Research in Research Triangle Park, NC.

Medco stands to lose licensing payments made to Nordion, as well as its investment in clinical trials and related development efforts. That's a relatively modest sum, however, according to Andrews. The upside is that the company will be able to focus on what it does best: adenosine-based pharmaceuticals for cardiac applications.

To be competitive, small drug companies must make the best use of limited resources. For Medco, over the past several years, that has meant focusing on cardiovascular drugs. In keeping with that focus, the company licensed rights to develop ViaScint from MDS Nordion five years ago. But in June, Medco shifted its focus, announcing to shareholders that it would divest its radiopharmaceutical business, probably by selling the marketing rights to ViaScint in favor of concentrating on the development of adenosine drugs. Another radiopharmaceutical affected by this decision is a technetium-labeled heart imaging agent that Medco licensed last year from Molecular Targeting Technologies (SCAN 1/17/96).

Medco is making the shift because the company sees prospects for its adenosine-based technology as much more promising than the radiopharmaceutical market. Medco developed Adenoscan, which is used to pharmacologically stress heart patients undergoing thallium imaging, and the product is sold by Fujisawa. Medco also owns two therapeutic preparations of adenosine, a treatment for abnormally rapid heartbeats and a cardioprotective adjunct to early thrombolytic therapy.

ViaScint is much better suited to the core competencies of MDS Nordion, which also has manufacturing rights to the agent. The Canadian firm is best known in the imaging community as the dominant source of molybdenum-99, the generator for technetium. But Nordion also supports two efforts in the development of radiopharmaceuticals: One is reliant on a reactor in Ottawa that makes iodine-125, the other on a cyclotron producing iodine-123 in British Columbia.

"Part of the company's strategy has been to label iodine onto other compounds that go to various organs within the body," said Jerry Porter, Nordion business manager of I-123 radiopharmaceuticals, located in Triumf, B.C.

Nordion originally acquired rights to ViaScint from the University of Texas, and in April 1992 cut a deal to manufacture the product for clinical trials to be conducted by Medco. To produce ViaScint, the staff at the Nordion cyclotron facility linked radioactive iodine-123 to a fatty acid called iodophenylpentadecanoic acid, then quickly shipped the product-which has a half-life of 13 hours-to clinical institutions. Supporting the trials required a major commitment on the part of Nordion, Porter said.

"We have cranked in quite a bit of money, because we've been doing all the manufacturing at our own cost," he said. "We were manufacturing four days a week for about six months, so you can see the treadmill we were on trying to do all these clinicals."

The rigid schedule was needed, because ViaScint is good for only about two days after manufacture, due to the short half-life of the isotope.

Whether Nordion will try to protect that investment if Medco chooses to abandon the product is not certain. Like Medco, Nordion is cautious.

"We really won't know how much work needs to be done and how many more dollars will have to be committed on this until we talk to the FDA," Porter said. "If we can do something in 12 or 18 months, and they kick it back to us, I'm pretty sure that Nordion will go ahead and follow through."