Myoscint nod heightens monoclonal anticipation

After passing a crucial review with flying colors last month,the first monoclonal imaging agent is expected to be formallyapproved by the Food and Drug Administration within the next fewmonths.

The agent, Myoscint, uses monoclonal fragments to seek outand bind to dead heart tissue. An FDA subcommittee reviewing clinicaldata recommended its full approval for detecting presence, locationand extent of myocardial necrosis in patients with acute ischemicheart disease. Myoscint was developed by Centocor of Malvern,PA.

Approval of the agent has implications for companies, physiciansand patients, said Dr. Hirsch Handmaker, director of nuclear medicineat California Pacific Medical Center in San Francisco.

"The notion of FDA approval for biologically active materialsmeans the agency is comfortable with the technology for use ina wide variety of patients," Handmaker said. "That hasa lot of import."

Companies will be encouraged to invest research and developmentdollars because approval of monoclonals is no longer concept butreality, he said.

"The new posture by the FDA should stimulate more interestin the products as they come out. It's something more physicianswill be paying attention to," he said. "For patients,approval sends the message that this isn't experimental medicineand that it is becoming routine."

The official word is expected within two to six months, accordingto Richard Koenig, director of corporate communications for Centocor.

"We're working with the FDA on the remaining details.Once we've taken care of those, this product will get to market,"he said.

The FDA committee reviewed clinical utility and adequacy ofthe agent in determining extent of myocardial necrosis. It alsoconsidered whether an additional study should be conducted todetermine the utility of Myoscint in conjunction with thallium-201,which binds to normal tissue.

"Because it's the first agent, we believe the FDA waslooking at it from all the angles. The FDA was viewing this asnot just one product, but as an exemplar of a class of products,"Koenig said.

APPROVAL OF THE AGENT may boost interest in monoclonals generallybut it would leave unanswered questions about cost versus benefit.For example, Myoscint aids in predicting risk of future cardiacevents by detecting the extent of tissue death. While this qualitativeassessment is valuable, the agent does not provide a quantitativeassessment--an important distinction, according to the FDA subcommittee.

Quantitative assessments may only be possible when the agentis paired with three-dimensional SPECT, currently available onlyin major medical and academic centers, said Dr. Jerome Groopman,chairman of the FDA review committee.

Cytogen and Hybritech, two companies with monoclonals for oncologyindications closing in on FDA approval, might be wise to takesuch concerns to heart.

"We need to see larger, broader availability if we areto determine the role of these agents in practice," Handmakersaid. "To justify expense, you have to be able to say thatsomething is not just marginally better, but significantly better.In the area of labeled monoclonals for oncology, it doesn't looklike we're there yet."

Once it is officially approved, Myoscint will be marketed byMcNeil Pharmaceutical, a Johnson & Johnson subsidiary (SCAN7/19/89).

Centocor managed the development and clinical trials whileMcNeil aided in preparing materials for FDA review. This strategywas critical to Myoscint's success, Handmaker said. But he wonderedwhether other, smaller companies would be able to follow in Centocor'smarketing footsteps.

"Getting these materials into the hands of professionals,who have the money to conduct extensive surveys and who have greatcredibility, was a great strategy," he said. "That'sthe good news. The bad news is, what's a smaller company likeCytogen or NeoRx going to do when it's their turn? It just layersin another level of profit that has to be generated."