BRISTOL-MYERS SQUIBB's CARDIOTEC AND DuPONT's CARDIOLITE MYOCARDIAL IMAGING AGENTS ARE AMONG LATE-YEAR APPROVALS; CARDIOTEC APPROVED WITH "1B" RATING

Bristol-Myers Squibb's myocardial imaging agent CardioTec was approved Dec. 19 with a "1B" therapeutic rating (new chemical entity representing a modest therapeutic gain) by FDA. CardioTec (technetium Tc 99m teboroxime) was cleared 13 months after being recommended for approval by the agency's Radiopharmaceutical Drugs Advisory Committee and just 15 months after FDA accepted the company's resubmission for the product. Approved labeling notes that CardioTec is "a myocardial perfusion agent that is useful in distinguising normal from abnormal myocardium in patients with suspected coronary artery disease, using rest and stress techniques." An NDA for the product initially was submitted on Dec. 23, 1988 and resubmitted on Sept. 12 of the following year. CardioTec was one of four diagnostic imaging agents approved by FDA in December. The others are Serono's growth hormone production test Geref and DuPont's cardiac imaging agent Cardiolite and I.V. Persantine for use as an alternative to exercise in cardiac imaging ("The Pink Sheet" Dec. 24, T&G 11). Malinckrodt's renal imaging agent TechneScan MAG3 was approved in June. FDA awarded CardioTec a higher therapeutic rating than Cardiolite for similar indications. The Bristol-Myers Squibb product was approved two days before Cardiolite. Both agents received an advisory committee recommendation at a Nov. 17, 1989 meeting. CardioTec joins a growing line of imaging agents at Bristol- Myers Squibb that were brought to the merged company by Squibb. The company demonstrated the market potential of new, higher priced imaging agents that offer advantages over traditional ionic imaging products with its successful launch of Isovue in 1986. CardioTec and Cardiolite respectively are the second and third cardiac imaging agents on the market. The existing standard product has been DuPont's Thallium-201. In a Dec. 21 press statement, Bristol-Myers Squibb said that CardioTec is "the first technetium-based agent to receive FDA approval" for myocardial imaging. The company also touted the speed of the product's effect and washout, which could allow reimaging "without long delays." Bristol-Myers Squibb indicated that it is conducting cost- effectiveness studies to support CardioTec. In the press release, the company suggested that CardioTec can improve productivity and may obviate the need for expanding work shifts or purchasing new equipment at many hospitals. It noted that CardioTec "can easily be prepared on site as needed," whereas "thallium must be ordered in advance. The company added that CardioTec's "faster testing" can mean that patients need to take "less time . . . off from work or from other activities." Robert Carretta, MD, University of California at Davis, is "currently engaged in research about the cost-effectiveness of CardioTec use," Bristol-Myers Squibb noted. DuPont has planned a March market introduction for Cardiolite. Approved on Dec. 21 with a "1C" rating, the nonradioactive product (technetium Tc-99m sestamibi) is indicated as "a myocardial perfusion agent that is useful in distinguishing normal from abnormal myocardium, and in the localization of the abnormality, in patients with suspected myocardial infarction," according to FDA-approved labeling. DuPont added that Cardiolite offers "distinct advantages" over Thallium-201, the company's cardiac imaging radioisotope marketed since 1977. For example, the press release states, Cardiolite allows the heart to be imaged more than 15 times longer than thallium. The approval followed an initial March 17, 1988 NDA submission by about 33 months; however, the application was resubmitted on Dec. 12 of that year. Cardiolite is one of the first two drugs that will be marketed by DuPont's joint venture with Merck. Established during 1990 ("The Pink Sheet" July 30, p. 13), the DuPont Merck Pharmaceutical Company also will market another imaging agent, I.V. Persantine (dipyridamole), which was approved Dec. 13 as an alternative to exercise during thallium myocardial perfusion imaging in patients who cannot exercise. Marketing rights to injectable dipyridamole were obtained by DuPont in 1987 from Boehringer Ingelheim, which markets oral dipyridamole. The Dec. 24 issue of "The Pink Sheet" inadvertantly reported that DuPont licensed Persantine to Boehringer (T&G-11). Mallinckrodt's renal imaging agent TechneScan MAG3 was approved two years following its Dec. 17, 1988 NDA submission ("The Pink Sheet" Aug. 13, p. 12). TechneScan MAG3 (Technetium Tc- 99m mertiatide) carries a list price of $ 765 for kits of five 10 ml vials. The radioactive isotope was launched June 19, four days after FDA approval with a 1C rating (new chemical entity with little or no therapeutic advantage over existing drugs). Mallinckrodt considers the product superior to earlier kidney imaging agents. "MAG3 is the only technetium-based renal imaging agent which can be used both to perform renal angiography (imaging of the renal blood vessels) and to assess renal tubular function," the firm said. Previously, two different agents had to be used for such studies, "requiring longer procedure time and two separate injections for patients." Serono's Geref diagnostic agent for measuring growth hormone production was approved by FDA Dec. 28. The injectable drug (sermorelin acetate) is indicated, according to official labeling "for evaluating the ability of the somatotroph of the pituitary gland to secrete growth hormone (GH)." Geref was approved 30 months after the April 29, 1988 submission of its NDA by Serono. The labeling notes that "a normal plasma GH response to Geref demonstrates that the somatotroph is intact." However, it continues, "a normal response does not exclude GH deficiency because this deficiency is frequently the result of hypothalamic dysfunction in the presence of an intact somatotroph." The label adds that a normal response to Geref suggests "hypothalamic dysfunction is the cause for the GH deficiency." The product is administered "in a single I.V. dose of 1.0 mcg/kg body weight in the morning following an overnight fast," the labeling states.