GLAXO’s IMITREX "APPROVABLE": CARDIOVASCULAR SIDE EFFECTS
GLAXO's IMITREX "APPROVABLE": CARDIOVASCULAR SIDE EFFECTS are likely to be a significant element of discussions between Glaxo and FDA in reaching final approval. Sumatriptan injection crossed the penultimate approval hurdle on Nov. 30. Glaxo has one month to negotiate the final labeling and any specific monitoring programs if the company wants the migraine treatment to clear FDA as one of the traditional end-of-the-year approvals. Foreign labeling of sumatriptan generally contraindicates use of the drug in patients with certain underlying cardiovascular conditions. In Canada, for example, Imitrex is contraindicated in patients with ischemic heart disease, angina, previous myocardial infarction and uncontrolled hypertension. Cardiovascular side effects seen in early clinical trials of Imitrex were discussed by FDA's Peripheral and Central Nervous System Drugs Advisory Committee during its favorable review of Imitrex in October 1991 ("The Pink Sheet" Oct. 28, 1991, p. 16). Glaxo's IND for sumatriptan was put on hold early in the development of the drug because two men receiving a high-dose injection experienced angina. Trials were resumed after Glaxo agreed to monitor patients and accept a label warning against use in patients with ischemic heart disease. Reports of electrocardiographic changes in patients with coronary artery disease and Prinzmetal's angina were published in the British Medical Journal this summer. With Imitrex entering a large but poorly defined and untapped market, FDA appears to be proceeding carefully. Glaxo estimates that about 12% of the population suffers migraines but that only 30% of sufferers consult physicians ("The Pink Sheet" Dec. 10, 1990, p. 11). A study of migraines presented at the Fifth International Headache Congress estimated that 11.2 mil. people suffer from migraines in the U.S. ("The Pink Sheet" July 8, 1991, T&G-8). FDA may be asking Glaxo to create a patient registry to track drug recipients for potential cardiovascular side effects. In addition to a warning against use in patients with underlying heart disease, FDA is understood to be seeking a warning against use in pregnancy. FDA is reportedly concerned about animal data showing a teratogenic effect of sumatriptan. A patient registery could also be used to evaluate the risk of sumatriptan in human pregnancy. Roche has such a monitoring program for its acne treatment Accutane (isotretinoin). While a patient registry is a logistical headache, it can provide a marketing and informational bonus. FDA is also likely to seek a large postmarketing study for Imitrex. The Peripheral & CNS advisory committee expressed concern about the relative lack of long-term safety data for the drug. Glaxo's price for sumatriptan has been the subject of controversy overseas. The French government balked at Glaxo's proposed price and delayed pricing approval for several months this spring. In the U.S., Imitrex will compete with Sandoz' D.H.E. 45 (dihydroergotamine). Sandoz recently relaunched the off-patent drug for migraine and is likely to promote it as a less costly alternative to Imitrex. Glaxo filed an NDA for the migraine treatment in June 1990. An NDA for an oral version of the drug has been pending since December 1990.
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