BOEHRINGER INGLEHEIM PERSANTINE HEART VALVE STUDIES ARE "NEW" UNDER WAXMAN/HATCH DEFINITION AND JUSTIFY THREE YEARS OF EXCLUSIVITY, FDA SAYS

Boehringer Ingleheim's Persantine (dipyridamole) studies supporting use with coumarin in heart valve replacement are "new" studies under the Waxman/Hatch law and, therefore, justify the three years of exclusivity granted to the company, FDA said in an Aug 9 letter. "FDA interprets the phrase 'new clinical investigations' to mean investigations conducted on humans that have not formed part of the basis of a finding of substantial evidence of effectiveness for any indication in a previously approved new drug application or supplement," the agency said. FDA also defined "new" studies as those "that do not duplicate the results of another investigation that was relied on by the FDA to demonstrate the effectiveness of a previously approved drug product." "FDA does not believe that Congress intended the term 'new' to refer to the chronological age of the study," the agency said in a response to a March 4, 1987 petition from the NYC firm, Bass & Ullman. Filed on behalf of Purpac Pharmaceuticals, the petition requested that FDA rescind its grant of exclusivity to Boehringer Ingelheim, asserting that the studies were not "new" as required by Waxman/Hatch. FDA approved a Persantine supplemental NDA in December 1986 for use as an adjunct to coumarin anticoagulants in the prevention of postoperative thromboembolic complications of cardiac valve replacement. The following month FDA reclassified dipyridamole under the DESI review as ineffective for the treatment of angina and offered an opportunity for a hearing on its proposal to withdraw approval of products carrying that indication ("The Pink Sheet" Jan. 26, 1987, p.5). FDA's Aug. 9 response to Bass & Ullman outlines the agency's position on the validity of Boehringer Ingelheim's heart valve indication studies as a basis for a grant of exclusivity. FDA confirmed that Boehringer Ingelheim "satisfactorily demonstrated" that it was the sponsor of nine of 10 studies included in the supplemental NDA -- a requirement for exclusivity under Waxman/Hatch. FDA also determined that studies sponsored by Boehringer Ingelheim were "essential" to the approval of the supplement, as is required for exclusivity under the legislation. The Bass & Ullman petition also questioned whether Persantine, as a pre-1962 drug, had an approved NDA at the time exclusivity was awarded. For an NDA supplement to be eligible for three years exclusivity, it must be a supplement to an approved application. FDA noted that "a long-standing principle" of the DESI program is that DESI products are "'approved' until an FDA proposal to withdraw approval (such as the one published Jan. 15, 1987, on dipyridamole labeled for angina) becomes final." A dipyridamole DESI hearing has not yet been scheduled, and according to FDA, there is no certainty that such a hearing will be held. The agency said that it can deny the hearing, if it concludes that there is no substantial issue of fact. Subsequently FDA could withdraw generic dipyridamole products from the market. The generics can remain on the market until or unless a final order is issued, FDA said. FDA also addressed the issue of a hearing on Persantine's exclusivity that was raised in a May 1987 petition submitted for Barr Labs et al. The agency said that the petition claims that a hearing on Persantine's exclusivity should be granted because a substantial issue of fact exists as whether Boehringer Ingelheim is entitled to exclusivity. FDA responded that "there are no material issues of fact. FDA disagrees that an administrative hearing is the proper forum to resolve issues of statutory interpretation."