Par Pharmaceutical hopes to capture a portion of the 15 mg buspirone market with the March 28 approval of its 7.5 mg strength of the anxiety drug buspirone, a generic equivalent of Bristol-Myers Squibb's BuSpar. Par has 180-day exclusivity for 7.5 mg buspirone.

Par predicts it can capture 10%-15% of the buspirone market in which the labeled BuSpar starting dose of 15 mg is broken in half for a 7.5 mg b.i.d. dose. The company estimates the 15 mg split-dose regimen accounts for 12% of buspirone prescriptions.

Buspirone 15 mg (split-dose or not) accounted for approximately $400 mil. of brand sales in the past 12 months, Par said. BuSpar sales totaled $709 mil. worldwide in 2000.

In its marketing of the 7.5 mg tablet, Par will emphasize the convenience of the new dose to physicians; 7.5 mg - not marketed by Bristol - gives patients the option of taking two smaller tablets. Par will also offer customers a cost advantage by pricing the 7.5 mg buspirone dose "competitively" to the 15 mg generic tablet, the company noted.

Par will communicate the advantages via a direct mail effort to 70,000 buspirone-prescribing physicians, a telemarketing program targeting 8,000-10,000 physicians and a sampling campaign. Buspirone is Par's third generic to be promoted to physicians.

Mylan received approval also on March 28 for the 15 mg strength of buspirone, with six months of marketing exclusivity. Watson subsidiary Danbury's 5 mg and 10 mg strengths were also approved on the same date, and the company has 180-day exclusivity.

Watson is launching its generic buspirone at a 10.5% discount to BuSpar. Buspirone 5 mg will cost $77.12 AWP for a 100-tablet bottle, compared to BuSpar's AWP of $86.18, according to First Data Bank. Watson's 10 mg dose will cost $134.50 for 100 tablets, versus BuSpar's $150.29 price tag.

Danbury also received tentative approval for a 15 mg buspirone, and has previously received tentative approvals for 5 mg and 10 mg. Other firms which have tentative ANDA approval for 5 mg and 10 strengths of buspirone include Teva, Chelsea, Novopharm, Egis, Zenith, Geneva, Pharmex and KV Pharmaceuticals. KV, Pharmex, Geneva and Zenith also have tentative approvals for 15 mg, as does ESI-Lederle.

The generic launches were triggered by a delisting of a BuSpar metabolite patent (No. 6,150,365) from the "Orange Book" after a federal appeals court denied Bristol's motion to stay the generic approvals.

Mylan filed suit against Bristol in Washington, D.C. federal court Nov. 30 after Bristol listed a metabolite patent in the "Orange Book" 12 hours before generic competition was expected (¹ Also see "Bristol BuSpar Metabolite Data Requested By FDA Before Final Patent Listing" - Pink Sheet, 4 December, 2000.).

The D.C. court ordered Bristol to delist the patent and instructed FDA to grant "immediate approval" of generic buspirone in a March 13 injunction. A subsequent motion for a stay of the injunction was also denied by the court (² Also see "Mylan Buspirone Launch Awaits Bristol Appeal Of BuSpar Patent Order" - Pink Sheet, 19 March, 2001.).

In an unusual legal move, Bristol appealed to both the D.C. and federal appeals courts on March 15. Federal appeals courts typically have exclusive jurisdiction over patent cases. The case remains active in the D.C. appeals court; Mylan has filed for summary judgement.

Bristol based its federal appeals court case on two points. First, the firm argued, Mylan's filing of a pre-emptive declaratory judgement to delist the BuSpar patent "undermines the purpose of the Hatch-Waxman Act by allowing generic drug makers to avoid filing paragraph IV certifications." The company also maintained that there is "no private right of action to enforce" the FD&C Act.

In denying the motion, the federal appeals court found that Bristol had "not established a likelihood of success on the merits regarding the district court's decision subject matter jurisdiction over Mylan's cause of action," Judge Raymond Clevenger's opinion states.

The issue of whether a patent can be delisted via a declaratory judgement "is an issue of first impression of this court," the opinion states. After reviewing Bristol's arguments and in light of conflicting decisions by district courts on the subject, however, the court concluded Bristol is unlikely to succeed at trial. Clevenger and Judges Paul Michel and Alvin Schall will hear oral arguments on the appeal in July.

Par 7.5 Mg Buspirone Aims To Capture Portion of 15 Mg Split-Tablet Market

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