Spring Valley, New York, June 2, 2004 — Par Pharmaceutical Companies, Inc. (NYSE:PRX) today announced that it has signed a definitive agreement with Advancis Pharmaceutical Corporation (NASDAQ:AVNC) to develop and market a novel formulation of the antibiotic amoxicillin. The product utilizes Advancis' proprietary once-a-day pulsatile delivery technology called PULSYS™. A New Drug Application, pursuant to Section 505(b)(2) of the Act, seeking marketing clearance for amoxicillin PULSYS™ is expected to be submitted to the U.S. Food and Drug Administration in 2005. This agreement finalizes the letter of intent that was signed and announced last March.

Under the terms of the agreement, Par will pay Advancis a $5 million upfront license fee and fund future development expenses. Advancis will grant Par the exclusive right to sell and distribute the product and the co-exclusive right to market the product. Advancis will be responsible for the manufacturing program. Par and Advancis will share equally in marketing expenses and profits.

Advancis Pharmaceutical Corp. (Nasdaq: AVNC) is a pharmaceutical company focused on the development and commercialization of pulsatile drug products that fulfill substantial unmet medical needs in the treatment of infectious disease. The company is developing a broad portfolio of anti-infective drugs based on its novel biological finding that bacteria exposed to antibiotics in front-loaded staccato bursts, or "pulses," are killed more efficiently and effectively than those under standard treatment regimens. Based on this finding, Advancis has developed a proprietary, once-a-day pulsatile delivery technology called PULSYS™. By examining the resistance patterns of bacteria and applying its delivery technologies, Advancis has the potential to redefine infectious disease therapy and significantly improve drug efficacy, shorten length of therapy, and reduce drug resistance versus currently available antibacterial products. For more on Advancis, please visit http://www.advancispharm.com.

Par Pharmaceutical Companies, Inc. develops, manufactures and markets generic pharmaceuticals through its principal subsidiary, Par Pharmaceutical, Inc. The company is also developing a line of proprietary specialty pharmaceuticals and expects to market the first of these in 2005. Through its FineTech subsidiary, Par also develops and utilizes synthetic chemical processes to design and develop intermediate ingredients used in the production of finished products for the pharmaceutical industry. Par currently manufactures and distributes more than 170 products representing various dosage strengths of 73 drugs. For press release and other company information, visit http://www.parpharm.com.

Certain statements in this press release may constitute "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. To the extent any statements made in this news release contain information that is not historical, these statements are essentially forward-looking and are subject to risks and uncertainties, including the anticipated closing of the Kali acquisition, difficulty of predicting FDA filings and approvals, acceptance and demand for new pharmaceutical products, the impact of competitive products and pricing, new product development and launch, reliance on key strategic alliances, uncertainty of patent litigation filed against us, availability of raw materials, the regulatory environment, fluctuations in operating results and other risks and uncertainties detailed from time to time in the company's filings with the Securities and Exchange Commission, such as the company's Form 10-K, Form 10-Q, and Form 8-K reports.