8-K

                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              Washington, DC 20549
                             ----------------------


                                    FORM 8-K
                                 CURRENT REPORT

                         PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


Date of report (Date of earliest event reported):  MAY 2, 2005


                       PAR PHARMACEUTICAL COMPANIES, INC.
             (Exact name of registrant as specified in its charter)


DELAWARE                       FILE NUMBER 1-10827                    22-3122182

(State or other jurisdiction of   (Commission File Number)      (I.R.S. Employer
incorporation or organization)                               Identification No.)


300 TICE BOULEVARD, WOODCLIFF LAKE, NEW JERSEY                             07677
     Address of principal executive offices)                          (Zip Code)

Registrant's telephone number, including area code:  (201) 802-4000


Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions (see General Instruction A.2. below):

     / /  Written communications pursuant to Rule 425 under the Securities Act
          (17 CFR 230.425)

     / /  Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17
          CFR 240.14a-12)

     / /  Pre-commencement communications pursuant to Rule 14d-2(b) under the
          Exchange Act (17 CFR 240.14d-2(b))

     / /  Pre-commencement communications pursuant to Rule 13e-4(c) under the
          Exchange Act (17 CFR 240.13e-4(c))



Item 1.01. Entry into a Material Definitive Agreement.
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     On May 2, 2005, Par Pharmaceutical Companies, Inc., or the Company, entered
into an agreement to acquire a 16 percent equity interest in Optimer
Pharmaceuticals, Inc., or Optimer, a privately held biotechnology company
located in San Diego, California, and also entered into a joint development and
collaboration agreement, or Joint Agreement, with Optimer for the antibiotic
compound now known as PAR-101, or the Compound. Under the terms of the Joint
Agreement, Optimer will fund all expenses associated with the clinical trials of
the Compound, while the Company will be responsible for the clinical
development, submission of a New Drug Application and coordination of legal and
regulatory responsibilities associated with the Compound. In the event that the
Compound is ultimately cleared for marketing, the Company will manufacture and
have exclusive rights to market, sell and distribute the Compound in the U.S.
and Canada. The Company will pay Optimer a royalty on sales of the Compound and
also has an option to extend the Agreement to include up to three additional
drug candidates from Optimer.

ITEM 9.01. FINANCIAL STATEMENTS AND EXHIBITS.

           (c)  Exhibits.

                99.1. Press release dated May 3, 2005.



                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.


Dated as of:  May 5, 2005


                                      PAR PHARMACEUTICAL COMPANIES, INC.
                                      ----------------------------------
                                                 (Registrant)



                                      /s/ Dennis J. O'Connor
                                      -------------------------------------
                                      Dennis J. O'Connor
                                      Vice President and Chief Financial Officer

EX-99

Par Pharmaceutical                                                  Exhibit 99.1




Contacts:
Stephen J. Mock
Cecelia C. Heer
Par Pharmaceutical Companies, Inc.
(201) 802-4000



                 PAR PHARMACEUTICAL ANNOUNCES EQUITY INVESTMENT
                           IN OPTIMER PHARMACEUTICALS

   PAR ENTERS INTO JOINT DEVELOPMENT AND COLLABORATION AGREEMENT WITH OPTIMER

                                      ---

            COMPANIES TO COLLABORATE IN THE DEVELOPMENT AND MARKETING
                            OF ANTIBIOTIC, PAR-101;
      PAR-101 REPRESENTS PROMISING ADDITION TO PAR'S EXPANDING PIPELINE OF
                              NEW DRUG CANDIDATES


SPRING VALLEY, NEW YORK, MAY 3, 2005 - Par Pharmaceutical Companies, Inc.
(NYSE:PRX) today announced that it has entered into a purchase agreement to
acquire a 16 percent equity interest in Optimer Pharmaceuticals, Inc. Optimer is
a privately held biotechnology company located in San Diego, California. The
company was founded in 1998 by Michael Chang, Ph.D., Professor Chi-Huey Wong of
Scripps Research Institute and Professor Samuel Danishefsky of Memorial
Sloan-Kettering Cancer Center.

Par and Optimer have also entered into a joint development and collaboration
agreement for the compound now known as PAR-101. PAR-101 is a narrow-spectrum
antibiotic with potent activity against CLOSTRIDIUM DIFFICILE (C. DIFFICILE). It
is orally active, with minimum systemic exposure, and is being developed for the
treatment of C. DIFFICILE-associated diarrhea (CDAD), the leading cause of
institutional enteric infections. Currently, there is no satisfactory treatment
for CDAD. PAR-101 has been granted Fast-Track status by the U.S. Food and Drug
Administration, and is now in Phase IIa clinical studies, with Phase IIb trials
expected to commence in the second half of 2005. If all proceeds well with the
product's development and regulatory review, Par believes that PAR-101 could be
available commercially as soon as 2008.

"Working closely with our accomplished colleagues at Optimer, we look forward to
demonstrating the utility of PAR-101 in addressing a significant, unmet medical
need," said Shankar Hariharan, Ph.D., executive vice president and chief
scientific officer of Par. "We are excited to add this new compound to Par's
expanding roster of new drug candidates in clinical development.

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"CDAD imposes significant costs on society both in terms of human suffering and
economics. We believe that PAR-101 has the potential to become an important
addition to the physician's armamentarium for treating this debilitating
infection," Dr. Hariharan added.

"We are proud and excited to have Par as our development and marketing partner,"
said Dr. Michael Chang, president and chief executive officer of Optimer. "We
believe that this collaboration will significantly expedite the
commercialization of PAR-101."

In the U.S., as many as 10 percent of all patients hospitalized for more than
two days are afflicted with CDAD. C. DIFFICILE infection is currently the most
common cause of nosocomial diarrhea, often adding up to two weeks to the length
of patient hospitalization. This can add as much as $10,000 to $15,000 to the
cost of a hospital stay. CDAD is also implicated in the majority of cases of
antibiotic-associated colitis, which is one of the leading causes of morbidity
and mortality among elderly debilitated patients. The rising incidence of CDAD
has been attributed to the increasingly frequent prescription of broad-spectrum
antibiotics for hospitalized patients.

PAR-101 is a novel macrocyclic antibiotic that is produced by fermentation. Its
narrow-spectrum activity is highly selective for C. DIFFICILE, thus preserving
gut microbial ecology, an important consideration for the treatment of CDAD. It
is believed that PAR-101 has the potential to address resistance to existing
therapies and increasing recurrence rates of CDAD. Recurrence rates of CDAD are
20 to 25 percent with existing therapies, representing a significant unmet
medical need. According to the Centers for Disease Control and Prevention, a
virulent new strain of C. DIFFICILE has been linked to an eightfold increase in
mortality in some outbreaks in the U.S. and Canada.

TERMS OF THE AGREEMENT

Under the terms of the agreement, Optimer will fund all expenses associated with
the clinical trials of PAR-101. Par will be responsible for clinical
development, and, if successful, Par will submit the New Drug Application for
the product. All legal and regulatory responsibilities also reside with Par. If
ultimately cleared for marketing, Par will manufacture and market PAR-101. Par
has exclusive rights to market, sell and distribute the product in the U.S. and
Canada. Par will pay Optimer a royalty on sales of the product. Par has an
option to extend the joint development and collaboration agreement to include up
to three additional drug candidates from Optimer's pipeline.

Optimer Pharmaceuticals, Inc. (San Diego, California, www.optimerpharma.com) is
an emerging biotechnology company focused on the research and development of
anti-infective products to treat serious bacterial infections. Optimer's core
drug discovery technologies are licensed from Scripps Research Institute and
Memorial Sloan-Kettering Cancer Center. The company has a solid portfolio of
preclinical and clinical stage antibiotic compounds. Optimer's other compound in
clinical development is prulifloxacin, a novel, broad-spectrum fluoroquinolone
antibiotic.

Par Pharmaceutical Companies, Inc. develops, manufactures and markets generic
pharmaceuticals through its principal subsidiary, Par Pharmaceutical, Inc., and
its recently acquired subsidiary, Kali Laboratories, Inc. The company is also
developing an additional line of branded pharmaceutical products for specialty
markets and expects to introduce the first of these in 2005. Par currently

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manufactures, markets or licenses more than 85 prescription drugs. For press
release and other company information, visit http://www.parpharm.com.

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Certain statements in this press release 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 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.

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