Just Announced Licensing Agreement for Opana ER(r) Outside U.S.
    is Tangible Evidence That Penwest is Successfully Executing Its
                  Strategy to Build Shareholder Value
   Leading Proxy Advisory Firms Recommend Penwest Shareholders Vote
              Against All Three Dissident Proxy Proposals

DANBURY, Conn., June 9, 2009 (GLOBE NEWSWIRE) -- In an open letter to shareholders leading up to the Company's annual meeting to be held this Wednesday, June 10, 2009, Penwest Pharmaceuticals Co. (Nasdaq:PPCO) urges shareholders to vote "FOR" Penwest's director nominees on the WHITE proxy card and "AGAINST" the proposals put forth by Tang Capital and Perceptive Life Sciences. Shareholders who have voted the dissidents' gold proxy card can still reconsider and vote for value on the Company's WHITE card.

The full text of the letter from Paul E. Freiman, Chairman, and Jennifer L. Good, President and Chief Executive Officer, follows:

 June 9, 2009

                  TIME IS SHORT -- YOUR VOTE IS CRITICAL
  TODAY'S ANNOUNCED LICENSING AGREEMENT FOR OPANA ER(r) OUTSIDE U.S.
  IS TANGIBLE EVIDENCE OF THE VALUE OF FOLLOWING PENWEST'S FOCUSED
  STRATEGY -- AND NOT PREMATURELY SHUTTING DOWN OPERATIONS
   LEADING PROXY ADVISORY FIRMS RECOMMEND PENWEST SHAREHOLDERS VOTE
           AGAINST ALL THREE DISSIDENT PROXY PROPOSALS

 Dear Fellow Penwest Shareholder:
 With our June 10 annual meeting just a couple of days away, we
 are writing to alert you to two important recent developments you
 should be aware of before voting your proxy. Time is short. If
 you have voted the dissidents' gold proxy card, you can still
 reconsider and vote for value on the Company's WHITE card.
   NEW OPANA ER LICENSING AGREEMENT SHOWS THAT PENWEST IS FOLLOWING
              THE RIGHT COURSE TO BUILD SHAREHOLDER VALUE
 While Tang Capital Management and Perceptive Life Sciences
 continue to engage us in a costly proxy contest, we are
 successfully executing our focused business plan for 2009. In
 fact, we have just achieved with our partner Endo Pharmaceuticals
 our first licensing agreement for Opana ER outside the U.S., an
 important milestone in maximizing revenues from Opana ER - the
 first of our plan's four targeted goals for 2009. This deal with
 Valeant Pharmaceuticals to market Opana ER in Canada, Australia
 and New Zealand is compelling evidence that we are pursuing the
 right strategy to build value for all Penwest shareholders.
 As the first licensing agreement for Opana ER outside the U.S.,
 this deal represents the achievement of one of the deliverables
 we committed to you as part of our plan to optimize the value of
 this important asset. We continue to work toward achieving
 additional licensing deals for Opana ER in other territories
 outside the U.S.
 You have a clear choice to make: Give Penwest a reasonable amount
 of time to execute its strategy to build value - or call it
 quits. The dissidents' proposed immediate wind down ignores the
 value of Penwest's assets and the value the Company can create
 with them in the near-term.