Enanta Pharmaceuticals Achieves Milestone in Alliance with Shionogi & Co., Ltd.

-- Phase 2 Studies Initiated in Japan on First-in-Class Antibiotic EDP-420

(S-013420) for the Treatment of Community Acquired Pneumonia --

Dec 20, 2005, 00:00 ET from Enanta Pharmaceuticals

    WATERTOWN, Mass., Dec. 20 /PRNewswire/ -- Enanta Pharmaceuticals today
 announced that it has received a milestone payment from its East Asia
 development and commercialization partner, Shionogi & Co., Ltd., as Phase 2
 studies have initiated in Japan for its community antibiotic, EDP-420
 (formerly known as EP-013420, and known in Japan as S-013420).
     Results of the Phase 1 trials in Japan showed that EDP-420 (S-013420) was
 generally well tolerated and possessed favorable pharmacokinetic properties.
 In addition, attractive drug levels in the lung were observed in healthy
 volunteers, supporting the evaluation of EDP-420 (S-013420) for the treatment
 of respiratory tract infections.
     "The development activities of EDP-420 (S-013420) in Japan have progressed
 rapidly since the announcement of our partnership with Shionogi in the summer
 of 2004, as indicated by Shionogi's successful IND submission, completion of
 Phase 1, and now Phase 2 start," said Jay Luly, Ph.D., President and CEO of
 Enanta Pharmaceuticals.  "We are delighted to advance our partnership with
 Shionogi, the established antibiotic leader in Japan, and to progress the
 global development of this important antibiotic together."
     "Shionogi is very pleased to announce the initiation of Phase 2 studies of
 S-013420 in Japan.  This marks an important milestone in our alliance with
 Enanta, and demonstrates Shionogi's commitment to steadfastly developing novel
 antibiotics that treat resistant bacterial infections that address important
 unmet medical needs in our communities," said Motozo Shiono, President of
     About EDP-420 (S-013420)
     Enanta is developing EDP-420 (S-013420) for the treatment of community
 respiratory tract infections with potential indications for community acquired
 pneumonia, acute exacerbation of chronic bronchitis, acute sinusitis,
 tonsilitis/pharyngitis, and otitis media.  EDP-420 (S-013420) is a first-in-
 class Bridged Bicyclic Macrolide antibiotic that is the result of Enanta's
 innovative medicinal chemistry approach to creating novel and proprietary
 chemical structures.  Preclinical studies have shown an excellent
 pharmacokinetic profile for EDP-420 (S-013420) and an improved activity
 profile relative to currently marketed macrolides and ketolides, including
 against many strains of resistant S. pneumoniae.  This is the most commonly
 implicated bacteria in respiratory infections, responsible for 45% of the
 cases of community acquired pneumonia (CAP) and 34% of acute sinusitis.
 Nearly one-third of S. pneumoniae infections in the US are resistant to
 penicillin and 31% are resistant to the macrolide antibiotic erythromycin.  S.
 pneumoniae resistance is more common in Asia, where 53% of S. pneumoniae
 infections are penicillin resistant and 80% are erythromycin resistant.
     The global respiratory antibiotic market was approximately $12 billion in
 2002.  Three major antibiotic classes dominate the respiratory antibiotic
 market: macrolides, beta-lactams, and quinolones.  Of these classes, several
 respiratory antibiotics generate annual sales well in excess of $1 billion.
 Worldwide sales of macrolide drugs amounted to approximately $4 billion in
 2003.  Macrolides alone represented almost 20% percent of the total antibiotic
 sales in 2000 and are expected to retain this share over time.
     About Shionogi & Co., Ltd.
     Shionogi & Co. Ltd. is a major research-driven Japanese pharmaceutical
 manufacturer.  The company's primary businesses are research and development,
 manufacturing, marketing, and import and export sales of pharmaceutical and
 diagnostics products.  Shionogi follows a basic policy of continually
 providing the superior medicines essential to people's health.  For more
 details, please visit http://www.shionogi.co.jp
     About Enanta
     Enanta Pharmaceuticals is a research and development company, which uses
 its novel chemistry approach and drug discovery capabilities to create best in
 class small molecule drugs in the anti-infective field.  The heart of Enanta
 is its commitment to innovative chemistry that surpasses traditional medicinal
 chemistry approaches.  The Company successfully integrates chemistry with
 biology and medicine, in order to discover and develop novel small molecules
 that address the following significant, unmet medical needs: a new class of
 macrolide and ketolide antibiotics to overcome bacterial resistance and
 antiviral agents targeted against the Hepatitis C virus (HCV).  Enanta is a
 privately held company with offices in Watertown, MA.  More information about
 the company can be found at http://www.enanta.com.
      For Investor Relations, please contact:
      Paul Mellett
      Senior Vice President and Chief Financial Officer
      (617) 607-0761
      For Public Relations, please contact MacDougall Biomedical
      Kari Watson
      (508) 647-0209

SOURCE Enanta Pharmaceuticals