Merck and Paratek Pharmaceuticals Sign Collaboration Agreement for Novel Antibiotic PTK 0796 Currently in Phase 1 Testing

PTK 0796 represents a significant advance over the well-knowntetracycline family, and has been shown to be highly effective inanimal models at treating increasingly problematic, clinicallyprevalent infections caused by gram-positive bacteria, such asmethicillin-resistant Staphylococcus aureus (MRSA), and bygram-negative, atypical and anaerobic bacteria, including thoseresistant to currently available classes of antibiotics and known tocause diseases such as pneumonias, urinary tract infections, skindiseases and blood-borne infections in both the hospital and communitysettings.

"Merck has long been a world leader in the fight againstinfections, and this agreement is a further demonstration of ourcommitment to this field of medicine," said Peter S. Kim, Ph.D.,President, Merck Research Laboratories. "We are excited about ourcollaboration with Paratek to develop new antibiotics that have thepotential to improve the care of patients and provide physicians withnew treatment options at a time of increased antibiotic resistance."

"We are pleased to announce our collaboration with Merck, a globalleader in the development and commercialization of anti-infectives andother innovative drugs that address serious medical problems, such asthe growing problem of antibiotic resistance," said Thomas J. Bigger,President and CEO of Paratek Pharmaceuticals. "We have been veryimpressed by Merck's commitment to antibiotic research and developmentand are pleased by the collaborative process of establishing thisimportant partnership. Their enthusiasm for our PTK 0796 project andembrace of the collaborative process demonstrate a new side of Merckthat we found very compelling, in addition to their strong currentpresence in the hospital anti-infectives market with CANCIDAS(R),INVANZ(R), and PRIMAXIN(R) and their legacy of innovating anddelivering important new therapeutics to the marketplace."

Under the terms of the agreement, Merck provided undisclosedupfront funding, will assume primary responsibility for clinicaldevelopment of the IV and oral formulations of PTK 0796 and has theright to market such products worldwide. Paratek will participate inclinical development and be eligible to receive payments uponachievement of certain milestones; these payments could total as muchas $127 million once PTK 0796 is approved for marketing. Paratek willalso receive royalties on net sales and have the opportunity toco-promote the IV formulation of PTK 0796 in the United States.

Background on AMCs

Using Paratek's novel medicinal chemistry techniques, AMCs wereevolved from tetracycline antibiotics as potential agents to combatmultiple antibiotic-resistant bacteria, including MRSA,penicillin-resistant Streptococcus pneumoniae (PRSP),vancomycin-resistant Enterococcus (VRE), multidrug resistantEscherichia coli and other difficult-to-treat pathogens. Introducedmore than 50 years ago, tetracyclines remain among the most commonlyused anti-infective agents to combat bacterial infections. However,the emergence of resistance has curtailed their effectiveness incertain infections. Paratek has utilized its expertise to create AMCcompounds, such as PTK 0796, that retain the appealing safety andspectrum of activity of the tetracyclines while overcomingtetracycline and multi-drug resistance. Evidence to date indicatesthat PTK 0796 is also not affected by resistance to other classes ofantibiotics. PTK 0796 is being evaluated in Phase I both as an IV andoral formulation and may have potential utility against the broadspectrum of pathogens prevalent in the community, including activityagainst resistant pathogens such as community-associated MRSA.

About Merck

Merck & Co., Inc. is a global research-driven pharmaceuticalcompany dedicated to putting patients first. Established in 1891,Merck discovers, develops, manufactures and markets vaccines andmedicines to address unmet medical needs. The Company devotesextensive efforts to increase access to medicines through far-reachingprograms that not only donate Merck medicines but help deliver them tothe people who need them. Merck also publishes unbiased healthinformation as a not-for-profit service. For more information, visitwww.merck.com.

About Paratek Pharmaceuticals

Paratek Pharmaceuticals, Inc. is engaged in the discovery andcommercialization of new therapeutics that treat serious andlife-threatening diseases, with a particular focus on the growingworldwide problem of antibiotic resistance. Paratek is advancing novelcompounds that can circumvent or block bacterial resistance involvingtechnology initially developed by Paratek co-founder Dr. Stuart Levy'slaboratory at Tufts University School of Medicine, and licensed byParatek. In addition to its tetracycline-derived antibacterials,Paratek is developing small molecule drugs that can prevent infectionby interfering with Multiple Adaptational Response (MAR) mechanisms inbacteria.

Outside the antibacterial therapeutic area, Paratek has alsoestablished an effort to exploit its novel tetracycline derivativesand their unique mechanism of action in selected anti-inflammatory andneurodegenerative conditions. Paratek has an active chemical synthesiseffort to produce novel and diverse small molecules, with the goal ofdeveloping non-antibacterial compounds with improved activity inserious inflammatory and neurodegenerative diseases based upon agrowing body of clinical and basic research supporting this approach.

Paratek is privately held and headquartered in Boston,Massachusetts, USA. For more information, visit Paratek's website athttp://www.paratekpharm.com/ .

Merck Forward-Looking Statement

This press release contains "forward-looking statements" as thatterm is defined in the Private Securities Litigation Reform Act of1995. These statements are based on management's current expectationsand involve risks and uncertainties, which may cause results to differmaterially from those set forth in the statements. The forward-lookingstatements may include statements regarding product development,product potential or financial performance. No forward-lookingstatement can be guaranteed, and actual results may differ materiallyfrom those projected. Merck undertakes no obligation to publiclyupdate any forward-looking statement, whether as a result of newinformation, future events, or otherwise. Forward-looking statementsin this press release should be evaluated together with the manyuncertainties that affect Merck's business, particularly thosementioned in the cautionary statements in Item 1 of Merck's Form 10-Kfor the year ended Dec. 31, 2004, and in its periodic reports on Form10-Q and Form 8-K, which the Company incorporates by reference.