Enanta Pharmaceuticals, Inc., (NASDAQ:ENTA) a research and development-focused biotechnology company dedicated to creating small molecule drugs in the infectious disease field, today announced that AbbVie, Enanta’s development partner for protease inhibitors for hepatitis C virus (HCV), has initiated a phase 2b clinical study with ABT-493, Enanta’s next-generation protease inhibitor. ABT-493 is the second clinical-stage protease inhibitor candidate developed within the Enanta-AbbVie collaboration.

The phase 2b study being conducted by AbbVie will evaluate the safety and efficacy of ABT-493 co-administered with ABT-530, AbbVie’s next generation NS5A inhibitor, in HCV patients. AbbVie has informed Enanta that results from this trial are expected in 2015 and AbbVie plans to start phase 3 development of the combination next year. Additional details regarding this study will be available when they are posted by AbbVie at www.clinicaltrials.gov.

“The goal of our collaboration’s next-generation protease inhibitor program is a pan-genotypic, ribavirin-free, once-daily dosing regimen for HCV patients,” stated Jay R. Luly, Ph.D., President and CEO.

About ABT-493

ABT-493 is a next-generation HCV NS3/4A protease inhibitor identified within the Enanta-AbbVie collaboration. Designed to enable once-daily dosing without ritonavir, ABT-493 is expected to be co-formulated with AbbVie’s next-generation NS5A inhibitor, ABT-530. Protease plays an essential role in the viral life cycle of the hepatitis C virus (HCV). Inhibition of the protease prevents non-structural (NS) proteins from forming and thereby prevents replication and survival of the HCV virus.

Protease Inhibitor Collaboration with AbbVie

In December 2006, Enanta and Abbott announced a worldwide agreement to collaborate on the discovery, development and commercialization of HCV NS3 and NS3/4A protease inhibitors and HCV- protease-inhibitor-containing drug combinations. ABT-450 and ABT-493 are protease inhibitors identified through the collaboration. Under the agreement, AbbVie is responsible for all development and commercialization activities for ABT-450, the collaboration’s lead compound that has been submitted for approval in the United States and the European Union as part of a multi-drug regimen. Enanta received $57 million in connection with signing the collaboration agreement and is eligible to receive payments for regulatory and reimbursement approval milestones, as well as tiered, double-digit royalties worldwide on any revenue allocable to the collaboration’s protease inhibitors. Also, for ABT-493 or any other additional collaborative HCV protease inhibitor product candidate developed under the agreement, Enanta holds an option to modify the U.S. portion of its rights to receive milestone payments and worldwide royalties. If it exercises this option, Enanta can fund 40 percent of U.S. development costs and U.S. commercialization efforts (sales and promotion costs) for the additional protease inhibitor in exchange for 40 percent of any U.S. profits ultimately achieved after regulatory approval, instead of receiving payments for U.S. commercial regulatory approval milestones and royalties on U.S. sales of that protease inhibitor.

About Enanta

Enanta Pharmaceuticals is a research and development-focused biotechnology company that uses its robust chemistry-driven approach and drug discovery capabilities to create small molecule drugs in the infectious disease field. Enanta is discovering, and in some cases developing, novel inhibitors designed for use against the hepatitis C virus (HCV). These inhibitors include members of the direct acting antiviral (DAA) inhibitor classes – protease (partnered with AbbVie), NS5A (partnered with Novartis) and nucleotide polymerase – as well as a host-targeted antiviral (HTA) inhibitor class targeted against cyclophilin. Additionally, Enanta has created a new class of antibiotics, called Bicyclolides, for the treatment of multi-drug resistant bacteria, with a focus on developing an intravenous and oral treatment for hospital and community MRSA (methicillin-resistant Staphylococcus aureus) infections.

Forward-Looking Statement Disclaimer

This press release contains forward-looking statements, including statements with respect to the potential of AbbVie’s HCV treatment regimen containing ABT-493 and Enanta’s expectations for the timing of future clinical development of such regimen. Statements that are not historical facts are based on our management’s current expectations, estimates, forecasts and projections about our business and the industry in which we operate and our management’s beliefs and assumptions. The statements contained in this release are not guarantees of future performance and involve certain risks, uncertainties and assumptions, which are difficult to predict. Therefore, actual outcomes and results may differ materially from what is expressed in such forward-looking statements. Important factors that may affect actual results include the efforts of AbbVie (our collaborator on ABT-493) to obtain regulatory approvals and commercialize treatment regimens containing ABT-493, the development, regulatory and marketing efforts of others with respect to competitive HCV treatment regimens, regulatory and reimbursement actions affecting any ABT-493-containing regimen, any competitive regimen, or both, and the level of market acceptance and the pricing and rate of reimbursement for any ABT-493-containing regimen. Enanta cautions investors not to place undue reliance on the forward-looking statements contained in this release. These statements speak only as of the date of this release, and Enanta undertakes no obligation to update or revise these statements, except as may be required by law.