Enanta Pharmaceuticals Reports Financial Results for its Fiscal First Quarter Ended

Enanta Pharmaceuticals Reports Financial Results for its

Fiscal First Quarter Ended December 31, 2015

Conference Call and Webcast Today at 4:30 p.m. ET

Mass., February 8, 2016 Enanta Pharmaceuticals, Inc., (NASDAQ:ENTA), a research and development-focused biotechnology company dedicated to creating small molecule drugs for viral infections and liver diseases, today reported financial

results for its fiscal first quarter ended December 31, 2015.

Enanta s cash, cash equivalents and short-term and long-term marketable

securities totaled $236.6 million at December 31, 2015. This compares to a total of $209.4 million in such accounts at September 30, 2015. Enanta expects that its current cash, cash equivalents and marketable securities will be sufficient

to meet the anticipated cash requirements of its existing business for the foreseeable future.

Fiscal First Quarter Ended December 31, 2015

Revenue for the three months ended December 31, 2015 was $48.4 million, compared to $77.5 million for the three months ended

December 31, 2014. For the 2015 period, revenue consisted primarily of a $30 million milestone payment earned and received from AbbVie for reimbursement approval of VIEKIRAX in Japan, as

well as royalties earned on contractually specified portions of AbbVie s worldwide net sales of hepatitis C virus (HCV) treatment regimens containing paritaprevir, Enanta s lead protease inhibitor identified within the ongoing

AbbVie-Enanta collaboration. Revenue in the 2014 period consisted primarily of a $75 million milestone payment received in the period ended December 31, 2014 for the initial commercialization regulatory approval of VIEKIRA PAK in the U.S. Milestone payments, royalties and other payments from collaborations have varied significantly from period to period, and are expected to continue to do so.

Research and development expenses totaled $9.0 million for the three months ended December 31, 2015, compared to $4.5 million for the three months ended

December 31, 2014. The increase in the three month period over the prior year period was primarily due to increased pre-clinical and clinical costs associated with Enanta s wholly-owned R&D programs in NASH, RSV, HBV and HCV

General and administrative expenses totaled $3.8 million for the three months ended December 31, 2015,

compared to $2.8 million for the three months ended December 31, 2014. The increase in the 2015 period primarily reflects increases in stock-based compensation expense, as well as additional expenses incurred as Enanta expands its operations.

Net income for the three months ended December 31, 2015 was $26.2 million, or $1.36 per diluted common share, compared to net income of $42.0

million or $2.18 per diluted common share, for the corresponding period in 2014.

Sustained by Enanta s financial resources generated by our

HCV collaboration product, 2016 will be a year in which Enanta continues to diversify beyond our partnered and wholly-owned HCV programs and advances its internal programs in NASH, hepatitis B virus and respiratory syncytial virus, commented

Jay R. Luly, Ph.D., President and Chief Executive Officer. We expect to advance our NASH program into clinical development this year and look forward to sharing updates on these new programs in the coming months.

Development Program and Business Review

For the quarter ending March 31,

2016, which marks the beginning of a new year for the calculation of Enanta s annually tiered royalties, Enanta expects its royalty revenue to be at least 3% percent of AbbVie s reported VIEKIRA sales. The actual percentage will depend

primarily on the amounts and portions of those sales that are 2-DAA or 3-DAA regimen sales. Under its agreement with AbbVie, Enanta is entitled to receive annually tiered, double-digit royalties on specified portions of sales that are allocated to

paritaprevir using 30% of 3-DAA sales (VIEKIRA PAK or VIEKIRAX + EXVIERA ) and 45% of 2-DAA sales (TECHNIVIE or VIEKIRAX ) for the allocation.

Upcoming Events and Presentations

Conference Call and Webcast Information

a conference call and webcast today at 4:30 p.m. ET. To participate in the live conference call, please dial

(855) 840-0595 in the U.S. or (518) 444-4814 for international callers. A replay of the conference call will be available

starting at approximately 6:30 p.m. Eastern time on February 8, 2016, through 11:59 p.m. Eastern time on February 12, 2016 by dialing (855) 859-2056 from the U.S. or (404) 537-3406 for international callers. The passcode for both

the live call and the replay is 36743436. A live audio webcast of the call and replay can be accessed by visiting the Calendar of Events section on the Investors page of Enanta s website at www.enanta.com.

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 for viral infections and liver diseases. Enanta s research and development is currently

focused on four disease targets: Hepatitis C Virus (HCV), Hepatitis B Virus (HBV), Non-alcoholic Steatohepatitis (NASH) and Respiratory Syncytial Virus (RSV).

Enanta has developed novel protease inhibitors and NS5A inhibitors that are members of the direct-acting-antiviral (DAA) inhibitor classes designed for use

against the hepatitis C virus (HCV). Enanta s protease inhibitors, developed through its collaboration with AbbVie, include paritaprevir, which is contained in AbbVie s marketed DAA regimens for HCV, and ABT-493, Enanta s

next-generation protease inhibitor, which AbbVie is developing in phase 3 studies in combination with ABT-530, AbbVie s next-generation NS5A inhibitor. Enanta has also discovered a cyclophilin inhibitor, EDP-494, a novel host-targeting

mechanism for HCV, which is now in phase 1 clinical development, and EDP-305, an FXR agonist, which Enanta plans to advance into clinical development for NASH later in 2016. Please visit www.enanta.com for more information on Enanta s programs

Forward Looking Statements Disclaimer

This press release contains forward-looking statements, including statements with respect to the prospects for future royalties on sales of AbbVie s HCV

treatment regimens containing paritaprevir, the prospects for AbbVie s development of a next-generation regimen containing ABT-493, the prospects for further clinical development of Enanta s cyclophilin inhibitor for the treatment of HCV,

the prospects for advancing an FXR agonist for the treatment of NASH into clinical trials, the prospects for advancement of another program in HBV or RSV, and the projected sufficiency of Enanta s cash-equivalent resources and marketable

securities. Statements that are not historical facts are based on management s current expectations, estimates, forecasts and projections about Enanta s business and the industry in which it operates and 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 and risks that may affect

actual results include: Enanta s revenues are dependent upon the success of AbbVie s planned regulatory approval and commercialization efforts for its HCV treatment regimens containing

paritaprevir; Enanta s longer term revenues will be dependent upon the success of AbbVie s planned clinical development and commercialization of next-generation regimens containing ABT-493; regulatory actions affecting any approval of an

HCV treatment regimen containing ABT-493; the pricing, market acceptance and reimbursement rates of treatment regimens containing paritaprevir or ABT-493 compared to competitive HCV products on the market and product candidates of other companies

under development; the discovery and development risks of early stage discovery efforts in new disease areas such as HBV, NASH and RSV; potential competition from the development efforts of others in those new disease areas; Enanta s lack of

clinical development experience; Enanta s need to attract and retain senior management and key scientific personnel; Enanta s need to obtain and maintain patent protection for its product candidates and avoid potential infringement of the

intellectual property rights of others; and other risk factors described or referred to in Risk Factors in Enanta s most recent Form 10-K for the fiscal year ended September 30, 2015 and other periodic reports filed more

recently with the Securities and Exchange Commission. 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.

ENANTA PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(in thousands, except per share amounts)

ENANTA PHARMACEUTICALS, INC.

CONDENSED CONSOLIDATED BALANCE SHEETS

Enanta Pharmaceuticals, Inc.

MacDougall Biomedical Communications