Enanta Pharmaceuticals Announces Investigational Regimen Containing Enanta’s Next-Generation Protease Inhibitor ABT-493 Demonstrates High Sustained Virologic Response Rates in Phase 2 Studies in Patients with Chronic Hepatitis C

• Data from AbbVie’s SURVEYOR-I and SURVEYOR-II studies demonstrate high sustained virologic response rates at 12 weeks post-treatment (SVR₁₂) in non-cirrhotic patients with genotype 1 (GT1), genotype 2 (GT2) and genotype 3 (GT3) chronic hepatitis C virus (HCV) infection
• Late-breaking data demonstrate 97 percent SVR₁₂ in GT1 non-cirrhotic HCV patients after 8 weeks of treatment with ABT-493 and ABT-530
• First patient enrolled in Phase 3 trials

WATERTOWN, Mass.--(BUSINESS WIRE)--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 announced data from AbbVie’s SURVEYOR studies of its investigational treatment regimen, consisting of ABT-493, an NS3/4A protease inhibitor, and ABT-530, an NS5A inhibitor, that show high rates of sustained virologic response at 12 weeks post-treatment (SVR₁₂) in non-cirrhotic patients with chronic hepatitis C virus (HCV) infection. After 12 weeks of treatment, SVR₁₂ rates achieved were 97-100 percent in genotype 1 (GT1) patients, 96-100 percent in genotype 2 (GT2), and 83-94 percent in genotype 3 (GT3).^1,2,3 These data will be presented at The Liver Meeting®, which is the Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in San Francisco.

Separately, in a late-breaking presentation of the SURVEYOR-1 trial, additional data will show non-cirrhotic GT1 chronic HCV patients who received a shorter duration of treatment for 8 weeks with ABT-493 and ABT-530 achieved a SVR₁₂ rate of 97 percent.⁴

SURVEYOR-I and SURVEYOR-II are ongoing Phase 2b clinical studies that evaluate the safety and efficacy of treatment with combinations of ABT-493 and ABT-530, with or without ribavirin (RBV), for 8 to 12 weeks. The data presented at the AASLD meeting will include non-cirrhotic patients with GT1, GT2 and GT3 chronic HCV infection. Data in additional patient populations (genotypes 4-6) will be presented at future meetings.

About SURVEYOR-I
SURVEYOR-I is an ongoing Phase 2b two-part study designed to evaluate the safety and efficacy of ABT-493 and ABT-530, with or without RBV, for 8 to 12 weeks, in cirrhotic and non-cirrhotic adult GT1 patients, and non-cirrhotic adult patients with genotypes 4, 5 or 6 chronic HCV infection who were new to therapy or did not respond to previous treatment with pegIFN/RBV (null responder).^1,4

In Part 1 of SURVEYOR-I, with 12 weeks of treatment, no patients discontinued treatment due to severe adverse events. The most commonly-reported DAA-related adverse reactions (>10 percent of patients) were fatigue, headache and nausea. One patient experienced a serious adverse event of metastatic prostate cancer, unrelated to the study drugs and had onset after completion of study treatment.¹ In Part 2, with 8 weeks of treatment, there were no study-related serious or severe adverse events reported. One subject discontinued the study at treatment week 4 due to adenocarcinoma, unrelated to study drugs. The most frequent adverse event (>5 percent of patients) was fatigue.⁴

About SURVEYOR-II
SURVEYOR-II is an ongoing Phase 2b three-part study designed to evaluate the safety and efficacy of ABT-493 and ABT-530, with or without RBV, in cirrhotic and non-cirrhotic adult patients with GT2 or GT3 chronic HCV infection who were new to therapy or had failed previous treatment with pegIFN/RBV.^2,3 In GT2 study patients, the most commonly-reported DAA-related adverse reactions (>10 percent of patients) were fatigue, nausea, diarrhea and headache. No GT2 study patients discontinued treatment due to an adverse event; one patient experienced a serious adverse event of atrial fibrillation unrelated to the study drugs.² In GT3 study patients, the most commonly-reported DAA-related adverse reactions (>10 percent of patients) were fatigue, nausea and headache. One patient discontinued treatment due to DAA- and RBV-related adverse events of abdominal pain and heat sensation. Two patients experienced a serious adverse event, one with pneumonia and one with B-cell lymphoma, both unrelated to the study drugs.³ Part 1 results of SURVEYOR-II are presented at AASLD.

Overview of SURVEYOR-I and SURVEYOR-II Clinical Data Presented at AASLD:
SURVEYOR-I (Genotype 1, Non-cirrhotic)
Number of Patients (n)/ Patient Population	Duration of Treatment	Treatment Arm	Treatment Regimen		SVR12 Rates
n=40 Treatment-naïve=63% pegIFN/RBV null responders=37%	12 Weeks	Arm A	ABT-493 (200mg) + ABT-530 (120mg) once daily		100% (n=40/40)
n=39 Treatment-naïve=64% pegIFN/RBV null responders=36%		Arm B	ABT-493 (200mg) + ABT-530 (40mg) once daily		97% (n=38/39)
n=34 Treatment-naïve=85% pegIFN/RBV treatment experienced=15%	8 weeks	Arm K (n=34)	ABT-493 (300mg) + ABT-530 (120mg) once daily		97% (n=33/34)
SURVEYOR-II (Genotype 2, Non-cirrhotic)
Number of Patients (n)/ Patient Population	Duration of Treatment	Treatment Arm	Treatment Regimen		SVR12 Rates
n=74 Treatment-naïve=88% pegIFN/RBV treatment experienced=12%	12 weeks	Arm A (n=25)	ABT-493 (300mg) + ABT-530 (120mg) once daily		96% (n=24/25)
		Arm B (n=24)	ABT-493 (200mg) + ABT-530 (120mg) once daily		100% (n=24/24)
		Arm C (n=25)	ABT-493 (200mg) + ABT-530 (120mg) once daily + RBV (weight-based, 1000 or 1200mg) twice daily		100% (n=25/25)
SURVEYOR-II (Genotype 3, Non-cirrhotic)
Number of Patients (n)/ Patient Population	Duration of Treatment	Treatment Arm		Treatment Regimen	SVR12 Rates
n=30 Treatment-naïve=90% pegIFN/RBV treatment experienced=10%	12 weeks	Arm D		ABT-493 (300mg) + ABT-530 (120mg) once daily	93% (n=28/30)
n=30 Treatment-naïve=93% pegIFN/RBV treatment experienced=7%		Arm E		ABT-493 (200mg) + ABT-530 (120mg) once daily	93% (n=28/30)
n=31 Treatment-naïve=90% pegIFN/RBV treatment experienced=10%		Arm F		ABT-493 (200mg) + ABT-530 (120mg) once daily + RBV (weight-based, 1000 or 1200mg) twice daily	94% (n=29/31)
n=30 Treatment-naïve=93% pegIFN/RBV treatment experienced=7%		Arm G		ABT-493 (200mg) + ABT-530 (40mg) once daily	83% (n=25/30)

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-493 is a protease inhibitor identified through the collaboration, as is paritaprevir, which is part of AbbVie’s existing approved regimens for HCV. AbbVie is Abbott’s successor under the agreement and is responsible for all development and commercialization activities for ABT-493, as well as paritaprevir.

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 for viral infections and liver diseases. Enanta has developed novel protease 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 partnered with AbbVie include paritaprevir, which is contained in AbbVie’s marketed DAA regimens for HCV, and ABT-493, Enanta’s next-generation protease inhibitor completing phase 2 development in combination with ABT-530, AbbVie’s next-generation NS5A inhibitor. Enanta also has a program to develop a host-targeted antiviral (HTA) inhibitor class for HCV targeted against cyclophilin, as well as another DAA program to develop nucleotide polymerase inhibitors. In addition, Enanta has a preclinical program in non-alcoholic steatohepatitis, or NASH, which is a condition that results in liver inflammation and liver damage caused by a buildup of fat in the liver.

Forward Looking Statements Disclaimer
This press release contains forward-looking statements, including statements with respect to the prospects for AbbVie’s next-generation treatment regimen under development for HCV. 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) regarding clinical development of ABT-493-containing regimens; the impact of competitive products on the regulatory requirements, use and sales of any ABT-493-containing regimen; 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, 2014 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.

¹ Poordad, F., et al. SURVEYOR-I: 98% – 100% SVR4 in HCV Genotype 1 Non-Cirrhotic Treatment-Naïve or Pegylated Interferon/Ribavirin Null-Responders with the Combination of the Next Generation NS3/4A Protease Inhibitor ABT-493 and NS5A Inhibitor ABT-530; Oral presentation #41; presented at The Liver Meeting®, the Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in San Francisco, November 13-17, 2015.

² Wyles, D., et al. SURVEYOR-II: High SVR4 Rates Achieved With the Next Generation NS3/4A Protease Inhibitor ABT-493 and NS5A Inhibitor ABT-530 in Non-Cirrhotic Treatment-Naïve and Treatment-Experienced Patients With HCV Genotype 2 Infection; Oral presentation #250; presented at The Liver Meeting®, the Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in San Francisco, November 13-17, 2015.

³ Kwo, P, et al. SURVEYOR-II: High SVR4 Rates Achieved With the Next Generation NS3/4A Protease Inhibitor ABT-493 and NS5A Inhibitor ABT-530 In Non-Cirrhotic Treatment-Naïve and Treatment-Experienced Patients With HCV Genotype 3 Infection; Oral presentation #248; presented at The Liver Meeting®, the Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in San Francisco, November 13-17, 2015.

⁴ Poordad, F., et al. 100% SVR4 in HCV Genotype 1 Non-Cirrhotic Treatment-Naïve or -Experienced Patients With the Combination of ABT-493 and ABT-530 for 8 Weeks (SURVEYOR-I); Poster presentation #; presented at The Liver Meeting®, the Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) in San Francisco, November 13-17, 2015.