Abbott and Enanta Present Positive 12-Week Results and 3-Day Resistance Data From Phase 2 Study of ABT-450/r for Treatment of Hepatitis C

ABBOTT PARK, Illinois, and WATERTOWN, Massachusetts, April 4, 2011 - Abbott (NYSE: ABT) and Enanta Pharmaceuticals today announced 12-week
results from a Phase 2 study of ABT-450/r, an investigational, oral protease
inhibitor being developed for the treatment of hepatitis C (HCV) infection.
Study results show that 92 percent (22 of 24) of patients taking ABT-450/r
once daily, combined with standard of care, achieved complete early virologic
response (HCV RNA levels <25 IU/mL) at 12 weeks. Results were presented at
the European Association for the Study of Liver Disease (EASL) annual meeting
in Berlin.

Key findings:

    - At week 12, 92 percent of patients receiving ABT-450/r (ABT-450 with
      100 mg of ritonavir to support once-daily dosing) in combination with
      standard of care (SOC) - pegylated interferon alpha and ribavirin
      (pegIFN/RBV) - achieved HCV RNA <25 IU/mL
    - In a separate analysis of 3-day resistance data, ABT-450/r dosed at
      200/100 mg appeared to more consistently suppress the emergence of
      ABT-450-associated resistant variants than the 50/100 mg and 100/100 mg
      doses
    - Previously presented 3-day and 4-week results from the study had
      suggested the ABT-450/r demonstrated significant antiviral activity in
      treatment-naive adults
    - After three days, treatment with ABT-450/r alone resulted in 4-log
      (10,000-fold) mean reductions of HCV RNA, across the three dose ranges
      of ABT-450 (50 mg, 100 mg, 200 mg, once-daily dosing)

"A significant number of HCV patients are unable to begin treatment with
peginterferon and ribavirin, and for those that do begin treatment, more than
50 percent will not be cured," said Fred Poordad, M.D., chief of hepatology
at the Liver Disease and Transplant Center at Cedars-Sinai Medical Center in
Los Angeles, and one of the investigators for the study. "These results
suggest that ABT-450/r could be an important component in combination therapy
approaches to treating HCV."

"Abbott is working to transform treatment options for patients with HCV
infection by investigating ways to simplify treatment and increase cure
rates," said Scott Brun, M.D., divisional vice president, infectious disease
development, Abbott. "We will continue to explore the use of ABT-450/r and
our other investigational HCV treatments in a variety of patient populations
and combinations, with and without pegylated interferon alpha."

"We continue to be encouraged by the results for ABT-450/r and the
potential it holds for treatment-experienced and treatment-naive patients
with HCV," said Jay Luly, Ph.D., president and chief executive officer,
Enanta Pharmaceuticals.

Study Objectives and Design

The objectives of the 48-week Phase 2 study are to assess the safety,
tolerability, pharmacokinetics, and antiviral activity of multiple dose
strengths of ABT-450/r in treatment-naive adults infected with HCV genotype
1, which is the most common and difficult to treat form of the infection in
the developed world. Trial endpoints include early virologic response and
rapid virologic response. Initial antiviral activity was evaluated via a
3-day treatment period during which ABT-450/r was administered alone.
Subsequently, ABT-450/r was administered with pegIFN/RBV (SOC) for 12 weeks,
followed by treatment with SOC alone for an additional 36 weeks. Participants
are then monitored post therapy for 24 weeks for sustained virologic
response.

In the trial, the most common adverse events reported in subjects
receiving ABT-450/r in combination with pegIFN/RBV were headache, fatigue,
insomnia and depression. A similar proportion of subjects reported at least
one adverse event in all treatment groups, including placebo.

ABT-450 is being developed with low-dose ritonavir, which enhances the
pharmacokinetic properties of ABT-450, allowing for once-daily dosing. The
use of ritonavir 100 mg with ABT-450 for the treatment of HCV is
investigational.

About the Hepatitis C Virus

Hepatitis C is a liver disease affecting more than 180 million people
worldwide. The virus is primarily spread through direct contact with the
blood of an infected person. HCV increases a person's risk of developing
chronic liver disease, cirrhosis, liver cancer and death.

Liver disease associated with HCV infection is growing rapidly, and
current therapies only cure about half of patients with the genotype 1 form
of the virus. Specifically targeted antiviral therapies for HCV, such as
protease inhibitors and non-nucleoside polymerase inhibitors, may have the
potential to increase the proportion of patients in whom the virus can be
eradicated.

Ritonavir Use in Treatment of HIV

Ritonavir is in a class of medicines called the HIV protease inhibitors.
Ritonavir is used in combination with other anti-HIV medicines to treat
people with human immunodeficiency virus (HIV) infection. Ritonavir is for
adults and for children greater than 1 month in age and older.

Ritonavir does not cure HIV infection or AIDS and does not reduce the
risk of passing HIV to others. People taking ritonavir may still get
opportunistic infections or other conditions that happen with HIV infection.
Some of these conditions are pneumonia, herpes virus infections, and
Mycobacterium avium complex (MAC) infections.

Ritonavir Safety in Treatment of HIV

Patients should not take ritonavir with certain medicines, as these can
cause serious or life-threatening problems such as irregular heartbeat,
breathing difficulties, or excessive sleepiness. Patients should not take
ritonavir if they have had a serious allergic reaction to any of its
ingredients. Some patients taking ritonavir may develop liver and pancreas
problems, which can cause death. Patients may develop large increases in
triglycerides and cholesterol, diabetes, high blood sugar, changes in body
fat, increased bleeding in people with hemophilia, allergic reactions, and/or
changes in heart rhythm. Patients may develop signs and symptoms of
infections that they already have after starting anti-HIV medicines.

For more information, please see the Important Safety Information
(www.norvir.com/important-safety-information.cfm) and full Prescribing
Information (www.rxabbott.com/pdf/norpi2a.pdf) for ritonavir.

About Enanta

Enanta Pharmaceuticals is a research and development company that uses
its novel chemistry approach and drug discovery capabilities to create best
in class small molecule drugs in the infectious disease field. Enanta is
developing novel protease, NS5A, nucleoside(tide) polymerase, and
cyclophilin-based inhibitors targeted against the Hepatitis C virus (HCV).
Additionally, the Company has created a new class of macrolide antibiotics,
called Bicyclolides, which overcomes bacterial resistance. Antibacterial
focus areas include superbugs, respiratory tract infections, and intravenous
and oral treatments for hospital and community MRSA. Enanta is a privately
held company headquartered in Watertown, Mass. Enanta's news releases and
other information are available on the company's web site at
www.enanta.com.

About Abbott

Abbott's HCV development programs include its partnership with Enanta
Pharmaceuticals to discover protease inhibitors, as well as internal programs
focused on additional viral targets, including polymerase inhibitors. Abbott
currently has four HCV compounds in phase 2 clinical trials, including a
protease inhibitor, two polymerase inhibitors and an NS5A inhibitor. Abbott
is well positioned to explore combinations of these compounds, a strategy
with the potential to markedly transform current treatment practices.

Abbott is a global, broad-based health care company devoted to the
discovery, development, manufacturing and marketing of pharmaceuticals and
medical products, including nutritionals, devices and diagnostics. The
company employs nearly 90,000 people and markets its products in more than
130 countries.

Abbott's news releases and other information are available on the
company's Web site at www.abbott.com.

Media, Tracy Sorrentino, +1-847-937-8712, or Financial, Larry Peepo, +1-847-935-6722, both of Abbott; or Media, Kari Watson, +1-781-235-3060, or Financial, Paul Mellett, +1-617-607-0761, both of Enanta