Interim results (SVR4) from a phase II all-oral combination study of Simeprevir and Samatasvir (IDX719) for the treatment of hepatitis C

Stockholm, Sweden—Medivir AB (OMX: MVIR), announces that Idenix Pharmaceuticals,
Inc. today released interim data from the ongoing phase II HELIX-1 clinical
trial evaluating an all-oral, direct-acting antiviral (DAA) HCV combination
regimen of samatasvir (IDX719), Idenix’s once-daily pan-genotypic NS5A
inhibitor, and simeprevir , a once-daily protease inhibitor jointly developed by
Janssen R&D Ireland and Medivir AB, and ribavirin.

The combination regimen of the study was well-tolerated. In the treatment-naïve,
non-cirrhotic, genotype 1b or 4 HCV-infected patients receiving 50 mg of
samatasvir and 150 mg of simeprevir plus ribavirin for 12 weeks, 85 percent
(n=17/20) of the patients achieved SVR4 (undetectable HCV RNA four weeks after
end of treatment). The 50 mg dose of samatasvir is the selected dose in the
ongoing 3-DAA HELIX-2 clinical trial. The HELIX-1 study results are expected to
be presented at a scientific meeting in 2014.

HELIX-1 study design
The HELIX-1 trial is the first study in HCV-infected patients to commence under
a non-exclusive collaboration agreement between Idenix and Janssen which was
established in January 2013. The HELIX-1 trial is a phase II 12-week,
randomized, parallel group study evaluating the antiviral activity, safety and
tolerability of samatasvir and simeprevir in treatment-naïve, non-cirrhotic,
genotype 1b or 4 HCV-infected patients.

Patients in part A of the study (n=63) were enrolled in one of three treatment
groups receiving 50, 100, or 150 mg samatasvir once-daily for 12 weeks in
combination with 150 mg of simeprevir plus a weight-based dose of ribavirin. In
part B of the ongoing HELIX-1 study, exploratory cohorts of patients have been
added to evaluate the safety and antiviral activity of a 25 mg dose of
samatasvir in genotype 1b-infected patients and of a 100 mg dose of samatasvir
in genotype 6-infected patients.

A second phase II trial (HELIX-2) was initiated in December 2013 evaluating
samatasvir, simeprevir and TMC647055, a once-daily non-nucleoside polymerase
inhibitor plus a low-dose ritonavir being developed by Janssen, with and without
ribarivin in genotype 1-infected patients who are either treatment-naïve or have
previously relapsed after treatment with pegylated interferon and ribavirin.

For additional information about the HELIX-1 study, please visit
www.clinicaltrials.gov

For more information please contact:
Rein Piir, EVP Corporate Affairs & IR, mobile: +46 708 537 292

Medivir is required under the Securities Markets Act to make the information in
this press release public. The information was submitted for publication at
13.15 p.m. CET on 13 January 2014.

About Simeprevir
Simeprevir is an NS3/4A protease inhibitor jointly developed by Medivir and
Janssen R&D Ireland for the treatment of chronic hepatitis C infection in
combination with other antivirals in HCV genotype 1 and 4 infected subjects with
compensated liver disease, including cirrhosis.

Simeprevir was approved for the treatment of genotype 1 hepatitis C in September
2013 in Japan (trade name Sovriad™) and in the USA (trade name Olysio™) and
Canada (trade name Galexos™) in November. A Marketing Authorisation Application
was submitted to the European Medicines Agency (EMA) in April 2013 by Janssen
-Cilag International NV seeking approval of simeprevir for the treatment of
genotype 1 and genotype 4 chronic hepatitis C. To date, more than 3,700 patients
have been treated with simeprevir in clinical trials.

About Samatasvir (IDX719)
Samatasvir is an NS5A inhibitor with low picomolar, pan-genotypic antiviral
activity in vitro. To date, samatasvir has been safe and well-tolerated after
single and multiple doses of up to 150 mg in healthy volunteers up to 14 days
duration, and in HCV-infected patients up to 12 weeks duration. There have been
no treatment-emergent serious adverse events reported in the program. Samatasvir
has demonstrated potent pan-genotypic antiviral activity in HCV-infected
patients with mean maximal viral load reductions up to approximately 4.0 log10
IU/mL across HCV genotypes 1-4 in a proof-of-concept, three-day monotherapy
study.

About Medivir
Medivir is an emerging research-based pharmaceutical company focused on
infectious diseases. Medivir has world class expertise in polymerase and
protease drug targets and drug development which has resulted in a strong
infectious disease R&D portfolio. The Company’s key pipeline asset is
simeprevir, a novel protease inhibitor for the treatment of hepatitis C that is
being developed in collaboration with Janssen R&D Ireland. The company is also
working with research and development in other areas, such as bone disorders and
neuropathic pain. Medivir has also a broad product portfolio with prescription
pharmaceuticals in the Nordics.

For more information about Medivir AB, please visit the Company’s website:
www.medivir.com