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February 8, 2012 8:08 am ET

Results of Pharmacokinetic Study in Healthy Volunteers May Indicate Clinically Significant Drug Interactions for Patients Co-Infected with Chronic Hepatitis C and HIV

Today, Merck (NYSE: MRK), known as MSD outside of the United States and Canada, said that it has informed U.S. physicians of the results of a recent pharmacokinetic study evaluating drug interactions between

VICTRELIS™ (boceprevir), the company’s oral chronic hepatitis C virus (HCV) NS3/4A protease inhibitor, and ritonavir-boosted HIV protease inhibitors in 39 healthy volunteers. In this study, concomitant administration of VICTRELIS with ritonavir (Norvir®) in combination with atazanavir (Reyataz®) or darunavir (Prezista®),or with lopinavir/ritonavir (Kaletra®) resulted in reduced exposures of the HIV medicines and VICTRELIS. These drug interactions may be clinically significant for patients infected with both chronic HCV and HIV by potentially reducing the effectiveness of the medicines when co-administered. Merck has shared these pharmacokinetic data with regulatory authorities in the countries where VICTRELIS is approved or under review for the regulatory agencies to review and to consider including these data in the labeling.

The safety and efficacy of VICTRELIS has not been established in patients co-infected with HIV and HCV. Merck does not recommend the co-administration of VICTRELIS and ritonavir-boosted HIV protease inhibitors.

“Though VICTRELIS is not indicated for the treatment of chronic HCV in those who are also infected with HIV, we recognize that some physicians have prescribed or may be considering prescribing VICTRELIS for patients taking ritonavir-boosted HIV protease inhibitors. We felt it was important to share these data as part of our commitment to patient safety and transparency,” said Robin Isaacs, vice president, Clinical Research, Infectious Diseases, Merck Research Laboratories. “What is most critical to remember is that all patients taking medicines for chronic HCV or HIV, or both, should not discontinue their medication regimens without first consulting with their physicians.”

In addition to notifying regulatory agencies of these results, Merck has informed the French National Agency for Research on AIDS and Viral Hepatitis (ANRS) and the AIDS Clinical Trials Group (ACTG), two organizations with whom Merck is collaborating on HCV/HIV coinfection clinical trials. Investigational studies evaluating the effectiveness and safety of VICTRELIS in patients co-infected with chronic HCV genotype 1 and HIV-1 are ongoing.

Indications and usage for VICTRELIS

VICTRELIS is indicated for the treatment of chronic hepatitis C virus (HCV) genotype 1 (G1) infection, in combination with peginterferon alfa and ribavirin (P/R), in adult patients (18 years and older) with compensated liver disease, including cirrhosis, who are previously untreated or who have failed previous interferon and ribavirin therapy.

The following points should be considered when initiating VICTRELIS for treatment of chronic HCV infection:

• VICTRELIS must not be used as monotherapy and should only be used in combination with peginterferon alfa and ribavirin.
• VICTRELIS efficacy has not been studied in patients who have previously failed therapy with a treatment regimen that includes VICTRELIS or other HCV NS3/4A protease inhibitors.
• VICTRELIS in combination with peginterferon alfa and ribavirin has not been studied in patients documented to be historical null responders (less than a 2 log HCV-RNA decline by treatment week 12) during prior therapy with peginterferon alfa and ribavirin. The clinical studies included patients who were poorly interferon responsive. Patients with less than 0.5 log HCV-RNA decline in viral load at treatment week 4 with peginterferon alfa plus ribavirin alone are predicted to have a null response (less than a 2 log viral load decline by treatment week 12) to peginterferon alfa and ribavirin therapy.
• Poorly interferon responsive patients who were treated with VICTRELIS in combination with peginterferon alfa and ribavirin have a lower likelihood of achieving a sustained virologic response (SVR), and a higher rate of detection of resistance-associated substitutions upon treatment failure, compared to patients with a greater response to peginterferon alfa and ribavirin.

Primary pharmacokinetic study results

The study was a single-center, three-arm, open-label, drug-interaction study in 39 healthy adults. Patients received 800 mg of VICTRELIS three times daily on Days 1-6. Following a 4-day “washout” period, patients received either 300 mg of atazanavir/100 mg of ritonavir once daily, 400 mg of lopinavir/100mg of ritonavir twice daily, or 600 mg of darunavir/100 mg of ritonvair twice daily on Days 10-31. From Days 25-31, patients also received 800 mg of VICTRELIS three times daily. Blood samples were collected for the pharmacokinetic assessment of the HIV medicines and VICTRELIS.

In the study, co-administration of VICTRELIS reduced mean trough concentrations of ritonavir-boosted atazanavir, lopinavir and darunavir by 49, 43 and 59 percent, respectively. Mean reductions of 34 to 44 percent and 25 to 36 percent were observed in AUC and Cmax of atazanavir, lopinavir and darunavir. Co-administration of ritonavir-boosted atazanavir with VICTRELIS did not alter the exposure of VICTRELIS, but co-administration of VICTRELIS with lopinavir/ritonavir or ritonavir-boosted darunavir decreased the exposure of VICTRELIS by 45 and 32 percent, respectively.

These data have been submitted for scientific presentation at an upcoming medical meeting. Interim data from the Phase IIb study evaluating the use of VICTRELIS in patients coinfected with chronic HCV and HIV-1 were presented at the Infectious Diseases Society of America in October 2011, and an update to those results also has been submitted for presentation at an upcoming medical meeting.

Important safety information about VICTRELIS

All contraindications to peginterferon alfa and ribavirin also apply since VICTRELIS must be administered with peginterferon alfa and ribavirin. Because ribavirin may cause birth defects and fetal death, VICTRELIS in combination with peginterferon alfa and ribavirin is contraindicated in pregnant women and in men whose female partners are pregnant. Avoid pregnancy in female patients and female partners of male patients. Patients must have a negative pregnancy test prior to therapy; have monthly pregnancy tests; and use two or more forms of effective contraception, including intrauterine devices and barrier methods, during treatment and for at least 6 months after treatment has concluded. Systemic hormonal contraceptives may not be as effective in women while taking VICTRELIS and concomitant ribavirin.

VICTRELIS is contraindicated in coadministration with drugs that are highly dependent on CYP3A4/5 for clearance, and for which elevated plasma concentrations are associated with serious and/or life-threatening events. VICTRELIS also is contraindicated in coadministration with potent CYP3A4/5 inducers where significantly reduced VICTRELIS plasma concentrations may be associated with reduced efficacy. Drugs that are contraindicated with VICTRELIS include: alfuzosin, carbamazepine, phenobarbital, phenytoin, rifampin, dihydroergotamine, ergonovine, ergotamine, methylergonovine, cisapride, St. John’s Wort (hypericum perforatum), lovastatin, simvastatin, drosperinone, Revatio® (sildenafil) or Adcirca® (tadalafil) (when used for the treatment of pulmonary arterial hypertension), pimozide, triazolam, and orally administered midazolam.

Anemia and/or Neutropenia — The addition of VICTRELIS to peginterferon alfa and ribavirin is associated with an additional decrease in hemoglobin concentrations compared to peginterferon alfa and ribavirin alone and/or may result in worsening of neutropenia associated with peginterferon alfa and ribavirin therapy alone. Dose reduction or discontinuation of peginterferon alfa and/or ribavirin may be required. Dose reduction of VICTRELIS is not recommended. VICTRELIS must not be administered in the absence of peginterferon alfa and ribavirin.

Complete blood counts (with white blood cell differential counts) must be conducted in all patients prior to initiating combination therapy with VICTRELIS. Complete blood counts should be obtained at treatment weeks 4, 8 and 12, and should be monitored closely at other time points, as clinically appropriate.

The most commonly reported adverse reactions (greater than 35 percent) in clinical trials in adult patients receiving the combination of VICTRELIS with peginterferon alfa and ribavirin were fatigue, anemia, nausea, headache and dysgeusia. Of these commonly reported adverse reactions, fatigue, anemia, nausea, and dysgeusia occurred at rates greater than or equal to 5 percent above the rates for peginterferon alfa and ribavirin alone in either clinical study. The incidence of these adverse reactions in previously untreated patients who were treated with combination therapy with VICTRELIS compared with peginterferon and ribavirin alone were: fatigue (58 vs. 59 percent), anemia (50 vs. 30 percent), nausea (46 vs. 42 percent) and dysgeusia (35 vs. 16 percent), respectively. The incidence of these adverse reactions in previous treatment-failure patients who were treated with combination therapy with VICTRELIS compared with peginterferon and ribavirin alone were: fatigue (55 vs. 50 percent), anemia (45 vs. 20 percent), nausea (43 vs. 38 percent) and dysgeusia (44 vs. 11 percent), respectively.

VICTRELIS is a strong inhibitor of CYP3A4/5 and is partly metabolized by CYP3A4/5. The potential for drug-drug interactions must be considered prior to and during therapy.

Please see U.S. prescribing information at:

http://www.merck.com/product/usa/pi_circulars/v/victrelis/victrelis_pi.pdf

Merck’s global commitment to advancing hepatitis therapy

Merck is committed to building on its strong legacy in the field of viral hepatitis by continuing to discover, develop and deliver vaccines and medicines to help prevent and treat viral hepatitis. In hepatitis C, company researchers developed the first approved therapy for chronic HCV in 1991 and the first combination therapy in 1998. In addition to ongoing studies with VICTRELIS, extensive research efforts are underway to develop additional innovative oral therapies for viral hepatitis treatment.

About Merck

Today’s Merck is a global healthcare leader working to help the world be well. Merck is known as MSD outside the United States and Canada. Through our prescription medicines, vaccines, biologic therapies, and consumer care and animal health products, we work with customers and operate in more than 140 countries to deliver innovative health solutions. We also demonstrate our commitment to increasing access to healthcare through far-reaching policies, programs and partnerships. For more information, visit www.merck.com and connect with us on Twitter, Facebook and YouTube.

Forward-Looking Statement

This statement includes “forward-looking statements” within the meaning of the safe harbor provisions of the United States Private Securities Litigation Reform Act of 1995. Such statements may include, but are not limited to, statements about the benefits of the merger between Merck and Schering-Plough, including future financial and operating results, the combined company’s plans, objectives, expectations and intentions and other statements that are not historical facts. Such statements are based upon the current beliefs and expectations of Merck’s management and are subject to significant risks and uncertainties. Actual results may differ from those set forth in the forward-looking statements.

The following factors, among others, could cause actual results to differ from those set forth in the forward-looking statements: the possibility that the expected synergies from the merger of Merck and Schering-Plough will not be realized, or will not be realized within the expected time period; the impact of pharmaceutical industry regulation and health care legislation; the risk that the businesses will not be integrated successfully; disruption from the merger making it more difficult to maintain business and operational relationships; Merck’s ability to accurately predict future market conditions; dependence on the effectiveness of Merck’s patents and other protections for innovative products; the risk of new and changing regulation and health policies in the United States and internationally and the exposure to litigation and/or regulatory actions.

Merck undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in Merck’s 2010 Annual Report on Form 10-K and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site (www.sec.gov).

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VICTRELIS™ is a trademark of Schering Corp., a subsidiary of Merck & Co., Inc., Whitehouse Station, N.J., USA.

Norvir®, Reyataz®, Prezista® and Kaletra® are trademarks of their respective owners and are not trademarks of Merck & Co., Inc., Whitehouse Station, N.J., USA.

Revatio® and Adcirca® are trademarks of their respective owners and are not trademarks of Merck & Co., Inc., Whitehouse Station, N.J., USA.

Please see Prescribing Information for VICTRELIS at http://www.merck.com/product/usa/pi_circulars/v/victrelis/victrelis_pi.pdf and Medication Guide for VICTRELIS at http://www.merck.com/product/usa/pi_circulars/v/victrelis/victrelis_mg.pdf.