The FDA has just approved Victrelis and Incivek, drugs that directly inhibit viral replication of the most common strain of Hepatitis C virus. Although the number of new infections has decreased steeply over the last 20 years, Hepatitis is still very prevalent in the U.S. population. According to the CDC, over 3 million Americans live with chronic HCV infection. As many as one in five of these patients will progress to cirrhosis. Now, general practitioners, gastroenterologists, and hepatologists have additional therapies to consider for patients who are in the early stages of liver disease.
Merck’s Clinical Trial Results for Victrelis
Victrelis (boceprevir) was the first of these direct-acting antiviral genotype 1 HCV medications to be made available outside clinical trials in the U.S. The drug was tested with a patient cohort of 1,500 adults with compensated liver disease in two phase 3 clinical trials. Patients in the control groups were administered pegylated interferon and ribavirin while those in the test groups were treated with Victrelis in combination with these standard therapies. Two out of three patients receiving Victrelis showed a substantial increase in their sustained virilogic response (SVR) compared to the control group.
In all, an average of 62.5% of patients receiving the combination therapy experienced SVR (with no detectable levels of HCV at 6 months after the end of treatment) compared to an average of 29.5% receiving standard treatment alone. Overall, the success rates were similar for patients receiving HCV treatment for the first time and those for whom previous interferon and ribavirin medications had failed. Patients who were unresponsive to protease inhibitor treatment in other studies were not included in these trials. The clinical trial results for Incivek also demonstrated a high success rate for achieving SVR.
Potential Benefits of These Therapies
Because SVR is considered the equivalent of a cure for Hepatitis C, Victrelis and Incivek represent a significant step forward in disease treatment if the results found in testing are borne out in a “real world” patient care setting. Besides improving quality of life, the long term benefits could include reduction in the rates of severe cirrhosis and liver cancer, reducing the demand for liver transplants. Keeping patients virus-free may also reduce the rates of new infections in the general population by limiting exposure. Now that the FDA has approved these drugs for safety, Merck plans to launch its medication immediately. Shipments to pharmacies are scheduled for late May making it available for patient treatment right away.
Challenges Facing Doctors and Patients
Patients taking these drugs in the clinical trial phase frequently reported nausea and fatigue as side effects. Anemia was also a very common problem. Patients were permitted to receive treatment with erythropoietin or have their ribavirin dose adjusted during the trial; so the precise degree or frequency of anemia as a Victrelis complication is unclear. Rashes were a frequent and sometimes serious side effect with Incivek.
As with other protease inhibitors, these drugs cannot be prescribed alone since the virus will rapidly become resistant to their effects. The standard therapies for HCV already come with a long list of hard-to-tolerate reactions. Some patients may be reluctant to begin taking yet another medication with additional side effects.
The other issue that could delay widespread use of the new Hepatitis C medications is the somewhat complex treatment protocol. The prescribing information for these drugs has garnered negative publicity for being difficult to decipher. Merck recommends a response-guided approach to Victrelis therapy. For example, previously untreated HCV patients might begin with 28 weeks of interferon and ribavirin treatment (with Victrelis added to the standard medications at week four). An additional 20 week course would be prescribed after the initial 28 weeks is completed if HCV is still detectable in blood tests at week 8 after the introduction of Victrelis to the patient’s dosing regimen. The recommended course for patients previously treated for HCV is substantially different.
Communication and Cooperation Essential for Optimal Outcomes
Survey results published in December of 2010 in the Digestive Diseases and Sciences journal(1) reveal an interesting possibility about how the approval of direct-acting antiviral (DAA) medications may affect treatment practices. Most general practitioners (81%) stated they would still feel comfortable with evaluating and treating HCV patients after DAAs were made available. However, 10% said they would begin referring to a hepatitis expert instead (compared to 6% who would have referred patients to a specialist previously). This is an indication that greater collaboration may be needed between gastroenterologists, hepatologists, and general practitioners to ensure that patients receive the safest and most effective treatments available.
(1) Direct-Acting Antiviral Therapy for Hepatitis C: Attitudes Regarding Future Use; Paul J. Gaglio, Noah Moss, Camille McGaw, John Reinus
Source: http://www.natap.org/2011/APSL/fulltext-1.pdf
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