Currently, there are about 350 million chronic HBV patients worldwide and nearly one million people die each year from HBV and related infections. The United States is the largest individual market with the highest absolute growth rate of HBV patients at around 15.4% through 2033 and around 9% growth in much of Europe.
Individuals with chronic hepatitis B are significantly more prone to developing cirrhosis of the liver and liver cancer. In fact, 20%-30% of all chronic hepatitis B patients develop these complications, and individuals with chronic hepatitis B are 100 times more likely to develop liver cancer than non-infected individuals. With limited efficacy of treatments for liver cancer and low survival rate (15%), the primary goal to develop a treatment targeted at suppressing HBV replication before these complications arise is important to increase longevity and fulfilling an unmet medical need.
The limited efficacy of current antiviral treatments highlights the need for new therapeutic tools for treating chronic HBV. Currently, there are seven FDA-approved drugs for the treatment of chronic HBV, including interferon-alpha, pegylated interferon-alpha, lamivudine, entecavir, telbivudine, adefovir dipivoxil, and tenofovir disporoxil fumarate. Despite these advances, no currently approved drug is completely effective at suppressing HBV replication permanently, but we are working on it.
For example, lamivudine often results in resistance development, with a 20% chance after one year and 70% chance after two years. Adefovir has a much lower rate of resistance development, but has a lower level of potency against HBV. Various combinations of treatment have respective advantages and disadvantages, with none being ideal. Nucleoside analog (“NA”) therapy has advantages over interferon therapy (“IFN”) including fewer side effects and easier administration. However, IFN therapy has the advantage of decreased frequency of resistance, and higher rates of HBeAg loss, but also disadvantages of high cost, limited patient response, and administration by injection with frequent side effects.
Tenofovir so far, is still is not completely effective in achieving the goals of chronic HBV therapy, which are to reduce the amount of detectable virus in the bloodstream of 95-100% of patients with no emergence of resistance, and the eradication of viral replication in the liver. However, in combination with other drugs such as entecavir, it is seen as the primary option for treatment, given its low cost, efficacy, and barrier to resistance development.