Commentary

Vanquishing hepatitis C: A remarkable success story


 

One of the most remarkable stories in medicine must be the relatively brief 25 years between the discovery of the hepatitis C virus (HCV) in 1989 to its eventual cure in 2014.

HCV afflicted over 5 million Americans and was the cause of death in approximately 10,000 patients annually, the leading indication for liver transplantation, and the leading risk factor for hepatocellular carcinoma, clearly signaling it as one of the era’s major public health villains. Within that span of time, it is the work beginning in the mid-1990s until today that perhaps best defines the race for the HCV “cure.”

In the early to mid-1990s, polymerase chain reaction techniques were just becoming commonplace for HCV diagnosis, whereas HCV genotypes were emerging as major factors determining response to interferon therapy. The sustained viral response (SVR) rates were mired at around 6%-12% for a 24- to 48-week course of three-times-weekly injection therapy. Severe side effects were common and there was a relatively high relapse rate, even in patients who responded to treatment.

By 1996, the addition of ribavirin to the interferon treatment was associated with a modest but significant improvement in SVR rates to above 20%. And by 2000, the use of pegylated interferon – allowing once-weekly injection therapy – along with ribavirin, improved SVR rates to above 50% for the first time. The therapy was still poorly tolerated but was associated with better compliance.

The real breakthrough in therapy came in the early 2000s with the discovery and availability of HCV protease inhibitors: telaprevir and boceprevir. These agents could induce a more rapid decline in viral replication than interferon but could not be administered alone owing to the rapid emergence of resistant HCV variants. Therefore, these agents were administered with interferon and ribavirin as a three-drug cocktail to take advantage of interferon to prevent emergence of resistant variants. Although SVR rates improved substantially to around 75%, adverse events also increased and limited its usefulness in patients with more advanced liver disease, precisely those who were most in need of better therapies.

Nonetheless, the incredible advances in understanding the replication machinery of HCV that led to the discovery of the protease inhibitors in turn led to further elucidation and unlocking of three additional classes of HCV protein targets and inhibitors: NS5A complex inhibitors (e.g., ledipasvir), the NS5B nonnucleoside inhibitors (e.g., dasabuvir), and NS5B nucleoside inhibitors (e.g., sofosbuvir). It quickly became apparent that the use of combinations of these direct-acting antivirals (DAAs) could limit emergence of resistant variants while also providing rapid and profound viral suppression. Because HCV required viral replication to persist in the hepatocyte, it became possible to induce HCV eradication, and thus cure, with combinations of DAAs.

In addition, investigators soon learned that the duration of therapy no longer needed to be the generally accepted 24-48 weeks for SVR, but instead could be reduced eventually to 8-12 weeks. This shortened treatment duration allowed for more rapid testing of new agents and combinations, and the field took a rapid step forward between 2011 and 2017. HCV cure rates rose to 90%-95%.

The competition for Food and Drug Administration approval of new agents among several pharmaceutical companies also meant that the time-honored process of issuing treatment guidelines every 3-5 years by societies would not be adequate. Therefore, in 2013, the American Association for the Study of Liver Diseases and the Infectious Diseases Society of America joined forces to establish more nimble and responsive online HCV guidance. This important resource debuted in January 2014 just as the FDA approved the first DAA therapies.

The high cost initially associated with many of these new therapies (up to $1,000 per pill) significantly limited uptake owing to insurance and health plan cost factors. Early on, the cost was also analyzed by price per cure, seemingly to justify the high cost by the high cure rate. However, advocacy and negotiations ultimately led to marked reductions in the cost of a course of therapy (with some therapies at $225 per pill), thus making these treatments now widely available.

By 2020, the HCV field has shifted from therapeutic development to improving the care cascade by enhanced identification and testing of unsuspected but HCV infected individuals. This is our current challenge.

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