In celebration of Medscape's 25th birthday, we are highlighting key breakthroughs that have defined the last quarter century of medicine, as chosen by experts in their respective fields.
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 (eg, ledipasvir), the NS5B nonnucleoside inhibitors (eg, dasabuvir), and NS5B nucleoside inhibitors (eg, 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 US Food and Drug Administration (FDA) 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 (AASLD) and the Infectious Diseases Society of America (IDSA) 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 $1000 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.
Moving Toward Noninvasive Tests
While curative therapy has revolutionized HCV management, innovation in diagnostics eliminated a significant barrier in access to therapy: the liver biopsy.
Staging, or accurately identifying advanced fibrosis in persons infected with HCV, is essential for long-term follow-up. The presence of advanced disease affects drug choices, especially before the approval of all-oral therapy. Historically, a liver biopsy was obligatory before treatment. Invasive with a significant risk for complications, this requirement effectively prevented treatment in those who were unwilling to undergo the procedure and deterred those at risk from even being tested.
Over the past 25 years, numerous methods to noninvasively assess for liver fibrosis have been used. Serum biomarkers can be either indirect (based on routine tests) or direct (reflecting components of the extracellular matrix). Although highly available, they are only moderately useful for identifying advanced fibrosis and thus cannot replace liver biopsy in the care cascade. The technique of elastography dates back to the 1980s, though the role of vibration-controlled transient liver elastography in the assessment of hepatic fibrosis in patients with HCV was not recognized until around 2005 and it was not commonly used for nearly another decade.
Yet, a paradigm shift in the care cascade occurred with the release of the AASLD/IDSA guidance document in 2014. For the first time in the United States, noninvasive tests were recommended as first-line testing for the assessment of advanced fibrosis. Prior guidelines specifically stated that although noninvasive tests might be useful, they "should not replace the liver biopsy in routine clinical practice." Current guidelines recommend combining elastography with serum biomarkers and considering biopsy only in patients with discordant results if the biopsy would affect clinical decision-making.
The Last Frontier
Curative therapy has also allowed the unthinkable: willingly exposing patients to the virus through donor-positive/recipient-negative solid organ transplant. Traditionally, an HCV-infected donor would be considered only for an HCV-positive recipient; however, with effective DAA therapy, the number of HCV actively infected patients in need of transplant has dwindled.
Unfortunately as a consequence of the opioid epidemic, the HCV-exposed donor population has blossomed. Given that HCV therapy is near universally curative, using organs from HCV-viremic donors can greatly expand the organ transplantation pool. Small studies[1,2,3,4,5] have demonstrated the safety and efficacy of this approach, both in HCV-positive liver donors as well as in other solid organs.
A Disease Pegged for Elimination
In the past 25 years, HCV has evolved from non-A, non-B hepatitis into a disease pegged for elimination. This is a direct reflection of improved therapeutics with highly effective DAAs. Yet, without improved diagnostics, we would be unable to navigate patients through the clinical care cascade. These incredible strides in diagnostics and therapeutics allow us to push the cutting edge through iatrogenic infection of organ recipients, while recognizing that the largest hurdle to elimination remains in finding those who are chronically infected. Ultimately, the crux of elimination remains unchanged over the past 25 years and resides in screening and diagnosis with effective linkage to care.
Donald M. Jensen, MD, is a professor of medicine at Rush University Medical Center. He was previously the director of the Center for Liver Disease at the University of Chicago until 2015. His research interest has been in newer HCV therapies. He recently received the Distinguished Service Award from the AASLD for his many contributions to the field.
Nancy S. Reau, MD, is chief of the hepatology section at Rush University Medical Center in Chicago and a regular contributor to Medscape. She serves as editor of Clinical Liver Disease, a multimedia review journal, and recently as a member of HCVGuidelines.org, a web-based resource from the AASLD and the IDSA, as well as educational chair for the AASLD hepatitis C special interest group. She continues to have an active role in the hepatology interest group of the World Gastroenterology Organisation and the American Liver Foundation at the regional and national levels.
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Any views expressed above are the author's own and do not necessarily reflect the views of WebMD or Medscape.
Cite this: Vanquishing Hepatitis C: A Remarkable Success Story - Medscape - Nov 17, 2020.