Wednesday, May 9, 2018

HCV genotype 4, 5 and 6 Cure Rates In Clinical Trials

In Case You Missed It

Journal of Viral Hepatitis
First published: 8 May 2018

HCV genotype 4, 5 and 6: Distribution of viral subtypes and sustained virologic response rates in clinical trials of approved direct‐acting antiviral regimens
S. D. Boyd P. Harrington T. E. Komatsu L. K. Naeger K. Chan‐Tack J. Murray D. Birnkrant K. Struble

First published: 25 March 2018

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Multiple direct‐acting antiviral (DAA)‐based regimens are now available for all hepatitis C virus (HCV) genotypes (GTs). Because HCV GT 4, 5 and 6 are less common in the United States (US) and worldwide, relatively small numbers of participants with these GTs were evaluated in individual clinical trials. To provide a comprehensive description of subtype diversity and treatment outcomes in clinical trials for these less common GTs, we analysed data from 744 participants with HCV GT4 (n = 573), GT5 (n = 81), or GT6 (n = 90) across 18 clinical trials of DAA regimens. These data are from US New Drug Applications submitted between 2014 and 2017, and our analyses included only approved regimens. Excluding unresolved or mixed subtypes, the distribution of reported GT4 subtypes was 49% 4a, 31% 4d and 16% for one of 14 other subtypes. The distribution of GT6 subtypes was 39% 6a, 27% 6e, 8% 6 L and 23% for one of 11 other subtypes. Across approved regimens, sustained virologic response rates 12 weeks post‐treatment (SVR12) for GT 4, 5 and 6 ranged from 91% to 100%, 93% to 97% and 96% to 100%, respectively. SVR12 by GT4 subtype ranged from 96% to 100% for 4a and 81% to 100% for 4d. Virologic failures occurred in GT 4a, 4b, 4d and 4r. For GT6, SVR12 was 100% for all subtypes except 6 L, for which 1 of 7 participants experienced virologic failure. To our knowledge, this is the largest compilation of HCV GT 4, 5 or 6 clinical trial data. These analyses may be useful for clinicians treating HCV GT 4, 5 or 6.

The recent FDA approvals of various IFN‐free DAA regimens provide highly effective treatment options for HCV GT 4, 5 or 6 infection. Individual registrational trials generally demonstrated high SVR12 rates in these populations, with virologic failure occurring in a small proportion of patients. To conduct a more comprehensive analysis of HCV GT 4, 5 and 6 patient populations in HCV DAA clinical trials, including treatment outcomes and viral subtypes represented, we conducted independent analyses of 18 registrational trials submitted to FDA from 2014 to 2017 in new drug applications (NDAs) for elbasvir/grazoprevir, glecaprevir/pibrentasvir, ledipasvir/sofosbuvir, ombitasvir/paritaprevir/ritonavir, sofosbuvir/velpatasvir and sofosbuvir/velpatasvir/voxilaprevir.

The analysis population comprises a substantially larger data set compared to individual clinical development programs for GT 4, 5 and 6 and allows for several observations. First, the combined clinical trial data in this analysis confirm that approved regimens for GT 4, 5 and 6 are all highly efficacious, with SVR12 rates similar to GT1. Overall, only a few participants did not achieve SVR12 with one of the FDA‐approved DAA regimens. No trends emerged associating virologic failure with baseline viral load, cirrhosis or prior treatment experience. Although limited sample sizes prevented statistical cross‐regimen comparisons, no clear differences in treatment efficacy emerged between any regimen with a reasonable sample size, and the few occurrences of virologic failure were distributed across different regimens.

A second observation is that the SVR12 rates for the most prevalent GT4 and GT6 subtypes either exceeded or corresponded with the SVR12 rates overall for these GTs. While the SVR12 rate for non‐4a, non‐4d GT4 subtypes was numerically lower, virologic failures in this group occurred only among participants with one of two uncommon subtypes, 4b and 4r. Extensive HCV genetic variability exists at multiple key NS5A resistance‐associated amino acid positions, both across and within different HCV subtypes.40 Recent studies have shown that reduced susceptibility to ledipasvir for some GT 4b and 4r isolates is associated with the presence of NS5A resistance‐associated substitutions, which may explain occurrences of ledipasvir/sofosbuvir virologic failure among patients with these subtypes.21, 41 Nevertheless, more data are needed with various NS5A inhibitor‐containing regimens before we can draw firm conclusions about the impact of NS5A genetic variability on treatment outcomes for patients with GT 4b, 4r and other less common subtypes. Importantly, the combined SVR12 rate for non‐4a, non‐4d GT4 subtypes across clinical trials still exceeded 90%. Because SVR12 rates were 100% for the most common GT6 subtypes, and only one participant with GT6 infection did not achieve SVR12, we cannot speculate on whether any of the less common GT6 subtypes may have a different response rate.

A third observation is our analysis confirms that the most common subtypes for GT4 and GT6 represented in clinical trials are consistent with previously published reports of subtype distribution in the United States, Europe and regions where these GTs are highly prevalent.40, 42, 43 For example, subtype 4a was not only the most common GT4 subtype in clinical trials that largely recruited participants located in the United States and Europe but is also the most common subtype in geographic areas with a high prevalence of GT4, such as Egypt.40, 42 Possibly, GT4 participants migrated from geographic areas where this genotype is highly prevalent, but specific demographic data such as geographic location of initial infection or country of origin usually were not available. Similarly, the two most common GT6 subtypes 6a and 6e observed in clinical trials are similar to previous reports.40

One limitation of our clinical trial analyses is the number of participants with uncommon subtypes was either low or not represented. This limitation makes it difficult to understand if treatment efficacy truly varies for certain infrequent subtypes and if baseline factors such as baseline viral load, presence of cirrhosis, HCV treatment history, or presence of baseline resistance‐associated substitutions affect response rates among different subtypes. However, we find the results reassuring because the SVR12 rates were close to 100% for the most common subtypes, and the overall SVR12 rates were high in the combined populations. Another limitation is that certain parts of the world (eg Sub‐Saharan Africa) are not well represented in clinical trials, and GT 4, 5 or 6 subtypes or other viral genetic characteristics may differ in these underrepresented regions.

This compilation of data from participants with HCV GT 4, 5 or 6 provides the largest pool of clinical trial data for FDA‐approved DAA regimens for these less common GTs. Combined clinical trial data enhance descriptive subgroup analysis such as frequency of viral subtypes and confirms high SVR12 or low virologic failure rates across FDA‐approved regimens. The geographic distribution of viral subtypes in our clinical trial database is consistent with the existing information on the general prevalence of these subtypes.

Overall, the data presented provide comprehensive information about efficacy including SVR and virologic failure rates. These analyses may be useful for clinicians treating patients with HCV GT 4, 5 or 6.

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