Partial TDF responders achieve virologic response with treatment continuation
medwireNews: Most patients with chronic hepatitis B virus (HBV) infection initially classed as partial responders to treatment with tenofovir disoproxil fumarate (TDF) achieve a virologic response without additional treatment adjustment, research suggests.
Partial virologic responses to nucleos(t)ide analog therapy are associated with antiviral resistance in the case of less potent agents with a low genetic barrier, which is why guidelines have recommended adding another drug to the treatment regimen, the team explains. But studies of the highly potent HBV inhibitor entecavir have shown that such adjustment is not necessary as continuing entecavir alone is sufficient to eventually lead to undetectable viral DNA.
Given the lack of data regarding TDF – also a highly potent antiviral agent – in such a situation, the researchers, from the University of Ulsan College of Medicine in South Korea, examined the medical records of 391 chronic HBV patients treated with TDF for at least a year at their institution. Of these, 177 (45.3%) were considered partial responders as although they had achieved a reduction in HBV DNA levels of more than 1 log10 IU/mL, they still had detectable HBV DNA after 24 weeks of treatment.
With continued TDF therapy, 71.8% of these partial responders achieved a virologic response – defined as the absence of serum HBV DNA in two consecutive measurements – at a median of 14 months. And the cumulative virologic response rates in these patients were 42.4%, 79.7%, and 90.2% at months 12, 24, and 36, respectively.
These findings suggest that, as for entecavir, the “adjustment of antiviral therapy is unnecessary for therapy” for patients who achieve a partial virologic response to TDF, and that TDF can simply be continued as a single agent, the team comments in Digestive Diseases and Sciences.
Neung Hwa Park and co-authors also aimed to identify factors independently associated with the achievement of a partial virologic response, finding that absolute baseline HBV DNA levels and hepatitis B e antigen (HBeAg) positivity were significant predictors, with respective odds ratios (ORs) of 0.496 and 0.622 (p<0.001 and p=0.021, respectively).
HBV DNA levels at or above a cutoff of 6.0 log10 IU/mL were associated with a partial virologic response in 62.9% of patients, while levels below this cutoff were associated with a partial response in 21.9% of patients, a significant difference (p<0.001). Similarly, HBeAg-positive patients were significantly more likely to achieve a partial response than their HBeAg-negative counterparts, at 66.2% versus 16.9% (p<0.001).
The authors also found that serum HBV DNA at week 24 was the only factor significantly associated with subsequently achieving a virologic response (OR=0.342, p<0.001), such that a significantly higher proportion of individuals with levels below versus at or above 250 IU/mL had a virologic response, with overall rates of 84.9% and 22.8%, respectively (p<0.001).
Noting the observational and retrospective nature of their study, Park et al conclude that further studies with longer follow-up are needed to confirm their preliminary results.
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