TDF switch effective in Asian chronic HBV patients

Switching therapy to tenofovir disoproxil fumarate (TDF) is effective in treatment-resistant chronic hepatitis B, show results from a cohort of Asian patients.

Administration of TDF resulted in a sustained virological response in the majority of nucleos(t)ide analogue (NUC)-experienced patients after nearly 2 years of follow-up, report the researchers.

But the findings also showed that those with a high baseline level of hepatitis B virus (HBV) were significantly less likely to achieve a sustained virological response than patients with lower baseline levels.

The Hong Kong-based study involved 252 NUC-experienced patients who switched from treatment with other antiviral agents, such as lamivudine and adefovir dipivoxil, to TDF (300 mg/day) between 2009 and 2013, primarily due to drug resistance. Of these, 152 had persistent viraemia at the time of the switch while the remaining 100 had undetectable HBV DNA.

At a median of 22 months, 214 (84.9%) TDF-treated patients had achieved a sustained virological response, defined as HBV DNA levels of less than 20 IU/mL until the final follow-up visit. And, in the remaining patients, HBV DNA levels were low at the final follow-up, at a median of 1.48 log IU/mL, the team reports.

Meanwhile, 11 (13.4%) of 82 patients positive for hepatitis B e antigen (HBeAg) at baseline achieved HbeAg seroconversion after 25 months of TDF treatment.

Among the 100 patients with undetectable HBV DNA at the time of switch, 97 continued to have undetectable HBV DNA at 20 months.

However, the team noted a dose–response relationship between HBV DNA levels at the time of TDF initiation and status at follow-up. Indeed, in multivariate analysis, this was the only independent predictor that patients had a sustained virological response.

Using area under the receiver operating characteristic curve analysis, the team found that 20,000 IU/mL was the optimum threshold to predict which patients would achieve a sustained virological response. Below this threshold, only 59.7% did so compared with 93.2% of patients with HBV DNA levels above the threshold.

Writing in Alimentary Pharmacology & Therapeutics, the researchers say that this finding could indicate that poor responders need combined treatment.

“In patients with HBV DNA ≥20 000 IU/mL at time of switching to TDF and persistent detectable HBV DNA after 6 months of treatment, we suggest one may consider adding another potent agent such as ETV [entecavir] at the discretion of the physician with joint decision of the patient”, write Henry Chan (The Chinese University of Hong Kong) and co-authors.

They note that a previous study found that the TDF and ETV combination could induce complete viral suppression in 90% of previously treated patients with chronic HBV.

“Future prospective studies are warranted to evaluate this strategy in patients with incomplete virologic response to TDF switch therapy”, they conclude.

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