Tenofovir Alafenamide Helpful for Chronic Hepatitis B Patients

Mandana Khalili, MD

Switching from tenofovir disoproxil fumarate (TDF) to tenofovir alafenamide (TAF) could be beneficial for patients with chronic hepatitis B (CHB).

In the first half of a phase 3 study, investigators demonstrated switching to tenofovir alafenamide compared to tenofovir disoproxil fumarate at week 48 for chronic hepatitis B patients who were virally suppressed on long-term TDF showed promise in achieving superior bone and renal safety.

In data presented at the annual American College of Gastroenterology (ACG) 2020 conference, a team, led by Mandana Khalili, MD, University of California San Francisco, reported the final efficacy and safety results from the study at week 96.

In the study, 488 patients with chronic hepatitis B taking TDF were evaluated for at least 48 weeks with HBV DNA < LLOQ (local lab) for >12 weeks and < 20 IU/mL at screening. Each patient was randomized to receive either TAF 25 mg qualifying dose (n = 243) or TDF 300 mg qualifying dose (n = 245) with a matching placebo. At week 48, each patient received open-label TAF 25 mg once daily for an additional 48 weeks.

The safety assessments in the study included changes in bone (hip and spine BMD) and renal (CrCl by Cockcroft-Gault [eGFRCG], serum creatinine) parameters. The investigators also assessed viral suppression and serological and biochemical responses in all patients.

Of the patient population, 472 individuals (997%; TAF, n = 235; TDF, n = 237) completed the 48 week double-blind treatment arm. Furthermore, 465 patients (95%; TAF, n = 233; TDF, n = 232) completed study treatment through week 96.

The investigators found virologic suppression (HBV DNA < 20 IU/mL) was similarly maintained at week 96 in patients who switched to TAF medications at baseline when compared to patients who switched to TAF after 48 weeks of TDF treatment.

In addition, the rates of ALT normalization increased in both groups at the conclusion of the study.

For the patients who switch to TAF at baseline, there were similar increases in spine BMD when compared to the patients who switched at week 48. However, increases in hip BMD were smaller. For the TDF arm of the study, eGFRCG ultimately decreased at week 48 -2.7mL/min), while an improvement was found after switching to TAF at week 96 (-0.39mL/min).

“In CHB patients on long-term TDF treatment who were switched to TAF, viral suppression was maintained, ALT normalization increased, and bone and renal safety parameters were improved at Week 96,” the authors wrote.

Currently, there are an estimated 257 million incidences of HBV infections worldwide.

The key to this is early screenings and detection, enabling doctors to start treatments as early as possible. There are several treatment options for patients, with new drugs currently being studied to further our ability to treat the virus.

The study, “A Phase 3 Study Comparing Switching: Tenofovir Disoproxil Fumarate (TDF) to Tenofovir Alafenamide (TAF) With Continued TDF Treatment in Virologically Suppressed Patients With Chronic Hepatitis B: Final Week 96 Results,” was published online by ACG 2020.