Tenofovir alafenamide may prevent HBV mother-to-child transmission

Tenofovir alafenamide (TAF), administered during the second or third trimester of pregnancy, may prevent mother-to-child transmission (MTCT) of hepatitis B virus (HBV) infection, according to two studies presented as posters at ILC 2021.

Participants in the first study were 89 pregnant women aged 20–35 years (mean age 28.82 years) with chronic HBV (HBeAg-positive, HBV DNA ≥1x10⁶ IU/mL [mean 7.94 IU/mL]). They received oral TAF (25 mg/day) from 24–28 weeks gestation (initiated at a mean 25.04 weeks) until week 4 postpartum. All infants received HBV immunoprophylaxis and mothers and infants were followed up until week 28 postpartum. At analysis, all women had delivered. The women received TAF for a mean 14.3 weeks before delivery.

Eighty-two percent of women had HBV DNA levels <2x10⁵ IU/mL at delivery, with 21.4 percent having HBV DNA levels <500 IU/mL. [ILC 2021, abstract PO-797]

Serum phosphate levels did not significantly change between baseline and delivery (mean 1.20 vs 1.21 mmol/L). Serum creatinine levels were higher at delivery compared with baseline (mean 52.23 vs 45.97 μmol/L; p<0.05) but still within normal range.  

TAF treatment was well tolerated in all women with none experiencing serious drug-related adverse events.

TAF was discontinued by 92.1 percent of women at a median 5.9 weeks postpartum. None of the women experienced alanine aminotransferase flares while on TAF treatment during pregnancy, while nine women who discontinued TAF postpartum experienced mild flares (less than twice the upper limit of normal).

There were no congenital defects detected in the 91 infants born. Seventy-nine and 48 infants, respectively, were followed up until week 28 and 48 postpartum. HBsAg-positivity rate was 0 percent in 79 infants at 28 weeks and 48 infants at 48 weeks, with no evidence of growth retardation.

“Elimination of MTCT of HBV is crucial because chronic infection is more likely to develop when infection occurs early in life, particularly from birth through MTCT,” said study author Dr Guorong Han from The Affiliated Nanjing Hospital of Nanjing University of Chinese Medicine, Nanjing, China, and co-authors.

“TAF therapy initiated during the second trimester for HBV-infected pregnant women with HBeAg positive and HBV DNA level >1x10⁶ IU/mL was effective in preventing MTCT, and there were no safety concerns for mothers and infants with 28 weeks of follow-up after delivery,” they said.

A separate prospective study from Taiwan, this time comprising 57 pregnant women aged 20–45 years with HBV who were HBsAg and HBeAg seropositive and with HBV viral load >1,000,000 IU/mL, also showed a reduction in MTCT with TAF. The women received TAF (25 mg/day) from the third trimester until 2 weeks postpartum in 2019–2021 and their outcomes were compared with 53 pregnant women who received tenofovir disoproxil fumarate (TDF; 300 mg/day) in 2016–2018. Maternal age at delivery was comparable between TAF and TDF recipients (35.56 vs 34.56 years).

Reduction in HBV DNA levels between baseline and delivery was comparable between TAF and TDF recipients (mean reduction 3.90 vs 3.83 log₁₀ IU/mL; p=0.67). [ILC 2021, abstract PO-2619]

The proportion of women with HBV DNA levels <6.0 log₁₀ IU/mL at delivery was also similar between TAF and TDF recipients (94.7 percent vs 96.2 percent; p=1.00).

In the TAF group, one woman each experienced dry eye and nausea with both symptoms resolving spontaneously. In the TDF group, two women experienced nausea, one woman had skin itch, and another diarrhoea.

There were 62 infants born to women in the TAF group and 55 to women in the TDF group. Gestational age did not differ between groups (average 38.3 vs 38.7 weeks; p=0.17), nor did infant body weight (mean 2,958 vs 3,052 g; p=0.30).

Thirty-two and 55 infants in the TAF and TDF groups, respectively, were followed up until 12 months. Of these, none in the TAF group were HBsAg-positive at 12 months vs one in the TDF group; p=1.00). No major or minor congenital anomalies were detected.

“Short-term antiviral therapy for pregnant women with chronic HBV infection and high viral load has been recommended to prevent [MTCT],” said the authors.

“[This study showed that] the effects of TAF treatment for highly viraemic HBV-infected pregnant women were comparable with TDF treatment in terms of maternal HBV DNA reduction and in preventing MTCT,” they concluded.