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Phase III study of a therapeutic vaccine candidate (NASVAC)
containing the hepatitis B virus core antigen (HBcAg)
and the HBV surface antigen (HBsAg) for treatment of patients
with chronic hepatitis B
Mamun-Al-Mahtab1, Mohammed Fazle Akbar2, Julio Ce´sar
Aguilar3, Vincent Serra4, Salimur Rahman1, Pascale Berthillon5,
Christian Trepo5, Josianne Nitcheu4, Pierre Vandepapelie`re4,
Gerardo Enrique Guillen Nieto3
1Department of Hepatology, Bangabandhu Sheikh Mujib Medical
University, Dhaka, Bangladesh, 2Toshiba General Hospital, Tokyo,
Japan, 3Center for Genetic Engineering and Biotechnology, Havana,
Cuba, 4Wittycell, Evry, France, 5INSERM 1052/CRCL, Lyon France
Background and aims: Curative therapies for patients with chronic
Hepatitis B (CHB) include pegylated interferon-alpha (pegIFN-a) and
nucleot(s)ide analogues (NUCs). However, pegIFN-a is effective in
approximately one-third of the treated patients only, while the need for
long term treatment is the main limitation of NUCs. Because immune
responses are impaired in patients suffering from CHB, therapeutic
vaccination has become an important strategy to help viral clearance, by
stimulating patients’ hepatitis B specific immune responses. We have
developed a therapeutic vaccine candidate (NASVAC) which is based
on the use of a combination of recombinant HBsAg and HBcAg. We
conducted a phase III clinical study in Bangladesh to evaluate the
clinical efficacy of repeated intranasal/subcutaneous immunizations of
NASVAC to CHB patients to reduce serum HBV DNA levels and to
induce HBsAg/HBeAg clearance or seroconversion.
Methods: One hundred and sixty subjects (of whom 20 % were
HbeAg positive and 80 % HBeAg negative) naı¨ve to anti-HBV
treatment for at least 6 months were randomly assigned to one of the
two following regimens: either NASVAC (100 mcg antigen per
dose), five intranasal (IN) inoculations every 14 days during the first
cycle followed by 5 IN and 5 subcutaneous (SC) inoculations every
14 days during the second cycle of inoculation for a total duration of
24 weeks or weekly SC injections of pegIFN-a for 48 weeks. Patients
in both groups were evaluated over time at week 12, 24, 48, 72 and 96
after beginning of the treatment for serum HBVDNA (quantitative
PCR), ALT, AST, HBeAg, HBsAg, and for safety.
Results: NASVAC was safe and well tolerated inducing reactions
similar to those caused by pegIFN-a but less frequently and less
severe. Both treatments induced a strong and similar antiviral
response during therapy. After cessation of treatment HBV DNA
levels increased again in both groups, but at very different rates. At
week 72 (24 weeks after the end of pegIFN-a treatment and 48 weeks
after the end of NASVAC treatment), the HBV DNA levels were
significantly lower in the NASVAC group than in the pegIFN-a group
(p = 0.03), with almost 80 % of NASVAC treated patients remaining
under 10’000 c/mL. This delayed rebound in the NASVAC group
suggests a sustained antiviral effect as compared to the pegIFN-a
group. Similarly, while at the end of treatment the percentage of
patients with HBeAg loss was similar in both groups (NASVAC 50 %
at week 24; pegIFN-a 55 % at week 48), at week 96 the percentages
in the NASVAC and pegIFN-a groups were 62 and 33 %
respectively. The level of HBsAg in the pegIFN-a group decreased
following treatment until W48, and then increased back to the baseline
levels at W96. However, while no difference in the level of
HBsAg was found from baseline until W72 in the NASVAC group,
the treatment had a significant influence on lowering the HBsAg at
W96 follow-up (p = 0.0074).
Conclusions: The data presented here demonstrate that therapeutic
vaccination with NASVAC has a profound antiviral effect that is
more sustained than pegIFN-a after the end of treatment. This delayed
viral rebound is accompanied by a sustained HBeAg loss. These
results do support further developments to evaluate the therapeutic
potential of NASVAC in endemic regions.
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