NASVAC therapeutic vaccine may lead to functional cure of hepatitis B
Liz Highleyman
Published:
17 November 2020
NASVAC, an experimental therapeutic vaccine that targets two different hepatitis B virus (HBV) antigens, led to a reduction in hepatitis B surface antigen levels and several study participants achieved a functional cure after 18 months of follow-up, according to report at the AASLD virtual Liver Meeting this week.
Unlike the widely used vaccines for hepatitis B prevention, NASVAC aims to treat people who already have chronic HBV infection. The nasally administered vaccine contains both hepatitis B surface antigen (HBsAg) and core antigen (HBcAg). The combination triggers the production of anti-HBs antibodies and promotes T-cell activity against the virus.
Osamu Yoshida of Ehime University Graduate School of Medicine in Japan presented updated results from a study of 71 people who received ten doses of NASVAC and were followed for up to 18 months. At last year's Liver Meeting, he reported results after six months of follow-up.
The study included 29 participants taking nucleoside/nucleotide antiviral drugs and 42 asymptomatic untreated people; 22 and 33, respectively, reached the 18-month mark. Antivirals such as tenofovir disoproxil fumarate (Viread), tenofovir alafenamide (Vemlidy) and entecavir (Baraclude) can suppress HBV replication indefinitely during treatment, but they seldom lead to a cure.
In the antiviral group, about 70% were men, the median age was 54 years and about 75% were hepatitis B 'e' antigen (HBeAg) negative. HBV DNA was undetectable and the median HBsAg level was 464 IU/ml. In the untreated group, about half were women, the median age was 53 and 95% were HBeAg negative. The median viral load was 2.4 log10 IU/ml and the median HBsAg level was 1488 IU/ml. Both groups had ALT and AST liver enzyme levels within the normal range and most had HBV genotype C.
All participants received NASVAC every two weeks for a total of ten doses. The study used a modified version of the vaccine (initially developed by the Center for Genetic Engineering and Biotechnology in Cuba) that is formulated with a polymer to increase viscosity and is administered using a special device that disperses it over a larger surface area in the nasal cavity.
About three-quarters of participants in both groups experienced a reduction in HBsAg at six months, and this proportion remained similar at 18 months. HBsAg levels, however, continued to fall.
HBsAg declined by an average of about 16% from baseline in the antiviral group and by about 18% in the untreated group at six months. But by 18 months, the corresponding drops were approximately 25% and 28%, respectively. At that point, the median log reductions in the two groups were -0.159 and -0.299 log10 IU/ml, respectively.
Two participants in each group achieved HBsAg loss by six months – considered a functional cure – and two additional people in the untreated group did so by 18 months. Rates of HBsAg loss among those who remained in the study at 18 months were 9.1% and 12.1%, – considerably higher than rates typically seen in people treated with antiviral therapy alone.
Looking at antibody immune responses in the antiviral group, only one person (3%) tested positive for anti-HBs antibodies prior to receiving the vaccine. This rose to 10 out of 29 people (35%) at six months, but fell slightly to seven out of 22 (32%) at 18 months. In the untreated group, anti-HBs positivity rose from nine people (21%) before vaccination to 25 out of 42 (60%) at six months and fell to 20 out of 33 (58%) at 18 months.
Most participants maintained the same HBeAg and anti-HBe antibody status. However, four initially HBeAg-negative people in the antiviral group developed anti-HBe antibodies, and one initially HBeAg-positive participant in the untreated group became HBeAg negative. Among those who started out HBeAg positive in both groups, HBeAg levels dropped by 44% at six months and by 65% at 18 months.
HBV DNA remained suppressed in the antiviral group and decreased by about 19% in the untreated group. Levels of hepatitis B core-related antigen (HBcrAg), a biomarker of cccDNA, declined slightly, but the change was not statistically significant. This form of DNA persists in liver cells despite antiviral therapy and is a barrier to a cure.
Treatment was generally safe and well tolerated, with no severe adverse events. Yoshida reported last year that ALT levels remained stable in the antiviral group but some people in the untreated group experienced steep increases. One of them went on to experience HBeAg loss after an ALT flare.
In summary, Yoshida said, HBsAg levels continued to decline with longer follow-up after receiving NASVAC. Anti-HBs antibody levels rose after vaccine administration, but then gradually decreased during extended follow-up. A total of six people achieved a functional cure, including two who did so during the extended follow-up period.
"Nasal administration of NASVAC could be an effective and safe immune therapy for achieving functional cure" in chronic hepatitis B patients, the researchers concluded.
Reference
Yoshida O et al. HBsAg reduction by nasal administration of a therapeutic vaccine containing HBsAg and HBcAg (NASVAC) in patients with chronic HBV infection: the results of 18 months follow up. AASLD Liver Meeting Digital Experience, abstract 80, 2020.
在抗病毒組中,大約70%是男性,中位年齡是54歲,大約75%是乙肝'e'抗原(HBeAg)陰性。無法檢測到HBV DNA,中位HBsAg水平為464 IU / ml。在未經治療的組中,大約一半是女性,中位年齡為53歲,HBeAg陰性為95%。中位病毒載量為2.4 log10 IU / ml,中位HBsAg水平為1488 IU / ml。兩組的ALT和AST肝酶水平均在正常範圍內,多數為HBV基因型C。
Baseline predictors of response in HBeAg‐positive patients are low viral load, high serum ALT levels, i.e. >2‐5 times x upper limit of normal (ULN), younger age, female gender, HBV genotype and high activity scores on liver biopsy. HBV genotypes A and B have been associated with higher rates of HBeAg seroconversion and HBsAg loss than genotypes C and D. A baseline score system (from 0 to 8) including 5 factors: female gender, quantitative HBsAg (qHBsAg), HBV genotype, ALT, HBV DNA predicted the patients with higher chance of response to Peg‐IFNα2a. Out of 443 treated patients, 134 (30%), 164 (37%), and 110 (25%) had HBV DNA ≤2000 IU/mL, HBeAg seroconversion, and a combined response (HBV DNA ≤2000 IU/mL and HBeAg seroconversion 1‐year post‐treatment), respectively. In patients with baseline scores ≥5, 63% (40/63) and 43% (27/63) had HBeAg seroconversion and a combined response, respectively, compared to a very low rate (5%, 2/43) in patients with scores of 0‐1 (95% negative predictive value [NPV]).8 High baseline ALT, low serum HBV DNA, younger age, female gender and HBV genotype were independent predictors of response in HBeAg‐negative patients. Patients with genotypes B or C infection had a better chance of response than those with genotype D. A baseline score system (from 0 to 7) that combined five variables: HBV genotype, HBV DNA, ALT, qHBsAg and age identified patients with a high and low likelihood of response. HBV DNA<2000 IU/mL and HBV DNA<2000 IU/mL plus normal ALT 48 weeks after EOT were achieved in 61% and 45% of patients with baseline scores ≥4, respectively, but in only 11% and 8% of patients with scores 0‐1 with a 89% and 92% NPV, respectively.9
Unfortunately, the fluctuating pattern of serum HBV DNA and ALT tends to make the prediction of response using these variables difficult. Thus, other pretreatment predictors of response to IFN‐based treatment were searched for using a genome‐wide association (GWAS) analysis of SNPs rs12979860 and rs8099917 mapping in the genomic region 3 kb upstream of the gene codifying for IL28B on chromosome 19, now renamed IFN lambda 4 (IFNλ4). However, the preliminary observations of an association between favorable IFNλ4 polymorphisms and increased chances of a sustained virological and serological response in both HBeAg‐positive and ‐negative patients were not confirmed in subsequent studies.10 Recently, IFNλ4 rs368234815 and rs117648444 variants were reported to strongly predict HBsAg clearance in 126 HBeAg‐negative patients treated with IFN and followed up for a median of 11 1-23 years.11 This study reported that the 15‐year cumulative probability of HBsAg loss in the 62 carriers of the rs368234815 TT/TT genotype, which abolishes IFNλ4 protein production and in the 19 patients carrying the rs117648444 T allele, which produces an impaired IFNλ4‐S70 protein, was significantly higher than in the 45 subjects who encoded only the fully functional IFNλ4‐P70 (42% vs 11%, P = .003). On multivariate analysis, a combination of the rs368234815 and rs117648444 genotypes strongly predicted HBsAg clearance (HR 5.90, 95% CI 1.70‐20.9, P = .006) together with pretreatment serum HBV DNA levels (HR 0.57, 95% CI 0.39‐0.83, P = .003). However, until further studies confirm these results in large cohorts of homogeneous ethnic and virological groups, baseline host genetic testing to prioritize CHB patients for Peg‐IFN therapy is not recommended in clinical practice.12 2.1 Peg-IFN反应的基线预测因子
HBeAg阳性患者反应的基线预测指标是低病毒载量,高血清ALT水平,即> 2-5倍x正常上限(ULN),年轻,女性,HBV基因型和肝活检活动评分高。 HBV基因型A和B与基因型C和D相比具有更高的HBeAg血清转化率和HBsAg丢失率。基线评分系统(从0到8)包括5个因素:女性,女性,定量HBsAg(qHBsAg),HBV基因型,ALT ,HBV DNA预测患者对Peg‐IFNα2a有更高的反应机会。在443例接受治疗的患者中,134(30%),164(37%)和110(25%)的HBV DNA≤2000 IU / mL,HBeAg血清转化以及合并反应(HBV DNA≤2000 IU / mL和HBeAg血清转化1年后)。在基线评分≥5的患者中,分别有63%(40/63)和43%(27/63)的患者发生HBeAg血清转化和合并反应,而在HBsAg评分较低的患者中(5%,2/43)评分为0-1(95%阴性预测值[NPV])。8高基线ALT,低血清HBV DNA,年龄,女性性别和HBV基因型是HBeAg阴性患者反应的独立预测因子。基因型为B或C的患者比基因型为D的患者有更好的反应机会。基线评分系统(从0到7)结合了五个变量:HBV基因型,HBV DNA,ALT,qHBsAg和年龄高的患者且回应可能性低。 EOT后48周,HBV DNA <2000 IU / mL和HBV DNA <2000 IU / mL以及正常ALT分别达到基线评分≥4的患者的61%和45%,但分别只有11%和8%的患者得分0-1分别具有89%和92%的净现值9。
Reports of a decline in HBsAg in HBeAg‐negative and ‐positive patients receiving IFN‐based therapy suggested the potential role of this marker for the prediction of a treatment response. A decline in HBsAg levels to below 1500 IU/mL at week 12 of treatment in HBeAg‐positive patients is a predictor of HBeAg seroconversion (PPV: 50%), while HBsAg levels >20 000 IU/mL in genotypes B and C or no decline in HBsAg levels in genotypes A and D are associated with a very low probability of HBeAg seroconversion.13 At week 24, HBsAg levels >20 000 IU/mL are predictive of non response regardless of genotype. A combination of a lack of decrease in HBsAg levels and <2log10 IU/mL decline in HBV DNA at 12 weeks of Peg‐IFN treatment in HBeAg‐negative patients is predictive of non‐response in genotype D patients (NPV: 100%), allowing discontinuation of Peg‐IFN in approximately 20% of subjects.14, 15 No robust on‐treatment stopping rules have been developed for HBeAg‐negative patients with genotypes B and C and very few data are available for those with genotypes A and E.14, 15 2.2 Peg-IFN反应的治疗中预测因子
接受基于干扰素治疗的HBeAg阴性和阳性患者HBsAg下降的报告表明,该标志物可能在预测治疗反应中具有潜在作用。 HBeAg阳性患者在治疗第12周时HBsAg水平降至1500 IU / mL以下是HBeAg血清转化(PPV:50%)的预测指标,而基因型B和C或无基因型的HBsAg> 20 000 IU / mL基因型A和D的HBsAg水平下降与HBeAg血清转化的可能性非常低相关。13在第24周,无论基因型如何,HBsAg水平> 20 000 IU / mL均预示无反应。 HBeAg阴性患者在接受Peg-IFN治疗12周后,HBsAg水平缺乏下降和HBV DNA下降<2log10 IU / mL的综合原因是基因型D患者无反应(NPV:100%),允许在大约20%的受试者中停用Peg-IFN。14、15对于B型和C型基因型的HBeAg阴性患者,尚未制定有效的治疗停止规则,而对于A型和E型基因型的患者,几乎没有可用的数据。 14、15作者: StephenW 时间: 2020-12-12 23:09