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标题: 慢性乙型肝炎病毒感染:开发治疗药物 [打印本页]

作者: StephenW    时间: 2022-4-16 14:02     标题: 慢性乙型肝炎病毒感染:开发治疗药物

慢性乙型肝炎病毒感染:开发治疗药物

行业指南



功效终点
可以使用以下任何疗效终点在临床试验中评估新的有限持续时间疗法:

• 在有限的治疗时间后,HBV DNA 持续抑制(6 个月或更长)(低于 LLOQ、TD 或 TND)
• 治疗后持续抑制(6 个月或更长) HBV DNA(低于 LLOQ、TD 或 TND)伴随 HBsAg 消失(低于 0.05 国际单位/毫升 (IU/mL)),有或没有 HBsAb 血清学转换治疗持续时间

目前,由于 qHBsAg 与临床反应之间的相关性不一致(Hu et al. 2018; Thompson et al. 2010; Chan et al. 2011),HBsAg 从基线降低(未完全清除)用于评估 CHB 治疗反应的效用尚不清楚)。
应考虑使用适当的多重性统计方法测试有限数量的次要终点(例如 HBeAg 消失、HBeAg 阳性患者的抗 HBe 血清学转换、ALT 正常化)。生化血清标志物(例如 ALT 值)在实验室之间存在差异,并且 ALT 缺乏正常化可能经常与其他慢性肝病(例如非酒精性脂肪肝病)的存在相混淆。

其他重要终点:评估肝病的进展
除了晚期或失代偿期肝硬化患者外,对肝脏进展终点进行统计学上严格的评估可能具有挑战性,因为这些事件很少发生,直到 CHB 病程的晚期。然而,对这些终点的治疗效果提供了有用的临床信息,评估它们的试验可用于支持扩大的适应症或患者群体,并可在标签的适当部分进行总结。

申办者可以考虑的一些参数或临床结果包括:

• 终末期肝病评分模型的变化
• Child-Turcotte-Pugh 分数的变化
• 进展为需要移植或导致死亡的肝功能衰竭
• HCC 的发生

通过肝活检或无创方法评估的与治疗相关的纤维化或肝硬化消退可能适合在标签中显示。然而,在设计评估这些终点的方案时,申办者应与部门讨论无创模式的标签和性能特征计划。

患者报告的结果测量
正在考虑将患者报告的结果测量 23 作为临床试验终点以测量治疗益处的申办者应在临床开发过程中与 FDA 讨论患者报告的结果工具。

在 NrtIs 上受到病毒抑制
为了评估在接受 NrtIs 病毒抑制的活动性疾病(HBeAg 阳性或 HBeAg 阴性 CHB)受试者中持续 HBV DNA 抑制治疗后 HBsAg 消失的主要疗效结果,申办者可以考虑针对安慰剂进行附加优势试验以当前的 NrtI 治疗方案作为背景治疗。应在治疗后 6 个月的时间点评估 HBsAg 消失和持续 HBV DNA 抑制的共同主要疗效终点 14,并进行额外的随访以监测治疗后反应的持久性(即持续 HBV DNA 抑制和 HBsAg 消失) .一般来说,停止治疗是指停止所有治疗(即研究药物和背景 NrtI 方案)。为了证明治疗后的持续反应,申办者应系统地评估治疗巩固期的持续时间,定义为在后期试验中实现 HBsAg 消失后所需的持续治疗持续时间。这可能因特定研究药物的作用机制和半衰期而异。
在评估有限持续时间的治疗时,申办者应使用以下标准在研究治疗期结束时停止 NrtI 治疗:(1)在适用的情况下,在治疗组中平等地应用; (2) 在协议中明确定义; (3) 严格的,例如 HBsAg 消失或 HBsAg 大幅下降或在 2 期试验中确定的其他重要生物标志物的显着降低。预计在安慰剂组中很少有受试者会满足这样的标准。停止 NrtI 治疗的标准应基于临床证据,该证据也反映了权威科学机构推荐的当前实践指南,以确保停止 NrtI 治疗不会对试验参与者造成过度的安全风险。申办者应在试验开始前与 FDA 讨论使用生物标志物作为治疗中断的触发因素。
或者,可以在有限的治疗持续时间后,使用比较研究药物加 NrtI 与单独 NrtI 的优势试验设计来评估持续 HBV DNA 抑制治疗而没有清除 HBsAg 的结果。

背景

HBV是属于肝炎病毒家族的包膜DNA病毒。高度稳定的共价闭合环状病毒 DNA (cccDNA) 作为非复制性微型染色体发挥作用,并在受感染肝细胞的整个生命周期中持续存在。目前批准的疗法并未消除 cccDNA,这些疗法包括核苷/核苷酸逆转录酶抑制剂 (NrtI) 类药物和聚乙二醇干扰素。

慢性 HBV (CHB) 感染导致进行性肝病,从无症状到严重疾病,并伴有并发症,包括肝硬化、肝功能衰竭和肝细胞癌 (HCC) 的发展。在未经治疗的慢性乙型肝炎成人患者中,肝硬化的累积 5 年发病率为 8% 至 20%;在肝硬化患者中,肝功能失代偿的 5 年累积风险为 20%,HCC 风险为 2% 至 5%(Terrault 等人,2016 年)。一种有效的疫苗和抗病毒疗法分别被批准用于预防 HBV 感染和治疗 CHB。

目前可用的疗法在治疗期间实现了对 HBV DNA 的持续抑制,但在有或没有血清转换为抗 HBsAg (HBsAb) 的情况下,HBV 表面抗原 (HBsAg) 的丢失率仍然很低。持续的 HBV DNA 抑制与血清丙氨酸氨基转移酶 (ALT) 正常化和肝脏组织学改善有关,包括肝纤维化和肝硬化的消退(Chang 等人,2010;Marcellin 等人,2013;Buti 等人,2015)。 CHB 的有效抗病毒治疗可减少疾病相关并发症,例如肝功能失代偿和肝功能衰竭,并降低 HCC 的风险(Lok 等人,2016;Papatheodoridis 等人,2017)。 HBsAg 的清除与肝脏失代偿风险的降低和生存率的提高有关(Terrault 等人,2016 年)。 HBsAg 消失被认为是治疗后持续缓解的最佳预测指标(Terrault 等人,2016 年)。新的有限持续时间治疗靶向治疗方案,可以实现持续抑制 HBsAg 消失(有或没有 HBsAb 血清学转换)的 HBV DNA 停止治疗,病毒学复发风险低(由 HBV DNA 定义)和肝病进展风险最小停止治疗(Lok et al. 2017)。

2. 药物开发人群
应开发用于广泛 CHB 患者(包括儿科人群)的治疗方法。
早期临床试验应侧重于没有肝硬化的成年人群。初始试验可以在 HBV e 抗原阳性(HBeAg 阳性)或 HBV e 抗原阴性(HBeAg 阴性)患有活动性疾病且未接受过治疗的患者或先前接受过治疗但目前病毒血症、停止治疗的患者中进行。也可以在 NrtIs 病毒抑制的 HBeAg 阳性或 HBeAg 阴性患者中进行试验。除了第三节中讨论的端点。 B.,申办者可以在早期试验中评估探索性终点以收集数据,以告知和支持在后期试验中选择适当的终点,特别是那些评估有限持续时间的治疗。其中一些探索性终点可能包括以下内容:

• 治疗中不同时间点的定量 HBsAg (qHBsAg) 浓度变化
• HBeAg 定量水平
• 定量 HBV RNA 水平
• 定量 HBV 核心相关抗原 (HBcrAg) 水平
• cccDNA 定量
• 来自整合的 HBV 基因组片段的定量 HBsAg 水平
• 定量 HBsAg-抗-HBs 免疫复合物水平

此外,根据药物的作用机制,肝活检结果可用于某些概念验证研究,以进一步了解药物对 cccDNA 储库的影响和/或帮助更好地了解潜在的抗病毒活性替代标志物。
慢性 HBV (CHB) 感染导致进行性肝病,从无症状到严重疾病,并伴有并发症,包括肝硬化、肝功能衰竭和肝细胞癌 (HCC) 的发展。在未经治疗的慢性乙型肝炎成人患者中,肝硬化的累积 5 年发病率为 8% 至 20%;在肝硬化患者中,肝功能失代偿的 5 年累积风险为 20%,HCC 风险为 2% 至 5%(Terrault 等人,2016 年)。一种有效的疫苗和抗病毒疗法分别被批准用于预防 HBV 感染和治疗 CHB。

目前可用的疗法在治疗期间实现了对 HBV DNA 的持续抑制,但在有或没有血清转换为抗 HBsAg (HBsAb) 的情况下,HBV 表面抗原 (HBsAg) 的丢失率仍然很低。持续的 HBV DNA 抑制与血清丙氨酸氨基转移酶 (ALT) 正常化和肝脏组织学改善有关,包括肝纤维化和肝硬化的消退(Chang 等人,2010;Marcellin 等人,2013;Buti 等人,2015)。 CHB 的有效抗病毒治疗可减少疾病相关并发症,例如肝功能失代偿和肝功能衰竭,并降低 HCC 的风险(Lok 等人,2016;Papatheodoridis 等人,2017)。 HBsAg 的清除与肝脏失代偿风险的降低和生存率的提高有关(Terrault 等人,2016 年)。 HBsAg 消失被认为是治疗后持续缓解的最佳预测指标(Terrault 等人,2016 年)。新的有限持续时间治疗靶向治疗方案,可以实现持续抑制 HBsAg 消失(有或没有 HBsAb 血清学转换)的 HBV DNA 停止治疗,病毒学复发风险低(由 HBV DNA 定义)和肝病进展风险最小停止治疗(Lok et al. 2017)。

2. 药物开发人群
应开发用于广泛 CHB 患者(包括儿科人群)的治疗方法。
早期临床试验应侧重于没有肝硬化的成年人群。初始试验可以在 HBV e 抗原阳性(HBeAg 阳性)或 HBV e 抗原阴性(HBeAg 阴性)患有活动性疾病且未接受过治疗的患者或先前接受过治疗但目前病毒血症、停止治疗的患者中进行。也可以在 NrtIs 病毒抑制的 HBeAg 阳性或 HBeAg 阴性患者中进行试验。除了第三节中讨论的端点。 B.,申办者可以在早期试验中评估探索性终点以收集数据,以告知和支持在后期试验中选择适当的终点,特别是那些评估有限持续时间的治疗。其中一些探索性终点可能包括以下内容:

• 治疗中不同时间点的定量 HBsAg (qHBsAg) 浓度变化
• HBeAg 定量水平
• 定量 HBV RNA 水平
• 定量 HBV 核心相关抗原 (HBcrAg) 水平
• cccDNA 定量
• 来自整合的 HBV 基因组片段的定量 HBsAg 水平
• 定量 HBsAg-抗-HBs 免疫复合物水平

此外,根据药物的作用机制,肝活检结果可用于某些概念验证研究,以进一步了解药物对 cccDNA 储库的影响和/或帮助更好地了解潜在的抗病毒活性替代标志物。
CHB是一种全球性疾病,临床试验通常在多个国家进行。如果试验是按照良好的临床实践进行的并且如果 FDA 能够验证数据,则 FDA 将接受并非在 IND 下进行的精心设计和实施良好的外国临床研究作为 IND 或上市申请的支持11 当申办者依赖国外数据时,应以该地区或多个地区的主要 HBV 基因型和亚型信息为依据(Schweitzer 等人,2015 年)。开发计划应包括足够数量的美国患者,以确保代表美国人群中的流行基因型。 FDA 强烈鼓励申办者在不迟于第 2 阶段会议结束时提供一个计划,以解决在临床试验中纳入与年龄、性别、种族和民族有关的临床相关亚群,以支持 NDA 或 BLA。 12
作者: StephenW    时间: 2022-4-16 14:03

Chronic Hepatitis B Virus Infection:  Developing Drugs for Treatment

Guidance for Industry



Efficacy Endpoints
New finite duration therapies could be evaluated in clinical trials using any of the following efficacy endpoints:   

•        Sustained suppression (6 months or longer) of HBV DNA (less than LLOQ, TD, or TND) off-treatment after a finite duration of therapy
•        Sustained suppression (6 months or longer) of HBV DNA (less than LLOQ, TD, or TND) off-treatment with HBsAg loss (less than 0.05 international unit/milliliter (IU/mL)) with or without HBsAb seroconversion after a finite duration of therapy

At present, utility of reduction in HBsAg from baseline (without complete clearance) for assessing response to CHB therapies is unclear because of inconsistent correlations between qHBsAg and clinical response (Hu et al. 2018; Thompson et al. 2010; Chan et al. 2011).   
A limited number of secondary endpoints (e.g., HBeAg loss, anti-HBe seroconversion in HBeAg positive patients, ALT normalization) should be considered for testing using appropriate statistical methods for multiplicity.  Biochemical serum markers such as ALT values vary between laboratories, and lack of normalization of ALT may often be confounded by the presence of other chronic liver diseases such as nonalcoholic fatty liver disease.

Other important endpoints:  Assessing progression of liver disease
Except for patients with advanced or decompensated cirrhosis, a statistically rigorous evaluation of endpoints of liver progression can be challenging because these events occur infrequently until late in the course of CHB.  However, treatment effects on these endpoints provide useful clinical information, and trials evaluating them could be used to support an expanded indication or patient population and could be summarized in appropriate sections of the label.   

Some of the parameters or clinical outcomes that sponsors can consider include the following:

•        Change in Model for End Stage Liver Disease scores
•        Change in Child-Turcotte-Pugh scores
•        Progression to liver failure requiring transplantation or resulting in death
•        Occurrence of HCC

Treatment-related regression of fibrosis or cirrhosis, as assessed by liver biopsy or noninvasive methods, may be appropriate for display in the label.  However, sponsors should discuss with the Division plans for labeling and performance characteristics of the noninvasive modality when protocols evaluating these endpoints are being designed.  

Patient-Reported Outcome Measures
Sponsors who are considering incorporating patient-reported outcome measures23 as endpoints in clinical trials to measure treatment benefit should discuss patient-reported outcome instruments with the Agency during the clinical development process.

Virally suppressed on NrtIs
To evaluate the primary efficacy outcome of sustained HBV DNA suppression off-treatment with HBsAg loss in subjects with active disease (HBeAg-positive or HBeAg-negative CHB) who are virally suppressed on NrtIs, sponsors can consider an add-on superiority trial against placebo with a current NrtI treatment regimen as the background therapy.  The co-primary efficacy endpoints14 of HBsAg loss and sustained HBV DNA suppression should be assessed at the 6-month posttreatment time point with additional follow-up to monitor for durability of response (i.e., sustained HBV DNA suppression and HBsAg loss) off-treatment.  In general, off-treatment refers to discontinuation of all therapies (i.e., investigational agent and background NrtI regimen).  To demonstrate sustained response off-treatment, sponsors should systematically assess the duration of a treatment consolidation period, defined as the duration of continued treatment needed after achieving HBsAg loss, during late phase trials.  This may vary based on the mechanism of action and half-life of the specific investigational drug.  
Sponsors should use the following criteria for stopping NrtI therapy at the end of the investigational treatment period when evaluating a finite duration therapy:  (1) applied equally across treatment arms, as applicable; (2) well-defined in the protocol; and (3) stringent, such as HBsAg loss or substantial HBsAg decline or marked reduction in other important biomarkers identified in phase 2 trials.  It is expected that few subjects would meet such criteria on the placebo arm.  The criteria for stopping NrtI therapy should be based on clinical evidence that also reflects current practice guidelines recommended by the authoritative scientific bodies to ensure that the discontinuation of NrtI therapy does not pose undue safety risk to the trial participants.  Sponsors should discuss with the FDA the use of biomarkers as a trigger for treatment interruption in advance of trial initiation.  
Alternatively, an outcome of sustained HBV DNA suppression off-treatment without HBsAg clearance can be evaluated after a finite treatment duration using a superiority trial design comparing the investigational drug plus an NrtI with an NrtI alone.

BACKGROUND

HBV is an enveloped DNA virus belonging to the Hepadnavirus family.  The highly stable covalently closed circular viral DNA (cccDNA) functions as a nonreplicative minichromosome and persists throughout the lifespan of infected hepatocytes.  The cccDNA is not eliminated by currently approved therapies that include drugs from the nucleoside/nucleotide reverse transcriptase inhibitor (NrtI) class, and pegylated interferon.   

Chronic HBV (CHB) infection results in progressive liver disease ranging from asymptomatic to severe disease with complications including cirrhosis, liver failure, and the development of hepatocellular carcinoma (HCC).  In untreated adults with CHB, the cumulative 5-year incidence of cirrhosis is 8 to 20 percent; and among those with cirrhosis, the 5-year cumulative risk of hepatic decompensation is 20 percent, and risk of HCC is 2 to 5 percent (Terrault et al. 2016).  An effective vaccine and antiviral therapies are approved for the prevention of HBV infection and treatment of CHB, respectively.   

Currently available therapies achieve sustained suppression of HBV DNA while on treatment, but rates of HBV surface antigen (HBsAg) loss with or without seroconversion to anti-HBsAg (HBsAb) remain low.  Sustained HBV DNA suppression is associated with serum alanine aminotransferase (ALT) normalization and improvement in liver histology including regression of hepatic fibrosis and cirrhosis (Chang et al. 2010; Marcellin et al. 2013; Buti et al. 2015).  Effective antiviral therapy for CHB reduces disease-related complications, such as hepatic decompensation and liver failure, and decreases risk of HCC (Lok et al. 2016; Papatheodoridis et al. 2017).  Clearance of HBsAg is associated with reduced risk of hepatic decompensation and improved survival (Terrault et al. 2016).  HBsAg loss is considered the best predictor of sustained remission off-treatment (Terrault et al. 2016).  New finite duration therapies target treatment regimens that can achieve sustained suppression of HBV DNA off-treatment with HBsAg loss (with or without HBsAb seroconversion) with low risk of virologic relapse (as defined by HBV DNA) and minimal risk of liver disease progression after the treatment is stopped (Lok et al. 2017).

2. Drug Development Population
Therapies should be developed for use in a wide range of patients with CHB, including pediatric populations.   
Early phase clinical trials should focus on the adult population without cirrhosis.  Initial trials can be conducted in HBV e antigen positive (HBeAg-positive) or HBV e antigen negative (HBeAg-negative) patients with active disease who are treatment-naïve, or those who were previously treated but currently viremic, off-treatment.  Trials can also be conducted in HBeAg-positive or HBeAg-negative patients who are virally suppressed on NrtIs.  In addition to endpoints discussed in section III. B., sponsors can evaluate exploratory endpoints in early phase trials to gather data to inform and support the choice of appropriate endpoints in late phase trials, particularly those evaluating treatments of finite durations.  Some of these exploratory endpoints may include the following:  

•        Change in quantitative HBsAg (qHBsAg) concentration at various time points on treatment
•        Quantitative HBeAg levels
•        Quantitative HBV RNA levels
•        Quantitative HBV core-related antigen (HBcrAg) levels
•        cccDNA quantification
•        Quantitative HBsAg levels from integrated HBV genome fragments
•        Quantitative HBsAg-anti-HBs immune complex levels

Also depending on the drug’s mechanism of action, liver biopsy findings can be used in certain proof-of-concept studies to further understand the effect of the drug on the cccDNA reservoir and/or to help better understand potential surrogate markers of antiviral activity.   
Chronic HBV (CHB) infection results in progressive liver disease ranging from asymptomatic to severe disease with complications including cirrhosis, liver failure, and the development of hepatocellular carcinoma (HCC).  In untreated adults with CHB, the cumulative 5-year incidence of cirrhosis is 8 to 20 percent; and among those with cirrhosis, the 5-year cumulative risk of hepatic decompensation is 20 percent, and risk of HCC is 2 to 5 percent (Terrault et al. 2016).  An effective vaccine and antiviral therapies are approved for the prevention of HBV infection and treatment of CHB, respectively.   

Currently available therapies achieve sustained suppression of HBV DNA while on treatment, but rates of HBV surface antigen (HBsAg) loss with or without seroconversion to anti-HBsAg (HBsAb) remain low.  Sustained HBV DNA suppression is associated with serum alanine aminotransferase (ALT) normalization and improvement in liver histology including regression of hepatic fibrosis and cirrhosis (Chang et al. 2010; Marcellin et al. 2013; Buti et al. 2015).  Effective antiviral therapy for CHB reduces disease-related complications, such as hepatic decompensation and liver failure, and decreases risk of HCC (Lok et al. 2016; Papatheodoridis et al. 2017).  Clearance of HBsAg is associated with reduced risk of hepatic decompensation and improved survival (Terrault et al. 2016).  HBsAg loss is considered the best predictor of sustained remission off-treatment (Terrault et al. 2016).  New finite duration therapies target treatment regimens that can achieve sustained suppression of HBV DNA off-treatment with HBsAg loss (with or without HBsAb seroconversion) with low risk of virologic relapse (as defined by HBV DNA) and minimal risk of liver disease progression after the treatment is stopped (Lok et al. 2017).

2. Drug Development Population
Therapies should be developed for use in a wide range of patients with CHB, including pediatric populations.   
Early phase clinical trials should focus on the adult population without cirrhosis.  Initial trials can be conducted in HBV e antigen positive (HBeAg-positive) or HBV e antigen negative (HBeAg-negative) patients with active disease who are treatment-naïve, or those who were previously treated but currently viremic, off-treatment.  Trials can also be conducted in HBeAg-positive or HBeAg-negative patients who are virally suppressed on NrtIs.  In addition to endpoints discussed in section III. B., sponsors can evaluate exploratory endpoints in early phase trials to gather data to inform and support the choice of appropriate endpoints in late phase trials, particularly those evaluating treatments of finite durations.  Some of these exploratory endpoints may include the following:  

•        Change in quantitative HBsAg (qHBsAg) concentration at various time points on treatment
•        Quantitative HBeAg levels
•        Quantitative HBV RNA levels
•        Quantitative HBV core-related antigen (HBcrAg) levels
•        cccDNA quantification
•        Quantitative HBsAg levels from integrated HBV genome fragments
•        Quantitative HBsAg-anti-HBs immune complex levels

Also depending on the drug’s mechanism of action, liver biopsy findings can be used in certain proof-of-concept studies to further understand the effect of the drug on the cccDNA reservoir and/or to help better understand potential surrogate markers of antiviral activity.   
CHB is a global disease, and clinical trials are often conducted in multiple countries.  FDA will accept a well-designed and well-conducted foreign clinical study not conducted under an IND as support for an IND or application for marketing approval if the trial was conducted in accordance with good clinical practice and if the FDA is able to validate the data from the trial through an onsite inspection if the Agency deems it necessary.11  When sponsors rely on foreign data, these should be supported with information about predominant HBV genotypes and subtypes in the region or regions (Schweitzer et al. 2015).  Development programs should include a sufficient number of U.S. patients to ensure prevalent genotypes in the U.S. population are represented.  FDA strongly encourages sponsors to provide a plan to address inclusion of clinically relevant subpopulations with regard to age, gender, race, and ethnicity in the clinical trials to support an NDA or BLA, no later than the end-of-phase 2 meeting.12




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