The devotion to surrogate outcomes in drug development for liver disease

The Placebo Response in Randomized Trials in Nonalcoholic Steatohepatitis Simply Explained

BACKGROUND & AIMS

Liver histology is the primary endpoint in phase III trials in nonalcoholic steatohepatitis (NASH). There is an appreciable response to placebo that confounds endpoint assessment. The aim of this study was to quantify contributors to the placebo response and its impact on liver fibrosis improvement.

METHODS

Estimates of fibrosis improvement in placebo-treated participants were made using probabilistic simulation. Each simulated trial included 120 participants. Parameters considered in the model included sampling and observer variability, regression to the mean, and net fibrosis progression calibrated to reported trial outcomes.

RESULTS

In large phase IIb and III trials, 22% of placebo-treated participants with fibrosis stage 2 or 3 NASH at baseline improved by at least 1 fibrosis stage with minimal net disease progression. Estimates of sampling and observer variability in simultaneous biopsy studies highlighted an imbalance where apparent fibrosis improvement was more likely than worsening. Using these estimates and known trial outcomes, net fibrosis progression was estimated at 0.05 stages per year. Simulations of the placebo response rate showed a rate of 22% with 80% of trials falling between 15 and 30%, in keeping with trials reported to date. Additional increases in observer variability further increased the placebo response.

CONCLUSIONS

The analyses presented simply define the placebo response in liver fibrosis in trials in NASH in terms of sampling and observer variability, regression to the mean, and fibrosis progression. Factors relating to liver biopsy are largely unmodifiable, and the variation in placebo response rates, both simulated and observed, challenges the role of biopsy in trial endpoint assessment.

Histological Endpoints for Nonalcoholic Steatohepatitis Trials: Lights and Shadows

Nonalcoholic steatohepatitis (NASH) with liver fibrosis is an increasingly important cause of liver-related morbidity and mortality. A diagnosis of NASH can only be made using liver biopsy. Liver histology also forms the endpoint for the expedited licensing strategies that have been approved by regulators to allow patients with NASH access to treatment before the impact of these on clinical outcomes is known. Validation of these histological surrogate endpoints is critical for the ongoing development of new therapies for NASH. The use of liver biopsy to define both trial entry and endpoints raises questions about the use of treatments for NASH in practice when the effectiveness of treatment will likely depend, at least in part, on the use of histology for patient selection in the real world.

High rates of ineligibility for participation in trials of new therapies in non-alcoholic steatohepatitis: a systematic review

BACKGROUND AND AIMS

Non-alcoholic fatty liver disease is common and there are a number of treatments in development. Patients with non-alcoholic steatohepatitis (NASH) and significant fibrosis are thought to be the population most in need of treatment. Identification of this group requires liver biopsy. The aim of this study was to identify the proportion of patients screened for phase 2 randomised controlled trials who subsequently entered these studies.

METHODS

Large, multicentre, phase 2 randomised controlled trials of pharmacological therapies for NASH were identified by systematic review. The pooled proportion of potential participants who entered the trials was estimated by meta-analysis. The reasons for trial ineligibility were separately extracted and analysed.

RESULTS

Thirteen reports of 14 trials were included. Overall, there were 4014 screened individuals included in the quantitative analyses and 53% were subsequently enrolled in a trial. Considering trials in which the entry criteria matched the current paradigm for treatment, that is, the presence of NASH and significant fibrosis, only 35% of screened individuals were eligible for trial entry. More than half of ineligible individuals were excluded on the basis of liver histology most often due to insufficient disease activity with or without insufficient fibrosis.

CONCLUSION

The majority of patients considered at risk of NASH and fibrosis sufficient for treatment in randomised controlled trials are ineligible for trial entry. Most often, this is due to ineligible liver histology. These findings have implications for the design of future trials in NASH and for the applicability of treatments after licensing.