Selection bias for treatments with positive Phase 2 results

Rapid Review and Meta‐Analysis of Adverse Events Associated with Molnupiravir in Patients with COVID‐19

Aims

The aim of this study was to evaluate the safety profile of molnupiravir in COVID‐19 patients.

Methods

PubMed, Cochrane Library, medRxive and Google Scholar were searched for articles published up to April 25, 2022. Meta‐analysis was performed using Comprehensive Meta‐Analysis software.

Results

Four trials involving 2241 patients met the inclusion criteria. No significant difference was observed between molnupiravir at 200, 400 and 800 mg compared with placebo (200 mg: risk ratio [RR] = 0.97; 95% confidence interval [CI]: 0.78–1.20; P = .80; 400 mg: RR = 0.81; 95% CI: 0.64–1.02; P = .07; 800 mg: RR = 0.94; 95% CI: 0.83–1.06; P = .36) for any adverse events (AEs); at 200, 400 and 800 mg compared with placebo (200 mg: RR = 0.81; 95% CI: 0.41–1.63; P = .57; 400 mg: RR = 0.82; 95% CI: 0.41–1.61; P = .56; 800 mg: RR = 0.80; 95% CI: 0.59–1.08; P = .15) for serious adverse events; at 200, 400 and 800 mg compared with placebo (200 mg: RR = 1.74; 95% CI: 0.48–6.30; P = .39; 400 mg: RR = 1.07; 95% CI: 0.28–4.09; P = .91; 800 mg: RR = 0.47; 95% CI: 0.17–1.28; P = .14) for AEs leading to death; and at 200, 400 and 800 mg compared with placebo (200 mg: RR = 1.50; 95% CI: 0.26–8.55; P = .64; 400 mg: RR = 0.99; 95% CI: 0.17–5.68; P = .99; 800 mg: RR = 0.61; 95% CI: 0.31–1.23; P = .17) for treatment discontinuation due to AEs.

Conclusion

This meta‐analysis showed that the use of three doses of molnupiravir (200, 400 and 800 mg) is safe for COVID‐19 patients. Further research is needed to confirm the present findings.

Adjusting for bias in the mean for primary and secondary outcomes when trials are in sequence

When designing a clinical trial, one key aspect of the design is the sample size calculation. The sample size calculation tends to rely on a target or expected difference. The expected difference can be based on the observed data from previous studies, which results in bias. It has been reported that large treatment effects observed in trials are often not replicated in subsequent trials. If these values are used to design subsequent studies, the sample sizes may be biased which results in an unethical study. Regression to the mean (RTM) is one explanation for this. If only health technologies which meet a particular continuation criterion (such as p < 0.05 in the first study) are progressed to a second confirmatory trial, it is highly likely that the observed effect in the second trial will be lower than that observed in the first trial. It will be shown how when moving from one trial to the next, a truncated normal distribution is inherently imposed on the first study. This results in a lower observed effect size in the second trial. A simple adjustment method is proposed based on the mathematical properties of the truncated normal distribution. This adjustment method was confirmed using simulations in R and compared with other previous adjustments. The method can be applied to the observed effect in a trial, which is being used in the design of a second confirmatory trial, resulting in a more stable estimate for the 'true' treatment effect. The adjustment accounts for the bias in the primary and secondary endpoints in the first trial with the bias being affected by the power of that study. Tables of results have been provided to aid implementation, along with a worked example. In summary, there is a bias introduced when the point estimate from one trial is used to assist the design of a second trial. It is recommended that any observed point estimates be used with caution and the adjustment method developed in this article be implemented to significantly reduce this bias.