The design and statistical aspects of VIETNARMS: a strategic post-licensing trial of multiple oral direct-acting antiviral hepatitis C treatment strategies in Vietnam

Treatment options to support the elimination of hepatitis C: an open-label, factorial, randomised controlled non-inferiority trial

BACKGROUND

WHO recommends treating hepatitis C infection with one of three antiviral combinations for 8-12 weeks. No randomised trials have compared these regimens, and high cure rates might be achievable with shorter durations of therapy. We aimed to compare sofosbuvir-daclatasvir with sofosbuvir-velpatasvir, and to evaluate potential novel treatment strategies.

METHODS

We conducted a multi-arm, open-label, randomised controlled non-inferiority trial in two public hospitals in Viet Nam. Adults (aged ≥18 years) with chronic hepatitis C infection and mild-to-moderate liver fibrosis were eligible. Recruitment was stratified by centre and viral genotype (1-5 vs 6) with 1:1 random allocation to an oral fixed-dose combination of sofosbuvir 400 mg plus daclatasvir 60 mg (sofosbuvir-daclatasvir) or sofosbuvir 400 mg plus velpatasvir 100 mg (sofosbuvir-velpatasvir). Participants were simultaneously factorially randomly assigned to one of four treatment strategies: 12 weeks' standard of care (SOC); 4 weeks' therapy with four weekly PEGylated interferon alfa-2a subcutaneous injections; induction and maintenance therapy with 2 weeks' standard therapy followed by 10 weeks' therapy 5 days a week; and response-guided therapy (RGT) for 4, 8, or 12 weeks determined by viral load on day 7. The primary outcome was sustained virological response (SVR) 12 weeks after treatment completion, analysed in all evaluable participants regardless of actual treatment received. We chose a 5% non-inferiority margin for the drug comparison, and a 10% non-inferiority margin for the treatment strategy comparisons. Safety was assessed in all randomised participants. This trial is registered with ISRCTN, 61522291, and is completed.

FINDINGS

Between June 19, 2020, and May 10, 2023, 624 participants were randomised (470 [75%] were male and 154 [25%] were female). 296 (47%) had genotype 6 and 328 (53%) had genotypes 1-5. The primary outcome was assessable in 609 (98%) participants. SVR occurred in 294 (97%) of 302 participants in the sofosbuvir-daclatasvir group and 292 (95%) of 307 participants in the sofosbuvir-velpatasvir group (risk difference 2·2%, 90% credible interval [CrI] -0·2 to 4·8, within the 5% non-inferiority margin; 93% probability that sofosbuvir-daclatasvir is superior to sofosbuvir-velpatasvir). SVR occurred in 148 (99%) of 150 in the SOC group, 143 (94%) of 152 in the 4-week antiviral plus interferon group (-4·5%, 90% CrI -8·3 to -1·3), 151 (99%) of 152 in the induction-maintenance group (0·6%, -1·1 to 2·7), and 144 (93%) of 155 in the RGT group (-5·7%, -9·6 to -2·3); all risk differences were within the 10% non-inferiority margin. Serious adverse events were rare (11 [4%] of 313 participants in the sofosbuvir-velpatasvir group vs six [2%] of 311 in the sofosbuvir-daclatasvir group; risk difference -1·6% [95% CrI -4·2 to 0·8]) with no evidence of differences between regimens or strategies, but adverse reactions were very common in the 4-week antiviral plus interferon group compared with the other treatment strategies (risk difference vs SOC group, 66·8% [59·2 to 74·0]; p<0·0001).

INTERPRETATION

Sofosbuvir-daclatasvir was non-inferior to sofosbuvir-velpatasvir. High efficacy was seen with novel strategies, which might help to inform approaches to treatment for harder-to-reach populations.

FUNDING

Wellcome Trust.

When should factorial designs be used for late-phase randomised controlled trials?

BACKGROUND

A 2×2 factorial design evaluates two interventions (A versus control and B versus control) by randomising to control, A-only, B-only or both A and B together. Extended factorial designs are also possible (e.g. 3×3 or 2×2×2). Factorial designs often require fewer resources and participants than alternative randomised controlled trials, but they are not widely used. We identified several issues that investigators considering this design need to address, before they use it in a late-phase setting.

METHODS

We surveyed journal articles published in 2000-2022 relating to designing factorial randomised controlled trials. We identified issues to consider based on these and our personal experiences.

RESULTS

We identified clinical, practical, statistical and external issues that make factorial randomised controlled trials more desirable. Clinical issues are (1) interventions can be easily co-administered; (2) risk of safety issues from co-administration above individual risks of the separate interventions is low; (3) safety or efficacy data are wanted on the combination intervention; (4) potential for interaction (e.g. effect of A differing when B administered) is low; (5) it is important to compare interventions with other interventions balanced, rather than allowing randomised interventions to affect the choice of other interventions; (6) eligibility criteria for different interventions are similar. Practical issues are (7) recruitment is not harmed by testing many interventions; (8) each intervention and associated toxicities is unlikely to reduce either adherence to the other intervention or overall follow-up; (9) blinding is easy to implement or not required. Statistical issues are (10) a suitable scale of analysis can be identified; (11) adjustment for multiplicity is not required; (12) early stopping for efficacy or lack of benefit can be done effectively. External issues are (13) adequate funding is available and (14) the trial is not intended for licensing purposes. An overarching issue (15) is that factorial design should give a lower sample size requirement than alternative designs. Across designs with varying non-adherence, retention, intervention effects and interaction effects, 2×2 factorial designs require lower sample size than a three-arm alternative when one intervention effect is reduced by no more than 24%-48% in the presence of the other intervention compared with in the absence of the other intervention.

CONCLUSIONS

Factorial designs are not widely used and should be considered more often using our issues to consider. Low potential for at most small to modest interaction is key, for example, where the interventions have different mechanisms of action or target different aspects of the disease being studied.

Utility of a buccal swab point-of-care test for the IFNL4 genotype in the era of direct acting antivirals for hepatitis C virus

BACKGROUND

The CC genotype of the IFNL4 gene is known to be associated with increased Hepatitis C (HCV) cure rates with interferon-based therapy and may contribute to cure with direct acting antivirals. The Genedrive® IFNL4 is a CE marked Point of Care (PoC) molecular diagnostic test, designed for in vitro diagnostic use to provide rapid, real-time detection of IFNL4 genotype status for SNP rs12979860.

METHODS

120 Participants were consented to a substudy comparing IFNL4 genotyping results from a buccal swab analysed on the Genedrive® platform with results generated using the Affymetix UK Biobank array considered to be the gold standard.

RESULTS

Buccal swabs were taken from 120 participants for PoC IFNL4 testing and a whole blood sample for genetic sequencing. Whole blood genotyping vs. buccal swab PoC testing identified 40 (33%), 65 (54%), and 15 (13%) had CC, CT and TT IFNL4 genotype respectively. The Buccal swab PoC identified 38 (32%) CC, 64 (53%) CT and 18 (15%) TT IFNL4 genotype respectively. The sensitivity and specificity of the buccal swab test to detect CC vs non-CC was 90% (95% CI 76-97%) and 98% (95% CI 91-100%) respectively.

CONCLUSIONS

The buccal swab test was better at correctly identifying non-CC genotypes than CC genotypes. The high specificity of the Genedrive® assay prevents CT/TT genotypes being mistaken for CC, and could avoid patients being identified as potentially 'good responders' to interferon-based therapy.

Efficacy of ultra-short, response-guided sofosbuvir and daclatasvir therapy for hepatitis C in a single-arm mechanistic pilot study

Background

World Health Organization has called for research into predictive factors for selecting persons who could be successfully treated with shorter durations of direct-acting antiviral (DAA) therapy for hepatitis C. We evaluated early virological response as a means of shortening treatment and explored host, viral and pharmacokinetic contributors to treatment outcome.

Methods

Duration of sofosbuvir and daclatasvir (SOF/DCV) was determined according to day 2 (D2) virologic response for HCV genotype (gt) 1- or 6-infected adults in Vietnam with mild liver disease. Participants received 4- or 8-week treatment according to whether D2 HCV RNA was above or below 500 IU/ml (standard duration is 12 weeks). Primary endpoint was sustained virological response (SVR12). Those failing therapy were retreated with 12 weeks SOF/DCV. Host IFNL4 genotype and viral sequencing was performed at baseline, with repeat viral sequencing if virological rebound was observed. Levels of SOF, its inactive metabolite GS-331007 and DCV were measured on days 0 and 28.

Results

Of 52 adults enrolled, 34 received 4 weeks SOF/DCV, 17 got 8 weeks and 1 withdrew. SVR12 was achieved in 21/34 (62%) treated for 4 weeks, and 17/17 (100%) treated for 8 weeks. Overall, 38/51 (75%) were cured with first-line treatment (mean duration 37 days). Despite a high prevalence of putative NS5A-inhibitor resistance-associated substitutions (RASs), all first-line treatment failures cured after retreatment (13/13). We found no evidence treatment failure was associated with host IFNL4 genotype, viral subtype, baseline RAS, SOF or DCV levels.

Conclusions

Shortened SOF/DCV therapy, with retreatment if needed, reduces DAA use in patients with mild liver disease, while maintaining high cure rates. D2 virologic response alone does not adequately predict SVR12 with 4-week treatment.

Funding

Funded by the Medical Research Council (Grant MR/P025064/1) and The Global Challenges Research 70 Fund (Wellcome Trust Grant 206/296/Z/17/Z).

A stochastically curtailed single‐arm phase II trial design for binary outcomes

Phase II clinical trials are a critical aspect of the drug development process. With drug development costs ever increasing, novel designs that can improve the efficiency of phase II trials are extremely valuable.Phase II clinical trials for cancer treatments often measure a binary outcome. The final trial decision is generally to continue or cease development. When this decision is based solely on the result of a hypothesis test, the result may be known with certainty before the planned end of the trial. Unfortunately, there is often no opportunity for early stopping when this occurs.Some existing designs do permit early stopping in this case, accordingly reducing the required sample size and potentially speeding up drug development. However, more improvements can be achieved by stopping early when the final trial decision is very likely, rather than certain, known as stochastic curtailment. While some authors have proposed approaches of this form, these approaches have various limitations.In this work we address these limitations by proposing new design approaches for single-arm phase II binary outcome trials that use stochastic curtailment. We use exact distributions, avoid simulation, consider a wider range of possible designs and permit early stopping for promising treatments. As a result, we are able to obtain trial designs that have considerably reduced sample sizes on average.