Joint WFH-ISTH session: issues in clinical trial design

The design of a Bayesian platform trial to prevent and eradicate inhibitors in patients with hemophilia

Among individuals with the rare congenital bleeding disorder hemophilia A, the major challenge is inhibitor formation, which is associated with significant morbidity and cost. Yet, as the optimal approach to prevent and eradicate inhibitors is not known, we are at equipoise. Because classic trial design is not practical in a rare disease setting, we designed 2 48-week randomized trials comparing ELOCTATE and emicizumab to prevent and eradicate inhibitors. To achieve statistical efficiency, we incorporated historic data (Bayesian priors) on inhibitor formation to allow preferential randomization to emicizumab, piecewise exponential survival models to determine mean and 95% confidence interval for inhibitor formation in each arm, and simulations to determine the best model design to optimize power. To achieve administrative efficiency, the trials will be performed with the same sites, staff, visit frequency, blood sampling, laboratories, and laboratory assays, with streamlined enrollment so patients developing inhibitors in the first trial may be enrolled on the second trial. The primary end point is the probability of inhibitor formation or inhibitor eradication, respectively. The design indicates early stopping rules for overwhelming evidence of superiority of the emicizumab arms. Simulations indicate that, with 66 subjects, the Prevention Trial will have 84% power to detect noninferiority of emicizumab to ELOCTATE with a margin of 10% if emicizumab is truly 10% superior to ELOCTATE; with 90 subjects, the Eradication Trial will have 80% power to detect 15% superiority of ELOCTATE immune tolerance induction with vs without emicizumab. Thus, a platform design provides statistical and administrative efficiency to conduct INHIBIT trials.

Consanguineous marriage and rare bleeding disorders

Introduction: Rare bleeding disorders (RBDs) are a heterogeneous group of bleeding disorders. Consanguineous marriage is the favorite partnership in many communities among a population of more than a billion. Consanguineous marriages allow the defective recessive genes in RBDs to remain in the family. Clinical approach to RBDs is not as straightforward as typical bleeding disorders, which are secondary to scarcity and variation of RBDs. However, in many developing countries, the limitations of diagnostic facilities, the supply of therapeutic coagulation concentrates, health budgets, and optimal health-care infrastructures may intensify the clinical practice of RBDs.Areas covered: The author addresses the role of consanguineous marriage in the incidence of RBDs and what preventive steps can be considered to minimize the incidence of RBDs. A literature review of PubMed and google Scholar was conducted in November of 2020 using the relevant keywords.Expert opinion: This review addresses the prevalence of consanguineous marriages in Middle Eastern countries and the various reasons behind the coexistence of consanguineous marriage with RBDs. Finally, prevention steps that may be considered by health-care systems to minimize the incidence of rare bleeding disorders have been discussed. Health-care systems should train partners with the intention of consanguineous marriage on the downside of consanguinity.

The national blueprint for future factor VIII inhibitor clinical trials: NHLBI State of the Science (SOS) Workshop on factor VIII inhibitors

INTRODUCTION

Inhibitor formation is a major complication of haemophilia for which clinical trials are planned. Despite emerging novel haemostatic agents, challenges of rare disease trials are limited subjects and lack of an organized research organization with strategic resources and partnerships.

AIM

The charge to Working Group 1 was to establish scientific priorities and innovative implementation strategies to conduct inhibitor prevention and eradication trials. To determine feasibility of trial design and strategic resources and partnerships to be leveraged, two clinical trial concepts were considered.

RESULTS

For the Inhibitor Prevention Trial, we considered adaptive design with early stopping rules, dynamic randomization and Master Protocol models to reduce sample size; and registries to provide concurrent controls and natural history data. For the Inhibitor Eradication Trial using gene therapy, an adaptive design was considered in a small number of subjects, and, if safe and meeting regulatory requirements, enrolment would be expanded. A Haemophilia Clinical Trials Group (HCTG) infrastructure was envisioned, with uniform procedures and standardized outcomes, data collection and assays, within which trial concepts would be developed, vetted and prioritized by a Steering Committee, and submitted to NIH and other research sponsors for review and funding. Mechanistic studies would be embedded within the trials, early stage investigators trained and mentored, and the research infrastructure established within the haemophilia centre (HTC) network and supported by partnerships with foundations, community, federal partners and industry.

CONCLUSION

The success of inhibitor trials will depend on innovative trial design and an organized HCTG research infrastructure, leveraged through community partnerships.

Strategies for eliciting and synthesizing evidence for guidelines in rare diseases

Background

Rare diseases are a global public health priority. Though each disease is rare, when taken together the thousands of known rare diseases cause significant morbidity and mortality, impact quality of life, and confer a social and economic burden on families and communities. These conditions are, by their nature, encountered very infrequently by individual clinicians, who may feel unprepared to address their diagnosis and treatment. Clinical practice guidelines are necessary to support clinical and policy decisions. However, creating guidelines for rare diseases presents specific challenges, including a paucity of high certainty evidence to inform panel recommendations.

Methods

This paper draws from the authors’ experience in the development of clinical practice guidelines for three rare diseases: hemophilia, sickle cell disease, and catastrophic antiphospholipid syndrome.

Results

We have summarized a number of strategies for eliciting and synthesizing evidence that are compatible with the rigorous, internationally accepted standards for guideline development set out by the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. These strategies include: use of pre-existing and ad hoc qualitative research, use of systematic observation forms, use of registry data, and thoughtful use of indirect evidence. Their use in three real guideline development efforts, as well as their theoretical underpinnings, are discussed. Avenues for future research to improve clinical practice guideline creation for rare diseases – and any disease affected by a relative lack of evidence - are also identified.

Conclusions

Rigorous clinical practice guidelines are needed to improve the care of the millions of people worldwide who suffer from rare diseases. Innovative evidence elicitation and synthesis methods will benefit not only the rare disease community, but also individuals with common diseases who have rare presentations, suffer rare complications, or require nascent therapies. Further refinement and improved uptake of these innovative methods should lead to higher quality clinical practice guidelines in rare diseases.

Partnering to change the world for people with haemophilia: 7th Haemophilia Global Summit, Madrid, Spain 22-24 September 2016

The 7th Haemophilia Global Summit was held in Madrid, Spain, in September 2016. With a programme designed, for the 6th consecutive year, by a Scientific Steering Committee of haemophilia experts, the aim of the summit was to share optimal management strategies for haemophilia at all life stages and to provide an opportunity for specialists from across the haemophilia multidisciplinary care team to engage in discussion and debate with leading international experts on current and future areas of research. Topics covered ranged from the optimisation of haemophilia management, emerging issues in clinical care, practical approaches and future perspectives, in addition to patient engagement and empowerment in modern haemophilia care.