Randomized start design (RSD), delayed start design, randomized withdrawal design to assess disease modification effect

In the latest Global CardioVascular Clinical Trialists (CVCT) Workshop", one of the topics was "How to assess the disease modification in pulmonary arterial hypertension". the academic and industry representatives discussed the definition of disease modification and if the various individual drugs met the criteria as disease modifiers. 

Disease modification requires that the intervention have an impact of the underlying pathology and pathophysiology of the disease. For regulatory purposes, a disease modifying effect is when an intervention delays the underlying pathological processes and is accompanied by improvement in clinical signs and symptoms of the disease. The opposite of the disease modifying effect is symptomatic improvement which is defined as "may improve symptoms but does not affect the long-term survival or outcome in the disease, for example, use of diuretics in PAH". 

For a drug to be defined as a disease modification therapy (DMT), disease modifier, or disease-modifying agent (DMA), the following criteria need to be met: 

• a drug targeting the underlying pathophysiology
• distinction should be made from the "symptomatic treatment" (do not affect underlying pathophysiology)
• Can achieve the goal of remission (partial or complete)
• endures sustained clinical benefit (referred to as DMA). 

The last criterion "endures sustained clinical benefit" is difficult to meet. The traditional randomized, controlled, parallel design will not be sufficient. Clinical trial designs like delayed start design and randomized withdrawal design are needed to assess the disease modification effect. 

A new article by Zamanian et al "Constructing the Framework for Disease Modification in Pulmonary Arterial Hypertension" attempted to define the disease modifier in PAH field and discussed designing the clinical trials to measure the disease modification effect.

Randomized Start Design or Delayed Start Design: 

This design was discussed in previous posts: 

• Randomized Start Design (RSD)
• Demonstrating the disease modifying effect through delayed start study design or delayed start analyses

Randomized withdrawal design: 

The randomized withdrawal design was extensively discussed in FDA's guidance "Enrichment Strategies for Clinical Trials to Support Determination of Effectiveness of Human Drugs and Biological Products". The following paragraphs are extracted from the guidance. 

The randomized withdrawal design was originally proposed as an approach to enrich the study and reduce the sample size. The randomized withdrawal design (if it is feasible to implement) can be used to evaluate the long-term disease-modifying effect. 

In practice, the randomized withdrawal design can be implemented after the RCT - the responders from both the experimental drug group and the placebo group are re-randomized to receive the experimental drug or placebo. This is exactly what we did in the ICE study ("Intravenous immune globulin (10% caprylate-chromatography purified) for the treatment of chronic inflammatory demyelinating polyradiculoneuropathy (ICE study): a randomised placebo-controlled trial") where the study contained a RCT portion to assess the treatment response and a re-randomized withdrawal portion to assess the relapse after the study drug withdrawal. 

The delayed start design and randomized withdrawal design have been mentioned frequently as a way to assess the disease modification effect. 

In FDA's guidance "Early Alzheimer’s Disease: Developing Drugs for Treatment", the randomized-start or randomized-withdrawal trial design was suggested:

In the FDA’s webinar on “Draft Guidance For Industry On Alzheimer’s Disease: Developing Drugs For The Treatment Of Early-Stage Disease”, the FDA presenters discussed the randomized start design or withdrawal design: 

“… If there is a significant effective treatment that couldn't serve as the basis of approval, we do not believe that that argument in and of itself does not demonstrate. This is where biomarkers come in. We learned in the trial results, the effect on up Alzheimer disease biomarker, it is still very and clear. Where the biomarker has been altered but there is no clinical effect. The clinical outcome was the opposite of what you want to see. The bottom line is that that understanding and how it relates to the clinical outcome still needs a bit of work. We would not be willing to accept the effect on the biomarker, as a basis for a circuit -- Sarah get approval. For that to be the case, it would be a fundamental itself in the disease process. In addition to biomarkers there are other ways to show disease modification, a randomized start design, or withdrawal design. These are based on clinical endpoints. These are difficult studies to design, and conduct, and interpret. We are open to use these approaches to show modification, let me show you what I mean by randomized start design. One would be on .8, the other will be on placebo, the patients on group to will be switched over to active treatment, patients in group 2 will be caught up to group 1, they will have a systematic effect of treatment. Patients that were switched to never really caught up to the first group, can argue for an effect on the disease, this is challenging to do, but we are open to the approach. It is a devastating condition, and an epidemic make -- particularly in late stages, the field is moving to conduct trials in early stages of the illness. As I pointed out they will pose regulatory challenges. We hope that's where our guidance will come in and suggest pathways forward. Thank you. I will have Russell Katz, come up and talk for the rest of the webinar.”

In one of the EMA presentations “The scientific and regulatory approaches to facilitating disease-modifying drug development and registration in a global environment”, the delayed start design (or randomized start) and randomized withdrawal design were mentioned.

 

In 2011, there was an FDA advisory committee meeting to discuss Teva's Parkinson's drug ((rasagiline mesylate)) for disease modification indication. Even though the disease modification claim was voted down), the delayed start design was confirmed to be adequate to evaluate the disease modification effect. Arterial Hypertension