February 19, 2018
The FDA has released five guidances on clinical trial designs and endpoints for developing treatments for a variety of neurological disorders, including Alzheimer’s disease, Duchenne muscular dystrophy (DMD) and ALS. The revised draft guidance on Alzheimer’s disease noted a greater focus on evaluating drug treatments during the disease’s earliest stages, partially due to the failures of clinical trials that aimed to alter later stage disease progression. Diagnostic criteria that reliably define an early Alzheimer’s population are suited for evaluating drugs that try to delay or prevent overt symptoms, the agency said. Enrollment eligibility for Alzheimer’s drug efficacy trials should be centered around current consensus diagnostic criteria, focusing on objective tests in addition to history and physical examination when appropriate, to determine the disease’s presence and rule out similar conditions. Alzheimer’s Stage 1 patients — who exhibit evidence of clinical impact — are important targets for clinical trials, although clinically meaningful benefits cannot be measured in them due to a lack of clinical impairment. However, effects on the characteristic pathophysiologic changes of AD — demonstrated by effects on biomarkers — may be measured in these patients, and the measurements may serve as the basis for an accelerated trial, as the biomarker effects would be “reasonably likely to predict clinical benefit,” with a post-approval study required for confirmation. The agency’s final guidance on DMD and related dystrophinopathies said endpoints measuring change of function in a wide range of deficits may offer advantages in the development of drugs that treat diseases like DMD and Becker muscular dystrophy, in addition to increasing the number of patients eligible for enrollment. Sponsors should consider using endpoints that are able to assess function across different stages of the disease — such as combining measures of upper body function and ambulation — and detect improvement and decline from baseline in order to capture the range of possible beneficial drug effects. Patient-reported outcomes (PRO) can be useful for assessing clinical meaningfulness of relatively small objective findings, and for contributing benefit and risk assessments. PRO instruments for dystrophinopathies should, in general, “include a limited number of items that assess the most important aspects of the outcome of interest.” The final guidance on drug development for acute treatment of migraines, which does not apply to over-the-counter products, elaborated on ideal trial design, trial population and entry criteria, dose selection, efficacy endpoints and concomitant medications, among other topics. Draft guidance issued on drugs for the treatment of partial onset seizures explained that “efficacy can be extrapolated from adults to pediatric patients when it is reasonable to assume that children, compared with adults, have a similar progression of disease, similar response of disease to treatment, and similar exposure-response relationship.” The draft guidance on developing drugs for ALS treatment addresses the clinical development of drugs intended to treat the main neuromuscular aspects of the disease and focuses on specific clinical drug development and trial design issues that are unique to the study of ALS. The guidances “signal how modernization of the new drug regulatory program includes an enhanced focus on incorporation of patient input into our thinking,” said FDA Commissioner Scott Gottlieb. Read the five guidances here: www.fdanews.com/02-15-18-Guidances.pdf.