…both ALNY and ISIS act confidently that the TTR composite surrogate endpoint employed for tafamidis will be acceptable for their respective pivotal trials.
Which composite endpoint, specifically? It’s clear from the FDA briefing docs for the tafamidis panel that TTR stabilization per se is not a valid surrogate endpoint for accelerated approval:
TTR stabilization status is not a clinical endpoint; it is a reflection of stabilization of the biomarker, TTR. With the exception of one subject who appeared to be non-compliant, all tafamidis subjects achieved TTR stabilization regardless of whether subjects were NIS-LL responders or non-responders. Based on the available results of the multicenter Study 005, approval under the provisions of Subpart H [i.e. accelerated approval] does not appear appropriate.