Requests that the FDA codify, regularize, and transparently administer a principle the Agency already recognizes in practice: that the adequacy of an investigation in rare diseases cannot be determined by default assumptions alone. It does not ask FDA to invent a new principle or apply distinct evidentiary thresholds or concessions to rare disease research programs. | Federal Regulations · Congress.wiki

Nonrulemaking

FDA

Open for Comments

FDA-2026-P-3666

Requests that the FDA codify, regularize, and transparently administer a principle the Agency already recognizes in practice: that the adequacy of an investigation in rare diseases cannot be determined by default assumptions alone. It does not ask FDA to invent a new principle or apply distinct evidentiary thresholds or concessions to rare disease research programs.

Documents

Comments

Description

Open

Key Dates

Comment Period OpensApr 7, 2026

Documents

Type	Title	Posted	Comments	Status
Supporting Material	Reference 6 - FDA, Adaptive Designs Guidance (2019)	Apr 7, 2026	--

Keywords

CDER

CBER

Haystack Project, Inc.

Requests that the FDA codify, regularize, and

transparently administer a principle the Agency

already recognizes in practice: that the

adequacy of an investigation in rare diseases

cannot be determined by default assumptions

Data from Regulations.gov