(a) It is an affirmative defense to the prosecution of an offense under this subchapter involving the manufacture, delivery, or possession of a controlled substance analogue that the analogue:
(1) was a substance for which there is an approved new drug application under Section 505 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 355); or
(2) was a substance for which an exemption for investigational use has been granted under Section 505 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 355), if the actor’s conduct with respect to the substance is in accord with the exemption.

(b) For the purposes of this section, Section 505 of the Federal Food, Drug, and Cosmetic Act (21 U.S.C. § 355) applies to the introduction or delivery for introduction of any new drug into intrastate, interstate, or foreign commerce.