I enjoy eating Chinese food with a group, because I can get a sample from each person’s plate. Such as in 505(b)(2) submissions, you can pick and choose parts of different RLD’s for your submission.
A reader was surprised when I previously commented that a 505(b)(2) submission can have more than one RLD. As long as the information is supprortive of your proposed drug product, then it can be used in the submission. For a simple example, in humans, estrone and estradiol interconvert. Assume I submit estradiol tablets, I can also take safety and efficacy information from estrone tablets. Along the same line of reasoning, information can be obtained from a pro-drug and metabolite(s).
A more complex case involves Reliant versus Abbott. While this case was mainly about patents (a paragraph IV challenge) it is instructive for our purposes. Abbott introduced fenofibrate capsules, obtaining various dosage strengths in a series of supplements. Abbott discontinued the capsules and introduced a tablet form, based on bioequivalence only. The tablets had listed patents while the capsules had only one patent. Reliant submitted a 505(b)(2) for capsules and referenced the original capsule NDA. In the FDA’s conclusion on the matter, it noted that an applicant can obtain, for example, safety and efficacy information from one NDA for dosage while citing safety and efficacy information from another NDA for indication.