37 C.F.R. § 3.16
Assignability of trademarks prior to filing of an allegation of use
Before an allegation of use under either 15 U.S.C. 1051(c) or 15 U.S.C. 1051(d) is filed, an applicant may only assign an application to register a mark under 15 U.S.C. 1051(b) to a successor to the applicant's business, or portion of the business to which the mark pertains, if that business is ongoing and existing.