Exhibit 10.21
 
November 11, 2020
 
Anthony Cataldo
GT Biopharma Inc.
9350 Wilshire Blvd., Suite 203
Beverly Hills, CA 990212
 
Mr. Cataldo:
 
This letter is my notice of resignation as the Chief Financial Officer and Director of GT Biopharma, Inc. effective immediately.
 
Sincerely,
 
/s/ Steven Weldon
Steven Weldon, MBA, CPA