X0306 4 2021-06-16 0001659617 Moleculin Biotech, Inc. MBRX 0001266800 PICKER DONALD H C/O MOLECULIN BIOTECH, INC. 5300 MEMORIAL DR., SUITE 950 HOUSTON TX 77007 1 Chief Science Officer Stock option (right to buy) 3.73 2021-06-16 4 A 0 62676 A 2031-06-16 Common Stock 62676 118510 D The options set forth in this table vest in four equal annual installments, beginning on the first anniversary of the Transaction Date, subject to the grantee's continued service to the Company on each vesting date. Issued in connection with the reporting person's employment with the Company. /s/ Donald Picker 2021-06-21