X0306 4 2017-07-25 0 0001420565 AILERON THERAPEUTICS INC ALRN 0001709976 Gallagher Brian M. Jr. C/O S.R. ONE, LIMITED 161 WASHINGTON STREET, SUITE 500 CONSHOHOCKEN PA 19428 1 0 0 0 Stock Option (right to buy) 13.00 2017-07-25 4 A 0 20000 0.00 A 2027-07-24 Common Stock 20000 20000 D This option was granted on July 25, 2017. The shares underlying the option are scheduled to vest in equal annual installments over three years from July 25, 2017. The option was granted to the Reporting Person as director's compensation. As a Vice President at S.R. One, Limited and an employee of GlaxoSmithKline LLC, the Reporting Person is obligated to transfer any shares issued under the option to S.R. One, Limited, an indirect wholly-owned subsidiary of GlaxoSmithKline plc. /s/ Kira A. Nelson, attorney-in-fact for Brian M. Gallagher, Jr. 2017-07-27