X0206 3 2017-01-20 0 0001509745 LEAP THERAPEUTICS, INC. LPTX 0001013473 CAVANAUGH JAMES H C/O LEAP THERAPEUTICS, INC. 47 THORNDIKE STREET SUITE B1-1 CAMBRIDGE MA 02141 1 0 1 0 Common Stock 2618406 I See Footnote Consists of 2,618,406 shares held by HealthCare Ventures VIII, L.P. Christopher K. Mirabelli, James H. Cavanaugh, John W. Littlechild, Harold Werner and Augustine Lawlor (collectively, the "HCVVIII Directors") are the Managing Directors of HealthCare Partners VIII, LLC ("HCPVIII LLC"), which is the General Partner of HealthCare Partners VIII, L.P. ("HCPVIII"), which is the General Partner of HealthCare Ventures VIII, L.P. Each of the HCVVIII Directors, HCPVIII LLC and HCPVIII beneficially own and share voting and dispositive power with respect to all of the securities owned by HealthCare Ventures VIII, L.P. James H. Cavanaugh disclaims beneficial ownership of these shares except to the extent of his proportionate pecuniary interest in these securities. Exhibit 24.1 Power of Attorney /s/ Douglas E. Onsi as attorney-in-fact for James Cavanaugh 2017-01-23