X0306 4 2020-10-20 0 0000879407 ARROWHEAD PHARMACEUTICALS, INC. ARWR 0001486672 Myszkowski Kenneth Allen 177 E. COLORADO BLVD SUITE 700 PASADENA CA 91105 0 1 0 0 Chief Financial Officer Common Stock 2020-10-20 4 M 0 29166 6.15 A 456834 D Common Stock 2020-10-20 4 S 0 29166 54.04 D 427668 D Stock Option (right to buy) 6.15 2020-10-20 4 M 0 29166 0.00 D 2016-02-01 2026-01-01 Common Stock 29166 43505 D Open market sale pursuant to a 10b5-1 trading plan adopted by the Reporting Person in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended. The price reported on Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $54.00 to $54.07, inclusive. The reporting person undertakes to provide to Arrowhead Pharmaceuticals, Inc., any security holder of Arrowhead Pharmaceuticals, Inc., or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote of this Form 4. Represents the first vesting date. Option vested over four years from date of grant. /s/Kenneth Myszkowski 2020-10-22