144 0001423029 XXXXXXXX LIVE 0000879407 Arrowhead 001-38042 177 East Colorado Blvd Suite 700 Pasadena CA 91105 6266964702 Christopher Anzalone Officer Common Merrill Lynch

75 Rockefeller Plz 2nd Flr New York NY 10019

85000 5443252.88 135809558 12/17/2025 NASDAQ Common 01/01/2020 Compensation Issuer N 400000 01/01/2020 Compensation Common 01/01/2022 Compensation Issuer N 49761 01/01/2022 Compensation Common 12/20/2022 Compensation Issuer N 46805 12/20/2022 Compensation N Christopher Anzalone

177 E Colorado Blvd Suite 700 Pasadena CA 91105

Common 12/16/2025 54298 3398141.91 Christopher Anzalone

177 E Colorado Blvd Suite 700 Pasadena CA 91105

Common 12/15/2025 130000 8950579.9 Shares sold exclusively to cover anticipated taxes on a performance awards that vested December 12, 2025. These performance awards were previously reported on form 4. 12/17/2025 Christopher Anzalone