X0407 4 2023-03-17 0001305253 Eiger BioPharmaceuticals, Inc. EIGR 0001686952 Mayer Eldon C. III C/O EIGER BIOPHARMACEUTICALS, INC. 2155 PARK BLVD. PALO ALTO CA 94306 true Ex VP & Chief Commerc. Officer false Common Stock 2023-03-17 4 S 0 2520 1.07 D 57948 D Common Stock 2023-03-17 4 S 0 1875 1.0707 D 56073 D These shares were sold by the reporting person in a pre-elected sell-to-cover transaction to cover tax withholding obligations in connection with the vesting of the Restricted Stock Units ("RSUs") granted on March 11, 2022 for 16,000 shares. These shares were sold by the reporting person in a pre-elected sell-to-cover transaction to cover tax withholding obligations in connection with the vesting of the RSUs granted on March 12, 2021 for 11,875 shares. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $1.07 to $1.08, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, 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 range set forth in this Form 4. /s/ Eldon C. Mayer III 2023-03-21