X0508 4 2026-01-27 0001010086 SIGA TECHNOLOGIES INC SIGA 0001814338 Nguyen Diem C/O SIGA TECHNOLOGIES, INC. 31 EAST 62ND STREET NEW YORK NY 10065 true true false false Chief Executive Officer false Common Stock, par value $.0001 per share 2026-01-27 4 M false 55902 0 A 123555 D Common Stock, par value $.0001 per share 2026-01-27 4 F false 22804 6.82 D 100751 D Restricted Stock Units 2026-01-27 4 M false 55902 0 D Common Stock, par value $.0001 per share 55902 55903 D Represents the acquisition of Common Stock from the vesting of one-third of the restricted stock units ("RSUs") granted on January 27, 2024. Represents the withholding by the Issuer of shares of Common Stock (based on $6.82 per share, the closing stock price on January 27, 2026) to satisfy tax withholding obligations associated with the vesting of RSUs and the consequent issuance of Common Stock. RSUs represent contingent rights to receive Common Stock on a one-for-one basis. The RSUs vest over three years, one-third on each of the first three anniversaries of the date of grant. /s/ Diem Nguyen 2026-01-28