X0609 4/A 2026-06-09 2026-08-19 0 0001274737 EXAGEN INC. XGN 0001289625 Robertson Bruce C false 1261 LIBERTY WAY VISTA CA 92081 1 0 0 0 0 Stock Option(right to buy) 4.31 2026-06-09 4 A 0 37500 0 A 2026-06-09 2036-06-08 Common Stock 37500 37500 D The entire number of shares subject to this option becomes fully vested and exercisable on the first to occur of (a) the first anniversary of the grant date or (b) the next occurring annual meeting of the Issuer's stockholders, subject to the Reporting Person's continued service on the board of directors of the Issuer through such vesting date. On August 19, 2026, the reporting person filed a Form 4 which inadvertently reported that, following his grant of 37,500 stock options, he beneficially owned 55,000 stock options. In fact, as reported in this amendment, the reporting person was granted 37,500 and beneficially owns 37,500 stock options. /s/ Jeffrey G. Black, as attorney-in-fact 2026-08-24