X0202 SCHEDULE 13D/A 0001104659-21-087437 0001725721 XXXXXXXX LIVE 4 Common Stock, par value $0.0001 per share 09/09/2026 false 0001808805 63909J108 Nautilus Biotechnology, Inc.

2701 Eastlake Avenue East Seattle WA 98102

a16z Capital Management (650) 798-5800 2865 Sand Hill Road, Suite 101 Menlo Park CA 94025 0001725721 N AH Bio Fund II, L.P. b WC N DE 5782188.00 0.00 5782188.00 0.00 5782188.00 N 4.5 PN 0001725722 N AH Equity Partners Bio II, L.L.C. b AF N DE 5782188.00 0.00 5782188.00 0.00 5782188.00 N 4.5 OO 0001829357 N Andreessen Horowitz LSV Fund II, L.P. b WC N DE 481047.00 0.00 481047.00 0.00 481047.00 N 0.4 PN 0001829384 N AH Equity Partners LSV II, L.L.C. b AF N DE 481047.00 0.00 481047.00 0.00 481047.00 N 0.4 OO 0001160077 N Marc L. Andreessen b AF N X1 0.00 6263235.00 0.00 6263235.00 6263235.00 N 4.9 IN 0001166586 N Benjamin A. Horowitz b AF N X1 0.00 6263235.00 0.00 6263235.00 6263235.00 N 4.9 IN Common Stock, par value $0.0001 per share Nautilus Biotechnology, Inc. 2701 Eastlake Avenue East Seattle WA 98102 This Amendment No. 4 (this "Amendment No. 4" or this "Schedule 13D/A") amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission (the "SEC") on June 30, 2021 and amended on June 4, 2026, June 30, 2026 and August 28, 2026 (as amended, the "Statement") by the Reporting Persons. Unless otherwise defined herein, capitalized terms used in this Amendment No. 4 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged. This Schedule 13D/A is filed by AH Bio Fund II, L.P. ("AH Bio II"), AH Equity Partners Bio II, L.L.C. ("AH Equity Bio II"), Andreessen Horowitz LSV Fund II, L.P. ("AH LSV II"), AH Equity Partners LSV II, L.L.C. ("AH Equity LSV II"), Marc Andreessen ("Andreessen") and Benjamin Horowitz ("Horowitz"). The foregoing entities and individuals are collectively referred to herein as the "Reporting Persons." The Reporting Persons' beneficial ownership of the Issuer's securities consists of (i) 5,782,188 shares of the Issuer's common stock directly held by AH Bio II for itself and as nominee for AH Bio Fund II-B, L.P. ("AH Bio II-B") and (ii) 481,047 shares of the Issuer's common stock directly held by AH LSV II for itself and as nominee for Andreessen Horowitz LSV Fund II-B, L.P. ("AH LSV II-B") and Andreessen Horowitz LSV Fund II-Q, L.P. ("AH LSV II-Q"). AH Equity Bio II is the general partner of AH Bio II and may be deemed to have sole power to vote and sole power to dispose of shares of the Issuer held of record by AH Bio II for itself and as nominee for AH Bio II-B. Andreessen and Horowitz are managing members of AH Equity Bio II and may be deemed to have shared power to vote and shared power to dispose of shares of the Issuer held of record by AH Bio II for itself and as nominee. AH Equity LSV II is the general partner of AH LSV II and may be deemed to have sole power to vote and sole power to dispose of shares of the Issuer held of record by AH LSV II for itself and as nominee for AH LSV II-B and AH LSV II-Q. Andreessen and Horowitz are managing members of AH Equity LSV II and may be deemed to have shared power to vote and shared power to dispose of shares of the Issuer held of record by AH LSV II for itself and as nominee. The address of the principal place of business of each of the Reporting Persons is c/o Andreessen Horowitz, 2865 Sand Hill Road, Suite 101, Menlo Park, CA 94025. The principal occupation of each of Andreessen and Horowitz is co-founder and managing member of the venture capital firm Andreessen Horowitz. The principal business of each of the other Reporting Persons is the venture capital investment business. During the last five years, none of the Reporting Persons have been convicted in any criminal proceeding (excluding traffic violations or similar misdemeanors). During the last five years, none of the Reporting Persons have been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws. The responses of the Reporting Persons with respect to row 6 of their respective cover pages to this Schedule 13D/A are incorporated herein by reference. Rows 11 and 13 of each Reporting Person's cover page to this Schedule 13D/A set forth the aggregate number of shares of common stock of the Issuer and percentage of the shares of common stock of the Issuer beneficially owned by such Reporting Person and are incorporated herein by reference. The percentage set forth in row 13 of each cover page is based upon 127,255,223 shares of common stock outstanding as of July 24, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on July 28, 2026. Rows 7 through 10 of each Reporting Person's cover page to this Schedule 13D/A set forth the number of shares of common stock of the Issuer as to which such Reporting Person has the sole or shared power to vote or direct the vote and sole or shared power to dispose or to direct the disposition and are incorporated herein by reference. Except as set forth below, none of the Reporting Persons has effected any transactions with respect to the securities of the Issuer since the most recent amendment to the Statement filed with the SEC on August 28, 2026. Weighted Low High Reporting Transaction No. of Average Price Price Transaction Person Date Shares Price ($) ($) ($) Open Market Sale AH Bio II 08/31/2026 116,045 0.9597 0.94005 0.97425 Open Market Sale AH LSV II 08/31/2026 9,654 0.9597 0.94005 0.97425 Open Market Sale AH Bio II 09/01/2026 135,580 0.9241 0.92 0.9547 Open Market Sale AH LSV II 09/01/2026 11,280 0.9241 0.92 0.9547 Open Market Sale AH Bio II 09/02/2026 254,695 0.9586 0.93 0.97835 Open Market Sale AH LSV II 09/02/2026 21,189 0.9586 0.93 0.97835 Open Market Sale AH Bio II 09/03/2026 105,254 0.9124 0.90 0.9214 Open Market Sale AH LSV II 09/03/2026 8,757 0.9124 0.90 0.9214 Open Market Sale AH Bio II 09/04/2026 77,084 0.9040 0.90 0.9181 Open Market Sale AH LSV II 09/04/2026 6,413 0.9040 0.90 0.9181 Open Market Sale AH Bio II 09/08/2026 197,705 0.9446 0.9123 0.9901 Open Market Sale AH LSV II 09/08/2026 16,448 0.9446 0.9123 0.9901 Open Market Sale AH Bio II 09/09/2026 426,140 1.0312 0.98 1.085 Open Market Sale AH LSV II 09/09/2026 35,453 1.0312 0.98 1.085 Each of AH Bio II and AH LSV II undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the SEC, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth above. Under certain circumstances set forth in the limited partnership agreement of each of AH Bio II, AH Bio II-B, AH LSV II, AH LSV II-B, AH LSV II-Q and the limited liability company agreement of each of AH Equity Bio II and AH Equity LSV II, the partners or members, as the case may be, of each of such entities may be deemed to have the right to receive dividends from, or the proceeds from the sale of, shares of the Issuer directly or indirectly owned by each such entity of which they are a partner or member. The Reporting Persons ceased to be the beneficial owners of more than five percent of the Issuer's common stock on September 9, 2026. Exhibit 24.1 Power of Attorney (Marc Andreessen), dated June 23, 2023 (incorporated by reference to Exhibit 24.1 to the amendment to the Statement filed with the SEC on June 4, 2026). Exhibit 24.2 Power of Attorney (Benjamin Horowitz), dated June 22, 2023 (incorporated by reference to Exhibit 24.2 to the amendment to the Statement filed with the SEC on June 4, 2026). Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to the amendment to the Statement filed with the SEC on June 4, 2026). AH Bio Fund II, L.P. /s/ Phil Hathaway 09/11/2026 AH Equity Partners Bio II, L.L.C. /s/ Phil Hathaway 09/11/2026 Andreessen Horowitz LSV Fund II, L.P. /s/ Phil Hathaway 09/11/2026 AH Equity Partners LSV II, L.L.C. /s/ Phil Hathaway 09/11/2026 Marc L. Andreessen /s/ Phil Hathaway 09/11/2026 Benjamin A. Horowitz /s/ Phil Hathaway 09/11/2026 Note 1 AH Bio Fund II, L.P. for itself and as nominee for AH Bio Fund II-B, L.P. Note 2 Andreessen Horowitz LSV Fund II, L.P. for itself and as nominee for Andreessen Horowitz LSV Fund II-B, L.P. and Andreessen Horowitz LSV Fund II-Q, L.P.