WALSH COLIN sold ATTO

Footnotes

The previous report on Form 3 reflected an administrative error with respect to the number of shares of common stock issuable upon conversion of the Preferred Stock, which is corrected in this Form 4.; Each share of Series B Preferred Stock and Series C Preferred Stock (the "Preferred Stock") automatically converted into shares of the Issuer's common stock on a 9.29-for-1 basis upon the closing of the Issuer's initial public offering (the "IPO") on August 6, 2026 without payment of consideration. The Preferred Stock has no expiration date.; The Reporting Person disclaims beneficial ownership of the securities reported herein except to the extent of the Reporting Person's pecuniary interest therein, if any, and this report shall not be deemed an admission that any such Reporting Person is the beneficial owner of, or has any pecuniary interest in, such securities for purposes of Section 16 of the Exchange Act, or for any other purpose.; The Reporting Person is a managing director of GS&Co, a subsidiary of The Goldman Sachs Group Inc. ("GS Group"). GS Group is the direct owner of GS&Co and an indirect owner of Goldman Sachs Asset Management, L.P. ("GSAM LP"). GS&Co is the manager of Broad Street Principal Investments L.L.C. ("BSPI") which directly holds 96,190 shares of common stock purchased in the IPO and 468,565 shares of common stock converted from 3,497,806 shares of Series B Preferred Stock and 855,179 shares of Series C Preferred Stock of the Issuer. GSAM LP is the investment manager of WSLS Offshore Investments, SLP ("WSLS Offshore") which directly holds 131,283 shares of common stock purchased in the IPO and 639,518 shares of common stock converted from 4,773,948 shares of Series B Preferred Stock and 1,167,182 shares of Series C Preferred Stock of the Issuer,... (continued in footnote 7); (continued from footnote 6)... West Street Life Sciences I, L.P. ("WSLS I") which directly holds 137,708 shares of common stock purchased in the IPO and 670,812 shares of common stock converted from 5,007,564 shares of Series B Preferred Stock and 1,224,299 shares of Series C Preferred Stock of the Issuer, WSLS Emp Offshore Investments, L.P. ("WSLS Emp Offshore") which directly holds 36,927 shares of common stock purchased in the IPO and 179,879 shares of common stock converted from 1,342,794 shares of Series B Preferred Stock and 328,300 shares of Series C Preferred Stock of the Issuer, and WSLS Emp Onshore Investments, L.P. ("WSLS Emp Onshore") which directly holds 97,892 shares of common stock purchased in the IPO and 476,858 shares of common stock converted from 3,559,718 shares of Series B Preferred Stock and 870,315 shares of Series C Preferred Stock of the Issuer,... (continued in footnote 8); (continued from footnote 7)... GS&Co is a direct subsidiary of GS Group and is the manager of BSPI. WSLS Offshore, WSLS I, WSLS Emp Offshore, and WSLS Emp Onshore are investment vehicles managed by GSAM LP, an indirect subsidiary of GS Group.