Institutional HoldersBeta
Who holds a company, from every 13F filed for the quarter, one row per filer exactly as filed, against the latest share count the company reported.
Share classes (cover page of the 10-Q filed 2026-09-02, as of 2026-08-31)
| Class | Listed | Shares outstanding | Held by 13F filers | % of class | Holders | CUSIP |
|---|---|---|---|---|---|---|
| Common stock | ATTO · NASDAQ | 45,651,262 | — | — |
Each class is compared with its own share count; classes are not added together. A class that is not exchange-listed cannot be held by 13F filers.
Top holders (0 of 0 · )
change vs 2026-03-31No 13F holders for the selected CUSIPs this quarter.
Large holders from 13D/13G (latest per reporting person, last 2 years)
Filed when a holder crosses 5% or changes materially, so often more current than the quarter-end 13F. Percentages are the filer's own, against the share count they used.
| Reporting person | Form | Filed | Event | Shares | % of class |
|---|---|---|---|---|---|
| David Kroin | SCHEDULE 13G | 2026-08-12 | 2026-08-05 | 3,207,138 | 7.45% |
| Deep Track Biotechnology Master Fund, Ltd. | SCHEDULE 13G | 2026-08-12 | 2026-08-05 | 3,207,138 | 7.45% |
| Deep Track Capital, LP | SCHEDULE 13G | 2026-08-12 | 2026-08-05 | 3,207,138 | 7.45% |
| FHMLSP, L.L.C. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 760,327 | 1.7% |
| FHMLSP, L.P. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 760,327 | 1.7% |
| FHMLS XII, L.L.C. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 54,163 | 0.1% |
| FHMLS XII, L.P. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 54,163 | 0.1% |
| FHMLS XI, L.L.C. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 6,154,213 | 13.5% |
| FHMLS XI, L.P. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 6,154,213 | 13.5% |
| Frazier Life Sciences Public Fund, L.P. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 760,327 | 1.7% |
| Frazier Life Sciences XII, L.P. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 54,163 | 0.1% |
| Frazier Life Sciences XI, L.P. | SCHEDULE 13D | 2026-08-11 | 2026-08-06 | 6,154,213 | 13.5% |
Source: SEC Form 13F-HR information tables for the quarter ending 2026-06-30 (filed within 45 days of quarter end; amendments applied; values normalised to dollars), the share count from the company's latest 10-K/10-Q XBRL cover page, and Schedule 13D/13G filings. Each row is a legal 13F filer as filed — related entities (e.g. Vanguard's advisers) are not merged. Retail brokerage accounts are not reported on 13F, so the remainder is mostly retail and insiders.