ALTIMMUNE INC ALT
COM NEW · Common Stock · CUSIP 02155H200 · ISIN US02155H2004
American biopharmaceutical company
- SectorHealth care
- IndustryPharmaceutical Preparations
- HeadquartersGaithersburg, MD
- Founded1997
- Websitealtimmune.com
- FilingsSEC EDGAR
* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once ($34.0k this quarter). Holder counts are more reliable. Shares outstanding: 130.1m as of 2026-02-27, from the company's own SEC filing; the percentage can still exceed 100%: lent-out shares are counted by the lender and the buyer, and some reports overlap without saying so. Implied quarter-end price ≈ $3.08. Options: 10 managers hold calls ($10.4m notional), 7 hold puts ($3.2m).
Trends to Q1 2026
Institutional holders
Managers reporting a position, each quarter
Numbers
| Quarter | Holders |
|---|---|
| Q3 2022 | 122 |
| Q4 2022 | 129 |
| Q1 2023 | 134 |
| Q2 2023 | 120 |
| Q3 2023 | 113 |
| Q4 2023 | 143 |
| Q1 2024 | 171 |
| Q2 2024 | 173 |
| Q3 2024 | 169 |
| Q4 2024 | 182 |
| Q1 2025 | 178 |
| Q2 2025 | 181 |
| Q3 2025 | 158 |
| Q4 2025 | 184 |
| Q1 2026 | 173 |
Buyers vs sellers
Managers adding to or starting a position, vs cutting or selling out
Numbers
| Quarter | Bought or added | Cut or sold out |
|---|---|---|
| Q2 2024 | 95 | 86 |
| Q3 2024 | 79 | 71 |
| Q4 2024 | 90 | 68 |
| Q1 2025 | 80 | 78 |
| Q2 2025 | 108 | 75 |
| Q3 2025 | 79 | 89 |
| Q4 2025 | 117 | 50 |
| Q1 2026 | 106 | 71 |
Calls vs puts
Options held, notional value, last 4 quarters. P/C = puts ÷ calls
Numbers
| Quarter | Calls | Puts | P/C |
|---|---|---|---|
| Q2 2025 | $26.3m | $22.6m | 0.86 |
| Q3 2025 | $19.2m | $14.1m | 0.73 |
| Q4 2025 | $13.4m | $15.7m | 1.18 |
| Q1 2026 | $10.4m | $3.2m | 0.31 |
Biggest buyers
| MARSHALL WACE, LLP | Added | +3.1m |
| BlackRock, Inc. | Added | +3.1m |
| MILLENNIUM MANAGEMENT LLC | Added | +3.1m |
| Alyeska Investment Group, L.P. | New | +2.6m |
| STATE STREET CORP | Added | +2.0m |
| TWO SIGMA INVESTMENTS, LP | Added | +1.2m |
| Nuveen, LLC | Added | +1.1m |
| GEODE CAPITAL MANAGEMENT, LLC | Added | +814.7k |
| DIMENSIONAL FUND ADVISORS LP | Added | +762.2k |
| Point72 Asset Management, L.P. | New | +665.3k |
Biggest sellers
| JANE STREET GROUP, LLC | Sold out | -1.8m |
| TANG CAPITAL MANAGEMENT LLC | Reduced | -1.5m |
| Knoll Capital Management, LLC | Reduced | -961.5k |
| CITADEL ADVISORS LLC | Reduced | -889.1k |
| TWO SIGMA ADVISERS, LP | Sold out | -793.9k |
| D. E. Shaw & Co., Inc. | Reduced | -616.6k |
| MORGAN STANLEY | Reduced | -584.6k |
| Soviero Asset Management, LP | Sold out | -400.0k |
| Sculptor Capital LP | Sold out | -276.7k |
| Jump Financial, LLC | Sold out | -242.0k |
Biggest calls
| GROUP ONE TRADING LLC | Added | $2.7m868.9k shares |
| GERBER, LLC | New | $2.3m750.0k shares |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Added | $1.7m561.4k shares |
| CITADEL ADVISORS LLC | Reduced | $1.0m337.9k shares |
| IMC-Chicago, LLC | Added | $950.2k308.5k shares |
| JANE STREET GROUP, LLC | Added | $937.2k304.3k shares |
| SIMPLEX TRADING, LLC | Reduced | $623.4k202.4k shares |
| DCF Advisers, LLC | Reduced | $114.0k37.0k shares |
| Walleye Capital LLC | Reduced | $33.3k10.8k shares |
| HUB Investment Partners, LLC | Added | $15.4k5.0k shares |
Biggest puts
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Reduced | $1.7m555.0k shares |
| CITADEL ADVISORS LLC | Reduced | $602.4k195.6k shares |
| GROUP ONE TRADING LLC | Reduced | $342.5k111.2k shares |
| SIMPLEX TRADING, LLC | Reduced | $231.0k75.0k shares |
| JANE STREET GROUP, LLC | Reduced | $173.7k56.4k shares |
| IMC-Chicago, LLC | Reduced | $150.3k48.8k shares |
| Walleye Capital LLC | Reduced | $2.5k800 shares |
Options at notional value: the value of the shares the contracts control, as filers report them, not what the options cost. Not included in the holders, shares or buying above.
Major shareholders (over 5%)
Anyone who owns more than 5% of a class of the company's shares has to say so: on Schedule 13D if they may try to influence or control the company, on 13G if they're a passive investor, and update it as the stake changes. Each holder's latest filing, from 19 Dec 2024 on; percentages are of the share class, as the holder worked them out.
| Holder | Stake |
|---|---|
| Deep Track Capital, LP 13G · passive investor new · filed 2026-04-30 | 10.0% |
| TCG Crossover GP II, LLC 13G · passive investor new · filed 2026-05-01 | 9.8% |
| BlackRock, Inc. 13G · institution -1.1 pts · filed 2025-07-16 | 7.6% |
| VIKING GLOBAL INVESTORS LP 13G · passive investor new · filed 2026-05-01 | 6.7% |
| RA CAPITAL MANAGEMENT, L.P. 13G · passive investor new · filed 2026-05-01 | 6.5% |
| STATE STREET CORP 13G · institution new · filed 2026-05-12 | 5.5% |
Fell to 5% or below in the last year: TANG CAPITAL MANAGEMENT LLC (0.3%, 2026-05-15), VANGUARD GROUP INC (0.0%, 2026-03-26)
Insider purchases and sales in Q1 2026
Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.
Officers and directors buying vs selling
Number of people, by quarter (10% owners not included)
Numbers
| Quarter | Buying | Bought | Selling | Sold | Sold under a plan |
|---|---|---|---|---|---|
| Q2 2024 | 0 | — | 0 | — | — |
| Q3 2024 | 0 | — | 1 | $110.5k | — |
| Q4 2024 | 0 | — | 0 | — | — |
| Q1 2025 | 2 | $57.8k | 0 | — | — |
| Q2 2025 | 0 | — | 0 | — | — |
| Q3 2025 | 0 | — | 0 | — | — |
| Q4 2025 | 3 | $104.9k | 0 | — | — |
| Q1 2026 | 4 | $111.0k | 0 | — | — |
| Date | Insider | Trade | Value |
|---|---|---|---|
| 2026-03-06 | Durso Jerome Benedict President and CEO, director | Bought | $70.8k20.0k shares |
| 2026-03-06 | WEAVER GREGORY L Chief Financial Officer | Bought | $17.7k5.0k shares |
| 2026-01-08 | Pisano Wayne Director | Bought | $20.4k5.0k shares |
| 2026-01-05 | Sohn Catherine A. Director | Bought | $2.1k500 shares |
Their holding: how much the trade added to or took from the insider's holding (direct, or the trust or fund named). The same trade is sometimes reported by more than one insider, such as a fund and the director who represents it; totals count it once. A value is left blank where the reported price is far from the market price (usually a typo).
Holders, Q1 2026
| Manager | Shares | Change |
|---|---|---|
| BlackRock, Inc. 0.00% of their portfolio | 12.8m $39.4m | Added +3.1m |
| STATE STREET CORP 0.00% of their portfolio | 7.1m $22.0m | Added +2.0m |
| VANGUARD CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 5.7m $17.4m | First filing |
| VANGUARD PORTFOLIO MANAGEMENT LLC 0.00% of their portfolio | 5.4m $16.6m | First filing |
| MARSHALL WACE, LLP 0.01% of their portfolio | 4.0m $12.4m | Added +3.1m |
| MILLENNIUM MANAGEMENT LLC 0.01% of their portfolio | 3.3m $10.0m | Added +3.1m |
| GEODE CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 3.1m $9.6m | Added +814.7k |
| Alyeska Investment Group, L.P. 0.02% of their portfolio | 2.6m $8.1m | New |
| TWO SIGMA INVESTMENTS, LP 0.01% of their portfolio | 2.5m $7.6m | Added +1.2m |
| Nuveen, LLC 0.00% of their portfolio | 2.3m $7.2m | Added +1.1m |
| GOLDMAN SACHS GROUP INC 0.00% of their portfolio | 1.4m $4.2m | Added +1.4k |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP 0.01% of their portfolio | 1.3m $4.1m | Reduced -43.1k |
| DIMENSIONAL FUND ADVISORS LP 0.00% of their portfolio | 1.0m $3.2m | Added +762.2k |
| NORTHERN TRUST CORP 0.00% of their portfolio | 996.7k $3.1m | Added +280.7k |
| UBS Group AG 0.00% of their portfolio | 904.8k $2.8m | Added +262.7k |
| VANGUARD FIDUCIARY TRUST CO 0.00% of their portfolio | 869.3k $2.7m | First filing |
| MORGAN STANLEY 0.00% of their portfolio | 775.3k $2.4m | Reduced -584.6k |
| D. E. Shaw & Co., Inc. 0.00% of their portfolio | 727.0k $2.2m | Reduced -616.6k |
| FMR LLC 0.00% of their portfolio | 674.0k $2.1m | Added +109.9k |
| SCHRODER INVESTMENT MANAGEMENT GROUP 0.00% of their portfolio | 667.8k $1.9m | Added +198.8k |
| TANG CAPITAL MANAGEMENT LLC 0.10% of their portfolio | 666.0k $2.1m | Reduced -1.5m |
| Point72 Asset Management, L.P. 0.00% of their portfolio | 665.3k $2.0m | New |
| BANK OF AMERICA CORP /DE/ 0.00% of their portfolio | 570.2k $1.8m | Added +186.4k |
| CITADEL ADVISORS LLC 0.00% of their portfolio | 448.9k $1.4m | Reduced -889.1k |
| BNP PARIBAS FINANCIAL MARKETS 0.00% of their portfolio | 435.1k $1.3m | Added +257.8k |
| Bank of New York Mellon Corp 0.00% of their portfolio | 413.5k $1.3m | Added +59.3k |
| Beirne Wealth Consulting Services, LLC 0.36% of their portfolio | 411.9k $1.3m | Added +35.4k |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC 0.00% of their portfolio | 351.7k $1.1m | Added +68.0k |
| Steward Partners Investment Advisory, LLC 0.00% of their portfolio | 251.8k $775.5k | Added +6.4k |
| WELLINGTON MANAGEMENT GROUP LLP 0.00% of their portfolio | 248.2k $764.3k | Reduced -9.1k |
| MANGROVE PARTNERS IM, LLC 0.06% of their portfolio | 239.3k $737.0k | New |
| Baird Financial Group, Inc. 0.00% of their portfolio | 237.5k $731.6k | Added +118.1k |
| BROWN WEALTH MANAGEMENT, LLC 0.19% of their portfolio | 236.1k $727.3k | Reduced -22.5k |
| Rafferty Asset Management, LLC 0.00% of their portfolio | 231.3k $712.3k | Added +35.5k |
| Invesco Ltd. 0.00% of their portfolio | 227.9k $701.8k | Added +13.0k |
| Hennion & Walsh Asset Management, Inc. 0.02% of their portfolio | 202.0k $622.1k | Reduced -12.6k |
| BARCLAYS PLC 0.00% of their portfolio | 192.9k $594.0k | Reduced -207.7k |
| Janney Montgomery Scott LLC 0.00% of their portfolio | 172.6k $532.0k | Added +70.0k |
| COMMONWEALTH EQUITY SERVICES, LLC 0.00% of their portfolio | 160.4k $493.9k | Reduced -21.1k |
| Knoll Capital Management, LLC 0.26% of their portfolio | 160.0k $492.8k | Reduced -961.5k |
| RHUMBLINE ADVISERS 0.00% of their portfolio | 155.7k $479.5k | Added +34.2k |
| HSBC HOLDINGS PLC 0.00% of their portfolio | 154.4k $476.2k | Reduced -110.1k |
| STIFEL FINANCIAL CORP 0.00% of their portfolio | 134.6k $414.6k | Added +11.2k |
| WEALTH EFFECTS LLC 0.14% of their portfolio | 131.9k $406.4k | Added +20.2k |
| Man Group plc 0.00% of their portfolio | 129.8k $399.9k | Added +110.9k |
| JPMORGAN CHASE & CO 0.00% of their portfolio | 127.5k $367.2k | Added +23.0k |
| Grantham, Mayo, Van Otterloo & Co. LLC 0.00% of their portfolio | 126.4k $389.3k | Reduced -46.2k |
| DEUTSCHE BANK AG\ 0.00% of their portfolio | 124.5k $383.5k | Added +44.6k |
| Engineers Gate Manager LP 0.00% of their portfolio | 116.1k $357.6k | Added +28.8k |
| Jefferies Financial Group Inc. 0.00% of their portfolio | 110.0k $338.8k | Reduced -47.8k |
| ALPS ADVISORS INC 0.00% of their portfolio | 105.9k $326.1k | Added +20.2k |
| LPL Financial LLC 0.00% of their portfolio | 103.8k $319.6k | Added +55.1k |
| SILVERCREST ASSET MANAGEMENT GROUP LLC 0.00% of their portfolio | 103.5k $318.8k | Unchanged |
| Summit Financial Wealth Advisors, LLC 0.05% of their portfolio | 103.3k $318.1k | Unchanged |
| PROFUND ADVISORS LLC 0.01% of their portfolio | 103.1k $317.7k | Added +30.8k |
| NOMURA ASSET MANAGEMENT INTERNATIONAL INC. 0.00% of their portfolio | 100.0k $308.0k | Unchanged |
| WELLS FARGO & COMPANY/MN 0.00% of their portfolio | 95.9k $295.4k | Reduced -45.4k |
| PRICE T ROWE ASSOCIATES INC /MD/ 0.00% of their portfolio | 92.5k $285.0k | Added +42.6k |
| AQR CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 85.5k $263.2k | Added +64.3k |
| Brevan Howard Capital Management LP 0.00% of their portfolio | 78.4k $241.5k | Reduced -35.7k |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. 0.00% of their portfolio | 77.3k $234.8k | Added +24.7k |
| KINGSWOOD WEALTH ADVISORS, LLC 0.01% of their portfolio | 76.5k $235.6k | Added +40.5k |
| CITIGROUP INC 0.00% of their portfolio | 76.3k $235.1k | Added +48.0k |
| Caption Management, LLC 0.01% of their portfolio | 74.4k $229.3k | Unchanged |
| MetLife Investment Management, LLC 0.00% of their portfolio | 72.2k $222.4k | Added +34.0k |
| AMERIPRISE FINANCIAL INC 0.00% of their portfolio | 72.0k $221.7k | Reduced -1.9k |
| ALLIANCEBERNSTEIN L.P. 0.00% of their portfolio | 71.8k $259.1k | Unchanged |
| Virtu Financial LLC 0.01% of their portfolio | 70.5k $217.0k | Added +12.1k |
| PVG ASSET MANAGEMENT CORP 0.10% of their portfolio | 66.1k $174.6k | New |
| Leonteq Securities AG 0.01% of their portfolio | 65.0k $200.2k | Added +64.0k |
| AMERICAN CENTURY COMPANIES INC 0.00% of their portfolio | 62.9k $193.8k | New |
| SG Americas Securities, LLC 0.00% of their portfolio | 55.6k $171.0k | Added +45.0k |
| RAYMOND JAMES FINANCIAL INC 0.00% of their portfolio | 53.8k $165.7k | Reduced -2.1k |
| CANADA PENSION PLAN INVESTMENT BOARD 0.00% of their portfolio | 53.3k $164.2k | Added +23.3k |
| Virtus Investment Advisers, LLC 0.04% of their portfolio | 51.7k $159.4k | Added +1.3k |
| ExodusPoint Capital Management, LP 0.00% of their portfolio | 48.6k $149.7k | Added +36.7k |
| AXQ CAPITAL, LP 0.02% of their portfolio | 47.8k $147.1k | Added +22.1k |
| Rockefeller Capital Management L.P. 0.00% of their portfolio | 46.4k $142.8k | Added +3.2k |
| Vanguard Global Advisers, LLC 0.00% of their portfolio | 42.8k $131.9k | First filing |
| Creative Planning 0.00% of their portfolio | 39.2k $120.8k | Reduced -7.7k |
| Kovack Advisors, Inc. 0.01% of their portfolio | 36.2k $111.7k | Added +1.0k |
| EverSource Wealth Advisors, LLC 0.00% of their portfolio | 35.6k $109.8k | Added +18.0k |
| Cetera Investment Advisers 0.00% of their portfolio | 35.5k $109.2k | Added +5.8k |
| Police & Firemen's Retirement System of New Jersey 0.00% of their portfolio | 35.4k $109.1k | Added +11.9k |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE 0.00% of their portfolio | 34.8k $107.1k | Added +7.2k |
| MML INVESTORS SERVICES, LLC 0.00% of their portfolio | 34.5k $106.4k | Unchanged |
| INTECH INVESTMENT MANAGEMENT LLC 0.00% of their portfolio | 30.8k $94.7k | Reduced -21.8k |
| Corient Private Wealth LP 0.00% of their portfolio | 30.6k $94.1k | New |
| HUB Investment Partners, LLC 0.00% of their portfolio | 30.2k $93.1k | Added +16.0k |
| E Fund Management Co., Ltd. 0.00% of their portfolio | 29.1k $89.5k | First filing |
| BLAIR WILLIAM & CO/IL 0.00% of their portfolio | 28.2k $86.9k | Reduced -28.2k |
| FARALLON CAPITAL MANAGEMENT, L.L.C. 0.00% of their portfolio | 27.6k $85.0k | Unchanged |
| Voleon Capital Management LP 0.00% of their portfolio | 27.1k $83.6k | Reduced -19.9k |
| Concurrent Investment Advisors, LLC 0.00% of their portfolio | 26.5k $81.6k | Unchanged |
| JONES FINANCIAL COMPANIES LLLP 0.00% of their portfolio | 25.9k $78.1k | Added +13.3k |
| ROYAL BANK OF CANADA 0.00% of their portfolio | 25.3k $78.0k | Reduced -2.1k |
| ProShare Advisors LLC 0.00% of their portfolio | 24.5k $75.5k | Added +3.7k |
| Polymer Capital Management (US) LLC 0.01% of their portfolio | 24.0k $73.9k | New |
| SIMPLEX TRADING, LLC 0.00% of their portfolio | 22.8k $70.3k | New |
| China Universal Asset Management Co., Ltd. 0.01% of their portfolio | 22.2k $68.4k | Added +5.2k |