Latest Period
Q1 2026
Security Snapshot
Upstream Bio, Inc. - Common Stock, par value $0.001 per share (UPB) Institutional Ownership
CUSIP: 91678A107
13F Institutional Holders and Ownership History from Q4 2024 to Q1 2026
Institutions Reporting
131
Shares (Excl. Options)
44,348,694
Price
$9.00
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- Type / Class
- Equity / Common Stock, par value $0.001 per share
- Symbol
- UPB on Nasdaq
- Shares outstanding
- 54,497,360
- Price per share
- $9.99
- All holders as of 31 Mar 2026
- Q1 2026
- Total 13F shares
- 44,348,694
- Total reported value
- $399,061,908
- % of total 13F portfolios
- 0%
- Share change
- -6,814,228
- Value change
- -$248,908,006
- Number of holders
- 131
Reported Shares, Excluding Options vs Price
Reported Value, Excluding Options
Total Investors
Quick Takeaways
- UPB - Upstream Bio, Inc. - Common Stock, par value $0.001 per share is tracked under CUSIP 91678A107.
- 131 institutions reported positions in Q1 2026.
- 5 significant owners is listed from Schedule 13D/13G reporting.
What Changed
- Holder count moved from 131 to 131 between Q4 2025 and Q1 2026.
- Reported value moved from $1,389,324,241 to $399,061,908.
Why This Matters
- You can quickly see who holds this security, then open quarter and manager detail pages for full evidence.
- 13F and Schedule 13D/13G sections are kept together so you can cross-check institutional and beneficial ownership context.
Source Evidence
Source: SEC Form 13F
Open SEC Evidence
Latest holder context comes from 131 institutions filings for Q1 2026.
Investment Quick Answers
What is CUSIP 91678A107?
CUSIP 91678A107 identifies UPB - Upstream Bio, Inc. - Common Stock, par value $0.001 per share in SEC 13F datasets.
Where can I see the latest institutional holders?
Review the Q1 2026 holders report and the ownership history table below.
Next ownership checks
Use the next link that matches the question you still need to answer about this security.
- Latest 13F filings when you want to inspect fresh institutional portfolio moves.
- Latest Schedule 13D/13G reports when you need large-owner changes outside the 13F cycle.
- All institutional ownership pages to compare this security with other holder-history pages.
Recent Quarterly Holder Reports
Open recent reporting periods for CUSIP 91678A107:
Significant Owners of Upstream Bio, Inc. - Common Stock, par value $0.001 per share (UPB) based on Schedule 13D/G filings
| Filer | Ownership | Change % | Holdings Value | Net Change | Nb Shares | Change % | Reporting Name | Report Period |
|---|---|---|---|---|---|---|---|---|
| FMR LLC | 15% | +11% | $93,972,663 | +$9,006,605 | 7,936,880 | +11% | FMR LLC | 30 Jun 2025 |
| NORGES BANK | 5.3% | $54,226,626 | 2,882,647 | Norges Bank | 30 Sep 2025 | |||
| Decheng Capital Global Life Sciences Fund IV, L.P. | 5% | -18% | $25,886,246 | -$5,324,038 | 2,724,868 | -17% | Decheng Capital Global Life Sciences Fund IV, L.P. | 31 Mar 2026 |
| HBM Healthcare Investments (Cayman) Ltd. | 4.1% | -20% | $41,290,257 | -$9,780,217 | 2,195,111 | -19% | HBM Healthcare Investments (Cayman) Ltd. | 30 Sep 2025 |
| TCG Crossover GP I, LLC | 3.9% | -26% | $39,822,919 | -$12,878,523 | 2,117,103 | -24% | TCG Crossover GP I, LLC | 30 Sep 2025 |
As of 31 Mar 2026, 131 institutional investors reported holding 44,348,694 shares of Upstream Bio, Inc. - Common Stock, par value $0.001 per share (UPB). This represents 81% of the company’s total 54,497,360 outstanding shares.
Top 25 Institutional Shareholders
The largest institutional shareholders of Upstream Bio, Inc. - Common Stock, par value $0.001 per share (UPB) together control 70% of the company’s outstanding shares — a level of ownership often associated with strong institutional conviction and long‑term capital commitment.
| Institution | Ownership % | Shares Held | Share Change % | Portfolio % | Holdings Value |
|---|---|---|---|---|---|
| FMR LLC | 15% | 8,101,563 | +7.8% | 0% | $72,914,070 |
| ORBIMED ADVISORS LLC | 10% | 5,693,589 | 0% | 1.2% | $51,242,301 |
| BlackRock, Inc. | 6.2% | 3,370,689 | +0.78% | 0% | $30,336,201 |
| Decheng Capital LLC | 5% | 2,724,868 | -13% | 3.7% | $24,523,812 |
| ENAVATE SCIENCES GP, LLC | 4.5% | 2,459,703 | 0% | 6.3% | $22,137,327 |
| VANGUARD CAPITAL MANAGEMENT LLC | 3.4% | 1,873,574 | 0% | 0% | $16,862,166 |
| Y-Intercept (Hong Kong) Ltd | 1.8% | 1,000,631 | +2049% | 0.17% | $9,005,679 |
| FEDERATED HERMES, INC. | 1.8% | 979,758 | +203169% | 0.01% | $8,817,822 |
| GEODE CAPITAL MANAGEMENT, LLC | 1.7% | 950,617 | +12% | 0% | $8,557,453 |
| MILLENNIUM MANAGEMENT LLC | 1.7% | 937,323 | +81% | 0.01% | $8,435,907 |
| SEB Asset Management AB | 1.6% | 878,473 | 0% | 0.03% | $7,906,247 |
| Bain Capital Life Sciences Investors, LLC | 1.6% | 867,211 | -35% | 0.7% | $7,804,899 |
| Woodline Partners LP | 1.5% | 831,481 | +9.4% | 0.03% | $7,483,329 |
| D. E. Shaw & Co., Inc. | 1.5% | 820,480 | +2929% | 0.01% | $7,384,320 |
| Parkman Healthcare Partners LLC | 1.4% | 786,783 | -5.7% | 0.73% | $7,081,047 |
| SAMSARA BIOCAPITAL, LLC | 1.4% | 736,047 | 0% | 0.64% | $6,624,423 |
| Pictet Asset Management Holding SA | 1.3% | 733,431 | -5.1% | 0.01% | $6,600,879 |
| VANGUARD PORTFOLIO MANAGEMENT LLC | 1.3% | 727,711 | 0% | 0% | $6,549,399 |
| STATE STREET CORP | 1.3% | 705,350 | -47% | 0% | $6,348,150 |
| HSBC HOLDINGS PLC | 1.2% | 640,326 | 0% | $5,762,934 | |
| Qube Research & Technologies Ltd | 1.1% | 619,321 | 0.01% | $5,573,889 | |
| MORGAN STANLEY | 1% | 552,609 | +353% | 0% | $4,973,481 |
| JPMORGAN CHASE & CO | 0.85% | 463,001 | +320% | 0% | $4,065,149 |
| Nantahala Capital Management, LLC | 0.73% | 400,000 | -19% | 0.22% | $3,600,000 |
| SPHERA FUNDS MANAGEMENT LTD. | 0.66% | 358,000 | 0.55% | $3,222,000 |
Institutional Holders of Upstream Bio, Inc. - Common Stock, par value $0.001 per share (UPB) across Reporting Periods
| Period | Reported Shares, Excl. Options | Value, Excl. Options | Value Change | Price (Median) | Investors |
|---|---|---|---|---|---|
| 2026 Q1 | 44,348,694 | $399,061,908 | -$248,908,006 | $9.00 | 131 |
| 2025 Q4 | 51,174,207 | $1,389,324,241 | +$178,186,919 | $27.15 | 131 |
| 2025 Q3 | 44,461,719 | $836,327,467 | -$50,813,162 | $18.81 | 94 |
| 2025 Q2 | 48,353,677 | $530,923,062 | +$32,738,813 | $10.98 | 82 |
| 2025 Q1 | 42,073,968 | $257,482,324 | -$17,702,490 | $6.12 | 76 |
| 2024 Q4 | 42,074,592 | $690,108,943 | +$649,643,232 | $16.44 | 70 |