Company · Ownership research

Upstream Bio, Inc. UPB

CIK 0002022626 · CUSIP 91678A107

Insider tradingInitial holdingsInstitutional holders

Quarter-end disclosures, not live holdings.

3 CUSIPs are reported under this ticker. This page covers the one most managers report; the others are not merged in.
This page lists the top 20 of 141 rows by value; the complete set is available through the API.

Top 20 institutions

Weight means this stock's share of the manager's own portfolio.

By reported value
#ManagerValueManager weightChange vs priorSource

Showing 20 / 141 institutions. The complete set is available through the API.

Coverage & totals by quarter

Reporting institutions
141
Cancelled or null records excluded
Disclosed shares
44,886,514
Not deduplicated across managers
Disclosed value
$404.47M
Not market cap or free float

Reporting institutions by quarter

Counts also change with data coverage and reporting entities; they do not measure net buying. Distinct managers with a live stock row in this CUSIP; totals may include overlapping filings and are not a share of the company.

Upstream Bio, Inc. · Q1 2026

Explore all 141 reporting institutions.

This page includes 20 of 141 reporting institutions. Sign in to look up the full history beyond 3 years, use advanced screening & filtering, download CSV, and get the complete set through the Akkru API.

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The initial HTML of this page carries its exact data as script#research-data (JSON): values, units, scope, preview limits and SEC sources. Read it directly, no script or API key needed; script#research-access says what needs an account. This page lists 20 of 141 reporting institutions; totals use the complete disclosed data.

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{"cusip":"91678A107","quarter":"2026Q1","type":"positions","page_size":100}

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Sources, coverage & how to read this data

Figures are as reported to the SEC and merged with later amendments where Akkru could match them. Preview limits apply to what is listed, not to the totals, which come from the complete reported data. Nothing is zero-filled: a missing quarter or month is shown as missing.