UPB in the 13F filings

Upstream Bio Inc · CUSIP 91678A107

Sector · Pharmaceuticals and biotechnology Theme · Healthcare: biopharma and medtech· L3VLUP-defined Theme · Pharmaceutical preparations

Quarter

Q4 2025 Q3 2025 Q4 2024

Quarter end: 31 Dec 2025; the date the book describes
Filed: 19 Feb 2026; latest of these filings; the earliest 12 Feb 2026
Managers listing it: 18; at least, of 95 tracked, among listed positions
Comparable managers: 92; filed both Q3 2025 and Q4 2025; 1 listed it in both
Shares listed: 12,133,016; combined, among listed positions
Reported value: $329m; combined, at the quarter end

Among the 92 comparable managers: 12 buyers (opened or added shares) and 6 sellers (trimmed or exited), at least, among listed positions. Their net change in shares was +1,004,473.

Managers listing UPB in Q4 2025

Share of 13F value is the position’s reported value over everything the manager reported that quarter. The share change is against Q3 2025, and only where both filings list the position. A rise in value with no rise in shares is the price, not buying.

ActionShare of book at least

18 of 18 holders

				Action		Filing
Fidelity (FMR LLC)	7,518,202	$204m	under 0.1%	Trimmed	-568,211	17 Feb 2026 (the filing on sec.gov)
Janus Henderson Group Ltd	1,527,958	$41m	under 0.1%	New	new	17 Feb 2026 (the filing on sec.gov)
Wellington Management Group LLP	894,733	$24m	under 0.1%	Trimmed	-230,662	17 Feb 2026 (the filing on sec.gov)
Woodline Partners LP	760,252	$21m	0.08%	Added	+158,000	17 Feb 2026 (the filing on sec.gov)
Millennium Management LLC	517,264	$14m	under 0.1%	Added	+477,151	17 Feb 2026 (the filing on sec.gov)
Marshall Wace LLP	343,791	$9.3m	under 0.1%	Trimmed	-524,208	13 Feb 2026 (the filing on sec.gov)
Invesco Ltd	163,186	$4.4m	under 0.1%	Added	+145,996	19 Feb 2026 (the filing on sec.gov)
Schonfeld Strategic Advisors LLC	115,807	$3.1m	under 0.1%	Trimmed	-74,437	17 Feb 2026 (the filing on sec.gov)
ExodusPoint Capital Management LP	75,402	$2.0m	under 0.1%	New	new	17 Feb 2026 (the filing on sec.gov)
Susquehanna International Group LLP	55,841	$1.5m	under 0.1%	New	new	17 Feb 2026 (the filing on sec.gov)
AllianceBernstein LP	31,010	$842k	under 0.1%	Added	+11,160	17 Feb 2026 (the filing on sec.gov)
AQR Capital Management LLC	30,503	$828k	under 0.1%	Added	+549	17 Feb 2026 (the filing on sec.gov)
D. E. Shaw & Co.	27,091	$736k	under 0.1%	New	new	17 Feb 2026 (the filing on sec.gov)
T. Rowe Price Associates Inc	19,636	$534k	under 0.1%	Added	+1,135	17 Feb 2026 (the filing on sec.gov)
Renaissance Technologies LLC	16,400	$445k	under 0.1%	New	new	12 Feb 2026 (the filing on sec.gov)
Citadel Advisors LLC	13,420	$364k	under 0.1%	New	new	17 Feb 2026 (the filing on sec.gov)
Verition Fund Management LLC	12,020	$326k	under 0.1%	Trimmed	-34,981	13 Feb 2026 (the filing on sec.gov)
Two Sigma Investments LP	10,500	$285k	under 0.1%	Held	0	17 Feb 2026 (the filing on sec.gov)

Largest increases and reductions, by shares

Q3 2025 to Q4 2025, among managers that listed it in both quarters or opened it.

Increases

Janus Henderson Group Ltdnew position · 1,527,958 shares now+1,527,958
Millennium Management LLCexisting position · 517,264 shares now+477,151
Woodline Partners LPexisting position · 760,252 shares now+158,000
Invesco Ltdexisting position · 163,186 shares now+145,996
ExodusPoint Capital Management LPnew position · 75,402 shares now+75,402

Reductions

Fidelity (FMR LLC)existing position · 7,518,202 shares now-568,211
Marshall Wace LLPexisting position · 343,791 shares now-524,208
Wellington Management Group LLPexisting position · 894,733 shares now-230,662
Schonfeld Strategic Advisors LLCexisting position · 115,807 shares now-74,437
Verition Fund Management LLCexisting position · 12,020 shares now-34,981

New positions and exits

At least these many: a manager is shown exiting only where its own filing shows the position gone.

New (6)

Janus Henderson Group Ltd$41m
ExodusPoint Capital Management LP$2.0m
Susquehanna International Group LLP$1.5m
D. E. Shaw & Co.$736k
Renaissance Technologies LLC$445k
Citadel Advisors LLC$364k

Exited (1)

Balyasny Asset Management LLCwas $1.4m

Ownership over time

Every quarter on file. A quarter-end value moves with the price as well as with the shares held; buyers and sellers count comparable managers, by shares.

3 in Q4 2024 to 2 in Q4 2025

Tracked managers listing it, at least.

the quarter shown share split complete books; unmarked quarters rest on listed positionsClick a quarter to open it.

Compare with…

Holders over time, buyers and sellers, and the managers holding both, side by side for up to four stocks.

UPB and LLY →UPB and JNJ →UPB and VRTX →Choose a stock to compare with UPB →

How much of the picture this is

A 13F is a manager’s long US-listed equity book at a quarter end, filed up to 45 days later. It shows no shorts, cash, bonds or performance, and it is never today’s portfolio. Large books are listed to their largest positions, so a manager missing from this table may still hold a small position below that line. These are 95 tracked managers, not the institutional market.

Which funds own UPB, latest filings →Back to the 13F Explorer →

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UPB by quarter
Quarter	Holders	Reported value	Buyers	Sellers
Q4 2024	3	$9.6m	3	0
Q3 2025	1	$11m	1	0
Q4 2025	2	$62m	12	6