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PCEliquiditysentimentbreakoutsdowngradesP/E 28.4threadsAAPLSPXvolatilityNDXflowscyclesliquidityestimatesEPS 4.12

BOLD · NASDAQ · Biotechnology

Boundless Bio (BOLD)

Wind-down-stage ecDNA oncology developer pursuing a merger with Serapha Bio.

$2.90

At close+0.00 (+0.17%)

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Breakdown13F · 13D/G · Form 4

Institutions36 holders · as of Mar 31, 2026	37.30%	8.49M shares
Insiders3 holders · as of Aug 28, 2026	23.16%	5.27M shares
Strategic holders2 holders · as of Aug 14, 2026	19.79%	4.50M shares
Otherremainder	19.75%	4.49M shares

22.75M company shares as of Sep 3, 2026 · institutions as of Mar 31, 2026 · holders as of their latest filing

Top shareholders13F · 13D/G · Form 4

Holder	Stake	Shares	Evidence
Kevin TangInsider10 percent owner	12.49%	2.84M	Form 4filed Aug 28, 2026 ↗
FMR LLCInstitution	11.85%	2.70M	13Fas of Mar 31, 2026
Tang Capital Management, LLCStrategic	11.14%	2.53M	13Gfiled Jun 29, 2026 ↗
Zachary Hornby¹Insiderdirector, officer: President & CEO	10.67%	2.43M	13Gfiled Aug 27, 2026 ↗
ADAR1 Capital Management, LLCStrategic	8.65%	1.97M	13Gfiled Aug 14, 2026 ↗
Citadel Advisors LLCInstitution	5.90%	1.34M	13Fas of Mar 31, 2026
Sectoral Asset Management IncInstitution	2.98%	678,574	13Fas of Mar 31, 2026
Stonepine Capital Management, LLCInstitution	2.63%	597,682	13Fas of Mar 31, 2026
Vanguard Capital Management LLCInstitution	2.63%	597,192	13Fas of Mar 31, 2026
Wellington Management Group LLPInstitution	2.45%	556,233	13Fas of Mar 31, 2026
Renaissance Technologies LLCInstitution	1.75%	399,000	13Fas of Mar 31, 2026
Alyeska Investment Group, L.P.Institution	1.32%	300,000	13Fas of Mar 31, 2026
RBF Capital, LLCInstitution	0.88%	200,000	13Fas of Mar 31, 2026
Ensign Peak Advisors, IncInstitution	0.82%	187,500	13Fas of Mar 31, 2026
Sio Capital Management, LLCInstitution	0.72%	163,679	13Fas of Mar 31, 2026
Geode Capital Management, LLCInstitution	0.56%	127,576	13Fas of Mar 31, 2026
Millennium Management LLCInstitution	0.44%	99,875	13Fas of Mar 31, 2026
Gsa Capital Partners LLPInstitution	0.43%	96,824	13Fas of Mar 31, 2026
Landscape Capital Management, L.L.C.Institution	0.38%	85,792	13Fas of Mar 31, 2026
BlackRock, Inc.Institution	0.31%	70,675	13Fas of Mar 31, 2026
Vanguard Fiduciary Trust CoInstitution	0.29%	65,136	13Fas of Mar 31, 2026
Bridgeway Capital Management, LLCInstitution	0.22%	50,500	13Fas of Mar 31, 2026
Walleye Capital LLCInstitution	0.17%	39,624	13Fas of Mar 31, 2026
XTX Topco LtdInstitution	0.15%	34,671	13Fas of Mar 31, 2026
Qube Research & Technologies LtdInstitution	0.08%	17,492	13Fas of Mar 31, 2026

Zachary Hornby's transaction reports restate only vehicles that traded; the 2026 ownership statement (2.43M) is used instead.

13F — a manager's quarterly holdings · 13D/13G — an ownership statement filed at 5% or more · Form 4 — an insider's transaction report

Institutions13F, as of Mar 31, 2026

36 holders · 8.49M shares · 8 new positions · 14 increased · 9 reduced · 7 closed

Holder	Shares	% outstanding	Chg q/q	Filed
FMR LLC	2.70M	11.85%	+11.4K	May 15, 2026
Citadel Advisors LLC	1.34M	5.90%	−11.8K	May 15, 2026
Sectoral Asset Management Inc	678.6K	2.98%	0	May 15, 2026
Stonepine Capital Management, LLC	597.7K	2.63%	−112.4K	May 14, 2026
Vanguard Capital Management LLC	597.2K	2.63%	+597.2Knew	May 15, 2026
Wellington Management Group LLP	556.2K	2.45%	0	May 15, 2026
Renaissance Technologies LLC	399.0K	1.75%	+57.6K	May 14, 2026
Alyeska Investment Group, L.P.	300.0K	1.32%	0	May 15, 2026

Ownership statements13D/G · 5% or more, as filed

Holder	% of class	Shares	Form	Filed
Kristina Burowincl. Steven Gillis, Robert Nelsen +10 more	12.10%	2.70M	13D	Oct 29, 2024 ↗
FMR LLC	12.00%	2.68M	13G	Feb 5, 2026 ↗
Tang Capital Management, LLC	11.30%	2.53M	13G	Jun 29, 2026 ↗
Zachary Hornby	9.80%	2.43M	13G	Aug 27, 2026 ↗
ADAR1 Capital Management, LLC	8.80%	1.97M	13G	Aug 14, 2026 ↗

Insider tradesForm 4

Latest trades

Date	Insider	Type	Shares	Avg price	Owned after
Aug 26, 2026	Kevin Tang10 percent owner	Sale	18,300	$2.97	2,840,635
Jul 17, 2026	Kevin Tang10 percent owner	Purchase	265	$2.44	2,854,337
Jul 20, 2026	Kevin Tang10 percent owner	Purchase	1,623	$2.44	2,855,960
Jul 21, 2026	Kevin Tang10 percent owner	Purchase	2,975	$2.44	2,858,935
Jul 14, 2026	Kevin Tang10 percent owner	Purchase	43,878	$2.43	2,833,981
Jul 15, 2026	Kevin Tang10 percent owner	Purchase	1,600	$2.44	2,835,581
Jul 16, 2026	Kevin Tang10 percent owner	Purchase	18,491	$2.44	2,854,072
Jul 9, 2026	Kevin Tang10 percent owner	Purchase	7	$2.48	2,698,525
Jul 10, 2026	Kevin Tang10 percent owner	Purchase	43,367	$2.43	2,741,892
Jul 13, 2026	Kevin Tang10 percent owner	Purchase	48,211	$2.42	2,790,103

CongressHouse and Senate disclosures

Not reported.