Who owns Prothena Corporation (PRTA)
Which tracked institutional funds hold PRTA, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See PRTA company fundamentals →
Ownership as of the 2026-Q2 13F filings (latest filed 2026-09-22). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
25 tracked funds added or opened PRTA while 22 trimmed or exited it between 2026-Q1 and 2026-Q2 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
PRTA’s largest tracked holder by dollar value, FMR LLC, sizes it at 0.0% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 0.0pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in PRTA divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2026-Q1 and 2026-Q2, across 184 tracked filers holding PRTA, 81 increased or opened the position and 86 reduced or closed it; over the same quarter, open-market insider Form 4s were net purchases.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in PRTA between the 2026-Q1 and 2026-Q2 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 4
- MACKENZIE FINANCIAL CORP$2M
- Coppell Advisory Solutions LLC$2M
- DIADEMA PARTNERS LP$1M
- STATE OF WISCONSIN INVESTMENT BOARD$688K
Full exits 8
- ACADIAN ASSET MANAGEMENT LLC$15M
- ARMISTICE CAPITAL, LLC$4M
- Point72 Asset Management, L.P.$4M
- Walleye Capital LLC$3M
- JANE STREET GROUP, LLC$1M
- Y-Intercept (Hong Kong) Ltd$980K
Largest adds
- STATE STREET CORP$5M
- Man Group plc$3M
- BlackRock, Inc.$3M
- VANGUARD PORTFOLIO MANAGEMENT LLC$2M
- Qube Research & Technologies Ltd$2M
- GOLDMAN SACHS GROUP INC$2M
Largest trims
- EverSource Wealth Advisors, LLC$3M
- FMR LLC$3M
- MORGAN STANLEY$2M
- Nuveen, LLC$2M
- BANK OF AMERICA CORP /DE/$2M
- MONIMUS CAPITAL MANAGEMENT, LP$1M
Institutional holders
One row per tracked fund, most shares held first (every row is from one quarter; reported value breaks ties). “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding.
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| FMR LLC trimmed | 7,199,218 | $70M | 15.9% | 2026-Q2 |
| Rubric Capital Management LP | 5,000,000 | $49M | 11.1% | 2026-Q2 |
| BlackRock, Inc. added | 4,867,955 | $48M | 10.8% | 2026-Q2 |
| STATE STREET CORP added | 2,393,424 | $23M | 5.3% | 2026-Q2 |
| VANGUARD PORTFOLIO MANAGEMENT LLC added | 1,651,293 | $16M | 3.7% | 2026-Q2 |
| D. E. Shaw & Co., Inc. trimmed | 1,611,457 | $16M | 3.6% | 2026-Q2 |
| ADAR1 Capital Management, LLC trimmed | 1,554,535 | $15M | 3.4% | 2026-Q2 |
| TWO SIGMA INVESTMENTS, LP added | 1,264,987 | $12M | 2.8% | 2026-Q2 |
| Palo Alto Investors LP trimmed | 1,143,155 | $11M | 2.5% | 2026-Q2 |
| GEODE CAPITAL MANAGEMENT, LLC added | 1,125,877 | $11M | 2.5% | 2026-Q2 |
| FEDERATED HERMES, INC. added | 1,084,401 | $11M | 2.4% | 2026-Q2 |
| MORGAN STANLEY trimmed | 995,348 | $10M | 2.2% | 2026-Q2 |
| GOLDMAN SACHS GROUP INC added | 979,730 | $10M | 2.2% | 2026-Q2 |
| JACOBS LEVY EQUITY MANAGEMENT, INC trimmed | 965,988 | $9M | 2.1% | 2026-Q2 |
| DIMENSIONAL FUND ADVISORS LP added | 905,651 | $9M | 2.0% | 2026-Q2 |
| Qube Research & Technologies Ltd added | 791,169 | $8M | 1.8% | 2026-Q2 |
| RENAISSANCE TECHNOLOGIES LLC added | 697,615 | $7M | 1.5% | 2026-Q2 |
| Man Group plc added | 678,116 | $7M | 1.5% | 2026-Q2 |
| Mariner, LLC added | 625,095 | $6M | 1.4% | 2026-Q2 |
| Nuveen, LLC trimmed | 557,157 | $5M | 1.2% | 2026-Q2 |
| VANGUARD CAPITAL MANAGEMENT LLC trimmed | 479,945 | $5M | 1.1% | 2026-Q2 |
| NORTHERN TRUST CORP added | 457,124 | $4M | 1.0% | 2026-Q2 |
| Birchview Capital, LP | 449,019 | $4M | 1.0% | 2026-Q2 |
| Rangeley Capital, LLC trimmed | 417,270 | $4M | 0.9% | 2026-Q2 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC trimmed | 355,896 | $3M | 0.8% | 2026-Q2 |
| CITADEL ADVISORS LLC trimmed | 338,810 | $3M | 0.8% | 2026-Q2 |
| MONIMUS CAPITAL MANAGEMENT, LP trimmed | 329,052 | $3M | 0.7% | 2026-Q2 |
| BNP PARIBAS FINANCIAL MARKETS trimmed | 315,803 | $3M | 0.7% | 2026-Q2 |
| AQR CAPITAL MANAGEMENT LLC added | 302,572 | $3M | 0.7% | 2026-Q2 |
| Penbrook Management LLC | 271,720 | $3M | 0.6% | 2026-Q2 |
| VANGUARD FIDUCIARY TRUST CO added | 259,064 | $3M | 0.6% | 2026-Q2 |
| UBS Group AG trimmed | 241,425 | $2M | 0.5% | 2026-Q2 |
| MACKENZIE FINANCIAL CORP new | 239,899 | $2M | 0.5% | 2026-Q2 |
| Squarepoint Ops LLC trimmed | 223,971 | $2M | 0.5% | 2026-Q2 |
| BANK OF AMERICA CORP /DE/ trimmed | 208,246 | $2M | 0.5% | 2026-Q2 |
| Focused Wealth Management, Inc added | 207,445 | $2M | 0.5% | 2026-Q2 |
| Connor, Clark & Lunn Investment Management Ltd. added | 191,693 | $2M | 0.4% | 2026-Q2 |
| MARSHALL WACE, LLP added | 190,834 | $2M | 0.4% | 2026-Q2 |
| Quantinno Capital Management LP added | 158,331 | $2M | 0.4% | 2026-Q2 |
| DIADEMA PARTNERS LP added | 149,482 | $1M | 0.3% | 2026-Q2 |
| Bank of New York Mellon Corp trimmed | 133,906 | $1M | 0.3% | 2026-Q2 |
| MASSACHUSETTS FINANCIAL SERVICES CO /MA/ trimmed | 126,990 | $1M | 0.3% | 2026-Q2 |
| Russell Investments Group, Ltd. added | 121,901 | $1M | 0.3% | 2026-Q2 |
| PRICE T ROWE ASSOCIATES INC /MD/ added | 109,252 | $1M | 0.2% | 2026-Q2 |
| Hennion & Walsh Asset Management, Inc. added | 90,795 | $889K | 0.2% | 2026-Q2 |
| AMERICAN CENTURY COMPANIES INC added | 90,644 | $887K | 0.2% | 2026-Q2 |
| AMERIPRISE FINANCIAL INC trimmed | 87,215 | $854K | 0.2% | 2026-Q2 |
| XTX Topco Ltd trimmed | 85,717 | $839K | 0.2% | 2026-Q2 |
| Susquehanna Portfolio Strategies, LLC added | 82,710 | $810K | 0.2% | 2026-Q2 |
| ExodusPoint Capital Management, LP added | 82,023 | $803K | 0.2% | 2026-Q2 |
| MARTINGALE ASSET MANAGEMENT L P added | 78,800 | $771K | 0.2% | 2026-Q2 |
| Trexquant Investment LP added | 76,731 | $751K | 0.2% | 2026-Q2 |
| DCF Advisers, LLC | 73,247 | $717K | 0.2% | 2026-Q2 |
| Invesco Ltd. added | 71,479 | $700K | 0.2% | 2026-Q2 |
| STATE OF WISCONSIN INVESTMENT BOARD trimmed | 70,326 | $688K | 0.2% | 2026-Q2 |
| Duncan Williams Asset Management, LLC | 70,281 | $688K | 0.2% | 2026-Q2 |
| ALLIANCEBERNSTEIN L.P. trimmed | 69,217 | $673K | 0.2% | 2026-Q2 |
| Campbell & CO Investment Adviser LLC trimmed | 68,345 | $669K | 0.2% | 2026-Q2 |
| Assenagon Asset Management S.A. trimmed | 62,785 | $615K | 0.1% | 2026-Q2 |
| Creative Planning trimmed | 62,620 | $613K | 0.1% | 2026-Q2 |
| PINNACLE ASSOCIATES LTD trimmed | 57,918 | $567K | 0.1% | 2026-Q2 |
| CITIGROUP INC added | 57,827 | $566K | 0.1% | 2026-Q2 |
| RHUMBLINE ADVISERS added | 55,896 | $547K | 0.1% | 2026-Q2 |
| Schonfeld Strategic Advisors LLC added | 50,350 | $493K | 0.1% | 2026-Q2 |
| Quinn Opportunity Partners LLC | 50,000 | $490K | 0.1% | 2026-Q2 |
| EDGEWOOD MANAGEMENT LLC | 50,000 | $490K | 0.1% | 2026-Q2 |
| HSBC HOLDINGS PLC trimmed | 49,569 | $492K | 0.1% | 2026-Q2 |
| WELLS FARGO & COMPANY/MN added | 49,520 | $485K | 0.1% | 2026-Q2 |
| Seven Fleet Capital Management LP | 43,300 | $424K | 0.1% | 2026-Q2 |
| DEUTSCHE BANK AG\ added | 43,270 | $424K | 0.1% | 2026-Q2 |
| PUBLIC EMPLOYEES RETIREMENT SYSTEM OF OHIO | 42,158 | $413K | 0.1% | 2026-Q2 |
| Engineers Gate Manager LP trimmed | 41,270 | $404K | 0.1% | 2026-Q2 |
| Rafferty Asset Management, LLC trimmed | 40,397 | $395K | 0.1% | 2026-Q2 |
| Virtus Investment Advisers, LLC added | 39,660 | $388K | 0.1% | 2026-Q2 |
| SHELTON CAPITAL MANAGEMENT added | 39,472 | $386K | 0.1% | 2026-Q2 |
| Persistent Asset Partners Ltd added | 38,100 | $373K | 0.1% | 2026-Q2 |
| BARCLAYS PLC trimmed | 37,623 | $368K | 0.1% | 2026-Q2 |
| SEI INVESTMENTS CO added | 30,877 | $302K | 0.1% | 2026-Q2 |
| WINTON GROUP Ltd trimmed | 30,500 | $299K | 0.1% | 2026-Q2 |
| RBF Capital, LLC | 29,200 | $286K | 0.1% | 2026-Q2 |
| GREAT LAKES ADVISORS, LLC trimmed | 28,733 | $281K | 0.1% | 2026-Q2 |
| PNC Financial Services Group, Inc. | 28,386 | $278K | 0.1% | 2026-Q2 |
| JPMORGAN CHASE & CO added | 26,620 | $265K | 0.1% | 2026-Q2 |
| MetLife Investment Management, LLC added | 25,890 | $253K | 0.1% | 2026-Q2 |
| Aquatic Capital Management LLC new | 25,419 | $249K | 0.1% | 2026-Q2 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. added | 25,174 | $247K | 0.1% | 2026-Q2 |
| Purkiss Capital Advisors LLC | 25,086 | $246K | 0.1% | 2026-Q2 |
| TUDOR INVESTMENT CORP ET AL trimmed | 24,445 | $239K | 0.1% | 2026-Q2 |
| CANADA PENSION PLAN INVESTMENT BOARD added | 24,000 | $235K | 0.1% | 2026-Q2 |
| ENVESTNET ASSET MANAGEMENT INC new | 22,908 | $224K | 0.1% | 2026-Q2 |
| MOGY JOEL R INVESTMENT COUNSEL INC | 20,750 | $203K | 0.0% | 2026-Q2 |
| PROFUND ADVISORS LLC trimmed | 20,570 | $201K | 0.0% | 2026-Q2 |
| Savant Capital, LLC added | 19,503 | $190K | 0.0% | 2026-Q2 |
| JONES FINANCIAL COMPANIES LLLP added | 19,430 | $195K | 0.0% | 2026-Q2 |
| Foundation Wealth Management, LLC | 19,236 | $188K | 0.0% | 2026-Q2 |
| Graham Capital Management, L.P. added | 18,496 | $181K | 0.0% | 2026-Q2 |
| Vanguard Global Advisers, LLC | 18,249 | $179K | 0.0% | 2026-Q2 |
| STRS OHIO added | 17,900 | $175K | 0.0% | 2026-Q2 |
| Coppell Advisory Solutions LLC new | 12 | $2M | 0.5% | 2026-Q2 |
| FORTRESS FINANCIAL GROUP, LLC new | 6 | $220K | 0.0% | 2026-Q2 |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.