$PRTA

$8.52 +$0.12 (1.43%) Live

$PRTA Overview Financial Statements SEC Filings Executives News Red Flags Capital Raising Ownership Insider Transactions Congressional Trades

Ownership

13F as of Q2 2026 · 51.3M shares outstanding

Who owns PRTA?

By type of holder

Institutions 91.9% Insiders 0.0% Everyone else 8.1%

Concentration Top 10 holders own 55.6%

FMR LLC 14.0% · Rubric Capital Management LP 9.7%

Institutional ownership

91.9%

-0.2 pts vs last qtr

Institutional holders

185

-1 vs last qtr

Net shares bought

−104.0K

by institutions in Q2 2026

New / sold out

28 / 29

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

Acadian Asset Management LLC +463.1K
State Street Corp +454.9K

Biggest sellers in Q2 2026

Armistice Capital, LLC SOLD OUT −439.4K
Point72 Asset Management, L.P. SOLD OUT −399.8K

Who is planning to sell?

Notices of proposed sale, last 12 months

$876K

3 notices from 3 people

Shares covered

96.0K

0.19% of the company

Arranged in advance

16%

of the value is under a 10b5-1 plan

Under a 10b5-1 plan No plan

Largest proposed sellers

Malecek Michael J Previous officer $740K
Michael John Isaacs Officer 10b5-1 $71.1K

Every notice on Red Flags →

A Form 144 is notice of a planned sale, not the sale itself. What insiders actually sold is on Insider Transactions.

Is your stake being diluted?

Diluted share count, FY2019–FY2025

+35.0%

+5.13% a year

Each share's claim on the business

−25.9%

shrank without buying or selling a share

Spent on buybacks vs paid in stock

— vs $226M

over 7 fiscal years

Diluted shares, split-adjusted

Buybacks Stock-based comp

How patient are the owners?

Institutional shares by how long they've been held

5+ years55% 3–5 years2% 1–3 years28% Under 1 year16%

Quarterly turnover

8.3%

of institutional shares changed hands

Top 10 managers, median time held

5 years

Super Investors

Investment managers reporting PRTA on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
F FMR LLC	7.2M	14.02%	−352.0K (−4.7%)	≤2021	0.0%
Shares held by quarter Peak holding8.1M (Q4'24) Change over 8 quarters−867.8K Share of the company14.020% FMR LLC's full portfolio →
RC Rubric Capital Management LP	5.0M	9.74%	Unchanged	Q3 '25	0.5%
Shares held by quarter Peak holding5.0M (Q1'26) Change over 8 quarters+5.0M Share of the company9.740% Rubric Capital Management LP's full portfolio →

FMR LLC

7.2M

% of company

14.02%

Change vs last qtr

−352.0K (−4.7%)

Held since

≤2021

Rubric Capital Management LP

5.0M

% of company

9.74%

Change vs last qtr

Unchanged

Held since

Q3 '25

28 more super investors behind a free account

See every manager holding Prothena Corporation PLC, how their position has changed, and how long they've held it.

Institutional Funds

Mutual funds and ETFs reporting PRTA on Form N-PORT; together they hold 7.3% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
NQ Nuveen Quant Small Cap Equity Fund TIAA-CREF Funds	$7.21M	652.1K	1.27%	0.19%	April 30, 2026
VE Vanguard Explorer Fund Vanguard Explorer Fund	$6.15M	757.2K	1.47%	0.03%	July 31, 2026

Nuveen Quant Small Cap Equity Fund

TIAA-CREF Funds

Position value

$7.21M

% of company

1.27%

% of the fund

0.19%

As of

April 30, 2026

Vanguard Explorer Fund

Position value

$6.15M

% of company

1.47%

% of the fund

0.03%

As of

July 31, 2026

23 more funds behind a free account

See every fund holding Prothena Corporation PLC and how much of the fund the position is.

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