Prothena Corporation plc
US ˙ NasdaqGS ˙ IE00B91XRN20

SecurityPRTA / Prothena Corporation plc
InstitutionSquarepoint Ops LLC
Latest Disclosed Ownership230,920 shares
Latest Disclosed Value $ 2,244,542
Squarepoint Ops LLC ownership in PRTA / Prothena Corporation plc

On May 15, 2026 - Squarepoint Ops LLC filed a 13F-HR form disclosing ownership of 230,920 shares of Prothena Corporation plc (US:PRTA) valued at $2,244,542 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 218,041 shares of Prothena Corporation plc. This represents a change in shares of 5.91% during the quarter. The current value of the position is $2,059,806 USD.

Squarepoint Ops LLC has a history of taking positions in derivatives of the underlying security (PRTA) in the form of stock options. The firm currently holds call options representing 0 of underlying shares valued at $0 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

Upgrade to unlock premium data and export to Excel .

Institutional Put/Call Ratios
(Premium Subscription Required)

In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

PRTA / Prothena Corporation plc Historical Put/Call Ratio
Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date
Effective
Date
Form Security Class ID Avg Price
Paid (Est)
Reported
Shares
ΔShares ΔShares
(%)
Reported
Value
(x1000)
ΔValue
(%)
Alloc
(%)
ΔAlloc ΔAlloc (%) Cost Basis
(x1000)
Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F PROTHENA CORP SHS G72800108 230,920 12,879 5.91 2,245 7.78 0.0026
2026-02-13 2025-12-31 13F PROTHENA CORP SHS G72800108 218,041 91,008 71.64 2,082 68.04 0.0022
2025-11-14 2025-09-30 13F PROTHENA CORP SHS G72800108 127,033 -82,216 -39.29 1,240 -2.44 0.0012
2025-08-27 2025-06-30 13F/A-1 PROTHENA CORP SHS G72800108 209,249 209,249 1,270 0.0013
2025-08-14 2025-06-30 13F PROTHENA CORP SHS G72800108 209,249 209,249 1,270 0.0013
2024-05-15 2024-03-31 13F PROTHENA CORP SHS G72800108 0 -74,030 -100.00 0 -100.00
2024-02-14 2023-12-31 13F PROTHENA CORP SHS G72800108 74,030 41,691 128.92 2,690 72.44 0.0051
2023-11-14 2023-09-30 13F PROTHENA CORP SHS G72800108 32,339 32,339 1,560 0.0039
2023-08-14 2023-06-30 13F PROTHENA CORP SHS G72800108 0 -78,309 -100.00 0 -100.00
2023-05-15 2023-03-31 13F PROTHENA CORP SHS G72800108 78,309 72,793 1,319.67 3,796 1,043.07 0.0155
2023-02-14 2022-12-31 13F PROTHENA CORP SHS G72800108 5,516 5,516 332 0.0013
2022-05-16 2022-03-31 13F PROTHENA CORP SHS G72800108 0 -6,606 -100.00 0 -100.00
2022-02-14 2021-12-31 13F PROTHENA CORP SHS G72800108 6,606 6,606 326 0.0009
2021-11-15 2021-09-30 13F PROTHENA CORP SHS G72800108 0 -25,886 -100.00 0 -100.00
2021-08-16 2021-06-30 13F PROTHENA CORP SHS G72800108 25,886 11,650 81.83 1,331 271.79 0.0051
2021-05-17 2021-03-31 13F PROTHENA CORP SHS G72800108 14,236 -3,563 -20.02 358 67.29 0.0021
2021-02-16 2020-12-31 13F PROTHENA CORP SHS G72800108 17,799 17,799 214 0.0016
2020-11-16 2020-09-30 13F PROTHENA CORP SHS G72800108 0 -15,064 -100.00 0 -100.00
2020-08-14 2020-06-30 13F PROTHENA CORP SHS G72800108 15,064 -12,959 -46.24 158 -47.33 0.0026
2020-05-15 2020-03-31 13F PROTHENA CORP SHS G72800108 28,023 -60,676 -68.41 300 -78.63 0.0077
2020-02-14 2019-12-31 13F PROTHENA CORP SHS G72800108 88,699 50,772 133.87 1,404 372.73 0.0084
2019-11-14 2019-09-30 13F PROTHENA CORP SHS G72800108 37,927 -109,721 -74.31 297 -80.97 0.0027
2019-08-14 2019-06-30 13F PROTHENA CORP SHS G72800108 147,648 101,772 221.84 1,561 180.76 0.0152
2019-05-15 2019-03-31 13F PROTHENA CORP SHS G72800108 45,876 27,915 155.42 556 200.54 0.0059
2019-02-14 2018-12-31 13F PROTHENA CORP SHS G72800108 17,961 -36,298 -66.90 185 -73.94 0.0022
2018-11-14 2018-09-30 13F PROTHENA CORP SHS G72800108 54,259 54,259 710 0.0085
2018-02-14 2017-12-31 13F PROTHENA CORP SHS G72800108 0 -3,997 -100.00 0 -100.00
2017-11-14 2017-09-30 13F PROTHENA CORP SHS G72800108 3,997 3,997 259 0.0050
2016-11-14 2016-09-30 13F PROTHENA CORP SHS G72800108 0 -15,000 -100.00 0 -100.00
2016-08-15 2016-06-30 13F PROTHENA CORP SHS G72800108 15,000 15,000 0.00 524 0.0327
2016-05-16 2016-03-31 13F PROTHENA CORP SHS G72800108 0 -4,900 -100.00 0 -100.00
2016-02-16 2015-12-31 13F PROTHENA CORP SHS G72800108 4,900 4,900 334 0.0366
Disclosed Call Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share
Price
Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2025-08-27 2025-03-31 13F/A PROTHENA CORP SHS Call 0 -100.00 0 -100.00 n/a n/a n/a
2025-05-15 2025-03-31 13F PROTHENA CORP SHS Call 0 0 n/a n/a n/a
2025-02-14 2024-12-31 13F PROTHENA CORP SHS Call 24,300 337 n/a n/a n/a
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.