Prothena Corp Public (PRTA)
Prothena Corp Public on one page: short interest, daily short volume, fails to deliver, planned sales, large holders, 13F holders, financials, earnings dates and insider trades. Listed on Nasdaq, classified by the SEC as pharmaceutical preparations.
7.9M
Short interest
settlement 2026-10-15
13.3
Days to cover
-0.5 days vs prior
69.5%
Short share of volume
2026-11-02
318
Fails to deliver
settlement 2026-09-29
Thu 5 Nov
Next earnings
estimated date
$9.0M
Insider flow, 90 days
14 buys, 0 sells
As of 2026-11-02.
Short interest
FINRA, twice a month. The newest 48 settlements in the table, 48 in the chart. JSONAs of 15 October 2026, short interest in PRTA is 7,939,666 shares, down 604,998 shares over the last month. Over the last 48 readings it ranged from 3,763,878 shares (15 September 2025) to 9,349,701 shares (15 January 2025). At the reported average volume of 598K shares a day that is 13.3 days to cover.
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| Settlement | Shares short | Change | Avg daily volume | Days to cover |
|---|---|---|---|---|
| 2026-10-15 | 7,939,666 | -0.9% | 597,798 | 13.28 |
| 2026-09-30 | 8,010,864 | -6.3% | 580,885 | 13.79 |
| 2026-09-15 | 8,544,664 | +0.6% | 322,027 | 26.53 |
| 2026-08-31 | 8,495,796 | -0.6% | 341,894 | 24.85 |
| 2026-08-14 | 8,545,127 | +4.6% | 436,939 | 19.56 |
| 2026-07-31 | 8,172,438 | -0.3% | 585,253 | 13.96 |
| 2026-07-15 | 8,196,964 | -2.1% | 499,741 | 16.40 |
| 2026-06-30 | 8,369,568 | +6.4% | 759,430 | 11.02 |
| 2026-06-15 | 7,866,857 | +1.7% | 492,334 | 15.98 |
| 2026-05-29 | 7,737,902 | +9.0% | 558,736 | 13.85 |
| 2026-05-15 | 7,097,854 | +3.3% | 547,700 | 12.96 |
| 2026-04-30 | 6,871,465 | -2.9% | 374,817 | 18.33 |
| 2026-04-15 | 7,076,832 | +0.9% | 461,513 | 15.33 |
| 2026-03-31 | 7,016,080 | -0.4% | 569,553 | 12.32 |
| 2026-03-13 | 7,044,790 | +2.8% | 628,888 | 11.20 |
| 2026-02-27 | 6,854,767 | -3.2% | 398,107 | 17.22 |
| 2026-02-13 | 7,083,043 | +0.3% | 390,797 | 18.12 |
| 2026-01-30 | 7,063,694 | -0.1% | 508,225 | 13.90 |
| 2026-01-15 | 7,069,471 | +7.4% | 490,187 | 14.42 |
| 2025-12-31 | 6,584,532 | +40.1% | 827,377 | 7.96 |
| 2025-12-15 | 4,699,126 | +1.3% | 692,839 | 6.78 |
| 2025-11-28 | 4,639,338 | -0.4% | 514,550 | 9.02 |
| 2025-11-14 | 4,657,490 | +12.4% | 631,094 | 7.38 |
| 2025-10-31 | 4,144,115 | +7.4% | 513,944 | 8.06 |
| 2025-10-15 | 3,857,015 | +0.3% | 718,695 | 5.37 |
| 2025-09-30 | 3,845,694 | +2.2% | 764,721 | 5.03 |
| 2025-09-15 | 3,763,878 | -7.2% | 830,200 | 4.53 |
| 2025-08-29 | 4,055,435 | -3.1% | 1,041,258 | 3.89 |
| 2025-08-15 | 4,184,841 | -4.3% | 1,251,348 | 3.34 |
| 2025-07-31 | 4,374,625 | -8.1% | 806,446 | 5.42 |
| 2025-07-15 | 4,757,454 | +9.9% | 868,580 | 5.48 |
| 2025-06-30 | 4,330,532 | -7.0% | 2,497,532 | 1.73 |
| 2025-06-13 | 4,655,763 | +5.5% | 1,213,691 | 3.84 |
| 2025-05-30 | 4,414,727 | -50.7% | 3,006,617 | 1.47 |
| 2025-05-15 | 8,952,748 | +20.1% | 2,403,915 | 3.72 |
| 2025-04-30 | 7,453,961 | -5.9% | 624,288 | 11.94 |
| 2025-04-15 | 7,922,712 | -5.5% | 663,666 | 11.94 |
| 2025-03-31 | 8,384,570 | -4.5% | 456,509 | 18.37 |
| 2025-03-14 | 8,779,086 | -3.8% | 446,550 | 19.66 |
| 2025-02-28 | 9,129,265 | +1.1% | 428,701 | 21.30 |
| 2025-02-14 | 9,034,843 | +1.5% | 291,628 | 30.98 |
| 2025-01-31 | 8,900,074 | -4.8% | 336,501 | 26.45 |
| 2025-01-15 | 9,349,701 | +6.6% | 462,780 | 20.20 |
| 2024-12-31 | 8,770,252 | -0.3% | 968,036 | 9.06 |
| 2024-12-13 | 8,797,843 | +9.2% | 485,033 | 18.14 |
| 2024-11-29 | 8,057,302 | +2.3% | 452,032 | 17.82 |
| 2024-11-15 | 7,877,213 | +4.6% | 440,920 | 17.87 |
| 2024-10-31 | 7,531,620 | +11.0% | 472,306 | 15.95 |
Daily short volume
FINRA Reg SHO, the last 30 sessions. JSONAs of 2 November 2026, the short share of PRTA volume is 69.5%, down 0.6 points over the last five sessions. Over the last 30 readings it ranged from 43.9% (16 October 2026) to 79.9% (22 October 2026). The latest reading is 4.3 points above the 30-session average of 65.3%, on 156K shares reported.
| Date | Short volume | Total volume | Short share | Exempt |
|---|---|---|---|---|
| 2026-11-02 | 108K | 156K | 69.5% | 0 |
| 2026-10-30 | 87K | 116K | 74.9% | 0 |
| 2026-10-29 | 54K | 83K | 65.7% | 0 |
| 2026-10-28 | 124K | 262K | 47.5% | 0 |
| 2026-10-27 | 90K | 177K | 51.2% | 0 |
| 2026-10-26 | 208K | 296K | 70.2% | 0 |
| 2026-10-23 | 119K | 171K | 69.9% | 8 |
| 2026-10-22 | 145K | 182K | 79.9% | 1,700 |
| 2026-10-21 | 117K | 171K | 68.0% | 0 |
| 2026-10-20 | 98K | 159K | 61.4% | 0 |
| 2026-10-19 | 72K | 119K | 60.4% | 0 |
| 2026-10-16 | 73K | 165K | 43.9% | 0 |
| 2026-10-15 | 50K | 88K | 57.2% | 0 |
| 2026-10-14 | 111K | 195K | 56.7% | 0 |
| 2026-10-13 | 204K | 273K | 74.5% | 0 |
| 2026-10-12 | 86K | 176K | 48.7% | 0 |
| 2026-10-09 | 160K | 361K | 44.4% | 0 |
| 2026-10-08 | 202K | 279K | 72.3% | 0 |
| 2026-10-07 | 228K | 287K | 79.5% | 1,019 |
| 2026-10-06 | 112K | 164K | 68.0% | 0 |
| 2026-10-05 | 158K | 238K | 66.1% | 1,900 |
| 2026-10-02 | 186K | 261K | 71.1% | 0 |
| 2026-10-01 | 90K | 152K | 59.1% | 0 |
| 2026-09-30 | 109K | 201K | 54.1% | 0 |
| 2026-09-29 | 215K | 270K | 79.8% | 0 |
| 2026-09-28 | 174K | 219K | 79.4% | 0 |
| 2026-09-25 | 105K | 150K | 70.3% | 0 |
| 2026-09-24 | 123K | 165K | 74.9% | 0 |
| 2026-09-23 | 98K | 123K | 79.8% | 0 |
| 2026-09-22 | 69K | 115K | 60.2% | 0 |
Fails to deliver
SEC, the last 30 settlement dates with a fail. JSONAs of 29 September 2026, the fails-to-deliver balance in PRTA is 318 shares, down 3,213 shares over the last settlement date. Over the last 30 readings it ranged from 1 share (30 July 2026) to 8,398 shares (3 August 2026). The latest reading sits at the bottom of that range.
| Settlement | Shares failed | Price | Value |
|---|---|---|---|
| 2026-09-29 | 318 | $8.72 | $3K |
| 2026-09-24 | 3,531 | $8.68 | $31K |
| 2026-09-21 | 5,860 | $8.58 | $50K |
| 2026-09-11 | 535 | $9.02 | $5K |
| 2026-09-09 | 349 | $9.54 | $3K |
| 2026-09-02 | 23 | $9.61 | $221 |
| 2026-08-31 | 6,503 | $9.33 | $61K |
| 2026-08-26 | 20 | $9.42 | $188 |
| 2026-08-25 | 21 | $9.39 | $197 |
| 2026-08-18 | 183 | $8.88 | $2K |
| 2026-08-17 | 63 | $8.86 | $558 |
| 2026-08-06 | 368 | $8.49 | $3K |
| 2026-08-03 | 8,398 | $8.12 | $68K |
| 2026-07-30 | 1 | $8.56 | $9 |
| 2026-07-23 | 8,290 | $8.44 | $70K |
| 2026-07-13 | 397 | $9.24 | $4K |
| 2026-07-08 | 200 | $9.68 | $2K |
| 2026-07-07 | 200 | $9.50 | $2K |
| 2026-07-06 | 200 | $9.69 | $2K |
| 2026-07-02 | 200 | $9.58 | $2K |
| 2026-07-01 | 200 | $9.79 | $2K |
| 2026-06-18 | 241 | $8.49 | $2K |
| 2026-06-15 | 365 | $8.25 | $3K |
| 2026-06-11 | 339 | $7.91 | $3K |
| 2026-06-09 | 288 | $8.56 | $2K |
| 2026-06-02 | 225 | $9.59 | $2K |
| 2026-05-26 | 480 | $9.83 | $5K |
| 2026-05-21 | 327 | $9.35 | $3K |
| 2026-05-20 | 1,627 | $9.07 | $15K |
| 2026-05-19 | 3,392 | $9.59 | $33K |
Insider trades
SEC Form 4, newest first. JSONInsiders at PRTA reported 14 open-market buys worth $9.0M in the last 90 days and no open-market sells. Latest filing: SCULLY WILLIAM P (10% owner) on 2026-10-27.
| Date | Insider | Title | Type | Shares | Price | Value | Owned after |
|---|---|---|---|---|---|---|---|
| 2026-10-27 | SCULLY WILLIAM P | 10% owner | Gift | 566K | $0.00 | $0 | 1.8M |
| 2026-10-23 | SCULLY WILLIAM P | 10% owner | Buy | 50K | $8.07 | $404K | 1.2M |
| 2026-10-22 | SCULLY WILLIAM P | 10% owner | Buy | 100K | $8.19 | $819K | 1.1M |
| 2026-10-14 | SCULLY WILLIAM P | 10% owner | Buy | 10K | $8.46 | $85K | 1.0M |
| 2026-10-13 | SCULLY WILLIAM P | 10% owner | Buy | 100K | $8.35 | $835K | 1.0M |
| 2026-10-08 | SCULLY WILLIAM P | 10% owner | Buy | 90K | $8.57 | $771K | 529K |
| 2026-10-07 | SCULLY WILLIAM P | 10% owner | Buy | 125K | $8.40 | $1.1M | 439K |
| 2026-10-02 | SCULLY WILLIAM P | 10% owner | Buy | 100K | $8.57 | $857K | 314K |
| 2026-09-29 | SCULLY WILLIAM P | 10% owner | Buy | 162K | $8.68 | $1.4M | 214K |
| 2026-09-28 | SCULLY WILLIAM P | 10% owner | Buy | 104K | $8.60 | $890K | 187K |
| 2026-09-18 | SCULLY WILLIAM P | 10% owner | Buy | 100K | $8.43 | $843K | 927K |
| 2026-09-02 | SCULLY WILLIAM P | 10% owner | Buy | 27K | $9.47 | $256K | 827K |
| 2026-08-20 | SCULLY WILLIAM P | 10% owner | Buy | 50K | $8.79 | $439K | 800K |
| 2026-08-18 | SCULLY WILLIAM P | 10% owner | Gift | 628K | $0.00 | $0 | 750K |
| 2026-08-17 | SCULLY WILLIAM P | 10% owner | Gift | 336K | $0.00 | $0 | 1.4M |
| 2026-08-10 | SCULLY WILLIAM P | 10% owner | Gift | 252K | $0.00 | $0 | 1.0M |
| 2026-08-07 | SCULLY WILLIAM P | 10% owner | Buy | 4K | $8.62 | $30K | 84K |
| 2026-08-07 | SCULLY WILLIAM P | 10% owner | Buy | 34K | $8.62 | $293K | 790K |
| 2026-07-29 | Kingston Anne Evans | Chief Strategy Officer | Sell | 8K | $8.47 | $65K | 56K |
| 2026-07-29 | Isaacs Michael John | General Counsel & Company Sec. | Sell | 8K | $8.47 | $71K | 36K |
| 2026-07-28 | Zago Wagner M. | Chief Scientific Officer | Returned to company | 51K | $8.56 | $437K | 34K |
| 2026-07-28 | Zago Wagner M. | Chief Scientific Officer | Exercise or conversion | 51K | price not stated in the filing | not stated | 85K |
| 2026-07-28 | Walker Karin L | Chief Accounting Officer | Returned to company | 15K | $8.56 | $128K | 10K |
| 2026-07-28 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 15K | price not stated in the filing | not stated | 25K |
| 2026-07-28 | Swanson Chad J. | Chief Development Officer | Tax withholding | 3K | $8.56 | $30K | 41K |
| 2026-07-28 | Swanson Chad J. | Chief Development Officer | Returned to company | 41K | $8.56 | $349K | 44K |
| 2026-07-28 | Swanson Chad J. | Chief Development Officer | Exercise or conversion | 51K | price not stated in the filing | not stated | 85K |
| 2026-07-28 | Smith Brandon S. | Chief Operating Officer | Returned to company | 78K | $8.56 | $668K | 52K |
| 2026-07-28 | Smith Brandon S. | Chief Operating Officer | Exercise or conversion | 78K | price not stated in the filing | not stated | 130K |
| 2026-07-28 | Nguyen Tran | Chief Strategy Officer and CFO | Returned to company | 57K | $8.56 | $488K | 40K |
| 2026-07-28 | Nguyen Tran | Chief Strategy Officer and CFO | Exercise or conversion | 57K | price not stated in the filing | not stated | 97K |
| 2026-07-28 | Kinney Gene G. | President and CEO | Returned to company | 84K | $8.56 | $719K | 69K |
| 2026-07-28 | Kinney Gene G. | President and CEO | Exercise or conversion | 84K | price not stated in the filing | not stated | 153K |
| 2026-07-28 | Kingston Anne Evans | Chief Strategy Officer | Tax withholding | 3K | $8.56 | $30K | 63K |
| 2026-07-28 | Isaacs Michael John | General Counsel & Company Sec. | Tax withholding | 5K | $8.56 | $40K | 44K |
| 2026-06-16 | SCULLY WILLIAM P | TenPercentOwner | Buy | 20K | $7.90 | $158K | 756K |
| 2026-06-15 | SCULLY WILLIAM P | TenPercentOwner | Gift | 325K | $0.00 | $0 | 736K |
| 2026-06-11 | SCULLY WILLIAM P | TenPercentOwner | Buy | 125K | $8.17 | $1.0M | 1.1M |
| 2026-06-04 | SCULLY WILLIAM P | 10% owner | Buy | 50K | $9.31 | $465K | 936K |
| 2026-06-02 | SCULLY WILLIAM P | 10% owner | Buy | 50K | $9.43 | $471K | 886K |
| 2026-05-22 | SCULLY WILLIAM P | 10% owner | Buy | 100K | $9.81 | $981K | 836K |
| 2025-07-28 | Zago Wagner M. | Chief Scientific Officer | Grant | 85K | $0.00 | $0 | 85K |
| 2025-07-28 | Walker Karin L | Chief Accounting Officer | Grant | 25K | $0.00 | $0 | 25K |
| 2025-07-28 | Swanson Chad J. | Chief Development Officer | Grant | 85K | $0.00 | $0 | 85K |
| 2025-07-28 | Smith Brandon S. | Chief Operating Officer | Grant | 130K | $0.00 | $0 | 130K |
| 2025-07-28 | Nguyen Tran | Chief Strategy Officer and CFO | Grant | 95K | $0.00 | $0 | 97K |
| 2025-07-28 | Malecek Michael J | Chief Legal Officer | Grant | 80K | $0.00 | $0 | 80K |
| 2025-07-28 | Kinney Gene G. | President and CEO | Grant | 140K | $0.00 | $0 | 153K |
| 2025-05-06 | EcoR1 Capital, LLC | TenPercentOwner | Sell | 2.0M | $7.64 | $15.2M | 5.3M |
| 2025-05-05 | EcoR1 Capital, LLC | TenPercentOwner | Sell | 978K | $8.11 | $7.9M | 7.3M |
| 2025-05-02 | EcoR1 Capital, LLC | TenPercentOwner | Sell | 3.3M | $8.36 | $27.7M | 8.3M |
| 2025-01-15 | SCULLY WILLIAM P | TenPercentOwner | Gift | 12K | $0.00 | $0 | 47K |
| 2025-01-14 | SCULLY WILLIAM P | TenPercentOwner | Buy | 100K | $12.79 | $1.3M | 736K |
| 2025-01-03 | SCULLY WILLIAM P | TenPercentOwner | Gift | 1K | $0.00 | $0 | 636K |
| 2025-01-02 | SCULLY WILLIAM P | TenPercentOwner | Gift | 13K | $0.00 | $0 | 637K |
| 2024-12-31 | SCULLY WILLIAM P | TenPercentOwner | Buy | 1K | $13.37 | $16K | 619K |
| 2024-12-31 | SCULLY WILLIAM P | TenPercentOwner | Buy | 800 | $13.39 | $11K | 620K |
| 2024-12-31 | SCULLY WILLIAM P | TenPercentOwner | Buy | 30K | $12.99 | $390K | 650K |
| 2024-12-20 | SCULLY WILLIAM P | TenPercentOwner | Buy | 2K | $15.91 | $32K | 619K |
| 2024-12-20 | SCULLY WILLIAM P | TenPercentOwner | Gift | 500 | $0.00 | $0 | 618K |
| 2024-12-20 | SCULLY WILLIAM P | TenPercentOwner | Gift | 40K | $0.00 | $0 | 59K |
| 2024-12-19 | SCULLY WILLIAM P | TenPercentOwner | Gift | 681K | $0.00 | $0 | 617K |
| 2024-12-18 | SCULLY WILLIAM P | TenPercentOwner | Gift | 430K | $0.00 | $0 | 1.2M |
| 2024-12-18 | SCULLY WILLIAM P | TenPercentOwner | Buy | 73K | $13.93 | $1.0M | 1.3M |
| 2024-01-24 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 5K | $13.53 | $68K | 5K |
| 2024-01-24 | Walker Karin L | Chief Accounting Officer | Sell | 5K | $34.00 | $170K | 0 |
| 2023-12-20 | Walker Karin L | Chief Accounting Officer | Sell | 3K | $37.45 | $124K | 0 |
| 2023-12-20 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 5K | $13.53 | $68K | 5K |
| 2023-12-20 | Walker Karin L | Chief Accounting Officer | Sell | 2K | $36.68 | $62K | 3K |
| 2023-11-30 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 5K | $13.53 | $68K | 5K |
| 2023-11-30 | Walker Karin L | Chief Accounting Officer | Sell | 5K | $34.00 | $170K | 0 |
| 2023-10-25 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 5K | $13.53 | $68K | 5K |
| 2023-10-25 | Walker Karin L | Chief Accounting Officer | Sell | 3K | $41.38 | $121K | 294 |
| 2023-10-25 | Walker Karin L | Chief Accounting Officer | Sell | 294 | $42.28 | $12K | 0 |
| 2023-10-25 | Walker Karin L | Chief Accounting Officer | Sell | 2K | $40.27 | $72K | 3K |
| 2023-10-11 | Smith Brandon S. | Chief Operating Officer | Sell | 4K | $46.62 | $166K | 444 |
| 2023-10-11 | Smith Brandon S. | Chief Operating Officer | Exercise or conversion | 4K | $11.12 | $44K | 4K |
| 2023-10-11 | Smith Brandon S. | Chief Operating Officer | Sell | 444 | $47.74 | $21K | 0 |
| 2023-10-04 | Karp Carol D. | Chief Regulatory Officer | Exercise or conversion | 5K | $12.15 | $61K | 5K |
| 2023-10-04 | Karp Carol D. | Chief Regulatory Officer | Sell | 4K | $46.51 | $202K | 663 |
| 2023-10-04 | Karp Carol D. | Chief Regulatory Officer | Sell | 663 | $47.29 | $31K | 0 |
| 2023-09-27 | Malecek Michael J | Chief Legal Officer | Sell | 404 | $48.31 | $20K | 0 |
| 2023-09-27 | Malecek Michael J | Chief Legal Officer | Exercise or conversion | 5K | $10.27 | $51K | 5K |
| 2023-09-27 | Malecek Michael J | Chief Legal Officer | Sell | 5K | $47.29 | $217K | 404 |
| 2023-09-19 | Walker Karin L | Chief Accounting Officer | Sell | 5K | $52.36 | $262K | 0 |
| 2023-09-19 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 5K | $15.04 | $75K | 5K |
| 2023-09-13 | Smith Brandon S. | Chief Operating Officer | Exercise or conversion | 4K | $11.12 | $44K | 4K |
| 2023-09-13 | Smith Brandon S. | Chief Operating Officer | Sell | 114 | $55.96 | $6K | 0 |
| 2023-09-13 | Smith Brandon S. | Chief Operating Officer | Sell | 4K | $55.48 | $216K | 114 |
| 2023-09-13 | Garren Hideki | Chief Medical Officer | Sell | 2K | $55.48 | $111K | 0 |
| 2023-09-13 | Garren Hideki | Chief Medical Officer | Exercise or conversion | 2K | $24.90 | $50K | 2K |
| 2023-09-06 | Karp Carol D. | Chief Regulatory Officer | Sell | 5K | $54.76 | $273K | 6 |
| 2023-09-06 | Karp Carol D. | Chief Regulatory Officer | Sell | 6 | $55.27 | $332 | 0 |
| 2023-09-06 | Karp Carol D. | Chief Regulatory Officer | Exercise or conversion | 5K | $12.15 | $61K | 5K |
| 2023-08-30 | Malecek Michael J | Chief Legal Officer | Sell | 3K | $55.39 | $148K | 14 |
| 2023-08-30 | Malecek Michael J | Chief Legal Officer | Sell | 2K | $54.58 | $127K | 3K |
| 2023-08-30 | Malecek Michael J | Chief Legal Officer | Exercise or conversion | 5K | $10.27 | $51K | 5K |
| 2023-08-30 | Malecek Michael J | Chief Legal Officer | Sell | 14 | $56.21 | $787 | 0 |
| 2023-08-18 | Walker Karin L | Chief Accounting Officer | Sell | 5K | $57.18 | $286K | 0 |
| 2023-08-18 | Walker Karin L | Chief Accounting Officer | Exercise or conversion | 5K | $15.04 | $75K | 5K |
Form 4 filings are due within two business days of the trade. Insiders sell for many reasons that say nothing about the company; open-market buys are rarer.
Planned sales (Form 144)
Newest first. JSON3 Form 144 notices on file for PRTA worth $876K at the prices reported; 0 in the last 90 days worth $0. Latest: ANNE KINGSTON filed on 2026-07-29 to sell 7,662 shares ($65K) from 2026-07-29.
| Filed | Seller | Shares | Market value | Of outstanding | Sale from | Broker |
|---|---|---|---|---|---|---|
| 2026-07-29 | ANNE KINGSTONOfficer | 8K | $65K | 0.015% | 2026-07-29 | Morgan Stanley Smith Barney LLC Executive Financial Services |
| 2026-07-29 | MICHAEL JOHN ISAACSOfficer | 8K | $71K | 0.016% | 2026-07-29 | Morgan Stanley Smith Barney LLC Executive Financial Services |
| 2026-06-09 | MALECEK MICHAEL JPrevious Officer | 80K | $740K | 0.153% | 2026-06-09 | ETRADE FINANCIAL CORPORATION |
Large holders (13D and 13G)
One row per reporting person with its latest filing, newest first. JSON7 holders report 5% or more of PRTA in their latest filing, all on Schedule 13G (passive). The largest reported stake is FMR LLC at 13.8% of the class (7,199,218 shares), filed 2026-08-06 for an event on 2026-06-30.
| Filed | Form | Holder | Shares | Of class | Event |
|---|---|---|---|---|---|
| 2026-08-19 | 13G/Ano. 7 | Fennell Todd W.individual | 5.2M | 10.2% | 2026-08-18 |
| 2026-08-06 | 13G/Ano. 4 | FMR LLCparent holding company | 7.2M | 13.8% | 2026-06-30 |
| 2026-08-06 | 13G/Ano. 4 | Abigail P. Johnsonindividual | 7.2M | 13.8% | 2026-06-30 |
| 2026-07-29 | 13G/Ano. 11 | BlackRock, Inc.parent holding company | 3.6M | 6.9% | 2026-06-30 |
| 2026-05-15 | 13G/Ano. 1 | Rubric Capital Management LPinvestment adviser, partnership | 5.0M | 9.3% | 2026-03-31 |
| 2026-05-15 | 13G/Ano. 1 | David Rosenparent holding company, individual | 5.0M | 9.3% | 2026-03-31 |
| 2026-05-11 | 13G/Ano. 6 | SCULLY WILLIAM Pindividual | 5.4M | 10.3% | 2026-05-07 |
| 2025-11-14 | 13G/Ano. 1 | ADAR1 Capital Management, LLCinvestment adviser, other entity | 1.5M | 2.7% | 2025-09-30 |
| 2025-11-14 | 13G/Ano. 1 | Daniel Schneebergerparent holding company, individual | 1.5M | 2.7% | 2025-09-30 |
| 2025-11-14 | 13G/Ano. 1 | ADAR1 Capital Management GP, LLCother entity | 1.2M | 2.2% | 2025-09-30 |
13F holders
Tracked managers holding PRTA at their latest 13F. JSON5 of the 30 tracked managers held PRTA at their latest 13F, $41.3M in total at quarter-end prices. D. E. Shaw & Co. is the largest at $15.8M (0.0% of its portfolio) as of 2026-06-30. Over the prior quarter 3 added shares and 2 cut.
| Fund | Quarter | Shares | Value | Of portfolio | Change in shares |
|---|---|---|---|---|---|
| D. E. Shaw & Co. | 2026-06-30 | 1.6M | $15.8M | 0.01% | -152K |
| Two Sigma Investments | 2026-06-30 | 1.3M | $12.4M | 0.01% | +59K |
| Renaissance Technologies | 2026-06-30 | 698K | $6.8M | 0.01% | +90K |
| Citadel Advisors | 2026-06-30 | 339K | $3.3M | 0.00% | -97K |
| AQR Capital Management | 2026-06-30 | 303K | $3.0M | 0.00% | +99K |
Only the 30 tracked managers on the funds hub; a 13F reports long positions in US listed stock at quarter end, 45 days late, and says nothing about shorts or positions sold since.
Financials
SEC XBRL, as filed. JSONIn Q2 FY 2026 (quarter ended 2026-06-30) Prothena Corp Public reported revenue of $1.0M, down 77.1% from the same quarter a year earlier, and net loss of $18.6M (-0.36 diluted EPS). In FY 2025 it generated -$163.6M of operating cash flow.
- Cash
- $288.2M
- Equity
- $286.9M
- Total assets
- $302.6M
- Shares outstanding
- 51,336,974
Quarterly, last 8 quarters
| Quarter | Period end | Revenue | Net income | Margin | Diluted EPS |
|---|---|---|---|---|---|
| Q2 FY 2026 | 2026-06-30 | $1.0M | -$18.6M | -1839.9% | -0.36 |
| Q1 FY 2026 | 2026-03-31 | $51.1M | $32.7M | 64.1% | 0.60 |
| Q4 FY 2025derived | 2025-12-31 | $21K | -$21.6M | -102804.8% | n/a |
| Q3 FY 2025 | 2025-09-30 | $2.4M | -$36.5M | -1513.1% | -0.68 |
| Q2 FY 2025 | 2025-06-30 | $4.4M | -$125.8M | -2845.4% | -2.34 |
| Q1 FY 2025 | 2025-03-31 | $2.8M | -$60.2M | -2128.5% | -1.12 |
| Q4 FY 2024derived | 2024-12-31 | $2.1M | -$58.0M | -2729.9% | n/a |
| Q3 FY 2024 | 2024-09-30 | $970K | -$59.0M | -6082.6% | -1.10 |
Fiscal years, with buybacks and dividends
| Fiscal year | Ends | Revenue | Net income | Operating cash flow | Capex | Buybacks | Dividends |
|---|---|---|---|---|---|---|---|
| FY 2025 | 2025-12-31 | $9.7M | -$244.1M | -$163.6M | $138K | n/a | n/a |
| FY 2024 | 2024-12-31 | $135.2M | -$122.3M | -$150.1M | $298K | n/a | n/a |
| FY 2023 | 2023-12-31 | $91.4M | -$147.0M | -$133.9M | $2.8M | n/a | n/a |
| FY 2022 | 2022-12-31 | $53.9M | -$116.9M | -$108.8M | $464K | n/a | n/a |
| FY 2021 | 2021-12-31 | $200.6M | $67.0M | $92.6M | $575K | n/a | n/a |
Quarters are the three-month figures the company reports; a fourth quarter marked derived is the fiscal year less the three reported quarters, since companies report it only inside the 10-K. Fiscal years are the annual figures. Buybacks are the cash the company paid to repurchase its common stock in the year, not the amount authorized. Balance sheet lines are as of 2026-06-30; shares outstanding as of 2026-07-30 from the cover page.
What this page is
Prothena Corp Public in the regulatory record
Regulators publish company data in separate files that never sit next to each other: FINRA's twice-monthly short interest, its daily short sale volume, the SEC's fails-to-deliver counts, and each insider's Form 4. A company page puts those series for one ticker on one URL, with planned sales, large holders, 13F holders and financials beside them, so the short position, the daily flow, the settlement fails and what insiders are doing can be read together.
Each section has its own history table, a one-line summary of the latest figures and its own JSON and CSV links, and says when its source last updated.
This page follows Prothena Corp Public (PRTA), SEC CIK 1559053, listed on Nasdaq, classified by the SEC as pharmaceutical preparations. The cross-market tables live on the short interest and insider transactions hubs.
Source and updates
- Short interest
- FINRA consolidated short interestSource: FINRA.Twice a month, about eight business days after settlement. Latest 2026-10-15.JSON and CSV
- Daily short volume
- FINRA Reg SHO daily filesSource: FINRA.Every trading day, the morning after FINRA posts it. Latest 2026-11-02.JSON and CSV
- Fails to deliver
- SEC fails-to-deliver dataSource: SEC.Twice a month, a few weeks after the half month ends. Latest 2026-09-29.JSON and CSV
- Planned sales
- SEC EDGAR Form 144Source: SEC.New notices appear shortly after the SEC posts them; a notice is filed on or before the sale. Latest 2026-07-29.JSON and CSV
- Large holders
- SEC EDGAR Schedule 13D and 13GSource: SEC.New filings appear shortly after the SEC posts them. A 13D is due within five business days of crossing 5%; a 13G follows the passive schedule. Latest 2026-08-19.JSON and CSV
- 13F holders
- SEC EDGAR Form 13F-HRSource: SEC.Quarterly, filed within 45 days of quarter end; 30 tracked managers. Latest 2026-06-30.JSON and CSV
- Financials
- SEC EDGAR 10-K and 10-Q filingsSource: SEC.Weekly; values are as filed in the 10-Q and 10-K. Latest 2026-06-30.JSON and CSV
- Earnings dates
- SEC EDGAR 8-K filings (Item 2.02)Source: SEC.Twice a day. Reported dates come from the company's 8-K filings; the next date is marked as an estimate until the 8-K arrives. Latest 2026-08-06.JSON and CSV
- Insider trades
- SEC EDGAR Form 4Source: SEC.New filings appear shortly after the SEC posts them; they're due two business days after the trade. Latest 2026-10-27.JSON and CSV
- Company record
- EDGAR filing index for CIK 1559053Ticker, name and exchange from the SEC's company list, refreshed weekly.
- Rate limits
- 10 requests a minute without a key, 30 with a free key from a free account.
How to read it
- Read the position against the flow: rising short interest with a high daily short share is new shorting; rising short interest with a normal short share is old shorts holding on.
- Insider buys next to a large short position are rare and stand out; insider sells next to one are common and mean little.
- Fails to deliver matter relative to the float, not in absolute shares; a million failed shares in a mega cap is noise.
Analysis of what the data shows, not advice. XOOMAR does not recommend buying, selling or holding anything.
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Datasets
Frequently Asked Questions
How much of PRTA is sold short?
7,939,666 shares were held short at the 2026-10-15 settlement, 13.3 days of average volume. FINRA publishes the next count about eight business days after the 15th and the last business day of the month.
What is PRTA's daily short volume?
On 2026-11-02, 108,289 of the 155,696 PRTA shares reported to FINRA were sold short, 69.5% of the day's reported volume. Short volume is a flow for one day, not a position.
Does PRTA have fails to deliver?
The SEC's latest file shows 318 PRTA shares failed to deliver at settlement 2026-09-29. Fails are reported per settlement date and published twice a month with a lag.
Are PRTA insiders buying or selling?
Insiders at PRTA reported 14 open-market buys worth $9.0M in the last 90 days and no open-market sells. Latest filing: SCULLY WILLIAM P (10% owner) on 2026-10-27.
Have PRTA insiders filed to sell?
3 Form 144 notices on file for PRTA worth $876K at the prices reported; 0 in the last 90 days worth $0. Latest: ANNE KINGSTON filed on 2026-07-29 to sell 7,662 shares ($65K) from 2026-07-29.
Who owns 5% or more of PRTA?
7 holders report 5% or more of PRTA in their latest filing, all on Schedule 13G (passive). The largest reported stake is FMR LLC at 13.8% of the class (7,199,218 shares), filed 2026-08-06 for an event on 2026-06-30.
What did PRTA report last quarter?
In Q2 FY 2026 (quarter ended 2026-06-30) Prothena Corp Public reported revenue of $1.0M, down 77.1% from the same quarter a year earlier, and net loss of $18.6M (-0.36 diluted EPS). In FY 2025 it generated -$163.6M of operating cash flow.
Which tracked 13F managers own PRTA?
5 of the 30 tracked 13F managers held PRTA shares at their latest filing, $41.3M in all. The largest: D. E. Shaw & Co. (1.6M shares, $15.8M), Two Sigma Investments (1.3M shares, $12.4M), Renaissance Technologies (698K shares, $6.8M), Ken Griffin's Citadel Advisors (339K shares, $3.3M), Cliff Asness's AQR Capital Management (303K shares, $3.0M).
Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.