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PRTA · PROTHENA CORP PUBLIC LTD CO

Prothena Corporation plc, a late-stage clinical biotechnology company, focuses on discovery and development of novel therapies to treat diseases caused by protein dysregulation. Its product pipeline includes Prasinezumab, an investigational humanized monoclonal antibody which is in Phase 3 clinical trial for the treatment of parkinson's disease and other synucleinopathies. The company also develops Coramitug, an investigational antibody, which is in Phase 3 clinical trial for the treatment of transthyretin amyloidosis; BMS-986446, an anti-tau antibody which is in Phase 2 clinical trial to treat Alzheimer's disease; PRX019, an investigational antibody which is in Phase 1 clinical trial for the treatment of neurodegenerative diseases; and PRX123, a Dual Aß-Tau Vaccine, which is in preclinical trial for treating Alzheimer's disease. In addition, it develops discovery- and late-preclinical-stage programs include TDP-43 CYTOPE for the treatment of amyotrophic lateral sclerosis; PRX012, a next-generation anti-Aß antibody which is in phase 1 clinical trial to treat Alzheimer's disease; and PRX012-TfR, a preclinical program for the treatment of Alzheimer's disease. It has a license, development, and commercialization agreement with F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. to develop and commercialize antibodies that target a-synuclein, including prasinezumab; and master collaboration agreement with Bristol Myers Squibb to develop and commercialize antibodies targeting tau, TDP-43. Prothena Corporation plc was incorporated in 2012 and is based in Dublin, Ireland.

Cap structure and valuation

Cap structure
SP$9.12
SO51.3M
Options11.8M
Warrants0.0M
FD SO63.1M
MC$575.5M
Cash$288.2M
Total debt
EV$287.3M
TTM Multiples
EV / Revenue5.3x
EV / EBITDA
MC / Net Income
EV / FCF
MC / FCF
Ownership & coverage
Institutional93.3%
Insiders20.5%
# Institutions257
Analysts5
ConsensusBuy
Avg target$21.40
Short % float18.8%
Days to cover12.84

MC = SP × FD SO. EV = MC + Debt − Cash. SP = previous yfinance close. Balance-sheet figures as of 2026-07-30. Multiples use TTM (sum of last 4 quarters); shown as "—" when the denominator is zero or negative, or when fewer than four quarters are reported — a partial sum is not a trailing twelve months. Ownership & coverage per Yahoo Finance as of 2026-08-11 — institutional % is 13F-based, so it can lag a quarter and exceed 100% on share-count timing. Short interest per FINRA bi-monthly reporting, as of 2026-07-15; the float denominator can be unreliable on tiny floats.

Financial statements

LTM12/31/2512/31/2412/31/2312/31/22
Total Revenue 54.539.68135.1691.3753.91
Revenue YoY % 463.1%(92.8%)47.9%69.5%
SG&A 49.4559.3967.2061.8449.90
R&D 64.95134.85222.52220.57135.56
Operating Income (55.51)(214.64)(154.56)(191.04)(131.56)
Operating Income YoY % 74.1%(38.9%)19.1%(45.2%)
Operating Margin % (101.8%)(2216.4%)(114.4%)(209.1%)(244.1%)
EBITDA (54.68)(213.75)(153.67)(190.11)(130.81)
EBITDA Margin % (100.3%)(2207.2%)(113.7%)(208.1%)(242.7%)
Interest Expense 10.9714.1425.8231.016.35
Other Income / (Expense) 22.1227.9551.4561.5712.30
Pretax Income (44.35)(200.83)(128.93)(160.48)(125.61)
Tax Provision (0.36)43.26(6.62)(13.45)(8.66)
Net Income (43.99)(244.09)(122.31)(147.03)(116.95)
Net Margin % (80.7%)(2520.6%)(90.5%)(160.9%)(217.0%)
Diluted EPS -$0.84-$4.53-$2.27-$2.76-$2.47
Basic EPS -$0.83-$4.53-$2.27-$2.76-$2.47
Diluted Avg Shares 52.153.853.853.247.4
Basic Avg Shares 52.153.853.853.247.4

Insider activity (last 2 years)

Date Filed Reporter Relationship Trans. Date Code Shares Price Total Value
2026-08-10 SCULLY WILLIAM P 10% Owner 2026-08-07 P 34,000 $8.62 $293,053
2026-08-10 SCULLY WILLIAM P 10% Owner 2026-08-07 P 3,500 $8.62 $30,167
2026-07-30 Kingston Anne Evans Officer (Chief Strategy Officer) 2026-07-29 S (7,662) $8.47 -$64,919
2026-07-30 Isaacs Michael John Officer (General Counsel & Company Sec.) 2026-07-29 S (8,386) $8.47 -$71,055
2026-07-30 Zago Wagner M. Officer (Chief Scientific Officer) 2026-07-28 M 51,000 $0
2026-07-30 Zago Wagner M. Officer (Chief Scientific Officer) 2026-07-28 D (51,000) $8.56 -$436,560
2026-07-30 Zago Wagner M. Officer (Chief Scientific Officer) 2026-07-28 M (51,000) $-0
2026-07-30 Walker Karin L Officer (Chief Accounting Officer) 2026-07-28 M 15,000 $0
2026-07-30 Walker Karin L Officer (Chief Accounting Officer) 2026-07-28 D (15,000) $8.56 -$128,400
2026-07-30 Walker Karin L Officer (Chief Accounting Officer) 2026-07-28 M (15,000) $-0
2026-07-30 Swanson Chad J. Officer (Chief Development Officer) 2026-07-28 M 51,000 $0
2026-07-30 Swanson Chad J. Officer (Chief Development Officer) 2026-07-28 D (40,800) $8.56 -$349,248
2026-07-30 Swanson Chad J. Officer (Chief Development Officer) 2026-07-28 F (3,467) $8.56 -$29,678
2026-07-30 Swanson Chad J. Officer (Chief Development Officer) 2026-07-28 M (51,000) $-0
2026-07-30 Smith Brandon S. Officer (Chief Operating Officer) 2026-07-28 M 78,000 $0
2026-07-30 Smith Brandon S. Officer (Chief Operating Officer) 2026-07-28 D (78,000) $8.56 -$667,680
2026-07-30 Smith Brandon S. Officer (Chief Operating Officer) 2026-07-28 M (78,000) $-0
2026-07-30 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2026-07-28 M 57,000 $0
2026-07-30 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2026-07-28 D (57,000) $8.56 -$487,920
2026-07-30 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2026-07-28 M (57,000) $-0
2026-07-30 Kinney Gene G. Director, Officer (President and CEO) 2026-07-28 M 84,000 $0
2026-07-30 Kinney Gene G. Director, Officer (President and CEO) 2026-07-28 D (84,000) $8.56 -$719,040
2026-07-30 Kinney Gene G. Director, Officer (President and CEO) 2026-07-28 M (84,000) $-0
2026-07-30 Kingston Anne Evans Officer (Chief Strategy Officer) 2026-07-28 F (3,498) $8.56 -$29,943
2026-07-30 Isaacs Michael John Officer (General Counsel & Company Sec.) 2026-07-28 F (4,694) $8.56 -$40,181
2026-06-18 SCULLY WILLIAM P 10% Owner 2026-06-16 P 20,000 $7.90 $157,990
2026-06-16 SCULLY WILLIAM P 10% Owner 2026-06-15 G (325,000) $-0
2026-06-12 SCULLY WILLIAM P 10% Owner 2026-06-11 P 125,000 $8.17 $1,021,225
2026-06-05 SCULLY WILLIAM P 10% Owner 2026-06-04 P 50,000 $9.31 $465,295
2026-06-03 SCULLY WILLIAM P 10% Owner 2026-06-02 P 50,000 $9.43 $471,300
2026-05-26 SCULLY WILLIAM P 10% Owner 2026-05-22 P 100,000 $9.81 $981,300
2026-05-15 WELCH DANIEL G Director 2026-05-15 A 27,000 $0
2026-05-15 Selkoe Dennis J. Director 2026-05-15 A 27,000 $0
2026-05-15 Ekman Lars Director 2026-05-15 A 27,000 $0
2026-05-15 Dunn William H. Jr. Director 2026-05-15 A 27,000 $0
2026-05-15 Cooke Shane Director 2026-05-15 A 27,000 $0
2026-05-15 COLLIER RICHARD T Director 2026-05-15 A 27,000 $0
2026-04-10 Kingston Anne Evans Officer (Chief Strategy Officer) 2026-04-10 A 100,000 $0
2026-03-05 Zago Wagner M. Officer (Chief Scientific Officer) 2026-03-03 A 190,000 $0
2026-03-05 Walker Karin L Officer (Chief Accounting Officer) 2026-03-03 A 150,000 $0
2026-03-05 Swanson Chad J. Officer (Chief Development Officer) 2026-03-03 A 190,000 $0
2026-03-05 Smith Brandon S. Officer (Chief Operating Officer) 2026-03-03 A 190,000 $0
2026-03-05 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2026-03-03 A 230,000 $0
2026-03-05 Malecek Michael J Officer (Chief Legal Officer) 2026-03-03 A 190,000 $0
2026-03-05 Kinney Gene G. Director, Officer (President and CEO) 2026-03-03 A 520,000 $0
2025-07-30 Zago Wagner M. Officer (Chief Scientific Officer) 2025-07-28 A 85,000 $0
2025-07-30 Walker Karin L Officer (Chief Accounting Officer) 2025-07-28 A 25,000 $0
2025-07-30 Swanson Chad J. Officer (Chief Development Officer) 2025-07-28 A 85,000 $0
2025-07-30 Smith Brandon S. Officer (Chief Operating Officer) 2025-07-28 A 130,000 $0
2025-07-30 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2025-07-28 A 95,000 $0
2025-07-30 Malecek Michael J Officer (Chief Legal Officer) 2025-07-28 A 80,000 $0
2025-07-30 Kinney Gene G. Director, Officer (President and CEO) 2025-07-28 A 140,000 $0
2025-05-16 WELCH DANIEL G Director 2025-05-14 A 20,183 $0
2025-05-16 Selkoe Dennis J. Director 2025-05-14 A 20,183 $0
2025-05-16 Kim Helen Susan Director 2025-05-14 A 20,183 $0
2025-05-16 Ekman Lars Director 2025-05-14 A 20,183 $0
2025-05-16 Dunn William H. Jr. Director 2025-05-14 A 20,183 $0
2025-05-16 Cooke Shane Director 2025-05-14 A 20,183 $0
2025-05-16 COLLIER RICHARD T Director 2025-05-14 A 20,183 $0
2025-05-16 Cobb Paula K Director 2025-05-14 A 20,183 $0
2025-05-06 EcoR1 Capital, LLC 10% Owner 2025-05-06 S (1,984,053) $7.64 -$15,164,712
2025-05-06 EcoR1 Capital, LLC 10% Owner 2025-05-05 S (977,693) $8.11 -$7,930,166
2025-05-06 EcoR1 Capital, LLC 10% Owner 2025-05-02 S (3,317,938) $8.36 -$27,744,929
2025-05-02 SCULLY WILLIAM P 10% Owner 2025-01-15 G (12,000) $-0
2025-05-02 SCULLY WILLIAM P 10% Owner 2025-01-14 P 100,000 $12.79 $1,279,040
2025-05-02 SCULLY WILLIAM P 10% Owner 2025-01-03 G (1,000) $-0
2025-05-02 SCULLY WILLIAM P 10% Owner 2025-01-02 G (13,200) $-0
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-31 P 1,200 $13.37 $16,038
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-31 P 800 $13.39 $10,715
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-31 P 30,000 $12.99 $389,640
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-20 P 2,000 $15.91 $31,813
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-20 G (500) $-0
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-20 G (40,000) $-0
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-19 G (681,000) $-0
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-18 G 430,000 $0
2025-05-02 SCULLY WILLIAM P 10% Owner 2024-12-18 P 73,436 $13.93 $1,022,670
2025-03-07 Zago Wagner M. Officer (Chief Scientific Officer) 2025-03-05 A 107,500 $0
2025-03-07 Walker Karin L Officer (Chief Accounting Officer) 2025-03-05 A 70,000 $0
2025-03-07 Swanson Chad J. Officer (Chief Development Officer) 2025-03-05 A 107,500 $0
2025-03-07 Smith Brandon S. Officer (Chief Operating Officer) 2025-03-05 A 107,500 $0
2025-03-07 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2025-03-05 A 107,500 $0
2025-03-07 Malecek Michael J Officer (Chief Legal Officer) 2025-03-05 A 107,500 $0
2025-03-07 Kinney Gene G. Director, Officer (President and CEO) 2025-03-05 A 375,000 $0
2025-03-07 Karp Carol D. Officer (Chief Regulatory Officer) 2025-03-05 A 107,500 $0
2025-03-07 Ford David A Officer (Chief People Officer) 2025-03-05 A 107,500 $0
2025-02-14 Nguyen Tran Officer (Chief Strategy Officer and CFO) 2020-04-08 J (995) $-0
2024-10-03 Swanson Chad J. Officer (Chief Development Officer) 2024-10-01 A 40,000 $0