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Prothena Corporation plc

PRTA Healthcare Biotechnology

Prothena Corporation plc’s revenue for fiscal 2025 (year ended December 2025) was $9.7 million, down 92.8% from fiscal 2024.

Revenue
−77.2%
EPS
+84.6%
Free cash flow
+44.6%

Quarter to June 2026, against a year earlier

8.38 0.17 +2.07%
Market cap
$421.5M
P/E
0.0×
Fwd P/E
71.4×
Dividend yield
—
F-score
2/9
Altman Z
−0.24
Beneish M
n/a
Dividend safety
n/a
Overview
Financials
Income Statement Balance Sheet Cash Flow Metrics & Ratios

Insider Decisions last twelve months

Bought, $m 12.07
Sold, $m 0.14
Trades a month
Jan 26 Apr 26 Jul 26 Oct 26
Buy — — — — — 1 4 — 2 4 4 —
Sell — — — — — — — 2 — — — —
Insider Ownership 15.79%

Capital & Financial Ratios $m

Size
Market Cap 421.47
Revenue ttm 54.53
Net income ttm (43.99)
Free cash flow ttm (60.80)
Net debt Q (288.19)
Valuation
P/E 0.00
Forward P/E 71.40 (above 35: high)
Price / sales 7.89
Forward P/S Powerpack
Price / FCF 0.00
Price / book 1.50
Financial health
Current ratio Q 25.05 (at or above 1.5: strong)
Debt / equity Q 0.00 (at or below 0.5: strong)
Interest coverage Q —
Growth
Revenue growth Q −77.15% (below 0%: shrinking)
Operating income growth Q +75.06% (above 0%: growing)
EPS, this year +102.62% (at or above 15%: strong)
EPS, next year A −962.65% (below 0%: weak)
Revenue, next year A +753.99% (at or above 10%: strong)
EPS, past 5 yrs —
EPS, next 5 yrs A +60.56% (at or above 15%: strong)

Green and red mark values outside typical ranges; (Q) is the latest quarter, (A) analysts’ estimates. How we judge →

Valuation vs history

EV/Sales, ten years
EV/Sales is 2.6×, against a ten-year median of 33.0×; over the ten years it ranged from −103× in 2019 to 1,543× in 2017.
P/S against its own 10 years 12.70%
10-year low 10-year high
P/B against its own 10 years 17.76%
10-year low 10-year high
EV/Sales against its own 10 years 6.79%
10-year low 10-year high

Dividends

Yield
—
Annual rate
—
Payout ratio
—

Assets vs Liabilities $m

2023 2024 2025 Q'26
Cash 620 471 308 288
Receivables 5 — — —
Inventory — — — —
Other — — — —
639 485 315 292
2023 2024 2025 Q'26
Payables 25 8 6 2
ST’ Debt — — — —
Other 16 16 25 6
57 49 41 12

Compound Annual Growth %

10y 5y 3y
Sales 19.68% 62.56% (43.57%)
Cash Flow 0.00% 0.00% 0.00%
Earnings 0.00% 0.00% 0.00%
Book Value (2.48%) 8.80% (23.32%)

Earnings Trends EPS, adjusted, against the consensus

Q2 FY26 Estimate −0.39 Actual −0.32

Earnings per share against the consensus, by quarter
Quarter Estimate Reported Result
Q3 FY25 −0.60 −0.67 Miss by 0.07
Q4 FY25 −0.45 −0.44 Beat by 0.01
Q1 FY26 −0.31 0.52 Beat by 0.83
Q2 FY26 −0.39 −0.32 Beat by 0.07
Q3 FY26 −0.38 — Reports 5 November 2026

EPS $

Mar Jun Sep Dec Year
’26 0.60 (0.36) — — —
’25 (1.12) (2.34) (0.68) (0.40) (4.53)
’24 (1.34) 1.22 (1.10) (1.08) (2.27)
’23 (0.89) (1.03) 0.38 (1.26) (2.76)
’22 (0.78) (0.88) (0.97) 0.12 (2.47)
’21 (0.91) 0.58 2.13 (0.71) 1.38
’20 (0.59) (0.66) (0.77) (0.77) (2.78)
Fiscal quarters ending in the months shown.

Revenue $m

Mar Jun Sep Dec Year
’26 51 1 — — —
’25 3 4 2 0 10
’24 0 132 1 2 135
’23 2 4 85 0 91
’22 1 1 2 50 54
’21 0 60 139 1 201
’20 0 0 0 0 1
Fiscal quarters ending in the months shown.

Operating Cash Flow $m

Mar Jun Sep Dec Year
’26 29 (25) — — —
’25 (53) (46) (41) (23) (164)
’24 (73) 16 (45) (48) (150)
’23 (47) (45) 10 (51) (134)
’22 (37) (35) (31) (5) (109)
’21 (34) 37 112 (22) 93
’20 (23) (19) (19) (19) (80)
Fiscal quarters ending in the months shown.

Free Cash Flow $m

Mar Jun Sep Dec Year
’26 29 (26) — — —
’25 (53) (46) (41) (23) (164)
’24 (73) 16 (45) (48) (150)
’23 (48) (46) 9 (53) (137)
’22 (37) (35) (31) (5) (109)
’21 (34) 37 112 (23) 92
’20 (23) (19) (19) (19) (81)
Fiscal quarters ending in the months shown.

Target Price Range

Analyst price targets

Recommendation Rating

2
1Buy 2 3Hold 4 5Sell

Ten years at a glance Fiscal years to December

Ten-year view Analyst estimates Powerpack
Group Line 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 TTM Jun ’26 Trend 10 yrs 2026e 2027e 2028e Next 3/yr
Income, $m
Income, $m Revenue 1 28 1 1 1 201 54 91 135 10 55 +27.9% 83 21 81 +102.9%
Gross margin, % 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 0.0 pt
EBT (159) (158) (156) (77) (111) 72 (126) (160) (129) (201) (44) +2.6%
EBT margin, % (15,067.68) (572.71) (16,347.12) (9,496.07) (13,062.95) 35.86 (233.01) (175.64) (95.39) (2,073.82) (81.33) +12,993.9 pt
Net income (160) (153) (156) (78) (111) 67 (117) (147) (122) (244) (44) +4.8%
Per share, $
Per share, $ Revenue 0.03 0.73 0.02 0.02 0.02 4.54 1.14 1.72 2.51 0.18 1.05 +21.7%
Earnings (4.66) (4.07) (3.93) (1.95) (2.78) 1.51 (2.47) (2.76) (2.27) (4.53) (0.83) (0.3%)
Cash flow (3.38) (3.48) (0.71) (1.33) (2.01) 2.09 (2.30) (2.52) (2.79) (3.04) (1.15) (1.2%)
Capex (0.48) (0.09) (0.04) (0.01) 0.00 (0.01) (0.01) (0.05) (0.01) 0.00 (0.01) (44.1%)
Free cash flow (3.87) (3.58) (0.76) (1.34) (2.02) 2.08 (2.31) (2.57) (2.80) (3.04) (1.17) (2.6%)
Book value 10.64 10.81 8.17 6.84 4.61 10.54 13.13 10.55 9.06 5.21 5.50 (7.6%)
Shares, m 34 38 40 40 40 44 47 53 54 54 53 +5.1%
Valuation, ×
Valuation, × P/E 0.00 0.00 0.00 0.00 0.00 35.54 0.00 0.00 0.00 0.00 0.00 3.6
P/S 1,621.17 51.72 426.66 775.59 561.99 10.89 47.01 22.45 5.51 53.08 7.89 357.6
P/B 4.68 3.50 1.26 2.31 2.61 4.69 4.07 3.65 1.53 1.83 1.50 3.0
EV/Sales 1,254.42 36.55 (21.15) 314.02 214.12 8.01 33.83 15.66 2.02 21.33 2.60 187.9
EV/FCF (9.96) (7.47) 0.67 (4.78) (2.27) 17.45 (16.69) (10.47) (1.82) (1.26) (2.34) (3.7)
Cash, $m
Cash, $m Operating cash flow (116) (131) (28) (53) (80) 93 (109) (134) (150) (164) (60) +3.9%
Capex (17) (4) (2) (1) 0 (1) 0 (3) 0 0 (1) (41.3%)
Free cash flow (133) (135) (30) (54) (81) 92 (109) (137) (150) (164) (61) +2.3%
Balance, $m
Balance, $m Working capital 350 389 416 361 273 551 669 582 437 274 280 (2.7%)
Net debt (387) (418) (428) (376) (297) (579) (710) (620) (471) (308) (288) (2.5%)
Shareholders’ equity 365 407 323 273 184 466 622 561 487 280 287 (2.9%)
Returns, %
Returns, % ROA (37.89) (32.05) (31.28) (16.92) (29.55) 14.21 (17.11) (20.22) (19.67) (55.86) (12.54) (18.0) pt
ROIC 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 (621.71) 0.00 0.00 0.0 pt
ROE (44.10) (39.67) (42.63) (26.07) (48.65) 20.61 (21.50) (24.85) (23.34) (63.62) (14.39) (19.5) pt
People
People Employees 96 125 59 51 66 82 127 173 163 67 — (3.9%)
Revenue/emp, $m 0.01 0.22 0.02 0.02 0.01 2.45 0.42 0.53 0.83 0.14 — +33.1%
Negative figures in brackets.
estimates

All 10 years →

Fiscal years to Dec 2025 · latest quarter Jun 2026

Prothena Corporation plc vs peers in Biotechnology (Q) = latest quarter vs a year earlier

Company Market cap P/E Fwd P/E Revenue growth (Q) EPS growth (Q) FCF growth (Q) Gross margin (Q) EBIT margin (Q) Compare
CAPR Capricor Therapeutics, Inc. $479.1M — (loss-making) — (loss-making) −7.92% (below 0%: shrinking) n/m −72.88% (below 0%: shrinking) 100.00% 0.00% Compare
MNPR Monopar Therapeutics Inc. $469.1M — (loss-making) — — n/m −201.41% (below 0%: shrinking) — 0.00% Compare
RLMD Relmada Therapeutics, Inc. $455.5M — (loss-making) — — n/m −50.06% (below 0%: shrinking) 0.00% 0.00% Compare
YDES YD Bio Limited $453.0M — — — — — — — Compare
EPRX Eupraxia Pharmaceuticals Inc. $447.3M — (loss-making) — — n/m −56.41% (below 0%: shrinking) — 0.00% Compare
CRMD CorMedix Inc $433.4M 2.3× 11.5× +156.52% (above 0%: growing) +13.79% (above 0%: growing) +185.90% (above 0%: growing) 75.66% 42.10% Compare
PRTCY PureTech Health PLC Sponsored ADR $424.0M — (loss-making) — (loss-making) −44.60% (below 0%: shrinking) +66.43% (above 0%: growing) +19.27% (above 0%: growing) 2.83% 0.00% Compare
PRTA Prothena Corporation plc $421.5M — (loss-making) 71.4× −77.15% (below 0%: shrinking) n/m +44.64% (above 0%: growing) 100.00% (2,089.21%)
ASMB Assembly Biosciences, Inc. $405.6M — (loss-making) — (loss-making) +38.94% (above 0%: growing) n/m +7.58% (above 0%: growing) 100.00% (47.44%) Compare
Median of peers $450.2M — — +15.51% — −50.06% 75.66% 0.00%

All 621 Biotechnology stocks →

Pay and ownership Proxy statement filed 27 March 2026

Chief executive’s pay

Year Total pay Actually paid $100 invested
2025 5.90m 2.87m 79.52
2024 7.23m (1.71m) 115.32
2023 7.04m (3.22m) 302.58
2022 6.74m 7.40m 501.67
2021 4.92m 41.14m 411.32
Total pay is as the Summary Compensation Table states it; actually paid revalues the year’s share awards at its end, as the SEC’s pay-versus-performance rule asks. $100 invested is what $100 in the company’s shares at the start of the earliest year shown was worth at each year’s end. Read the proxy statement

Prothena Corporation plc (PRTA) Latest News

20 Oct

Impact 4 · · Zacks
Impact 3 · · Simply Wall St.

19 Aug

Impact 3 ·

7 Aug

Impact 3 ·

6 Aug

Impact 3 ·
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11 May

Impact 4 · · Simply Wall St.

8 May

Impact 4 · · Zacks

7 May

Impact 3 · · Business Wire

27 Apr

Impact 4 · · Business Wire

1 Apr

Impact 4 ·
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26 Mar

Impact 4 · · Zacks

21 Mar

Impact 4 · · Business Wire

9 Mar

Impact 4 · · Business Wire

3 Mar

Impact 4 · · Zacks

27 Feb

Impact 4 · · Business Wire

20 Feb

Impact 4 · · Moby
Impact 4 · · GuruFocus.com
Impact 3 · · Zacks

19 Feb

Impact 4 · · MarketBeat
Impact 4 · · Associated Press Finance
Impact 4 · · Business Wire
Impact 3 · · Zacks

16 Feb

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13 Feb

Impact 3 · · Zacks

21 Jan

Impact 4 · · Zacks

20 Jan

Impact 4 · · Simply Wall St.

5 Jan

Impact 4 · · Simply Wall St.

2 Jan

Impact 4 · · Simply Wall St.
stockrow.com/PRTA · Data as of Jun 30, 2026 · For information only; not investment advice. · © 2026 stockrow.com