Prothena Corporation plc (PRTA) Key Metrics
PRTA valuation today
Trailing 12 months · as of October 18, 2026- Market cap
- $428.7M
- Enterprise value
- $164.4M
- P/E (TTM)
- —
- Forward P/E
- 10.6
- PEG ratio
- 0.80
- Price / sales
- 7.9 10-yr median 52.9
- Price / book
- 1.6 10-yr median 3.0
- EV / EBITDA
- —
- Dividend yield
- —
- Beta
- −0.29
PRTA key metrics, 2016–2025
Fiscal year ended December 31, 2025 · U.S. dollarsPRTA valuation Price multiples at each fiscal year-end price.
Price / sales+863.4%
53.1
2025 · hover or tap a bar for each year
20162025
Price / book+19.8%
1.8
2025 · hover or tap a bar for each year
20162025
Free cash flow yield−11.7 pts
−31.8%
2025 · hover or tap a bar for each year
20162025
PRTA returns How much profit the business earns on the capital it uses.
Return on equity−40.3 pts
−63.6%
2025 · hover or tap a bar for each year
20162025
Return on assets−36.2 pts
−55.9%
2025 · hover or tap a bar for each year
20162025
Asset turnover−89.8%
0.02
2025 · hover or tap a bar for each year
20162025
PRTA per-share figures Results divided by the shares outstanding at year-end.
Revenue per share−92.8%
$0.18
2025 · hover or tap a bar for each year
20162025
Earnings per share
−$4.53
2025 · hover or tap a bar for each year
20162025
Free cash flow per share
−$3.04
2025 · hover or tap a bar for each year
20162025
Book value per share−42.5%
$5.21
2025 · hover or tap a bar for each year
20162025
Shares outstanding+0.1%
53.8M
2025 · hover or tap a bar for each year
20162025
PRTA financial health Debt, liquidity and how easily interest is covered.
Debt / equity+121.9%
0.05
2025 · hover or tap a bar for each year
20162025
Net debt+$166.9M
−$293.7M
2025 · hover or tap a bar for each year
20162025
Current ratio−22.9%
7.72
2025 · hover or tap a bar for each year
20162025
Debt / assets+114.0%
0.04
2025 · hover or tap a bar for each year
20162025
PRTA efficiency & capital use Working capital cycle and where the cash goes.
Days payables outstanding−1,015 days
673 days
2025 · hover or tap a bar for each year
20162025
Capex / revenue+1.2 pts
1.4%
2025 · hover or tap a bar for each year
20162025
PRTA valuation history
Fiscal year-endToday10-year median
PRTA returns on capital
ROEROICROA
Net income (ROE, ROA) or after-tax operating income (ROIC) divided by the average of the opening and closing balance.
PRTA debt vs cash
Total debtCash & short-term investments
Debt includes short- and long-term borrowings and, where reported, lease liabilities.
PRTA cash returned to shareholders
DividendsBuybacksFree cash flow
PRTA price vs earnings per share
Share price at year-endEPS (right axis)
PRTA key metrics
2016–2025| 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | |
|---|---|---|---|---|---|---|---|---|---|---|
| Valuation | ||||||||||
| Market capitalization | $514.1M | $744.7M | $1.93B | $2.85B | $2.39B | $479.4M | $631.3M | $407.5M | $1.41B | $1.69B |
| Enterprise value | $220.4M | $284.2M | $1.33B | $2.15B | $1.83B | $201.8M | $278.5M | $31.3M | $1.05B | $1.35B |
| P/E ratio | — | — | — | — | 35.7 | — | — | — | — | — |
| Price / sales | 53.1 | 5.5 | 21.2 | 52.9 | 11.9 | 562.0 | 775.6 | 426.7 | 51.3 | — |
| Price / book | 1.8 | 1.5 | 3.4 | 4.6 | 5.1 | 2.6 | 2.3 | 1.3 | 3.5 | 4.6 |
| Price / free cash flow | — | — | — | — | 26.0 | — | — | — | — | — |
| Price / operating cash flow | — | — | — | — | 25.9 | — | — | — | — | — |
| EV / sales | 22.8 | 2.1 | 14.5 | 39.9 | 9.1 | 236.6 | 342.2 | 32.8 | 38.0 | — |
| EV / EBITDA | — | — | — | — | 23.2 | — | — | — | — | — |
| EV / free cash flow | — | — | — | — | 19.9 | — | — | — | — | — |
| Earnings yield | −47.5% | −16.4% | −7.6% | −4.1% | 2.8% | −23.2% | −12.3% | −38.2% | −10.9% | −9.5% |
| Free cash flow yield | −31.8% | −20.2% | −7.1% | −3.8% | 3.8% | −16.8% | −8.5% | −7.4% | −9.5% | −7.9% |
| Dividend yield | — | — | — | — | — | — | — | — | 0.0% | 0.0% |
| Shareholder yield (dividends + buybacks) | 0.0% | 0.0% | — | — | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% |
| Share price at fiscal year-end | $9.55 | $13.85 | $36.34 | $60.25 | $49.40 | $12.01 | $15.83 | $10.30 | $37.49 | $49.19 |
| Per share | ||||||||||
| Revenue per share | $0.18 | $2.51 | $1.72 | $1.14 | $4.14 | $0.02 | $0.02 | $0.02 | $0.73 | $0.03 |
| Earnings per share | −$4.53 | −$2.27 | −$2.76 | −$2.47 | $1.38 | −$2.78 | −$1.95 | −$3.93 | −$4.07 | −$4.66 |
| Operating cash flow per share | −$3.04 | −$2.79 | −$2.52 | −$2.30 | $1.91 | −$2.01 | −$1.33 | −$0.71 | −$3.48 | −$3.41 |
| Free cash flow per share | −$3.04 | −$2.80 | −$2.57 | −$2.31 | $1.90 | −$2.02 | −$1.34 | −$0.76 | −$3.58 | −$3.90 |
| Cash per share | $5.71 | $8.77 | $11.63 | $15.00 | $11.95 | $7.40 | $9.42 | $10.81 | $11.09 | $11.26 |
| Book value per share | $5.21 | $9.06 | $10.55 | $13.13 | $9.62 | $4.61 | $6.84 | $8.16 | $10.81 | $10.64 |
| Tangible book value per share | $5.21 | $9.06 | $10.55 | $13.13 | $9.62 | $4.61 | $6.84 | $8.16 | $10.81 | $10.64 |
| Dividends per share | — | — | — | — | — | — | — | — | $0.00 | $0.00 |
| Capex per share | $0.00 | $0.01 | $0.05 | $0.01 | $0.01 | $0.00 | $0.01 | $0.04 | $0.10 | $0.48 |
| Debt per share | $0.26 | $0.20 | $0.22 | $0.14 | $0.25 | $0.45 | $0.58 | $1.30 | $1.39 | $1.49 |
| Shares outstanding | 53.8M | 53.8M | 53.2M | 47.4M | 48.5M | 39.9M | 39.9M | 39.6M | 37.7M | 34.4M |
| Change in shares outstanding | +0.1% | +1.0% | +12.3% | −2.3% | +21.4% | +0.1% | +0.8% | +5.1% | +9.6% | +13.3% |
| Returns & profitability | ||||||||||
| Return on equity (ROE) | −63.6% | −23.3% | −24.8% | −21.5% | 20.6% | −48.6% | −26.1% | −42.6% | −39.7% | −44.1% |
| Return on invested capital (ROIC) | — | — | — | — | — | — | — | — | −342.5% | −355.6% |
| Return on assets (ROA) | −55.9% | −19.7% | −20.2% | −17.1% | 14.2% | −29.6% | −16.9% | −31.3% | −32.0% | −37.9% |
| Return on tangible assets | −74.7% | −22.4% | −21.1% | −15.4% | 11.0% | −33.4% | −18.5% | −31.2% | −30.9% | −34.8% |
| Free cash flow margin | — | −111.2% | −149.6% | −202.7% | 45.9% | — | — | — | −489.9% | — |
| Income quality (OCF / net income) | — | — | — | — | 1.38 | — | — | — | — | — |
| Financial health | ||||||||||
| Total debt | $13.9M | $10.8M | $11.8M | $6.5M | $12.3M | $17.8M | $22.9M | $51.5M | $52.2M | $51.3M |
| Cash & short-term investments | $307.5M | $471.4M | $618.8M | $710.4M | $579.1M | $295.4M | $375.7M | $427.7M | $417.6M | $386.9M |
| Net debt | −$293.7M | −$460.5M | −$607.0M | −$703.9M | −$566.8M | −$277.5M | −$352.8M | −$376.1M | −$365.4M | −$335.6M |
| Debt / equity | 0.05 | 0.02 | 0.02 | 0.01 | 0.03 | 0.10 | 0.08 | 0.16 | 0.13 | 0.14 |
| Debt / assets | 0.04 | 0.02 | 0.02 | 0.01 | 0.02 | 0.05 | 0.05 | 0.10 | 0.11 | 0.11 |
| Net debt / EBITDA | — | — | — | — | −7.19 | — | — | — | — | — |
| Current ratio | 7.72 | 10.01 | 11.24 | 14.34 | 17.48 | 11.58 | 21.36 | 28.90 | 11.41 | 9.53 |
| Quick ratio | 7.72 | 10.01 | 11.33 | 14.34 | 17.48 | 11.53 | 21.36 | 28.90 | 11.41 | 9.53 |
| Interest coverage | — | — | — | -19.6 | 10.7 | -13.6 | -10.4 | -43.0 | -42.1 | -184.9 |
| Working capital | $274.4M | $436.9M | $582.4M | $669.0M | $551.4M | $273.4M | $360.7M | $416.5M | $389.0M | $350.3M |
| Invested capital | −$13.2M | $26.4M | −$45.6M | −$81.9M | −$100.7M | −$93.5M | −$79.9M | −$53.1M | $41.8M | $29.8M |
| Tangible asset value | $280.5M | $486.9M | $561.4M | $622.0M | $466.0M | $184.0M | $272.9M | $323.0M | $407.2M | $365.4M |
| Net current asset value | $268.9M | $425.2M | $504.3M | $583.1M | $441.5M | $150.3M | $232.0M | $255.6M | $337.2M | $296.8M |
| Graham number | — | — | — | — | $17.29 | — | — | — | — | — |
| Graham net-net per share | $4.85 | $7.65 | $9.12 | $12.13 | $8.99 | $3.69 | $5.75 | $6.37 | $8.73 | $8.51 |
| Capital allocation | ||||||||||
| Dividends paid | — | — | — | — | — | — | — | — | $0 | $0 |
| Share buybacks (net) | $139,000 | $353,000 | — | — | $0 | $0 | $0 | $0 | $0 | $0 |
| Dividends + buybacks / free cash flow | — | — | — | — | 0.0% | — | — | — | — | — |
| Capex / revenue | 1.4% | 0.2% | 3.1% | 0.9% | 0.3% | 23.0% | 68.2% | 185.1% | 13.2% | 1,577.6% |
| Capex / operating cash flow | — | — | — | — | 0.6% | — | — | — | — | — |
| Capex / depreciation | 0.15 | 0.33 | 3.03 | 0.62 | 0.52 | 0.13 | 0.08 | 0.55 | 1.18 | 6.86 |
| Stock-based compensation / revenue | 388.7% | 34.0% | 44.8% | 58.1% | 12.3% | 2,580.8% | 2,897.4% | 2,828.3% | 97.3% | 2,362.9% |
| R&D / revenue | 1,392.5% | 164.6% | 241.4% | 251.5% | 41.0% | 8,778.9% | 6,245.2% | 10,595.1% | 488.9% | 11,330.2% |
| SG&A / revenue | 613.3% | 49.7% | 67.7% | 92.6% | 23.1% | 4,537.3% | 4,390.2% | 4,448.4% | 175.2% | 3,891.6% |
| Efficiency | ||||||||||
| Days sales outstanding | — | 7.0 | 10.4 | 0.3 | 0.0 | 17.8 | 15.7 | 46.2 | 2.8 | 118.8 |
| Days of inventory on hand | — | — | -4.3 | -2.0 | 3.0 | 3.1 | -0.2 | -0.4 | -0.6 | -1.0 |
| Days payables outstanding | 672.7 | 1,688.1 | 28.7 | 350.9 | 17.3 | 13.1 | 9.7 | 27.2 | 36.2 | 26.9 |
| Cash conversion cycle (days) | — | -1,681.1 | -22.6 | -352.7 | -14.3 | 7.8 | 5.7 | 18.6 | -34.0 | 90.9 |
| Receivables turnover | — | 52.40 | 35.00 | 1,437.47 | 14,326.93 | 20.55 | 23.26 | 7.89 | 131.67 | 3.07 |
| Payables turnover | 0.54 | 0.22 | 12.73 | 1.04 | 21.08 | 27.95 | 37.49 | 13.40 | 10.08 | 13.59 |
| Inventory turnover | — | — | — | — | — | 116.64 | — | — | — | — |
| Asset turnover | 0.02 | 0.22 | 0.13 | 0.08 | 0.43 | 0.00 | 0.00 | 0.00 | 0.06 | 0.00 |
| Average receivables | — | $2.6M | $2.6M | $37,500 | $14,000 | $41,500 | $35,000 | $121,000 | $209,000 | $343,500 |
| Average payables | $6.8M | $16.6M | $17.3M | $6.5M | $3.9M | $2.7M | $1.4M | $7.6M | $13.4M | $8.8M |
| Average inventory | — | — | −$2.6M | −$37,500 | $669,500 | $642,000 | −$34,000 | −$120,000 | −$209,000 | −$343,500 |
| Intangibles / total assets | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% |
Computed from PRTA's annual financial statements (latest annual report filed February 27, 2026) and the closing share price on each fiscal year-end, adjusted for stock splits. Figures in U.S. dollars; data from EODHD. Averages use the opening and closing balance of each year.
PRTA valuation and financial ratios
Prothena earned a return on equity of −63.6% in fiscal 2025. It ended the year with $13.9 million of debt and $307.5 million in cash and short-term investments, a net cash position of $293.7 million. It returned $0.1 million to shareholders: $0 in dividends and $0.1 million in share buybacks. The share count rose 56.7% from 34.4M to 53.8M over 9 years.
See the PRTA income statement, the PRTA chart for price history, or the PRTA stock overview for the latest quote and news.
PRTA key metrics FAQ
What is Prothena's return on equity?
Prothena's return on equity (ROE) was −63.6% in fiscal 2025: net income of -$244.1 million on average shareholders' equity of $383.7 million.
How much debt does Prothena have?
Prothena had total debt of $13.9 million at the end of fiscal 2025, a debt-to-equity ratio of 0.05 and more cash than debt.
Does Prothena buy back its shares?
Yes. Prothena spent $0.1 million on net share repurchases in fiscal 2025 Shares outstanding changed +0.1% over the year, to 53.8M..
What is Prothena's free cash flow yield?
Prothena generated -$163.7 million of free cash flow in fiscal 2025, a free cash flow yield of −31.8% on its market value at year-end ($514.1 million).
What is Prothena's current ratio?
Prothena's current ratio was 7.72 at the end of fiscal 2025: current assets were 7.72 times current liabilities.