Prothena Corp Public Ltd Co (PRTA) stock analysis
Close on Nov 11, 2026Market cap $448.17MP/E –Yield –
StockData Score
Prices as of Nov 11, 2026How the score works
Mixed12 of 30 checks passed
Prothena Corp Public passes 12 of the 30 checks behind our score; 13 could not be run for lack of data and count as not passed. Each dot in the shape is one check — hover it for the numbers.
- Valuation
- 2/6
- Growth
- 1/6
- Past performance
- 3/6
- Financial health
- 6/6
- Dividend
- 0/6
What stands out
Trading below fair value
The share price of $8.73 is below our fair value estimate of $10.14.
No debt
Prothena Corp Public has no borrowings on its latest balance sheet.
Interest well covered
No meaningful interest expense to cover.
Debt covered by cash flow
There is no debt to cover.
What to watch
Margin of safety under 20%
The price is 13.9% below fair value, less than the 20% cushion we look for.
Return on equity under 15%
Return on equity was -8.5% over the last twelve months and averaged -22.5% over five years; we look for 15% on both.
Revenue growing under 10% a year
Revenue grew -43.6% a year over the last three fiscal years, short of the 10% we look for.
Guidance lowered
Prothena Corp Public lowered its full year 2026 net loss outlook on Aug 6, 2026.
Valuation2/6
P/E against its history
Not enough price and earnings history to compare.
P/E against the industry
Needs positive earnings and enough profitable companies in the industry.
EV/EBITDA against its history
Needs positive EBITDA and price history.
P/B below the industry
Prothena Corp Public's price-to-book of 1.67 is below the Drugs median of 2.29.
Trading below fair value
The share price of $8.73 is below our fair value estimate of $10.14.
Margin of safety under 20%
The price is 13.9% below fair value, less than the 20% cushion we look for.
Growth1/6
Revenue growing under 10% a year
Revenue grew -43.6% a year over the last three fiscal years, short of the 10% we look for.
EPS growth over 3 years
Needs positive EPS three years ago and today.
Earnings acceleration
Needs positive net income now, a year ago and five years ago.
Growing faster than the industry
Revenue grew 347% over the last twelve months; the Drugs median is 8.0%.
Guidance lowered
Prothena Corp Public lowered its full year 2026 net loss outlook on Aug 6, 2026.
Gross margin trend
This company does not report gross profit.
Past performance3/6
Return on equity under 15%
Return on equity was -8.5% over the last twelve months and averaged -22.5% over five years; we look for 15% on both.
Return on invested capital
Needs operating income and invested capital.
Return on equity above the industry
Prothena Corp Public's return on equity of -8.5% is above the Drugs median of -58.9%.
Earnings over 5 years
Needs positive net income five years ago and in the latest year.
Net margin above its 5-year average
Net margin was -45.4% over the last twelve months, against a 5-year average of -591%.
Net margin above the industry
Prothena Corp Public's net margin of -45.4% is above the Drugs median of -53.0%.
Financial health6/6
No debt
Prothena Corp Public has no borrowings on its latest balance sheet.
Debt not rising
With no debt today, leverage cannot have risen.
Debt covered by cash flow
There is no debt to cover.
Interest well covered
No meaningful interest expense to cover.
Short-term assets cover short-term debts
Current assets are 23.95 times current liabilities.
Low bankruptcy risk
The Altman Z-score is 12.55; above 3 is the safe zone and below 1.8 the distress zone.
Dividend0/6
No dividend
Prothena Corp Public has not paid a dividend in the last twelve months.
Yield against Treasuries
No dividend.
Yield against the market
No dividend.
Dividend stability
No dividend.
Earnings cover
No dividend.
Cash-flow cover
No dividend.
Fair value
How we estimate itOur estimate per share
$10.14
The share price is 14% below this estimate.
| Method | Multiple used | Own 5Y median | Industry median | Value per share | Weight |
|---|---|---|---|---|---|
| P/B | 2.3× | 2.2× | 2.3× | $11.88 | 50% |
| P/S | 8.2× | 11.5× | 4.8× | $8.40 | 50% |
| Fair value | $10.14 | 100% | |||
Valuation over time
Using the earnings and balance sheet published at each date, not today's.
- P/B at month end
- Own 5-year median 2.2
- Drugs median 2.3
An estimate from reported numbers and market multiples, not a price target or investment advice. It can be far off for companies whose profits are about to change sharply.
Market risk
From the past year of daily prices.
Liquidity
Medium risk
- Average value traded per day
- $4.45M
- Value traded per 1% price move
- $1.48M
Downside
Medium risk
- Typical loss in a bad month
- 17.7%
- Volatility (annualized)
- 49%
- Sharpe ratio, 1 year
- -0.44
- Beta to the S&P 500 (5Y)
- 0.87
Typical bad-month loss, week by week
Margins
Share of revenue, fiscal years 2011 to 2025
Operating margin
Net margin
Growth rates
Compound annual growth to fiscal 2025
| Per year | 1 year | 3 years | 5 years | 10 years | Five-year pace |
|---|---|---|---|---|---|
| Revenue | -92.8% | -43.6% | +62.6% | +19.7% |
Returns and balance sheet
10 fiscal years. Hover a measure to see how it is calculated.
| Measure | FY2016 | FY2020 | FY2025 | Trend |
|---|---|---|---|---|
| Return on equity | -44.1% | -48.6% | -63.6% | |
| Return on assets | -37.9% | -29.6% | -55.9% | |
| Current ratio | 9.53 | 11.58 | 7.72 | |
| Diluted shares | 34M | 40M | 54M |
Cash use needs five years of cash flow figures
Prothena Corp Public does not report operating cash flow and capital expenditure for each of the last five fiscal years.
DuPont analysis
Return on equity split into margin, efficiency and leverage
| Fiscal year | Net margin | Asset turnover | Equity multiplier | Return on equity |
|---|---|---|---|---|
| FY2025 | -2520.6% | 0.02× | 1.14× | -63.6% |
| FY2024 | -90.5% | 0.22× | 1.19× | -23.3% |
| FY2023 | -160.9% | 0.13× | 1.23× | -24.8% |
| FY2022 | -217.0% | 0.08× | 1.26× | -21.5% |
| FY2021 | 33.4% | 0.43× | 1.45× | 20.6% |
| FY2020 | -13029.8% | 0.00× | 1.65× | -48.6% |
| FY2019 | -9542.6% | 0.00× | 1.54× | -26.1% |
| FY2018 | -16297.9% | 0.00× | 1.36× | -42.6% |
| FY2017 | -556.8% | 0.06× | 1.24× | -39.7% |
| FY2016 | -15176.1% | 0.00× | 1.16× | -44.1% |
Piotroski F-Score
Nine tests of profitability, balance sheet and efficiency, fiscal 2025 against fiscal 2024
- ProfitableNet income above zero-$244.09M
- Cash generatingOperating cash flow above zero-$163.58M
- Return on assets improvedROA up on the prior year-17.6% → -44.6%
- Earnings backed by cashOperating cash flow above net income-$163.58M vs -$244.09M
- Less leverageLong-term debt to assets fell– → –
- Better liquidityCurrent ratio rose10.01 → 7.72
- No dilutionShare count did not rise54M → 54M
- Gross margin improvedGross margin up on the prior year– → –
- More efficientAsset turnover rose0.19 → 0.02
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