Latest Ratios: P/E Ratio -1.7x · EV/EBITDA N/A · ROE -63.6%. (2010–2025 historical series)
Price-based multiples — how expensive the stock is relative to earnings, sales, book value, and cash flow
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Market Cap | $413M | $514M | $745M | $1.9B | $2.9B | $2.4B | $479M | $631M | $407M | $1.4B | $1.7B |
| Enterprise Value | $119M | $220M | $284M | $1.3B | $2.2B | $1.8B | $202M | $279M | $31M | $1.0B | $1.4B |
| P/E Ratio → | -1.74 | — | — | — | — | 35.80 | — | — | — | — | — |
| P/S Ratio | 42.65 | 53.08 | 5.51 | 21.17 | 52.94 | 11.94 | 561.99 | 775.59 | 426.66 | 51.30 | 1601.64 |
| P/B Ratio | 1.51 | 1.83 | 1.53 | 3.44 | 4.59 | 5.14 | 2.61 | 2.31 | 1.26 | 3.47 | 4.62 |
| P/FCF | — | — | — | — | — | 26.01 | — | — | — | — | — |
| P/OCF | — | — | — | — | — | 25.85 | — | — | — | — | — |
P/E links to full P/E history page with 30-year chart
Enterprise-value multiples — capital-structure-neutral measures of total business value
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| EV / Revenue | — | 22.76 | 2.10 | 14.52 | 39.89 | 9.11 | 236.62 | 342.20 | 32.82 | 38.02 | 1283.53 |
| EV / EBITDA | — | — | — | — | — | 25.00 | — | — | — | — | — |
| EV / EBIT | — | — | — | — | — | 25.41 | — | — | — | — | — |
| EV / FCF | — | — | — | — | — | 19.86 | — | — | — | — | — |
Margins and return-on-capital ratios measuring operating efficiency
Full margin charts and quarterly trend are on the Earnings History page
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Gross Margin | 61.8% | 61.8% | 100.0% | 100.0% | 100.0% | 100.0% | -8678.9% | -6145.2% | -10495.1% | -388.9% | -11230.2% |
| Operating Margin | -1905.8% | -1905.8% | -114.4% | -209.1% | -244.1% | 35.9% | -13216.2% | -10527.9% | -16634.0% | -564.2% | -15121.8% |
| Net Profit Margin | -2520.6% | -2520.6% | -90.5% | -160.9% | -217.0% | 33.4% | -13029.8% | -9542.6% | -16297.9% | -556.8% | -15176.1% |
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| ROE | -63.6% | -63.6% | -23.3% | -24.8% | -21.5% | 20.6% | -48.6% | -26.1% | -42.6% | -39.7% | -44.1% |
| ROA | -55.9% | -55.9% | -19.7% | -20.2% | -17.1% | 14.2% | -29.5% | -16.9% | -31.3% | -32.0% | -37.9% |
| ROIC | -2099.8% | -2099.8% | -439.4% | — | — | — | — | — | — | -325.2% | -1203.6% |
| ROCE | -47.0% | -47.0% | -27.2% | -28.4% | -20.5% | 16.3% | -31.8% | -19.4% | -33.7% | -35.4% | -40.8% |
Solvency and debt-coverage ratios — lower is generally safer
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Debt / Equity | 0.05 | 0.05 | 0.02 | 0.02 | 0.01 | 0.03 | 0.10 | 0.08 | 0.16 | 0.13 | 0.14 |
| Debt / EBITDA | — | — | — | — | — | 0.17 | — | — | — | — | — |
| Net Debt / Equity | — | -1.05 | -0.95 | -1.08 | -1.13 | -1.22 | -1.51 | -1.29 | -1.16 | -0.90 | -0.92 |
| Net Debt / EBITDA | — | — | — | — | — | -7.75 | — | — | — | — | — |
| Debt / FCF | — | — | — | — | — | -6.16 | — | — | — | — | — |
| Interest Coverage | — | — | — | — | — | — | — | — | -41.23 | -41.73 | -184.20 |
Net cash position: cash ($308M) exceeds total debt ($14M)
Short-term solvency ratios and asset-utilisation metrics
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Current Ratio | 7.72 | 7.72 | 10.01 | 11.24 | 14.34 | 17.48 | 11.58 | 21.36 | 28.90 | 11.41 | 9.53 |
| Quick Ratio | 7.72 | 7.72 | 10.01 | 11.24 | 14.34 | 17.48 | 11.58 | 21.36 | 28.90 | 11.41 | 9.53 |
| Cash Ratio | 7.53 | 7.53 | 9.72 | 10.88 | 14.17 | 17.31 | 11.43 | 21.21 | 28.65 | 11.17 | 9.42 |
| Asset Turnover | — | 0.03 | 0.25 | 0.13 | 0.07 | 0.33 | 0.00 | 0.00 | 0.00 | 0.06 | 0.00 |
| Inventory Turnover | — | — | — | — | — | — | — | — | — | — | — |
| Days Sales Outstanding | — | — | — | 20.61 | 0.42 | 0.02 | 6.42 | 30.49 | 0.76 | 3.18 | 61.58 |
Earnings, FCF, buyback, and dividend yields — total returns to shareholders
Full dividend history and growth charts are on the Dividend History page
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Dividend Yield | — | — | — | — | — | — | — | — | — | — | — |
| Payout Ratio | — | — | — | — | — | — | — | — | — | — | — |
| Metric | TTM | FY 2025 | FY 2024 | FY 2023 | FY 2022 | FY 2021 | FY 2020 | FY 2019 | FY 2018 | FY 2017 | FY 2016 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Earnings Yield | — | — | — | — | — | 2.8% | — | — | — | — | — |
| FCF Yield | — | — | — | — | — | 3.8% | — | — | — | — | — |
| Buyback Yield | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% |
| Total Shareholder Yield | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% | 0.0% |
| Shares Outstanding | — | $54M | $54M | $53M | $47M | $48M | $40M | $40M | $40M | $38M | $34M |
Includes 30+ ratios · 16 years · Updated daily
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10-year return with dividends reinvested.
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Quick answers to the most common questions about buying PRTA stock.
Prothena Corporation plc's current P/E ratio is -1.7x. The historical average is 35.8x.
Prothena Corporation plc's return on equity (ROE) is -63.6%. The historical average is -31.3%.
Based on historical data, Prothena Corporation plc is trading at a P/E of -1.7x. Compare with industry peers and growth rates for a complete picture.
Prothena Corporation plc has 61.8% gross margin and -1905.8% operating margin.
Key Metrics
Top Statement Risk
Sustained cash burn without profitability
Metrics are mathematically derived from official filings.
Valuation Reflects Speculative Pipeline Bets
Prothena's forward P/E of 89.27 and P/S of 53.09, as reported in current market data, price in significant future profitability that is not yet evident in its historical financial performance.
The valuation multiples are disconnected from current fundamentals, as the company has generated negative net income in eight of the last ten quarters. The high P/S ratio, in particular, suggests the market is valuing Prothena based on the potential of its pipeline rather than its current revenue generation, which is lumpy and milestone-driven. This creates a high-risk scenario where any clinical or partnership setbacks could lead to a severe re-rating.
Milestone Accounting Distorts True Earning Power
Reported gross margins are structurally misleading, swinging from 100% in most quarters to negative 43.9% in 2025Q4, a volatility that appears driven by the timing of revenue recognition rather than underlying operational efficiency.
The extreme volatility in profitability metrics, with operating margins ranging from -1630.6% to 50.5%, indicates that standard margin analysis is not meaningful for this business model. The company's true earning power is obscured by the non-recurring nature of its revenue, making it difficult to assess sustainable profitability. Investors should focus on the underlying cost structure, where R&D remains the dominant expense, rather than headline margin figures.
Negative Returns Reflect Pre-Commercial Stage
Prothena's ROIC has been negative in most recent quarters, with a -2.8% reading in 2026Q2, indicating the company is not generating returns on its invested capital as it remains in a heavy investment phase.
The negative and volatile ROIC, which swung from -174.6% in 2025Q1 to 146.4% in 2024Q2, is a function of the lumpy revenue and the company's pre-commercial status. The brief periods of positive returns are likely driven by large, one-time milestone payments rather than sustainable operational performance. This pattern suggests capital is being consumed to fund pipeline development, not to generate compounding returns.
Substantial Cash Cushion Eroding Steadily
Despite a current ratio of 25.05 in 2026Q2, Prothena's cash reserves have declined by 48% from $546.5M in 2024Q1 to $288.2M, a trend that warrants monitoring for long-term sustainability.
The exceptionally high current ratio is a function of the company's asset-light, cash-rich balance sheet, but it masks the underlying trend of capital consumption. The steady erosion of cash, driven by operating losses and share repurchases, suggests the liquidity buffer, while currently ample, is finite. The absence of inventory and receivables in the quick ratio calculation further highlights that the company's liquidity is almost entirely dependent on its cash position.
The Peril of Applying P/E to Pre-Revenue Biotech
The P/E ratio is the most commonly misapplied metric to Prothena, as its negative earnings make the ratio meaningless and obscure the company's true valuation driver: its pipeline optionality.
Applying a P/E multiple to a company with inconsistent and often negative earnings, as seen in Prothena's TTM P/E of -2.17, provides no useful insight into its value. The market is clearly pricing the company on a forward-looking basis, using metrics like EV/EBITDA (48.42 forward) and P/S, which attempt to capture future potential. Analysts should instead focus on pipeline progress, partnership structures, and cash burn rate to assess the risk/reward profile.