Free cash flow has been negative in nine of the last ten quarters, with a -25.4% FCF margin in 2026Q2, indicating a business model that consumes capital rather than generating it.
Prothena Corporation plc (PRTA) cash flow statement — 16-year operating, investing & financing cash flows
| Metric | TTM | Dec'25 | Dec'24 | Dec'23 | Dec'22 | Dec'21 | Dec'20 | Dec'19 | Dec'18 | Dec'17 | Dec'16 | Dec'15 | Dec'14 | Dec'13 | Dec'12 | Dec'11 | Dec'10 |
|---|
| Cash from Operations | -60.05M | -163.58M | -150.05M | -133.91M | -108.82M | 92.61M | -80.36M | -52.97M | -28.28M | -131.18M | -117.27M | -62.45M | -683K | -32.1M | -42.07M | -19.7M | -9.08M |
| Operating CF Margin % | - | -1689.18% | -111.02% | -146.55% | -201.88% | 46.17% | -9421.1% | -6507.25% | -2960.84% | -476.7% | -11115.55% | -3886.43% | -1.34% | -4748.22% | -1582.84% | -3885.01% | -730.73% |
| Operating CF Growth % | 261.49% | -9.02% | -12.06% | -23.05% | -217.51% | 215.23% | -51.72% | -87.33% | 78.45% | -11.87% | -87.77% | -9044.22% | 97.87% | 23.71% | -113.6% | -116.86% | - |
| Net Income | -43.99M | -244.09M | -122.31M | -147.03M | -116.95M | 66.97M | -111.14M | -77.68M | -155.65M | -153.24M | -160.11M | -80.61M | -7.15M | -41M | -41.41M | -29.67M | -12.48M |
| Depreciation & Amortization | 828K | 895K | 893K | 928K | 744K | 1.11M | 1.51M | 6.82M | 3.22M | 3.07M | 2.43M | 806K | 743K | 660K | 468K | 391K | 191K |
| Stock-Based Compensation | 29.07M | 37.64M | 45.96M | 40.91M | 31.32M | 24.66M | 22.01M | 23.59M | 27.01M | 26.76M | 24.93M | 10.41M | 5.6M | 3.13M | 6.1M | 2.97M | 1.6M |
| Deferred Taxes | 0 | 43.24M | -9.35M | -15.69M | -11.13M | 4.57M | -1.69M | -1.25M | -1.59M | -2.2M | -3.25M | -963K | -990K | -538K | 0 | 0 | 0 |
| Other Non-Cash Items | -3.94M | 2.91M | 2.69M | 7.5M | 6M | 5.69M | 5.46M | 0 | 4.28M | 1.59M | -156K | -3.57M | -261K | -29K | -1.13M | 0 | 0 |
| Working Capital Changes | -42.01M | -4.17M | -67.94M | -20.53M | -18.8M | -10.4M | 3.48M | -4.45M | 94.45M | -7.16M | 18.89M | 11.47M | 1.38M | 5.68M | -7.23M | 6.61M | 1.61M |
| Change in Receivables | 0 | 0 | 5.16M | -5.16M | 0 | 15K | 53K | 0 | 238K | -62K | 331K | 1.25M | -1.7M | 165K | -223K | -146K | 0 |
| Change in Inventory | 0 | 0 | 0 | -8.9M | 0 | 0 | 0 | 0 | 9.6M | -396.2M | -346.92M | -356.12M | -289.59M | -171.54M | -124.56M | 8.28M | 0 |
| Change in Payables | -21.93M | -15.78M | -18.3M | 22.86M | 11.87M | -492K | 7.73M | -78K | -25.63M | 147K | 15.19M | 11.16M | 5.43M | 6.23M | -6.54M | 6.76M | 1.69M |
| Cash from Investing | -662K | -138K | -298K | -2.77M | -464K | -575K | -196K | -547K | -1.73M | -3.52M | -16.64M | -1.38M | -499K | -535K | -1.3M | -595K | -2.61M |
| Capital Expenditures | -662K | -138K | -298K | -2.81M | -464K | -575K | -196K | -555K | -1.77M | -3.63M | -16.64M | -1.38M | -526K | -564K | -1.3M | -595K | -2.61M |
| CapEx % of Revenue | 1.21% | 1.43% | 0.22% | 3.08% | 0.86% | 0.29% | 22.98% | 68.18% | 185.13% | 13.18% | 1577.63% | 86% | 1.03% | 83.43% | 48.95% | 117.36% | 209.73% |
| Acquisitions | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 39K | 105K | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Investments | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - | - |
| Other Investing | 0 | 0 | 0 | 37K | 0 | 0 | 0 | 8K | 39K | 105K | 0 | 0 | 27K | 29K | 0 | 0 | 0 |
| Cash from Financing | -22.53M | -139K | 1.55M | 45.1M | 241.46M | 190.33M | 215K | 228K | 40.04M | 165.4M | 154.31M | 140.84M | 118.08M | 84.45M | 168.23M | 20.29M | 11.69M |
| Debt Issued (Net) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | -4.4M | -2.76M | -169K | 0 | 0 | 0 | 0 | 0 | 0 |
| Equity Issued (Net) | -22.53M | -139K | -353K | 23.58M | 223.62M | 174.79M | 0 | 0 | 39.76M | 150.32M | 128.78M | 131.34M | 117.35M | 84.53M | 26M | 0 | 0 |
| Dividends Paid | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Share Repurchases | -22.53M | 0 | -353K | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Other Financing | 0 | 0 | 1.91M | 21.52M | 17.84M | 15.54M | 215K | 228K | 4.69M | 17.84M | 25.7M | 9.5M | 736K | -84K | 142.23M | 20.29M | 11.69M |
| Net Change in Cash | -83.24M | -163.86M | -148.79M | -91.58M | 132.17M | 282.36M | -80.34M | -53.29M | 10.04M | 30.7M | 20.39M | 77.01M | 116.9M | 51.82M | 124.86M | 0 | 0 |
| Free Cash Flow | -60.71M | -163.72M | -150.35M | -136.72M | -109.28M | 92.03M | -80.56M | -53.52M | -30.04M | -134.81M | -133.91M | -63.84M | -1.21M | -32.66M | -43.37M | -20.29M | -11.69M |
| FCF Margin % | -111.34% | -1690.6% | -111.24% | -149.63% | -202.74% | 45.88% | -9444.08% | -6575.43% | -3145.97% | -489.88% | -12693.18% | -3972.43% | -2.38% | -4831.66% | -1631.79% | -4002.37% | -940.47% |
| FCF Growth % | 68.52% | -8.89% | -9.97% | -25.1% | -218.75% | 214.24% | -50.51% | -78.15% | 77.71% | -0.67% | -109.77% | -5180.15% | 96.3% | 24.7% | -113.74% | -73.58% | - |
| FCF per Share | -1.16 | -3.04 | -2.80 | -2.57 | -2.31 | 1.90 | -2.02 | -1.34 | -0.76 | -3.58 | -3.90 | -2.11 | -0.05 | -1.75 | -2.97 | -1.15 | -0.66 |
| FCF Conversion (FCF/Net Income) | 1.38x | 0.67x | 1.23x | 0.91x | 0.93x | 1.38x | 0.72x | 0.68x | 0.18x | 0.86x | 0.73x | 0.77x | 0.10x | 0.78x | 1.02x | 0.66x | 0.73x |
| Interest Paid | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Taxes Paid | -8K | 931K | 3.17M | 1.55M | 2.66M | 580K | 1.37M | 1.58M | 0 | 294K | 575K | 442K | 1.59M | 796K | 0 | 0 | 0 |
Quick answers to the most common questions about buying PRTA stock.
Prothena Corporation plc (PRTA) generated $-163.6M in net cash from operating activities in 2025. This reflects the cash generated directly from core business operations.
Prothena Corporation plc (PRTA) reported negative free cash flow of $163.7M in 2025, indicating capital requirements exceeded cash from operations.
Prothena Corporation plc (PRTA) spent $0.1M on capital expenditures in 2025. CapEx represents the cash invested in physical assets like property, plant, and equipment to maintain or grow the business.
Key Metrics
Top Statement Risk
Sustained cash burn without profitability
Metrics are mathematically derived from official filings.
Earnings Quality Masked by Non-Cash Items
The relationship between net income and operating cash flow is highly volatile, with the OCF/NI ratio swinging from 0.24 to 1.35 over the last ten quarters, suggesting that non-cash items like stock-based compensation and working capital shifts are the primary drivers of reported cash flow.
In quarters with large net losses, operating cash flow is consistently less negative than net income, primarily due to the add-back of significant stock-based compensation, which averaged over $9M per quarter. However, in profitable quarters like 2024Q2 and 2026Q1, operating cash flow was substantially lower than net income, indicating that cash collection from milestone-driven revenue is not immediate. This pattern implies that the quality of earnings is low and that reported profitability is not a reliable indicator of near-term cash generation.
FCF Trajectory Defined by Cash Burn
Free cash flow has been negative in nine of the last ten quarters, with the FCF margin averaging approximately -130%, indicating a business model that is consuming capital rather than generating it, as reported in the company's financial statements.
The trajectory shows no sustained improvement, with FCF ranging from a positive $28.9M in 2026Q1 to a negative $73.2M in 2024Q1. The single profitable FCF quarter appears to be an anomaly driven by a large revenue milestone, not a shift in operational cash generation. This persistent negative FCF trajectory, when compared to the lumpy net income, underscores that the company's core operations are not yet self-funding and rely on external capital or prior cash reserves.
Working Capital Swings Amplify Volatility
Working capital changes have been a major source of cash flow volatility, with a massive $61.1M use of cash in 2024Q2 followed by a $21.2M source in 2025Q2, suggesting that the timing of receivables from milestone payments creates significant quarterly cash flow noise.
The large negative working capital change in 2024Q2 likely represents the collection of a large receivable booked in a prior period, which temporarily boosted operating cash flow. Conversely, the positive working capital change in 2025Q2 suggests a build-up of receivables or a delay in cash collection. This erratic pattern makes it difficult to assess underlying operational efficiency and indicates that cash flow is heavily influenced by the timing of large, non-recurring payments from partners.
Capital Deployment Focused on Buybacks
Despite persistent cash burn, Prothena has consistently used cash for share repurchases, spending $15.6M in 2026Q2 alone, which appears to be a strategic use of capital that may not align with the company's cash generation profile.
The company has not paid dividends and has made no acquisitions, focusing its capital deployment on buybacks. This is notable given the negative free cash flow trend, as it suggests management is using existing cash reserves to repurchase shares rather than preserving capital for operations or pipeline development. Investors should monitor whether this deployment strategy is sustainable given the ongoing cash burn and the absence of consistent operating cash flow.
Cash Flow Statement Obscures True Burn
The cash flow statement may understate the true economic cost of operations by adding back stock-based compensation, which averaged $9.8M per quarter, a non-cash expense that still represents a real dilutive cost to shareholders.
While SBC is added back to calculate operating cash flow, it is a real cost to existing shareholders through dilution. Furthermore, the capitalization of certain costs, which would be reflected in the low capital expenditure figures, could be masking the full investment required to maintain the company's pipeline. The cash flow statement does not capture the potential future liability of these capitalized costs, which may require future cash outlays for amortization or write-offs.