Free cash flow remains deeply negative, with the company burning $46.4 million in 2025Q2, while stock-based compensation of $12.4 million in the same period continues to obscure the true economic cost of operations.
| 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 | -81.34M | -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 % | -174.83% | -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 | -151.18M | -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 | 856K | 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 | 33.61M | 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 | 44.91M | 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 | -2.24M | 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 | -7.3M | -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 | -18.91M | -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 | -96K | -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 | -96K | -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 | 0.17% | 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 | -7.04M | -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) | -7.04M | -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 | -7.04M | 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 | -88.47M | -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 | -81.44M | -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 % | -140.55% | -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 % | 37.64% | -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 | -1.51 | -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) | 0.54x | 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 | 941K | 0 | 3.17M | 1.55M | 2.66M | 580K | 1.37M | 1.58M | 0 | 294K | 575K | 442K | 1.59M | 796K | 0 | 0 | 0 |
Clinical milestone cash dependency
As indicated by the quarterly data, the relationship between net income and operating cash flow is highly erratic, with OCF/NI ratios fluctuating between 0.24 and 1.11, suggesting that reported earnings are frequently decoupled from actual cash generation due to the timing of milestone-based revenue recognition.
The wide variance in the conversion ratio highlights that net income is an unreliable proxy for liquidity in this business model. Investors should monitor these swings closely, as they reflect accounting adjustments rather than operational efficiency or sustainable cash-generating capacity.
Based on the reported financial statements, Prothena's free cash flow trajectory remains deeply negative in most periods, with the company recording a cash burn of $46.4 million in 2025Q2, underscoring the heavy reliance on external capital to fund ongoing late-stage clinical development programs.
The lack of consistent positive FCF margins suggests that the company is currently in a capital-intensive phase where cash outflows are dictated by trial enrollment rather than commercial success. This trajectory appears unsustainable without continued partnership inflows or further equity dilution.
According to the provided cash flow tables, working capital changes have been highly volatile, including a significant $21.2 million swing in 2025Q2, which suggests that the timing of milestone payments and associated receivables creates substantial, unpredictable fluctuations in the company's short-term liquidity position.
These shifts in working capital are likely tied to the lumpy nature of collaboration revenue rather than operational improvements in the supply chain. The unpredictability of these cash movements warrants further investigation into the specific contractual triggers governing the company's primary revenue streams.
Analysis of the cash flow statement reveals that stock-based compensation consistently offsets a portion of the reported operating losses, with SBC reaching $12.4 million in 2025Q2, effectively masking the true economic cost of talent retention during this high-burn clinical development phase.
While SBC is a non-cash expense, it represents a real dilution of shareholder value that is not fully captured in the headline cash burn figures. Investors should consider the impact of this ongoing dilution when evaluating the company's long-term capital requirements and runway.
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.