Prothena Corporation plc (PRTA)Healthcare | Biotechnology | Dublin, Ireland | NasdaqGS
8.35 USD
-0.15
(-1.765%) ⇩
(Oct. 16, 2026, 4 p.m.
EDT)
After hours: 8.35 |
Hot Take ↕ | Oct. 10, 2026, 4:05 a.m. EDT
The investment case for Prothena is currently defined by a stark divergence between its deteriorating financial reality and its speculative biotech potential. Fundamentally, the company is in a severe decline; the stock has lost over 83% of its value over the last nine years, with four consecutive years of negative annual returns. This multi-year trajectory, combined with shrinking revenues (-77% growth) and negative operating margins, suggests the market has priced in significant structural issues regarding the company's ability to sustain operations without external capital. The balance sheet, while currently showing low debt relative to equity, is propped up by cash reserves that are being consumed by heavy R&D spending and free cash flow outflows. Despite these grim fundamentals, the short-term outlook retains a sliver of hope due to specific catalysts. Recent news highlights a $50 million milestone from a Novo Nordisk trial and advancing Alzheimer's portfolios, which likely drove the recent price appreciation. However, the options market remains deeply bearish, with traders buying insurance against further drops rather than betting on a rally. The statistical forecast model offers only a moderate lean upward (+3.81%), which is insufficient to overcome the weight of the long-term decline. Until the company demonstrates a clear path to profitability or a definitive success in its late-stage programs that can reverse the multi-year price trend, the risk-reward profile remains skewed heavily toward caution. |
| Model | MAE |
|---|---|
| AutoARIMA ✓ | 0.042482 |
| MSTL | 0.058112 |
| AutoETS | 0.061587 |
| AutoTheta | 0.073862 |
Forecast horizon: 45 days | Selected: AutoARIMA
| Forecast Reliability | |
|---|---|
| Score | 51% |
| H-stat | 4.35 |
| Ljung-Box p | 0.000 |
| Jarque-Bera p | 0.283 |
| Excess Kurtosis | -1.10 |
| Attribute | Value |
|---|---|
| Sector | Healthcare |
| Debt to Equity Ratio | 2.437 |
| Revenue per Share | 1.022 |
| Market Cap | 428,663,776 |
| Forward P/E | -6.35 |
| Beta | -0.29 |
| Profit Margins | -80.68% |
| Website | https://www.prothena.com |
As of Oct. 10, 2026, 4:05 a.m. EDT: Speculators are heavily positioned for downside protection, with massive open interest in out-of-the-money puts (strikes 6.0 and 7.0) expiring in December 2026, suggesting a fear of further decline. Conversely, call activity is concentrated in deep out-of-the-money strikes (11.0, 12.0, 15.0) for later expirations, indicating speculative bets on a potential recovery driven by late-stage pipeline milestones rather than immediate price appreciation.
| Attribute | Value |
|---|---|
| 52 Week Change | -0.14314514 |
| Address1 | 77 Sir John Rogerson’s Quay |
| Address2 | Block C Grand Canal Docklands |
| All Time High | 79.749 |
| All Time Low | 0.0 |
| Ask | 10.63 |
| Ask Size | 2 |
| Audit Risk | 8 |
| Average Analyst Rating | 2.3 - Buy |
| Average Daily Volume10 Day | 620,360 |
| Average Daily Volume3 Month | 484,368 |
| Average Volume | 484,368 |
| Average Volume10Days | 620,360 |
| Beta | -0.292 |
| Bid | 6.15 |
| Bid Size | 2 |
| Board Risk | 5 |
| Book Value | 5.544 |
| City | Dublin |
| Compensation As Of Epoch Date | 1,767,139,200 |
| Compensation Risk | 7 |
| Country | Ireland |
| Crypto Tradeable | 0 |
| Currency | USD |
| Current Price | 8.35 |
| Current Ratio | 25.048 |
| Custom Price Alert Confidence | HIGH |
| Date Short Interest | 1,790,726,400 |
| Day High | 8.61 |
| Day Low | 8.24 |
| Debt To Equity | 2.437 |
| Display Name | Prothena |
| Dividend Yield | 0.0 |
| Earnings Call Timestamp End | 1,771,536,600 |
| Earnings Call Timestamp Start | 1,771,536,600 |
| Earnings Timestamp | 1,786,046,400 |
| Earnings Timestamp End | 1,793,908,800 |
| Earnings Timestamp Start | 1,793,908,800 |
| Ebitda | -59,040,000 |
| Ebitda Margins | -1.08271 |
| Enterprise To Ebitda | -2.628 |
| Enterprise To Revenue | 2.845 |
| Enterprise Value | 155,162,272 |
| Eps Current Year | 0.64 |
| Eps Forward | -1.315 |
| Eps Trailing Twelve Months | -0.82 |
| Esg Populated | 0 |
| Exchange | NMS |
| Exchange Data Delayed By | 15 |
| Exchange Timezone Name | America/New_York |
| Exchange Timezone Short Name | EDT |
| Fax | 353 1 902 3510 |
| Fifty Day Average | 8.8699 |
| Fifty Day Average Change | -0.51989937 |
| Fifty Day Average Change Percent | -0.058613896 |
| Fifty Two Week Change Percent | -14.314514 |
| Fifty Two Week High | 11.8 |
| Fifty Two Week High Change | -3.4499998 |
| Fifty Two Week High Change Percent | -0.29237285 |
| Fifty Two Week Low | 7.73 |
| Fifty Two Week Low Change | 0.62000036 |
| Fifty Two Week Low Change Percent | 0.080207035 |
| Fifty Two Week Range | 7.73 - 11.8 |
| Financial Currency | USD |
| First Trade Date Milliseconds | 1,355,841,000,000 |
| Float Shares | 34,226,361 |
| Forward Eps | -1.315 |
| Forward P E | -6.34981 |
| Free Cashflow | -54,222,500 |
| Full Exchange Name | NasdaqGS |
| Full Time Employees | 67 |
| Fullday Change | -0.14999962 |
| Fullday Change Percent | -1.7647014 |
| Fullday Price | 8.35 |
| Gmt Off Set Milliseconds | -14,400,000 |
| Governance Epoch Date | 1,790,812,800 |
| Gross Margins | -0.19107 |
| Gross Profits | -10,419,000 |
| Has Pre Post Market Data | 1 |
| Held Percent Insiders | 0.22348 |
| Held Percent Institutions | 0.93209 |
| Implied Shares Outstanding | 51,336,974 |
| Industry | Biotechnology |
| Industry Disp | Biotechnology |
| Industry Key | biotechnology |
| Is Earnings Date Estimate | 1 |
| Language | en-US |
| Last Fiscal Year End | 1,767,139,200 |
| Long Business Summary | Prothena Corporation plc, a late-stage clinical biotechnology company, focuses on discovery and development of novel therapies to treat diseases caused by protein dysregulation. Its product pipeline includes Prasinezumab, an investigational humanized monoclonal antibody which is in Phase 3 clinical trial for the treatment of parkinson's disease and other synucleinopathies. The company also develops Coramitug, an investigational antibody, which is in Phase 3 clinical trial for the treatment of transthyretin amyloidosis; BMS-986446, an anti-tau antibody which is in Phase 2 clinical trial to treat Alzheimer's disease; PRX019, an investigational antibody which is in Phase 1 clinical trial for the treatment of neurodegenerative diseases; and PRX123, a Dual Aß-Tau Vaccine, which is in preclinical trial for treating Alzheimer's disease. In addition, it develops discovery- and late-preclinical-stage programs include TDP-43 CYTOPE for the treatment of amyotrophic lateral sclerosis; PRX012, a next-generation anti-Aß antibody which is in phase 1 clinical trial to treat Alzheimer's disease; and PRX012-TfR, a preclinical program for the treatment of Alzheimer's disease. It has a license, development, and commercialization agreement with F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. to develop and commercialize antibodies that target a-synuclein, including prasinezumab; and master collaboration agreement with Bristol Myers Squibb to develop and commercialize antibodies targeting tau, TDP-43. Prothena Corporation plc was incorporated in 2012 and is based in Dublin, Ireland. |
| Long Name | Prothena Corporation plc |
| Market | us_market |
| Market Cap | 428,663,776 |
| Market State | POST |
| Max Age | 86,400 |
| Message Board Id | finmb_215515336 |
| Most Recent Quarter | 1,782,777,600 |
| Net Income To Common | -43,992,000 |
| Next Fiscal Year End | 1,798,675,200 |
| Non Diluted Market Cap | 445,604,934 |
| Number Of Analyst Opinions | 5 |
| Open | 8.58 |
| Operating Cashflow | -60,049,000 |
| Operating Margins | -18.50198 |
| Overall Risk | 5 |
| Payout Ratio | 0.0 |
| Phone | 353 1 236 2500 |
| Post Market Change | 0.0 |
| Post Market Change Percent | 0.0 |
| Post Market Price | 8.35 |
| Post Market Time | 1,792,180,871 |
| Previous Close | 8.5 |
| Price Eps Current Year | 13.046876 |
| Price Hint | 2 |
| Price To Book | 1.5061328 |
| Price To Sales Trailing12 Months | 7.861063 |
| Profit Margins | -0.80675006 |
| Quick Ratio | 24.721 |
| Quote Source Name | Nasdaq Real Time Price |
| Quote Type | EQUITY |
| Recommendation Key | buy |
| Recommendation Mean | 2.28571 |
| Region | US |
| Regular Market Change | -0.14999962 |
| Regular Market Change Percent | -1.7647014 |
| Regular Market Day High | 8.61 |
| Regular Market Day Low | 8.24 |
| Regular Market Day Range | 8.24 - 8.61 |
| Regular Market Open | 8.58 |
| Regular Market Previous Close | 8.5 |
| Regular Market Price | 8.35 |
| Regular Market Time | 1,792,180,800 |
| Regular Market Volume | 670,248 |
| Return On Assets | -0.10666 |
| Return On Equity | -0.14395 |
| Revenue Growth | -0.771 |
| Revenue Per Share | 1.022 |
| Sand P52 Week Change | 0.16207206 |
| Sector | Healthcare |
| Sector Disp | Healthcare |
| Sector Key | healthcare |
| Share Holder Rights Risk | 3 |
| Shares Outstanding | 51,336,974 |
| Shares Percent Shares Out | 0.156 |
| Shares Short | 8,010,864 |
| Shares Short Previous Month Date | 1,788,134,400 |
| Shares Short Prior Month | 8,495,796 |
| Short Name | Prothena Corporation plc |
| Short Percent Of Float | 0.1879 |
| Short Ratio | 17.58 |
| Source Interval | 15 |
| Symbol | PRTA |
| Target High Price | 36.0 |
| Target Low Price | 8.0 |
| Target Mean Price | 21.4 |
| Target Median Price | 20.0 |
| Total Cash | 288,192,992 |
| Total Cash Per Share | 5.614 |
| Total Debt | 6,991,000 |
| Total Revenue | 54,530,000 |
| Tradeable | 0 |
| Trailing Annual Dividend Rate | 0.0 |
| Trailing Annual Dividend Yield | 0.0 |
| Trailing Eps | -0.82 |
| Trailing Peg Ratio | None |
| Triggerable | 1 |
| Two Hundred Day Average | 9.272675 |
| Two Hundred Day Average Change | -0.9226742 |
| Two Hundred Day Average Change Percent | -0.09950464 |
| Type Disp | Equity |
| Volume | 670,248 |
| Website | https://www.prothena.com |
| Zip | D02 VK60 |