Prothena Corp Public LTD Co ended a material agreement
SEC 8-KRead source ↗
Prothena Corp Public LTD Co is a US-listed company in the biotechnology industry. Its financial year ends in December.
Stock price today
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Third-party market data · may be delayed
Model estimate per share
Not valued: the figures our models need are missing or failed our data-quality checks.
Price vs value
No model value: limited reported history: available models are shown without a Buy/Hold/Sell rating. How we value companies.
Prothena Corp Public LTD Co valuation: adjust assumptions and compare models →
Who’s trading
What company insiders, investment funds and members of Congress have been doing with the stock, from their own filings.
- Insiders1 buying, 2 selling19 purchases and 2 sales by directors and officers, last 12 monthsInsider trades
- Funds83 adding, 80 cuttingOf 33 active managers that changed their stake, 18 added; quarter to June 30, 2026Fund buyers and sellers
The Fundamentalytics view
Current signal Results well ahead of expectations: Reported earnings per share beat the analysts' consensus estimate by 18% in the quarter to 2026-06-30, the 3rd beat in the last four quarters.
Assembled from SEC-filed figures — the full workings are on this page and in our methodology. Observations, not recommendations.
Highlights
How we pick theseStrengths
Nothing in Prothena Corp Public LTD Co's latest figures clears our strength thresholds.
Things to watch
- Results due soon. Results are expected around 5 November; the share price can move sharply on the day.
- Volatile shares. Over the past year the shares showed annualised volatility of 48% and a beta of 0.9 against the S&P 500.
- Heavily shorted. 18.6% of the shares available to trade are sold short (13.6 days of average volume to cover).
Latest results
- Earnings per share
- -$0.31 against an average estimate of -$0.38: beat by 18.4%
- Share reaction
- +3.2% in the first session after the results on August 6, 2026, against +0.5% for the S&P 500
- Next report
- November 5, 2026; average EPS estimate -$0.30
Price chart
- 1 day-2.1%
- 1 week-1.3%
- 1 month-0.8%
- This year-13.2%
- 1 year-22.9%
- 5 years-86.0%
- S&P 500 this year+11.2%
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Third-party market data · may be delayed
At a glance
Earnings
- Last results
- August 6, 2026
- Next results (est.)
- November 5, 2026
News & updates
Company announcements, filed results and changes that matter to shareholders.
- Agreement ended
- Insider trade
Scully William P (10% owner) bought $1.1M of stock
SEC Form 4 - Leadership
Prothena Corp Public LTD Co announced a director or officer change
SEC 8-KRead source ↗ - Insider trade
Scully William P (10% owner) bought $1.4M of stock
SEC Form 4 - Results
Prothena Corp Public LTD Co reported results
SEC 8-KRead source ↗
Valuation models
We value Prothena Corp Public LTD Co as an operating company, with every model that fits that kind of business. Cost of equity 9.6%: the 10-year Treasury yield (4.9%) plus a beta of 1.03 times a 4.5% equity risk premium.
| Model | Value per share | In the combined value? |
|---|---|---|
| Price-to-earnings vs peers Earnings per share times peers' typical (harmonic-mean) price-to-earnings. | — | Does not apply: no twelve-month earnings or share count in the filings yet |
| Residual income Book value plus the present value of returns above the cost of equity, fading over ten years. | — | Does not apply: no twelve-month earnings or share count in the filings yet |
| Justified price-to-book Book value times (return on equity - growth) / (cost of equity - growth): steady-state returns. | — | Does not apply: no twelve-month earnings or share count in the filings yet |
| Revenue-to-maturity model Revenue grown to maturity with the cash margin moving to the industry's; for companies not yet profitable. | — | Does not apply: revenue and margins don't support a positive value |
| Price-to-sales vs peers Sales per share times peers' typical price-to-sales; used only when earnings are negative. | — | Does not apply: no twelve-month earnings or share count in the filings yet |
| Combined value Weighted average of the models that apply: the primary model (price-to-earnings vs peers) counts double. Models more than 5x or less than 0.2x the share price, or more than 3x away from the other models' median, are left out. | — | No model applies: the filings don’t yet support a value. |
Different models fail in different ways, so where several apply we average them rather than trust one. Peer-based models compare Prothena Corp Public LTD Co with Biotechnology in our coverage, using third-party market data. Model values are estimates under stated assumptions, updated as new filings arrive; not price targets or investment advice. How each model works.
Moat
Not assessed: fewer than five years of comparable figures in the filings. AI disruption exposure for this industry: Medium.
Forecasts and guidance
Next results: November 5, 2026, after the close. Analysts expect revenue of $8m and EPS of −$0.30 (range −$0.38 to −$0.22) for the quarter.
Analysts' consensus
| Fiscal year | EPS | Growth | Revenue | Growth |
|---|---|---|---|---|
| Current | $0.64 | +116% | $83m | +754% |
| Next | −$1.31 | −306% | $21m | −75% |
How the EPS forecast has moved
The consensus EPS forecast for the current fiscal year is +1180.0% on 90 days ago. In the last 30 days, 2 analysts raised Prothena Corp Public LTD Co's forecast and 0 cut it.
Average of analysts' published estimates (third-party data).
View chart data
| Period | Next fiscal year |
|---|---|
| 90 days ago | −$1.31 |
| 60 days ago | −$1.52 |
| 30 days ago | −$1.52 |
| 7 days ago | −$1.52 |
| Now | −$1.31 |
Earnings against estimates
| Quarter to | Estimate | Actual | Surprise |
|---|---|---|---|
| Jun 2026 | −$0.38 | −$0.31 | +18.4% |
| Mar 2026 | −$0.30 | $0.68 | +324.0% |
| Dec 2025 | −$0.46 | −$0.46 | +0.7% |
| Sept 2025 | −$0.54 | −$0.67 | −24.6% |
Adjusted EPS as companies report it, against the average analyst estimate.
Positioning
- Short interest
- 18.6% of tradable shares
- Days to cover
- 13.61 at average volume
- Short interest, 1 month
- −7% to October 15, 2026
- Held by institutions
- 93% of shares
- Held by insiders
- 22.9% of shares
- Employees
- 67 full time
Share-price performance
Market data may be delayedReturn and risk by year
| Calendar year | 2021 | 2022 | 2023 | 2024 | 2025 | 2026 to date |
|---|---|---|---|---|---|---|
| Return | ||||||
| PRTA | +311% | +22% | −40% | −62% | −31% | −13% |
| Industry peers (median) | −36% | −57% | −17% | −28% | −5% | −27% |
| S&P 500 | +29% | −18% | +26% | +25% | +18% | +11% |
| Months that ended higher | ||||||
| PRTA | 58% | 50% | 42% | 25% | 58% | 36% |
| S&P 500 | 75% | 42% | 67% | 75% | 75% | 46% |
| Largest fall from a high during the year | ||||||
| PRTA | −47% | −54% | −59% | −71% | −71% | −31% |
| S&P 500 | −5% | −25% | −10% | −8% | −19% | −9% |
Worst fall since November 3, 2015: 94% from September 23, 2021 to May 27, 2025. Getting back needed a 1623% gain, and the shares have not yet recovered.
Price behaviour
- 52-week range
- $7.91 – $11.51
- From 52-week high
- −28.0%
- vs 50-day average
- −5.2%
- vs 200-day average
- −10.2%
- Volatility (1 year)
- 48%
- Beta vs S&P 500
- 0.94
Share price after results
- Next day
- 7 up, 5 down typical move ±3.6%
- After a week
- 4 up, 8 down typical move ±8.4%
- After a month
- 4 up, 8 down typical move ±16.2%
| Results released | Next day | S&P 500 next day | 5 days | 21 days |
|---|---|---|---|---|
| August 6, 2026 | +3.2% | +0.5% | +6.9% | +15.7% |
| May 7, 2026 | −4.0% | +0.5% | −11.8% | −23.4% |
| February 19, 2026 | −0.8% | +0.5% | −5.0% | −3.7% |
| November 6, 2025 | +2.8% | −1.0% | −0.9% | +4.5% |
| August 4, 2025 | +3.2% | +1.0% | +12.6% | +23.2% |
| May 8, 2025 | +1.9% | +0.6% | −7.9% | −28.0% |
| February 20, 2025 | +3.9% | −2.1% | +1.0% | −13.4% |
| November 12, 2024 | −4.7% | −0.3% | −22.3% | −23.6% |
| August 8, 2024 | +6.7% | +2.8% | +8.4% | +6.0% |
| May 8, 2024 | −6.5% | +0.6% | −4.9% | −10.2% |
| February 15, 2024 | +2.7% | +0.2% | −0.3% | −8.1% |
| January 8, 2024 | −2.6% | +1.3% | −18.5% | −34.6% |
Fundamentals
Where the revenue comes from
| Line of business | Revenue | Share | YoY |
|---|---|---|---|
| Collaboration | $9.6M | 99.5% | ▼ 92.9% |
| Licenses | $50,000 | 0.5% | 0.0% |
From Prothena Corp Public LTD Co's 10-K filed February 27, 2026, as tagged in the filing. View filing. Indented rows are part of the line above; their share is of that line. In the bars, the faint bar behind is the year before.
Who owns it
Funds buying and selling- Reported value
- $463M
- Institutions reporting
- 188
- Shares held vs prior quarter
- ▲ 0.7%
- Positions opened / closed
- 27 / 23
| Manager | Value | Shares | Share of 13F value | Shares QoQ |
|---|---|---|---|---|
| FMR LLC | $70.5M | 7.2M | 15.2% | ▼ 4.7% |
| Rubric Capital Management LP | $49M | 5.0M | 10.6% | 0.0% |
| Blackrock, Inc. | $47.7M | 4.9M | 10.3% | ▲ 4.8% |
| State Street Corp | $23.4M | 2.4M | 5.1% | ▲ 23.5% |
| Acadian Asset Management LLC | $19.7M | 2.0M | 4.2% | ▲ 29.9% |
| Vanguard Portfolio Management LLC | $16.2M | 1.7M | 3.5% | ▲ 14.2% |
| D. E. Shaw & Co., Inc. | $15.8M | 1.6M | 3.4% | ▼ 8.6% |
| ADAR1 Capital Management, LLC | $15.2M | 1.6M | 3.3% | ▼ 1.7% |
| Two Sigma Investments, LP | $12.4M | 1.3M | 2.7% | ▲ 4.9% |
| Palo Alto Investors LP | $11.2M | 1.1M | 2.4% | ▼ 5.4% |
| Geode Capital Management, LLC | $11M | 1.1M | 2.4% | ▲ 2.5% |
| Federated Hermes, Inc. | $10.6M | 1.1M | 2.3% | ▲ 2.3% |
From Form 13F filings with the SEC ( quarterly data sets), as reported by each manager for June 30, 2026 and filed up to 45 days later. 13F reports cover long US-listed positions of managers above $100M only, so this is not Prothena Corp Public LTD Co's complete shareholder register. Values are as reported by the filers ; 1 inconsistently scaled filing rows were excluded.
Insider trading activity
Full insider history and chart Insider purchases History → $12.1M 19 trades by 1 insider, last 12 months Insider sales History → $135,927 2 trades by 2 insiders · 100% under pre-set plans
Net ▲ $11.9M net buying
| Insider | Date | Trade | Shares | Price | Value |
|---|---|---|---|---|---|
| Scully William P 10% owner | October 23, 2026 | Buy | 50,000 | $8.07 | $403,525 |
| Scully William P 10% owner | October 22, 2026 | Buy | 100,000 | $8.19 | $818,520 |
| Scully William P 10% owner | October 14, 2026 | Buy | 10,000 | $8.46 | $84,569 |
| Scully William P 10% owner | October 13, 2026 | Buy | 100,000 | $8.35 | $835,480 |
| Scully William P 10% owner | October 8, 2026 | Buy | 90,000 | $8.57 | $770,904 |
| Scully William P 10% owner | October 7, 2026 | Buy | 125,000 | $8.40 | $1.1M |
| Scully William P 10% owner | October 2, 2026 | Buy | 100,000 | $8.57 | $857,240 |
| Scully William P 10% owner | September 29, 2026 | Buy | 162,000 | $8.68 | $1.4M |
| Scully William P 10% owner | September 28, 2026 | Buy | 103,500 | $8.60 | $890,100 |
| Scully William P 10% owner | September 18, 2026 | Buy | 100,000 | $8.43 | $843,000 |
| Scully William P 10% owner | September 2, 2026 | Buy | 27,000 | $9.47 | $255,690 |
| Scully William P 10% owner | August 20, 2026 | Buy | 50,000 | $8.79 | $439,500 |
From insiders' Form 4 filings with the SEC. Excludes awards, option exercises and shares withheld for tax. "Pre-set plan" means the filing marks the trade as made under a Rule 10b5-1 plan. See every insider trade since five years ago, on a price chart.
Earnings dates and SEC filings
Results announcements
Next expected around November 5, 2026 estimated from the company's past filing pattern, not announced
- August 6, 2026
- May 7, 2026
- February 19, 2026
- November 6, 2025
- August 4, 2025
- May 8, 2025
Recent SEC filings
- 8-K Current report
- 8-K Current report
- 10-Q Quarterly report
- 8-K Current report
- 8-K Current report
- 10-Q Quarterly report
- 8-K Current report
- DEF 14A Proxy statement
Data status
| Data | Last updated | Source |
|---|---|---|
| Share price | Exchange closing prices | |
| News and updates | Company releases and SEC 8-K filings | |
| Analyst estimates | Aggregated analyst estimates | |
| Valuation and scores | Our models, from the filed figures |
Prothena Corp Public LTD Co in brief
- What does Prothena Corp Public LTD Co do?
- Prothena Corp Public LTD Co is a US-listed company in the biotechnology industry. Its financial year ends in December.
- What is Prothena Corp Public LTD Co's stock ticker?
- Prothena Corp Public LTD Co trades under the ticker PRTA on Nasdaq. This page brings together its financial statements, valuation models, ownership and recent company updates.
- Who are Prothena Corp Public LTD Co's largest institutional shareholders?
- By value reported in 13F filings for June 30, 2026, the largest reported holders are FMR LLC, Rubric Capital Management LP and Blackrock, Inc. 13F reports cover long US-listed positions of managers above $100M, filed up to 45 days after quarter end.
- Are insiders buying or selling Prothena Corp Public LTD Co stock?
- Over the last 12 months, Prothena Corp Public LTD Co's directors and officers reported 19 open-market purchases and 2 sales on Form 4. The insider trading page charts every trade.
- When is Prothena Corp Public LTD Co's next earnings date?
- Around November 5, 2026, estimated from the spacing of its past results announcements (8-K filings). That is an estimate, not a confirmed date — Prothena Corp Public LTD Co announces its own schedule.
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