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ProthenaPRTA -1.72%74 Earnings Yield (Joel Greenblatt) % is -26.60% as of Jun. 2026. GuruFocus rates PRTA with a GF Score™ of 74/100 and a GF Value™ of $12.96 (Modestly Undervalued). The stock has 2 warning signs investors should review. Among 1,345 Biotechnology companies, Prothena ranks worse than 73.31% on this metric.
Prothena's Enterprise Value for the quarter that ended in Jun. 2026 was $225.37 Mil.
Prothena's EBIT for the trailing twelve months (TTM) ended in Jun. 2026 was $-59.87 Mil. Prothena's Earnings Yield (Joel Greenblatt) for the quarter that ended in Jun. 2026 was -26.60%.
The historical rank and industry rank for Prothena's Earnings Yield (Joel Greenblatt) % or its related term are showing as below:
PRTA'
s Earnings Yield (Joel Greenblatt) % Range Over the Past 10 Years
Min: -5073.44 Med: -15.56 Max: 11915.83
Current: -31.95
During the past 13 years, the highest Earnings Yield (Joel Greenblatt) of Prothena was 11915.83%. The lowest was -5073.44%. And the median was -15.56%.
PRTA's Earnings Yield (Joel Greenblatt) % is ranked worse than 73.31% of 1345
companies
in the Biotechnology industry
Industry Median: -9.94
vs PRTA: -31.95
Joel Greenblatt's definition of earnings yield has the same problems the regular earnings yield does. It does not consider the growth of the company. It only looks at one-year's business operation. For cyclical companies, the earnings yield is usually highest at the peak of the business cycle. But these earnings are rarely sustainable.
A better indicator of the attractiveness of an investment which takes growth into account is the Forward Rate of Return (Yacktman) %. Prothena's Forward Rate of Return (Yacktman) % for the quarter that ended in Jun. 2026 was 0.00%. The Forward Rate of Return uses the normalized Free Cash Flow of the past five years, and considers growth. The forward rate of return can be thought of as the return that investors buying the stock today can expect from it in the future.
Joel Greenblatt defines the earnings yield using the above equation because it more accurately reflects the company's profitability relative to its stock price. Items like interest payment and tax etc. are not directly related to the company's operational profitability.
Enterprise Value instead of market cap (share price) is used in the calculation because it is the real price stock and bond investors together pay for the company.
Be Aware
Joel Greenblatt's definition of earnings yield has the same problems the regular earnings yield does. It does not consider the growth of the company. It only looks at one-year's business operation. For cyclical companies, the earnings yield is usually highest at the peak of the business cycle. But these earnings are rarely sustainable.
Prothena Earnings Yield (Joel Greenblatt) % Related Terms
Prothena Earnings Yield (Joel Greenblatt) % Historical Data
* Premium members only.
The historical data trend for Prothena's Earnings Yield (Joel Greenblatt) % can be seen below:
* For Operating Data section: All numbers are indicated by the unit behind each term and all currency related amount are in USD. * For other sections: All numbers are in millions except for per share data, ratio, and percentage. All currency related amount are indicated in the company's associated stock exchange currency.
For the Biotechnology subindustry, Prothena's Earnings Yield (Joel Greenblatt) %, along with its competitors' market caps and Earnings Yield (Joel Greenblatt) % data, can be viewed below:
* Competitive companies are chosen from companies within the same industry, with headquarter located in same country, with closest market capitalization; x-axis shows the market cap, and y-axis shows the term value; the bigger the dot, the larger the market cap. Note that "N/A" values will not show up in the chart.
Prothena Earnings Yield (Joel Greenblatt) % vs Biotechnology Industry
For the Biotechnology industry and Healthcare sector, Prothena's Earnings Yield (Joel Greenblatt) % distribution charts can be found below:
* The bar in red indicates where Prothena's Earnings Yield (Joel Greenblatt) % falls into.
In his book, The Little That Beat the Market, hedge fund manager Joel Greenblatt defines Earnings Yield as operating income divided by enterprise value.
Prothenas Earnings Yield (Joel Greenblatt) for the fiscal year that ended in Dec. 2025 is calculated as
Prothena's EBIT for the trailing twelve months (TTM) ended in Jun. 2026 adds up the quarterly data reported by the company within the most recent 12 months, which was $-59.87 Mil.
What does a Earnings Yield (Joel Greenblatt) % of -26.60% mean?
Prothena (PRTA) has a Earnings Yield (Joel Greenblatt) % of -26.60% as of Jun. 2026. Joel Greenblatt's earnings yield equals the ratio of earnings before interest and taxes to enterprise value. View historical data on Prothena and its competitors. According to the industry distribution chart, Prothena ranks #986 out of 1345 companies in the Biotechnology industry, placing it in the top 73.3%.
Is Prothena's Earnings Yield (Joel Greenblatt) % too high?
Prothena's current Earnings Yield (Joel Greenblatt) % is -26.60%. Based on the distribution chart, Prothena ranks #986 out of 1345 companies in the Biotechnology industry, which is below the industry midpoint. Overall, Prothena has a GF Score™ of 74/100 and is considered Modestly Undervalued, reflecting its overall financial health beyond just this single metric.
How does Prothena's Earnings Yield (Joel Greenblatt) % compare to KYTX and QTTB?
According to the Biotechnology industry distribution chart, Prothena ranks #986 out of 1345 companies for Earnings Yield (Joel Greenblatt) %. This places Prothena in the lower half of its industry. See the competitive comparison table and distribution chart on this page for a detailed peer-by-peer breakdown.
What is a good Earnings Yield (Joel Greenblatt) % for a Biotechnology company?
A good Earnings Yield (Joel Greenblatt) % depends on the Biotechnology industry context. However, Earnings Yield (Joel Greenblatt) % should not be evaluated in isolation — investors should consider it alongside profitability, growth, and financial strength metrics. Use the industry distribution chart on this page to see where any company falls relative to its peers.
What does a high Earnings Yield (Joel Greenblatt) % mean?
A high Earnings Yield (Joel Greenblatt) % can signal that a stock is expensive relative to its fundamentals. Joel Greenblatt's earnings yield equals the ratio of earnings before interest and taxes to enterprise value. View historical data on Prothena and its competitors. Prothena's current Earnings Yield (Joel Greenblatt) % is -26.60%. However, context matters — high-growth companies often justify higher valuations. Always evaluate alongside other metrics like GF Score™ and GF Value™.
Is Prothena stock overvalued right now?
Based on GuruFocus' analysis, Prothena (PRTA) is currently considered Modestly Undervalued. The stock's GF Value™ is $12.96, compared to a current price of $9.13 — trading 29.6% below its estimated fair value. The current Earnings Yield (Joel Greenblatt) % is -26.60%. Prothena's overall GF Score™ is 74/100 with 2 warning signs to review. Investors should evaluate multiple metrics — including profitability, growth, and financial strength — before making a decision.
How is Earnings Yield (Joel Greenblatt) % calculated?
Earnings Yield (Joel Greenblatt) % is calculated from a company's financial statements. For Prothena (PRTA), the current Earnings Yield (Joel Greenblatt) % is -26.60% as of Jun. 2026. GuruFocus calculates this using data sourced from SEC filings and annual reports. See the calculation section and 30-year financial data on this page for the full breakdown.
Is Prothena (PRTA) Overvalued in 2026?
Based on GuruFocus' analysis, Prothena stock appears to be undervalued.
The current stock price of $9.13 is trading 29.6% below its estimated GF Value™ of $12.96.
GuruFocus considers Prothena to be Modestly Undervalued.
Key valuation signals for PRTA:
Earnings Yield (Joel Greenblatt) %: -26.60%
GF Value™: $12.96 vs. price of $9.13 (29.6% below fair value)
No single metric tells the full story. See the PRTA stock analysis page for a complete view including 30-year financials, guru trades, and insider activity.
Prothena Corp PLC is a late-stage clinical biotechnology company that focuses on protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare and peripheral amyloid diseases. Prothena is developing and applying its proprietary CYTOPE technology to target a broad spectrum of intracellular disease pathways in the brain and periphery. The company's pipeline includes both wholly-owned and partnered programs like Prasinezumab, Coramitug (PRX004), BMS-986446 (PRX005), PRX019, TDP-43 CYTOPE, and PRX012-TfR, being developed for the potential treatment of Parkinson's disease, ATTR amyloidosis with cardiomyopathy, Alzheimer's disease, Amyotrophic lateral sclerosis (ALS), and other neurodegenerative diseases.
74GF Score
Get the complete analysis for PRTA
Earnings Yield (Joel Greenblatt) % is just one metric. See GF Value™, 30-year financials, guru trades, warning signs, and more.
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