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ProthenaSTU:0PT +4.10%78 Cyclically Adjusted PB Ratio is 0.88 as of Aug. 11, 2026, which is 62% below its 10-year median of 2.32. GuruFocus rates STU:0PT with a GF Score™ of 78/100 and a GF Value™ of €11.29 (Possible Value Trap). The stock has 2 warning signs investors should review. Among 693 Biotechnology companies, Prothena ranks better than 65.22% on this metric.
The historical rank and industry rank for Prothena's Cyclically Adjusted PB Ratio or its related term are showing as below:
STU:0PT'
s Cyclically Adjusted PB Ratio Range Over the Past 10 Years
Min: 0.41 Med: 2.32 Max: 7.75
Current: 0.89
During the past years, Prothena's highest Cyclically Adjusted PB Ratio was 7.75. The lowest was 0.41. And the median was 2.32.
STU:0PT's Cyclically Adjusted PB Ratio is ranked better than 65.22% of 693
companies
in the Biotechnology industry
Industry Median: 1.62
vs STU:0PT: 0.89
The Shiller PE Ratio was first used by professor Robert Shiller. He uses E10 for his Shiller PE Ratio calculation. E10 is the average of the inflation adjusted earnings per share of a company over the past 10 years. The similar calculation is applied by GuruFocus to calculate the Cyclically Adjusted PB Ratio. The Cyclically Adjusted Book per Share is the average of the inflation adjusted book value per share of a company over the past 10 years.
Prothena's adjusted book value per share data for the three months ended in Jun. 2026 was €4.776. Add all the adjusted book value per share for the past 10 years together and divide the count will get our Cyclically Adjusted Book per Share, which is €8.98 for the trailing ten years ended in Jun. 2026.
Shiller PE for Stocks: The True Measure of Stock Valuation
Prothena (STU:0PT) Cyclically Adjusted PB Ratio Explanation
Compared with the regular PB Ratio, which works poorly for cyclical businesses, the Cyclically Adjusted PB Ratio smoothed out the fluctuations of book value during business cycles. Therefore it is more accurate in reflecting the valuation of the company.
If a company has consistent business performance, the Cyclically Adjusted PB Ratio should give similar results to regular PB Ratio.
Prothena Cyclically Adjusted PB Ratio Related Terms
Prothena Cyclically Adjusted PB Ratio Historical Data
* Premium members only.
The historical data trend for Prothena's Cyclically Adjusted PB Ratio 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.
STU:0PT vs KYTX, QTTB, RZLT: Cyclically Adjusted PB Ratio Comparison
For the Biotechnology subindustry, Prothena's Cyclically Adjusted PB Ratio, along with its competitors' market caps and Cyclically Adjusted PB Ratio 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 Cyclically Adjusted PB Ratio vs Biotechnology Industry
For the Biotechnology industry and Healthcare sector, Prothena's Cyclically Adjusted PB Ratio distribution charts can be found below:
* The bar in red indicates where Prothena's Cyclically Adjusted PB Ratio falls into.
Like the Shiller PE Ratio, the Cyclically Adjusted PB Ratio takes the Book Value per Share from the past 10 years, adjusts it for inflation, and then calculates the average. This average is then used for the P/B calculation. Because it considers this 10-year average, it's often referred to as the CAPB Ratio.
The Shiller PE Ratio was first used by professor Robert Shiller to measure the valuation of the overall market. The similar calculation is applied by GuruFocus to calculate the Cyclically Adjusted PB Ratio.
Prothena's Cyclically Adjusted PB Ratio for today is calculated as
* 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.
Please note that we use the CPI data of the country/region where the company is headquartered. If the CPI data for that country/region is not available, then we will use the CPI data of the United States as default.
What does a Cyclically Adjusted PB Ratio of 0.88 mean?
Prothena (STU:0PT) has a Cyclically Adjusted PB Ratio of 0.88 as of Aug. 11, 2026. Cyclically Adjusted PB Ratio is the ratio of share price to a company's inflation-adjusted book value per share over a 10-year period. View historical data on Prothena and its competitors. This is 62% below median its historical median of 2.32. Over the past decade, Prothena's Cyclically Adjusted PB Ratio has ranged from 0.41 to 7.75. According to the industry distribution chart, Prothena ranks #241 out of 693 companies in the Biotechnology industry, placing it in the top 34.8%.
Is Prothena's Cyclically Adjusted PB Ratio too high?
Prothena's current Cyclically Adjusted PB Ratio of 0.88 is 62% below median its 10-year median of 2.32. Over the past 10 years, this metric has ranged from a low of 0.41 to a high of 7.75. The Biotechnology industry median Cyclically Adjusted PB Ratio is 1.62. Prothena's value of 0.88 is 45.7% below this industry median. Based on the distribution chart, Prothena ranks #241 out of 693 companies in the Biotechnology industry, which is above the industry midpoint. Overall, Prothena has a GF Score™ of 78/100 and is considered Possible Value Trap, reflecting its overall financial health beyond just this single metric.
How does Prothena's Cyclically Adjusted PB Ratio compare to KYTX and QTTB?
According to the Biotechnology industry distribution chart, Prothena ranks #241 out of 693 companies for Cyclically Adjusted PB Ratio. This puts Prothena in the upper half of its industry. The industry median Cyclically Adjusted PB Ratio is 1.62. Prothena's value of 0.88 is 45.7% below this benchmark. Historically, Prothena's own Cyclically Adjusted PB Ratio has ranged from 0.41 to 7.75 over the past decade. While the company's 10-year median is 2.32 vs. the industry median of 1.62, Prothena has consistently been below the industry average. See the competitive comparison table and distribution chart on this page for a detailed peer-by-peer breakdown.
What is a good Cyclically Adjusted PB Ratio for a Biotechnology company?
The median Cyclically Adjusted PB Ratio among Biotechnology companies is 1.62, based on 693 companies in the industry. Companies in the top quartile (top 25%) have a Cyclically Adjusted PB Ratio significantly above this median, while those in the bottom quartile fall well below. However, Cyclically Adjusted PB Ratio should not be evaluated in isolation — investors should consider it alongside profitability, growth, and financial strength metrics. Prothena's current Cyclically Adjusted PB Ratio of 0.88 is 45.7% below the industry median. Use the industry distribution chart on this page to see where any company falls relative to its peers.
What does a high Cyclically Adjusted PB Ratio mean?
A high Cyclically Adjusted PB Ratio can signal that a stock is expensive relative to its fundamentals. Cyclically Adjusted PB Ratio is the ratio of share price to a company's inflation-adjusted book value per share over a 10-year period. View historical data on Prothena and its competitors. For the Biotechnology industry, the median Cyclically Adjusted PB Ratio is 1.62 — values significantly above this may indicate overvaluation, while values below may suggest a bargain or underlying issues. Prothena's current Cyclically Adjusted PB Ratio is 0.88, which is 62% below median its own 10-year median of 2.32. 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 (STU:0PT) is currently considered Possible Value Trap. The stock's GF Value™ is €11.29, compared to a current price of €7.88 — trading 30.2% below its estimated fair value. The current Cyclically Adjusted PB Ratio is 0.88, which is 62% below median its 10-year median of 2.32 and 45.7% below the Biotechnology industry median of 1.62. Prothena's overall GF Score™ is 78/100 with 2 warning signs to review. Investors should evaluate multiple metrics — including profitability, growth, and financial strength — before making a decision.
How is Cyclically Adjusted PB Ratio calculated?
Cyclically Adjusted PB Ratio is calculated from a company's financial statements. For Prothena (STU:0PT), the current Cyclically Adjusted PB Ratio is 0.88 as of Aug. 11, 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 (STU:0PT) Overvalued in 2026?
Based on GuruFocus' analysis, Prothena stock appears to be undervalued.
The current stock price of €7.88 is trading 30.2% below its estimated GF Value™ of €11.29.
GuruFocus considers Prothena to be Possible Value Trap.
Key valuation signals for STU:0PT:
Cyclically Adjusted PB Ratio: 0.88 (62% below median its 10-year median of 2.32)
GF Value™: €11.29 vs. price of €7.88 (30.2% below fair value)
Industry Position: 45.7% below the Biotechnology median (#241 of 693)
No single metric tells the full story. See the STU:0PT 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.
78GF Score
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