Spero TherapeuticsSPRO -4.04%55 PB Ratio is 2.21 as of Jun. 26, 2026, which is 4% above its 10-year median of 2.12. GuruFocus rates SPRO with a GF Score™ of 55/100 and a GF Value™ of $1.06 (Significantly Overvalued). The stock has 4 warning signs investors should review. Among 1,232 Biotechnology companies, Spero Therapeutics ranks better than 58.6% on this metric.
Spero Therapeutics Inc stock PB Ratio (=2.21) is close to 1-year low of 2.07.
The historical rank and industry rank for Spero Therapeutics's PB Ratio or its related term are showing as below:
SPRO'
s PB Ratio Range Over the Past 10 Years
Min: 0.49 Med: 2.12 Max: 6.3
Current: 2.21
During the past 11 years, Spero Therapeutics's highest PB Ratio was 6.30. The lowest was 0.49. And the median was 2.12.
SPRO's PB Ratio is ranked better than 58.6% of 1232
companies
in the Biotechnology industry
Industry Median: 2.8
vs SPRO: 2.21
During the past 12 months, Spero Therapeutics's average Book Value Per Share Growth Rate was 51.10% per year.
During the past 3 years, the average Book Value Per Share Growth Rate was -10.30% per year.
During the past 5 years, the average Book Value Per Share Growth Rate was -25.90% per year.
During the past 11 years, the highest 3-Year average Book Value Per Share Growth Rate of Spero Therapeutics was -8.50% per year. The lowest was -32.30% per year. And the median was -24.75% per year.
Back to Basics: PB Ratio
Spero Therapeutics (NAS:SPRO) PB Ratio Explanation
The PB Ratio works the best for the businesses that earn most of their profit from their assets, e.g. banks and insurance companies.
Be Aware
Some businesses have very light assets, such as software companies or insurance agencies. The PB Ratio does not work well for these companies. Some companies even have negative equity, so the PB Ratio cannot be applied to them.
Spero Therapeutics PB Ratio Related Terms
Spero Therapeutics PB Ratio Historical Data
* Premium members only.
The historical data trend for Spero Therapeutics's 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.
For the Biotechnology subindustry, Spero Therapeutics's PB Ratio, along with its competitors' market caps and 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.
Spero Therapeutics PB Ratio vs Biotechnology Industry
For the Biotechnology industry and Healthcare sector, Spero Therapeutics's PB Ratio distribution charts can be found below:
* The bar in red indicates where Spero Therapeutics's PB Ratio falls into.
The PB Ratio, or Price-to-Book ratio, or Price/Book, is a financial ratio used to compare a company's market price to its Book Value per Share. It is a ratio widely used to value stocks.
* 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.
It can also be calculated from the numbers for the whole company:
A closely related ratio is called Price-to-Tangible-Book. The difference between Price-to-Tangible-Book and PB Ratio is that book value other than intangibles are used in the calculation.
Spero Therapeutics (SPRO) has a PB Ratio of 2.21 as of Jun. 26, 2026. Price-to-Book ratio is the ratio of share price to a company's book value per share. View historical data on Spero Therapeutics and its competitors. This is near median its historical median of 2.12. Over the past decade, Spero Therapeutics' PB Ratio has ranged from 0.49 to 6.30. According to the industry distribution chart, Spero Therapeutics ranks #510 out of 1232 companies in the Biotechnology industry, placing it in the top 41.4%.
Is Spero Therapeutics' PB Ratio too high?
Spero Therapeutics' current PB Ratio of 2.21 is near median its 10-year median of 2.12. Over the past 10 years, this metric has ranged from a low of 0.49 to a high of 6.30. The Biotechnology industry median PB Ratio is 2.80. Spero Therapeutics' value of 2.21 is 21.1% below this industry median. Based on the distribution chart, Spero Therapeutics ranks #510 out of 1232 companies in the Biotechnology industry, which is above the industry midpoint. Overall, Spero Therapeutics has a GF Score™ of 55/100 and is considered Significantly Overvalued, reflecting its overall financial health beyond just this single metric.
How does Spero Therapeutics' PB Ratio compare to ORMP and PLYX?
According to the Biotechnology industry distribution chart, Spero Therapeutics ranks #510 out of 1232 companies for PB Ratio. This puts Spero Therapeutics in the upper half of its industry. The industry median PB Ratio is 2.80. Spero Therapeutics' value of 2.21 is 21.1% below this benchmark. Historically, Spero Therapeutics' own PB Ratio has ranged from 0.49 to 6.30 over the past decade. While the company's 10-year median is 2.12 vs. the industry median of 2.80, Spero Therapeutics 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 PB Ratio for a Biotechnology company?
The median PB Ratio among Biotechnology companies is 2.80, based on 1,232 companies in the industry. Companies in the top quartile (top 25%) have a PB Ratio significantly above this median, while those in the bottom quartile fall well below. However, PB Ratio should not be evaluated in isolation — investors should consider it alongside profitability, growth, and financial strength metrics. Spero Therapeutics's current PB Ratio of 2.21 is 21.1% 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 PB Ratio mean?
A high PB Ratio can signal that a stock is expensive relative to its fundamentals. Price-to-Book ratio is the ratio of share price to a company's book value per share. View historical data on Spero Therapeutics and its competitors. For the Biotechnology industry, the median PB Ratio is 2.80 — values significantly above this may indicate overvaluation, while values below may suggest a bargain or underlying issues. Spero Therapeutics's current PB Ratio is 2.21, which is near median its own 10-year median of 2.12. However, context matters — high-growth companies often justify higher valuations. Always evaluate alongside other metrics like GF Score™ and GF Value™.
Is Spero Therapeutics stock overvalued right now?
Based on GuruFocus' analysis, Spero Therapeutics (SPRO) is currently considered Significantly Overvalued. The stock's GF Value™ is $1.06, compared to a current price of $2.02 — trading 90.6% above its estimated fair value. The current PB Ratio is 2.21, which is near median its 10-year median of 2.12 and 21.1% below the Biotechnology industry median of 2.80. Spero Therapeutics' overall GF Score™ is 55/100 with 4 warning signs to review. Investors should evaluate multiple metrics — including profitability, growth, and financial strength — before making a decision.
How is PB Ratio calculated?
PB Ratio is calculated from a company's financial statements. For Spero Therapeutics (SPRO), the current PB Ratio is 2.21 as of Jun. 26, 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 Spero Therapeutics (SPRO) Overvalued in 2026?
Based on GuruFocus' analysis, Spero Therapeutics stock appears to be overvalued.
The current stock price of $2.02 is trading 90.6% above its estimated GF Value™ of $1.06.
GuruFocus considers Spero Therapeutics to be Significantly Overvalued.
Key valuation signals for SPRO:
PB Ratio: 2.21 (near median its 10-year median of 2.12)
GF Value™: $1.06 vs. price of $2.02 (90.6% above fair value)
Industry Position: 21.1% below the Biotechnology median (#510 of 1232)
No single metric tells the full story. See the SPRO stock analysis page for a complete view including 30-year financials, guru trades, and insider activity.
Spero Therapeutics Inc is a clinical-stage biopharmaceutical firm. It focuses on identifying, developing, and commercializing novel treatments for MDR (Multi-drug-resistant) bacterial infections and rare diseases. The company's product candidate, tebipenem pivoxil hydrobromide or tebipenem HBr, is designed to be an oral carbapenem-class antibiotic for use in adults to treat MDR Gram-negative infections. It is also developing SPR720, a novel oral antibiotic designed for the treatment of a rare, orphan disease caused by pulmonary non-tuberculous mycobacterial infections, or NTM disease. It is also focused on SPR206, a next-generation polymyxin investigational product candidate being developed as an IV-administered medicine to treat MDR Gram-negative infections in the hospital.
55GF Score
Get the complete analysis for SPRO
PB Ratio is just one metric. See GF Value™, 30-year financials, guru trades, warning signs, and more.
Quick Browse
Personalize
Premium Gurus 
Create New Portfolio
SPRO has been successfully added to your 
