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Spero Therapeutics, Inc. (SPRO) stock

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NASDAQ: SPRO Nasdaq Biotechnology Next results ~November 12, 2026

B Fundamentals grade

Spero Therapeutics, Inc. 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

Fair value per share

Under review: valuation models disagree too widely to rate.

Price vs value

Under review: valuation models disagree too widely to rate. We'll show the comparison once resolved.

Spero Therapeutics, Inc. 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.

  • Insiders0 buying, 2 selling0 purchases and 9 sales by directors and officers, last 12 monthsInsider trades
  • Funds38 adding, 18 cuttingOf 14 active managers that changed their stake, 6 added; quarter to June 30, 2026Fund buyers and sellers

Value diary

Our note on each quarter Spero Therapeutics files

Where Spero Therapeutics stands after its latest 10-Q

Revenue for the twelve months to June 2026 was $47m, down 3.3% on a year earlier, against growth of 37.2% a quarter earlier. Free-cash-flow margin rose to 41.7% from -66.6% a year earlier. Operating margin widened to 12.8% from -118.4%. The diluted share count is up 9.1% on a year earlier, which dilutes existing holders. Against its peers on growth, profitability, cash generation and balance sheet, it grades B. It passes 2 of our 2 financial-health checks.

Our model value for Spero Therapeutics is under review, so past values are not shown until it is resolved.

Source: 10-Q filed August 12, 2026 on SEC EDGAR · Financials · Valuation

Written from the company's filings and our models when each quarter's report arrives. Figures in older notes are as published at the time. Not investment advice.

The Fundamentalytics view

Next results ~November 12, 2026 (estimated)

Spero Therapeutics, Inc.'s trailing-twelve-month revenue fell 3.3% year on year, with a free-cash-flow margin of 41.7%. Where it stands out: free-cash-flow margin of 41.7% ranks 11 of 176 biotechnology companies we cover. Where it lags: change in growth rate of -40.5pp ranks 140 of 172 biotechnology companies we cover.

Current signal Revenue growth decelerating: TTM revenue growth slowed to -3.3% (-40.5pp vs the prior quarter), the 2nd consecutive quarterly slowdown.

Assembled from SEC-filed figures — the full workings are on this page and in our methodology. Observations, not recommendations.

Highlights

How we pick these

Strengths

  • Margins widening. Operating margin is up 131.2 points on a year ago.
  • Strong cash generation. 41.7% of revenue turned into free cash flow, against a median of -145.4% for biotechnology companies we cover.
  • Net cash. Cash exceeds long-term debt by $0.1bn.

Things to watch

  • Results due soon. Results are expected around 12 November; the share price can move sharply on the day.
  • Revenue shrinking. Revenue fell 3.3% over the last 12 months.
  • Growth slowing. The growth rate is 40.5 points lower than a quarter earlier.
  • Share dilution. Diluted shares rose 9.1% in a year.
  • Volatile shares. Over the past year the shares showed annualised volatility of 64% and a beta of 1.5 against the S&P 500.
  • Estimates being cut. Analysts' consensus for next year's earnings per share has fallen 113.8% over 90 days.

Latest results: FY2026 Q2

Filed August 12, 2026
Share reaction
+0.8% in the first session after the results on August 12, 2026, against +0.9% for the S&P 500
Next report
November 12, 2026

Spero Therapeutics' figures from its SEC filings and results release; estimates are the analysts' average. Not a recommendation.

Price chart

  • 1 day-1.9%
  • 1 week-2.8%
  • 1 month-12.6%
  • This year-55.4%
  • 1 year-57.2%
  • 5 years-94.1%
  • S&P 500 this year+11.2%

Closing prices to 2026-11-02. Price change only, dividends excluded.

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Third-party market data · may be delayed

At a glance

Trailing twelve months, from SEC filings

Profitability

Revenue (TTM)
$47M
Operating margin
12.8%
Net margin
15.7%
EPS (TTM, diluted)
$0.12

Growth

Revenue growth
−3.3%
Change in growth rate
−40.5 pts
Share count change
+9.1%

Cash

Free cash flow (TTM)
$19.6M
FCF margin
41.7%
Stock pay % of revenue
8.5%

Earnings

Last results
August 12, 2026
Next results (est.)
November 12, 2026

News & updates

Updated October 31, 2026

Company announcements, filed results and changes that matter to shareholders.

  1. Leadership
  2. Agreement
  3. Results
  4. Agreement

Refreshed hourly when new source data is available. Summaries are checked against company releases and SEC filings. Company announcement headlines are labelled when a checked summary is unavailable.

Valuation

Spero Therapeutics, Inc. valuation models and calculator

Fundamentalytics rating

model v1.6 · 2026-11-03

Not rated: valuation models disagree too widely to rate: held for review.

The inputs used by the models below have passed source checks. Individual model values are available below and in the interactive valuator. Their differences are shown explicitly; the platform combined value and recommendation remain withheld.

Valuation models

We value Spero Therapeutics, Inc. as an operating company, with every model that fits that kind of business. Cost of equity 9.4%: the 10-year Treasury yield (4.9%) plus a beta of 1 times a 4.5% equity risk premium.

Value per share by model
Model Value per share In the combined value?
Revenue-to-maturity model Revenue grown to maturity with the cash margin moving to the industry's; for companies not yet profitable. ~$2.9 ~$2.9–$3.3 Primary model, counts double
Price-to-earnings vs peers Earnings per share times peers' typical (harmonic-mean) price-to-earnings. ~$1.2 ~$0.9–$2.7 Included
Residual income Book value plus the present value of returns above the cost of equity, fading over ten years. — Does not apply: This model is withheld pending its input or assumption review.
Justified price-to-book Book value times (return on equity - growth) / (cost of equity - growth): steady-state returns. — Does not apply: This model is withheld pending its input or assumption review.
Price-to-sales vs peers Sales per share times peers' typical price-to-sales; used only when earnings are negative. ~$1.0 ~$2.3–$7.6 Included, half weight
Combined value Individual source-checked model scenarios are available. The platform combined value and recommendation remain withheld. — Combined value withheld. Review the individual models and their assumptions.

Different models fail in different ways, so where several apply we average them rather than trust one. Peer-based models compare Spero Therapeutics, Inc. 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.

Valuation multiples over time Market data may be delayed

At fiscal year end 201720182019202020212022202320242025Now
Share price$11.75$6.15$9.62$19.39$16.01$1.73$1.47$1.03$2.33$1.04
Market value$30m$98m$175m$434m$495m$65m$78m$56m$138m$62m
+ Net debt (− = net cash)−$87m−$34m−$29m−$85m−$112m−$109m−$76m−$53m−$40m−$51m
Enterprise value−$57m$64m$145m$349m$382m−$44m$2m$3m$97m$12m
Multiples
Price / sales 15.4x24.8x9.6x46.5x27.1x1.2x0.8x1.2x2.1x1.3x
Price / earnings —————1.4x3.4x—16.0x8.5x
Price / free cash flow —————————3.2x
EV / EBITDA ——————0.1x—15.4x—

Market value uses the period's diluted share count; figures for each fiscal year use that year's results and the price at year end. "Now" uses today's price and the last twelve months.

Moat

11 /100

Weak moat

How hard Spero Therapeutics's competitive advantage looks for rivals to wear away, judged from 9 years of its own filings: returns on capital, pricing power, profit durability, cash conversion and discipline.

  • Returns on capital 0 / 20

    Net income has been a median -61.0% of total assets over 9 years.

  • Durability 10 / 20

    Operating margin has been a median -338.4%; its worst year was -1395.9%.

  • Cash conversion 3 / 20

    Free cash flow was positive in 2 of 7 years, at a median -66.6% of revenue.

  • Discipline 0 / 20

    The diluted share count rose 121.3% over five years; stock-based pay has been a median 27.3% of revenue.

AI disruption exposure: Medium. In this industry, AI could change how the product is made or sold, without replacing the core asset. The score above includes a 5-point deduction for that exposure (16 before it).

A rules-based reading of reported figures, not a forecast and not investment advice. How the score is built: methodology.

Forecasts and guidance

Next results: November 12, 2026, after the close. Analysts expect revenue of $0 for the quarter.

Analysts' consensus

Fiscal yearEPSGrowthRevenueGrowth
Current −$0.58 −487% $258000 —
Next −$0.10 +82% — −100%

Next year's EPS estimate has moved −113.8% in 90 days, across 2 analysts.

How the EPS forecast has moved

The consensus EPS forecast for the current fiscal year is −186.6% on 90 days ago. In the last 30 days, 0 analysts raised Spero Therapeutics, Inc.'s forecast and 0 cut it.

Consensus EPS forecast Spero Therapeutics, Inc., last 90 days
−$1.00 −$0.50 $0.00 $0.50 $1.00 90 days ago 60 days ago 30 days ago 7 days ago Now Current fiscal year, 90 days ago: $0.67 Current fiscal year, 60 days ago: −$0.29 Current fiscal year, 30 days ago: −$0.29 Current fiscal year, 7 days ago: −$0.29 Current fiscal year, Now: −$0.58 −$0.58 Next fiscal year, 90 days ago: $0.76 Next fiscal year, 60 days ago: $0.67 Next fiscal year, 30 days ago: $0.67 Next fiscal year, 7 days ago: $0.67 Next fiscal year, Now: −$0.10 −$0.10

Average of analysts' published estimates (third-party data).

View chart data
Period Current fiscal yearNext fiscal year
90 days ago $0.67$0.76
60 days ago −$0.29$0.67
30 days ago −$0.29$0.67
7 days ago −$0.29$0.67
Now −$0.58−$0.10

Earnings against estimates

Quarter toEstimateActualSurprise
Sept 2025 −$0.25 −$0.13 +48.0%

Adjusted EPS as companies report it, against the average analyst estimate.

Analyst recommendations

3 analysts, Oct 2026
Buy267%
Hold133%
Sell00%

Monthly trend

  1. Oct 2026213
  2. Sep 2026112

Counts of recommendations published by analysts covering Spero Therapeutics, Inc., by month. Source: Aggregated broker recommendations (third-party data). Aggregated counts only: we do not reproduce any firm's recommendation or price target, and these are not Fundamentalytics ratings.

Positioning

Short interest
1.7%
of tradable shares
Days to cover
1
at average volume
Short interest, 1 month
−14%
to October 15, 2026
Held by institutions
18%
of shares
Held by insiders
22.7%
of shares
Employees
25
full time

Consensus figures average analysts' published estimates (third-party data); guidance is the company's own. Neither is our forecast. Short interest is reported twice a month and lags. Market data may be delayed.

This section is general information, not investment advice or a personal recommendation, and it does not take account of your objectives or circumstances. Forecasts and guidance are estimates, not promises: companies miss their own guidance and analysts' figures are often revised. Prices can fall as well as rise, and you can lose money. See our disclaimer.

Share-price performance

Market data may be delayed

Recent prices are available. Older price history and the statistics that need it are being loaded in the background.

What moved the share price

Last 12 months −57.2%

$2.43 on October 31, 2025 to $1.04

ThenNowEffect
Revenue (last 12 months) $49m $47m −3.3%
P/S multiple 2.8x 1.3x −51.8%
Share count 55m 60m −8.3%

Biggest factor: p/s multiple. Loss-making at one end, so the split uses price/sales.

Last 3 years −12.6%

$1.19 on November 3, 2023 to $1.04

ThenNowEffect
Revenue (last 12 months) $54m $47m −13.3%
Net margin 152.5% 15.7% −89.7%
P/E multiple 0.7x 8.5x +1137.8%
Share count 47m 60m −20.9%

Biggest factor: p/e multiple.

The effects multiply back to the price change exactly. Results are the last 12 months as known on each date (filings assumed public 45 days after quarter end).

Return and risk by year

Calendar year 202120222023202420252026 to date
Return
SPRO−17%−89%−15%−30%+126%−55%
Industry peers (median)−36%−56%−18%−28%−5%−26%
S&P 500+29%−18%+26%+25%+18%+11%
Months that ended higher
SPRO33%17%42%33%25%36%
S&P 50075%42%67%75%75%46%
Largest fall from a high during the year
SPRO−43%−96%−50%−49%−49%−65%
S&P 500−5%−25%−10%−8%−19%−9%

Worst fall since November 2, 2017: 98% from December 28, 2020 to April 8, 2025. Getting back needed a 3841% gain, and the shares have not yet recovered.

Price behaviour

52-week range
$1.04 – $2.98
From 52-week high
−65.1%
vs 50-day average
−11.2%
vs 200-day average
−47.4%
Volatility (1 year)
64%
Beta vs S&P 500
1.52

Volatility is the annualised standard deviation of daily returns. Beta 1.5 means the shares typically moved 1.5% for each 1% move in the S&P 500 over the past year. Prices to November 2, 2026.

Share price after results

Next day
3 up, 9 down
typical move ±6.2%
After a week
4 up, 8 down
typical move ±8.7%
After a month
3 up, 9 down
typical move ±42.8%
Results releasedNext dayS&P 500 next day5 days21 days
August 12, 2026 +0.8% +0.9% 0.0% −8.1%
May 13, 2026 +8.7% +1.4% +3.5% +12.2%
March 26, 2026 −3.3% −3.5% +0.8% +10.8%
November 13, 2025 −9.4% −1.7% −15.0% −13.9%
August 12, 2025 −12.0% +1.4% −16.4% −11.4%
May 13, 2025 +6.6% +0.8% +11.5% +373.8%
March 27, 2025 −13.8% −2.3% −29.9% −20.2%
January 10, 2025 −5.1% −1.4% −9.0% −17.9%
November 14, 2024 −9.9% −1.9% −9.2% −18.3%
October 29, 2024 0.0% −0.1% +1.6% −12.4%
August 5, 2024 −3.1% −2.0% −1.5% 0.0%
May 15, 2024 −1.9% +1.0% −5.9% −15.0%

From the close before the release date to the close 1, 5 and 21 trading days after it, so releases before the open and after the close are both captured. Past moves don't predict future ones.

Spero Therapeutics, Inc. in five measures

Fundamentals grade B
Growth Profitability Cash Balance sheet

Growth, profitability, cash generation and balance sheet are percentiles against the companies we cover in the same industry, from SEC filings (100 = best). Value compares the share price with our modelled value range (50 = at our base value; higher = cheaper). A description of reported data and our model — not a quality score or advice.

Fundamentals

Revenue (TTM) Spero Therapeutics, Inc.
$0 $50M $100M $150M FY23 Q3 FY24 Q2 FY25 Q1 FY26 Q2 Revenue (TTM), FY23 Q3: $77.7M Revenue (TTM), FY23 Q4: $103.8M Revenue (TTM), FY24 Q1: $111M Revenue (TTM), FY24 Q2: $118.5M Revenue (TTM), FY24 Q3: $106.5M Revenue (TTM), FY24 Q4: $48M Revenue (TTM), FY25 Q1: $44.6M Revenue (TTM), FY25 Q2: $48.6M Revenue (TTM), FY25 Q3: $40.5M Revenue (TTM), FY25 Q4: $66.8M Revenue (TTM), FY26 Q1: $61.2M Revenue (TTM), FY26 Q2: $47M $47M

Source: SEC EDGAR filings. Retrieved October 29, 2026.

View chart data
Period Revenue (TTM)
FY23 Q3 $77.7M
FY23 Q4 $103.8M
FY24 Q1 $111M
FY24 Q2 $118.5M
FY24 Q3 $106.5M
FY24 Q4 $48M
FY25 Q1 $44.6M
FY25 Q2 $48.6M
FY25 Q3 $40.5M
FY25 Q4 $66.8M
FY26 Q1 $61.2M
FY26 Q2 $47M
Revenue growth, TTM YoY Spero Therapeutics, Inc.
-500% 0% 500% 1000% FY23 Q3 FY24 Q2 FY25 Q1 FY26 Q2 Revenue growth, TTM YoY, FY23 Q3: 781.7% Revenue growth, TTM YoY, FY23 Q4: 93.9% Revenue growth, TTM YoY, FY24 Q1: 107.4% Revenue growth, TTM YoY, FY24 Q2: 118.4% Revenue growth, TTM YoY, FY24 Q3: 37.0% Revenue growth, TTM YoY, FY24 Q4: -53.8% Revenue growth, TTM YoY, FY25 Q1: -59.8% Revenue growth, TTM YoY, FY25 Q2: -59.0% Revenue growth, TTM YoY, FY25 Q3: -61.9% Revenue growth, TTM YoY, FY25 Q4: 39.2% Revenue growth, TTM YoY, FY26 Q1: 37.2% Revenue growth, TTM YoY, FY26 Q2: -3.3% -3.3%

Source: SEC EDGAR filings. Retrieved October 29, 2026.

View chart data
Period Revenue growth, TTM YoY
FY23 Q3 781.7%
FY23 Q4 93.9%
FY24 Q1 107.4%
FY24 Q2 118.4%
FY24 Q3 37.0%
FY24 Q4 -53.8%
FY25 Q1 -59.8%
FY25 Q2 -59.0%
FY25 Q3 -61.9%
FY25 Q4 39.2%
FY26 Q1 37.2%
FY26 Q2 -3.3%
Operating margin (TTM) Spero Therapeutics, Inc.
-200% -150% -100% -50% 0% 50% FY23 Q3 FY24 Q2 FY25 Q1 FY26 Q2 Operating margin (TTM), FY23 Q3: -4.0% Operating margin (TTM), FY23 Q4: 20.7% Operating margin (TTM), FY24 Q1: 19.6% Operating margin (TTM), FY24 Q2: 13.1% Operating margin (TTM), FY24 Q3: -1.0% Operating margin (TTM), FY24 Q4: -152.9% Operating margin (TTM), FY25 Q1: -166.2% Operating margin (TTM), FY25 Q2: -118.4% Operating margin (TTM), FY25 Q3: -115.5% Operating margin (TTM), FY25 Q4: 9.5% Operating margin (TTM), FY26 Q1: 22.1% Operating margin (TTM), FY26 Q2: 12.8% 12.8%

Source: SEC EDGAR filings. Retrieved October 29, 2026.

View chart data
Period Operating margin (TTM)
FY23 Q3 -4.0%
FY23 Q4 20.7%
FY24 Q1 19.6%
FY24 Q2 13.1%
FY24 Q3 -1.0%
FY24 Q4 -152.9%
FY25 Q1 -166.2%
FY25 Q2 -118.4%
FY25 Q3 -115.5%
FY25 Q4 9.5%
FY26 Q1 22.1%
FY26 Q2 12.8%
FCF margin (TTM) Spero Therapeutics, Inc.
-100% -50% 0% 50% FY23 Q3 FY24 Q2 FY25 Q1 FY26 Q2 FCF margin (TTM), FY23 Q3: 37.3% FCF margin (TTM), FY23 Q4: -31.8% FCF margin (TTM), FY24 Q1: -12.8% FCF margin (TTM), FY24 Q2: -12.1% FCF margin (TTM), FY24 Q3: -16.5% FCF margin (TTM), FY24 Q4: -48.9% FCF margin (TTM), FY25 Q1: -74.9% FCF margin (TTM), FY25 Q2: -66.6% FCF margin (TTM), FY25 Q3: -68.2% FCF margin (TTM), FY25 Q4: -18.9% FCF margin (TTM), FY26 Q1: 11.8% FCF margin (TTM), FY26 Q2: 41.7% 41.7%

Source: SEC EDGAR filings. Retrieved October 29, 2026.

View chart data
Period FCF margin (TTM)
FY23 Q3 37.3%
FY23 Q4 -31.8%
FY24 Q1 -12.8%
FY24 Q2 -12.1%
FY24 Q3 -16.5%
FY24 Q4 -48.9%
FY25 Q1 -74.9%
FY25 Q2 -66.6%
FY25 Q3 -68.2%
FY25 Q4 -18.9%
FY26 Q1 11.8%
FY26 Q2 41.7%

Data: SEC EDGAR XBRL company facts (as filed in 10-K/10-Q); forms 10-K, 10-Q. Generated November 3, 2026. Definitions in our methodology.

Where the money goes

FY2025, from the 10-K

Each dollar Spero Therapeutics took in during FY2025, followed through to profit: what it cost to make, what went on research and running the business, and what was left after tax.

  1. Revenue $66.8M
  2. Other income $2.5M · 3.8%
  3. Research and development $38.5M · 57.6%
  4. Selling, general and admin $21.2M · 31.7%
  5. Other operating costs $845,000 · 1.3%
  6. Operating income $6.3M · 9.5%
  7. Net income $8.6M · 12.8%

Shares of revenue. Source: Spero Therapeutics's 10-K for FY2025, as filed with the SEC. "Other" lines are what the reported lines leave unexplained. Other income is income outside operations, such as investment gains.

Financial statements

US$ millions unless shown otherwise. Fiscal years, plus the last twelve months (LTM) when newer.

Fiscal year 2016 Dec 2016 2017 Dec 2017 2018 Dec 2018 2019 Dec 2019 2020 Dec 2020 2021 Dec 2021 2022 Dec 2022 2023 Dec 2023 2024 Dec 2024 2025 Dec 2025 LTM Jun 2026
Income
Revenue 0 2 4 18 9 18 54 104 48 67 47
EBITDA −33 −41 −42 −62 −78 −87 −41 22 −73 6 —
Operating income −33 −42 −43 −63 −79 −88 −42 21 −73 6 6
Net income −25 −39 −42 −61 −78 −90 46 23 −69 9 7
Diluted EPS −$11.98 −$17.82 −$2.60 −$3.35 −$3.52 −$2.91 −$1.23 $0.43 −$1.27 $0.15 $0.12
Growth (year on year)
Revenue — +490.7% +100.4% +357.6% −48.6% +95.7% +193.1% +94.0% −53.8% +39.2% −3.3%
EBITDA — — — — — — — — −435.8% — —
Operating income — — — — — — — — −441.5% — —
Net income — — — — — — — −50.9% −400.6% — —
Diluted EPS — — — — — — — — −395.3% — —
Margins
EBITDA margin <−999% <−999% <−999% −344.2% −839.8% −478.3% −77.2% 21.1% −152.9% 9.5% —
Operating margin <−999% <−999% <−999% −348.4% −847.9% −481.9% −78.9% 20.7% −152.9% 9.5% 12.8%
Net margin <−999% <−999% <−999% −335.6% −839.2% −491.9% 86.7% 22.0% −142.9% 12.8% 15.7%
Free-cash-flow margin <−999% <−999% <−999% −277.4% −922.1% −352.5% −14.4% −31.8% −48.9% −18.9% 41.7%
Cash flow
Cash from operations −29 −39 −40 −50 −86 −64 −8 −33 −23 −13 20
Capital spending 1 0 2 0 0 0 0 0 0 0 0
Free cash flow −30 −39 −42 −50 −86 −64 −8 −33 −23 −13 20
Stock-based pay 0 1 3 4 5 9 9 8 8 4 4
Free cash flow after stock pay −30 −41 −45 −54 −91 −74 −17 −41 −31 −17 16
Balance sheet
Cash 10 87 34 30 85 113 109 76 53 40 51
Total debt 0 0 0 0 0 0 0 0 0 0 0
Net debt (negative = net cash) −10 −87 −34 −29 −85 −112 −109 −76 −53 −40 −51
Diluted shares 2m 3m 16m 18m 22m 31m 38m 53m 54m 59m 60m

Source: SEC EDGAR XBRL company facts (US and foreign periodic filings); column headings link to the filing. EBITDA is operating income plus depreciation and amortisation. Free cash flow is cash from operations minus capital spending. Growth is left blank when last year's figure was a loss or under 2% of revenue. Share counts and EPS are restated for stock splits. A dash means the company didn't report the figure.

Financial health

2 of 2 checks passed · June 30, 2026
What it owns · $53m
Short-term assets $52mLonger-term assets $1m
What it owes, and who funded it · $53m
Short-term liabilities $8mLonger-term liabilities $0mShareholders' equity $44m
  • Short-term assets cover short-term liabilities $52m of assets due within a year against $8m of liabilities due within a year.
  • Short-term assets cover long-term liabilities $52m short-term assets against $134,000 of longer-dated liabilities.
  • More cash than debt Cash or debt not separately reported. Not assessable.
  • Debt below 40% of shareholders' equity Equity or debt not reported. Not assessable.
  • Debt burden no higher than five years ago Five-year comparison not available. Not assessable.
  • A year's operating cash flow covers at least 20% of debt Cash flow or debt not reported. Not assessable.
  • Operating profit covers interest at least five times over Interest not separately reported. Not assessable.

From Spero Therapeutics, Inc.'s latest balance sheet as filed. Checks are fixed, documented rules (methodology), counted only where the company reports the figures — a dot means the filing doesn't break the item out. Descriptions of reported data, not advice.

Dividends, buybacks and capital spending

Diluted share count
+9.1%
year over year
R&D spending
43.7%
of revenue

Competitors: side by side with peers

Closest by revenue in biotechnology
Last 12 months unless stated SPRO EDIT STRO OCUL LXRX GOSS Median
Revenue, last 12 months $47m $47m $46m $52m $41m $53m $56m
Revenue growth, last 12 months −3.3% 20.8% −56.3% −8.1% −29.0% 32.4% 12.6%
Revenue growth, 3-year average −4.7% 34.5% −7.0% −1.6% 366.7% — 13.7%
Revenue growth, latest quarter −100.0% 232.3% −84.6% 0.1% −97.6% −19.6% 10.2%
Gross margin — — — 87.1% 99.1% — 82.9%
Operating margin 12.8% −161.4% −319.6% −603.0% −131.4% −311.7% −189.4%
Operating margin, 3-year average −30.8% −365.3% −192.8% −397.7% <−999% −252.1% −363.5%
Net margin 15.7% −157.3% −395.2% −579.1% −147.4% −235.0% −169.8%
Cash from operations / revenue 41.7% −255.0% −317.7% −457.7% −156.7% −305.2% −168.0%
Free-cash-flow margin 41.7% −256.5% −330.9% −490.1% −156.7% −305.2% −162.4%
Free-cash-flow margin, 3-year average −12.3% −346.4% −208.2% −318.3% <−999% −231.0% −310.0%
Stock pay / revenue 8.5% 18.4% 14.8% 102.4% 30.4% 26.9% 20.0%
Change in share count 9.1% 21.7% 20.6% 26.4% 7.9% 14.3% 8.2%

Median of all 184 companies we cover in biotechnology. Shaded: best of the six on that line (lowest for stock pay and share-count growth). 3-year figures average the last three 12-month periods; 3-year growth is compound annual. Source: SEC filings.

Peer comparison

184 biotechnology companies
Measure Company Peer median Rank
Revenue growth Growth -3.3% 12.6% 112 of 172
Change in growth rate Growth -40.5pp -0.1pp 140 of 172
Operating margin Profitability 12.8% -189.4% 27 of 175
Net margin Profitability 15.7% -157.3% 27 of 180
Free-cash-flow margin Cash generation 41.7% -145.4% 11 of 176
Stock pay as % of revenue Cash generation 8.5% 19.2% 53 of 179
Change in share count Balance sheet 9.1% 7.9% 86 of 156

Rank 1 = best in the group (for spending, debt and dilution, lower ranks first).

Where the revenue comes from

Fiscal year to December 31, 2025
Products and services
Line of business Revenue Share YoY
Collaboration Revenue Related Party $47M 70.4% ▲ 74.0%
Collaboration Revenue $12.6M 18.8% ▲ 3292.5%
Grant Revenue $7.2M 10.8% ▼ 65.1%

From Spero Therapeutics, Inc.'s 10-K filed March 26, 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
$47.5M
Institutions reporting
60
Shares held vs prior quarter
▲ 1.9%
Positions opened / closed
21 / 12

Top buyers and sellers, Q2 2026: 38 institutions bought and 18 sold ; the biggest buyer was Raymond James Financial Inc (+522K shares) and the biggest seller Anson Funds Management LP (−844K). See which funds bought and sold →

Largest reported holders, June 30, 2026
Manager Value Shares Share of 13F value Shares QoQ
Gsk PLC $20.3M 9.2M 42.7% 0.0%
Pfizer Inc $5.3M 2.4M 11.2% 0.0%
Vanguard Capital Management LLC $4.5M 2.0M 9.5% ▲ 13.1%
Renaissance Technologies LLC $2.1M 948K 4.4% ▼ 20.3%
Alphabet Inc. $2M 890K 4.1% 0.0%
Susquehanna International Group, LLP $1.7M 759K 3.5% ▲ 127.9%
Blackrock, Inc. $1.3M 594K 2.8% ▲ 37.2%
Geode Capital Management, LLC $1.3M 566K 2.6% ▲ 8.9%
Raymond James Financial Inc $1.2M 522K 2.4% New
Two Sigma Investments, LP $846,019 383K 1.8% ▼ 56.8%
Arrowstreet Capital, Limited Partnership $735,864 333K 1.5% New
Vanguard Fiduciary Trust Co $635,702 288K 1.3% ▲ 8.9%

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 Spero Therapeutics, Inc.'s complete shareholder register. Values are as reported by the filers .

Insider trading activity

Full insider history and chart
Insider purchases History → $0 0 trades by 0 insiders, last 12 months Insider sales History → $552,042 9 trades by 2 insiders · 0% under pre-set plans
Net ▼ $552,042 net selling
Insider Date Trade Shares Price Value
Rajavelu Esther See Remarks May 4, 2026 Sell 25,240 $2.51 $63,352
Keutzer Timothy Chief Operating Officer February 6, 2026 Sell 18,652 $2.36 $44,019
Rajavelu Esther See Remarks February 6, 2026 Sell 50,816 $2.36 $119,926
Rajavelu Esther See Remarks February 6, 2026 Sell 37,101 $2.36 $87,558
Keutzer Timothy Chief Operating Officer February 4, 2026 Sell 3,471 $2.24 $7,775
Keutzer Timothy Chief Operating Officer February 3, 2026 Sell 24,224 $2.14 $51,839
Rajavelu Esther See Remarks February 2, 2026 Sell 18,442 $2.20 $40,572
Keutzer Timothy Chief Operating Officer February 2, 2026 Sell 18,891 $2.20 $41,560
Rajavelu Esther See Remarks November 7, 2025 Sell 40,270 $2.37 $95,440

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 12, 2026 estimated from the company's past filing pattern, not announced

  • August 12, 2026
  • May 13, 2026
  • March 26, 2026
  • November 13, 2025
  • August 12, 2025
  • May 13, 2025

Recent SEC filings

Data status

When each part of this page on Spero Therapeutics, Inc. was last updated.

DataLast updatedSource
Share priceExchange closing prices
Financial statementsSEC 10-K and 10-Q filings
News and updatesCompany releases and SEC 8-K filings
Analyst estimatesAggregated analyst estimates
Valuation and scoresOur models, from the filed figures

How we build and check these figures: methodology and data sources.

Spero Therapeutics, Inc. in brief

What does Spero Therapeutics, Inc. do?
Spero Therapeutics, Inc. is a US-listed company in the biotechnology industry. Its financial year ends in December.
What is Spero Therapeutics, Inc.'s stock ticker?
Spero Therapeutics, Inc. trades under the ticker SPRO on Nasdaq. This page brings together its financial statements, valuation models, ownership and recent company updates.
What is Spero Therapeutics, Inc.'s revenue, and how fast is it growing?
Over its most recent trailing twelve months, Spero Therapeutics, Inc. reported revenue of $47M, 3.3% lower than a year earlier, according to its SEC filings.
What is Spero Therapeutics, Inc.'s free cash flow?
Spero Therapeutics, Inc.'s free-cash-flow margin is 41.7% of revenue over the trailing twelve months, ranking 11 of the 176 biotechnology companies we cover.
Who are Spero Therapeutics, Inc.'s largest institutional shareholders?
By value reported in 13F filings for June 30, 2026, the largest reported holders are Gsk PLC, Pfizer Inc and Vanguard Capital Management LLC. 13F reports cover long US-listed positions of managers above $100M, filed up to 45 days after quarter end.
What is Spero Therapeutics, Inc.'s market cap?
On November 2, 2026, Spero Therapeutics, Inc.'s market capitalisation was about $62.4M, with a price-to-earnings ratio of 8.5 and net debt of -$50.7M. Market figures come from third-party market data and may be delayed.
Who are Spero Therapeutics, Inc.'s competitors?
In our Biotechnology peer group, the companies closest to Spero Therapeutics, Inc. are Editas Medicine, Inc., Sutro Biopharma, Inc., Ocular Therapeutix, Inc, Lexicon Pharmaceuticals, Inc. and Gossamer Bio, Inc. The side-by-side comparison below sets their revenue, margins and growth against Spero Therapeutics, Inc.'s.
Are insiders buying or selling Spero Therapeutics, Inc. stock?
Over the last 12 months, Spero Therapeutics, Inc.'s directors and officers reported 0 open-market purchases and 9 sales on Form 4. The insider trading page charts every trade.
When is Spero Therapeutics, Inc.'s next earnings date?
Around November 12, 2026, estimated from the spacing of its past results announcements (8-K filings). That is an estimate, not a confirmed date — Spero Therapeutics, Inc. announces its own schedule.