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Sionna Therapeutics

SION on Nasdaq. Sionna Therapeutics develops medicines for people with cystic fibrosis. Market value $219m.

Watch this stockFree. We tell you when something changes.

Price checks use the past 12 months to June 2026. Quality checks use five annual reports, the latest for the year to December 2025.

Should I look at this?

Not a fit for our list right now

Why it could be worth it

What to watch out for

See Health care stocks that passed both tests

This is not advice. Check the numbers below.

Compare with another stock

Cash yield
past 12 months to June 2026
-35.5%low

For every $100 of what the whole company costs, it produced $-35.48 of spare cash in the past 12 months. A savings account pays about $4.

Price to profit
past 12 months to June 2026
n/a

The filings do not give us enough to work this out.

Return on capital
five annual reports to December 2025
n/a

The filings do not give us enough to work this out.

Quality score: not known. Price score: 0 of 100. Our list needs 70 on quality and 60 on price.

$4.75 a share, 18% above its 1-year low

Over the past year the price has ranged from $4.01 to $54.97.

Pays no dividend

Prices from Tuesday’s close (6 October).

Five years of cash, in billions

-0.1
-0.1
202512 monthsto Jun '26
Revenue
n/a
Operating margin
n/a
Debt to equity
0.00
Shares outstanding
0.05bn

Health checks

  • Free cash flow positive0 of 1 years
  • Accounting looks honest (Beneish)Not enough data
  • Financial strength (Piotroski)Not enough data
  • Profit backed by cash (accruals)Not enough data
  • Debt0.00× equity
  • Revenue growth, five yearsUnknown
  • Buying back its own sharesRoughly flat

The quarter to June 2026

How the business did, compared with the same quarter a year earlier.

  • A loss of $30 million, compared with a loss of $18 million a year ago.
  • 2% more shares than a year ago. Each share owns a bit less of the company.
  • It has $63 million more cash than debt, up from $41 million a year ago.
Profit by quarter
Profit by quarter
Quarter toAmount
March 2025-$16m
June 2025-$18m
September 2025-$20m
December 2025-$20m
March 2026-$27m
June 2026-$30m

From the company's quarterly reports to the SEC.

Dates

Next results (estimated)
n/a
Last annual report (10-K)
2 March 2026
Next quarterly (estimated, 10-Q)
5 November 2026

Who owns it

1 long-term investor we follow owns it, down from 2 last quarter. 147 funds in all.

Jun '25
Dec '25
Jun '26

Sold out this quarter

Largest holders overall

From 13F filings for the quarter ended 30 June 2026.

Big holders and activists

8 investors own more than 5%.

  • TPG GP A, LLC
    Passive investor
    at least 15.2%
    (filed with 2 related holders)
    Since 10 February 2025
    What they said

    The information set forth in or incorporated by reference in Items 2, 3, 5 and 6 of this Schedule 13D is incorporated by reference in its entirety into this Item 4. Initial Public Offering On February 6, 2025, the Issuer entered into an underwriting agreement (the "Underwriting…

    Read the filing
  • at least 14.3%−8.3 pts
    (filed with 4 related holders)
    Since 17 September 2026
  • Viking Global Investors
    Passive investor
    at least 7.1%+0.4 pts
    (filed with 9 related holders)
    Since 31 March 2026
  • Ott David C.
    Passive investor
    6.7%
    Since 10 February 2025
  • ORBIMED ADVISORS LLC
    Passive investor
    at least 6.6%−1.8 pts
    (filed with 1 related holder)
    Since 15 April 2026
    What they said

    The Reporting Persons from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer's business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in…

    Read the filing
  • Enavate Sciences GP, LLC
    Passive investor
    at least 5.6%
    (filed with 1 related holder)
    Since 10 February 2025
    What they said

    The Reporting Persons purchased the aforementioned securities for investment purposes with the aim of increasing the value of their investments and the Issuer. Subject to applicable legal requirements, one or more of the Reporting Persons may purchase additional securities of…

    Read the filing
  • Atlas Venture Fund XI, L.P.
    Passive investor
    at least 5.4%−1.1 pts
    (filed with 5 related holders)
    Since 16 October 2025
  • Qatar Investment Authority
    Passive investor
    at least 4.5%−0.5 pts
    (filed with 1 related holder)
    Since 31 March 2026
  • JPMORGAN CHASE & CO.
    Passive investor
    Sold down below 5%
    Since 30 September 2025

From Schedule 13D and 13G filings: anyone owning more than 5% must file one.

What insiders did

No insider bought shares on the open market in the last 12 months. 6 sold $178m, $135m of it under preset trading plans.

  • RA CAPITAL MANAGEMENT, L.P.
    Director
    Sold
    Date
    17 September 2026
    Shares
    3,448,811
    Price
    $6.33
    Value
    $22m
  • Thompson Peter A.
    Director
    Sold
    under a preset trading plan
    Date
    7 July 2026
    Shares
    85,918
    Price
    $44.86
    Value
    $4m
  • ORBIMED ADVISORS LLC
    Director
    Sold
    under a preset trading plan
    Date
    7 July 2026
    Shares
    85,918
    Price
    $44.86
    Value
    $4m
  • Fitzpatrick Jennifer
    Chief Legal Officer
    Sold
    under a preset trading plan
    Date
    6 July 2026
    Shares
    10,250
    Price
    $43.60
    Value
    $446,862
  • Thompson Peter A.
    Director
    Sold
    under a preset trading plan
    Date
    30 June 2026
    Shares
    115,844
    Price
    $45.50
    Value
    $5m
  • ORBIMED ADVISORS LLC
    Director
    Sold
    under a preset trading plan
    Date
    30 June 2026
    Shares
    115,844
    Price
    $45.50
    Value
    $5m
  • Thompson Peter A.
    Director
    Sold
    under a preset trading plan
    Date
    27 May 2026
    Shares
    101
    Price
    $44.49
    Value
    $4,493
  • ORBIMED ADVISORS LLC
    Director
    Sold
    under a preset trading plan
    Date
    27 May 2026
    Shares
    101
    Price
    $44.49
    Value
    $4,493
  • Thompson Peter A.
    Director
    Sold
    under a preset trading plan
    Date
    11 May 2026
    Shares
    184,639
    Price
    $46.22
    Value
    $9m
  • ORBIMED ADVISORS LLC
    Director
    Sold
    under a preset trading plan
    Date
    11 May 2026
    Shares
    184,639
    Price
    $46.22
    Value
    $9m

From Form 4 filings: insiders must report trades in their own company's shares within two days.

What could go wrong

Cheap for a reason is the question the numbers cannot answer.

Whether the price already reflects the risks is what the deep dive is for.

The deep dive

Everything above is arithmetic on public filings. The deep dive reads the last ten years of annual reports, the proxy statements, and the earnings calls, then argues the case the way Buffett, Klarman, and Hohn would, and checks every claim against the source.

  • What the business is worth, as a range, and the margin of safety at today’s price
  • Prices to start buying, buy, and buy hard
  • The three things that would make this a mistake
  • Every number footnoted to the filing it came from
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What a finished deep dive looks like

Not advice. Numbers on this page come from SEC filings and are updated each night; prices are updated again after the US market closes. The five-year figures are rounded.