Sionna Therapeutics, Inc.
SION evidence brief
What we can confirm
- BioSniper Score:
- 6.5 / 10
- Market Cap:
- $338.2M
- Lead Asset:
- galicaftor (Phase 2)
What it means
What to watch
Prepared research question
What matters most for SION—catalysts, financial risk and supporting evidence?
Traceable citations · Unknowns marked
BioSniper AI · SION
Sionna Therapeutics (SION) is a clinical-stage biopharmaceutical company developing novel medicines for cystic fibrosis, currently refocusing its pipeline after a Phase 2a miss for lead candidate SION-719 and advancing a dual combination program (SION-451 + SION-2222) into Phase 2a.
Key risk: Pipeline concentration risk
BioSniper Score
Based on 4 of 6 signals
Market Cap
$338.2M
Cash Runway
—
Lead Asset
galicaftor (Phase 2)
Next Catalyst
—
Financial data as of Jun 30, 2026.
Tracking 8 pipeline candidates · 2 clinical trials for Sionna Therapeutics, Inc..
Sionna Therapeutics (SION) is a clinical-stage biopharmaceutical company developing novel medicines for cystic fibrosis, currently refocusing its pipeline after a Phase 2a miss for lead candidate SION-719 and advancing a dual combination program (SION-451 + SION-2222) into Phase 2a.
- Cash & equivalents of $63.3M as of 2026-06-30 [sec].
- Net income of -$29.9M for the period ending 2026-06-30 [sec].
- Shareholders' equity of $265.8M as of 2026-06-30 [sec].
- Lead candidate SION-719 failed to meet key activity endpoint in a Phase 2a proof-of-concept trial as add-on to Trikafta, prompting discontinuation in that setting [news · 2026-08-10].
- Company plans to advance SION-451 + SION-2222 dual combination into Phase 2a in Q1 2027, supported by post hoc analyses showing up to -8.6 mmol/L sweat chloride reduction [news · 2026-09-14].
What works
- Post hoc analyses of the SION-719 PreciSION CF subset showed a mean placebo-adjusted sweat chloride reduction of up to -8.6 mmol/L, consistent with NBD1 biological activity, supporting the dual combination approach [news · 2026-09-14].
- The company has a substantial cash position of $63.3M as of 2026-06-30 and management estimates that cost-saving measures, including a 46% workforce reduction, extend cash runway into the second half of 2029 [news · 2026-09-14].
- Sionna has a partnered pipeline with AbbVie, including in-licensed TMD1-directed CFTR corrector SION-2222 (galicaftor) [pipeline].
What to weigh
- Lead candidate SION-719 failed to meet its key activity endpoint in a Phase 2a proof-of-concept trial as an add-on to Trikafta, leading to program discontinuation in that setting [news · 2026-08-10].
- The company reported a net loss of -$29.9M for the period ending 2026-06-30 [sec].
- A 46% workforce reduction was approved to preserve capital, indicating significant operational restructuring [news · 2026-09-17].
- The dual combination program (SION-451 + SION-2222) is still early-stage (Phase 1 data supportive but not yet proof-of-concept in patients) [news · 2026-08-10].
From the filings
Quoted directly from source documents.
SION-719 failed to meet key activity endpoint in Phase 2a
“Precision CF Trial Did Not Meet Its Key Activity Endpoint”
News · August 10, 2026
Post hoc analyses showed sweat chloride reduction consistent with NBD1 activity
“Post hoc analyses of SION-719 PreciSION CF subset showed a mean placebo-adjusted sweat chloride reduction of up to -8.6 mmol/L consistent with NBD1 biological activity”
News · September 14, 2026
Workforce reduction of 46% to extend cash runway
“46% workforce reduction and other cost-saving measures prioritize advancing the dual combination program and extend cash runway into the second half of 2029”
News · September 14, 2026
Catalyst timeline
- 2025-07-23 · Phase 1 start for SION-451 and combinations — Phase 1 study evaluating safety, tolerability, and PK of SION-451 and combinations with SION-2222 and SION-109 in healthy participants.
- 2025-11-03 · Phase 2a start for SION-719 + Trikafta — Phase 2a proof-of-concept study of SION-719 added to Trikafta in F508del homozygous CF patients.
Risks & what to watch (4)›
Key risks
- Pipeline concentration risk — After SION-719 discontinuation, the entire pipeline hinges on early-stage dual combination SION-451 + SION-2222 [news · 2026-08-10].
- Clinical execution risk — Phase 2a for dual combo not yet initiated; proof-of-concept data expected no earlier than late 2027 [news · 2026-09-14].
- Cash burn rate — Net loss of -$29.9M in a single quarter (Q2 2026) implies high burn relative to $63.3M cash [sec].
- Competitive landscape — Vertex's Trikafta and Alyftrek dominate CF market; Sionna's candidates must demonstrate differentiation [pipeline].
What to watch
- Initiation of Phase 2a trial for SION-451 + SION-2222 dual combination, expected Q1 2027 [news · 2026-09-14].
- Cash runway updates: management estimates extension into H2 2029, but actual burn rate will be key [news · 2026-09-14].
- Any new partnership or financing moves given the reduced workforce and pipeline refocus [news · 2026-09-17].
Sources: Catalysts · News · Pipeline · Generated October 12, 2026 · How we verify sources →
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Evidence & data
Score breakdownBased on 4 of 6 signals · derived from public data
Cash runway data unavailable
D/E 0.07 · 0% dilution
Lead: Phase 2
8 candidates
No upcoming catalysts tracked
0 buys · 19 sells (180d)
Pipeline
Regulatory
Financials
Institutional Holdings
Source: SEC Form 13F · as of Mar 2026Institutional holders
122
Total value held
$1.79B
| Holder | Shares | Value |
|---|---|---|
| ra capital management, l.p. | 9,905,045 | $397.1M |
| tpg gp a, llc | 6,494,962 | $260.4M |
| orbimed advisors llc | 3,530,702 | $141.5M |
| viking global investors lp | 3,195,181 | $128.1M |
| atlas venture life science advisors, llc | 2,995,602 | $120.1M |
| enavate sciences gp, llc | 2,478,030 | $99.3M |
| jennison associates llc | 1,451,220 | $58.2M |
| jpmorgan chase & co | 1,465,014 | $53.7M |
| blackrock, inc. | 1,295,867 | $52.0M |
| citadel advisors llc | 1,166,931 | $46.8M |
Showing top 10 of 122 institutional holders of Sionna Therapeutics, Inc.. Open the full 13F history after sign-in.
Short Interest
as of Apr 30, 2026- % of float
- 14.0%
- Days to cover
- 9.8
- Shares short
- 3,799,971
- Daily short volume
- -
Short percent of float and days-to-cover reflect reported short positioning. Daily short volume is the exchange-reported short share of a single day's trading volume and is noisier. See the most-shorted biotech ranking →
SION short interestGovernance
Frequently asked questions
What is the AI investment thesis for Sionna Therapeutics, Inc.?
Sionna Therapeutics (SION) is a clinical-stage biopharmaceutical company developing novel medicines for cystic fibrosis, currently refocusing its pipeline after a Phase 2a miss for lead candidate SION-719 and advancing a dual combination program (SION-451 + SION-2222) into Phase 2a.
What is Sionna Therapeutics, Inc.'s lead drug candidate?
Sionna Therapeutics, Inc.'s most advanced tracked candidate is galicaftor (Phase 2) for Cystic fibrosis.
Who is the CEO of Sionna Therapeutics, Inc.?
Mr. Michael Cloonan M.B.A. is the chief executive officer of Sionna Therapeutics, Inc. (SION).
Where is Sionna Therapeutics, Inc. headquartered?
Sionna Therapeutics, Inc. (SION) is headquartered in Waltham, MA, United States.
What therapeutic areas does Sionna Therapeutics, Inc. focus on?
Sionna Therapeutics, Inc. develops therapies across Rare Disease, Respiratory.
The AI overview and BioSniper Score are neutral, data-derived signals built from public SEC filings, ClinicalTrials.gov and FDA records — not investment advice.