Market reactionShares fell 12% on Nov 5.
Sionna Therapeutics is a clinical-stage company developing cystic fibrosis drugs that stabilize part of the CFTR protein; none of its products is approved.
Sionna's original case was SION-719, added to Trikafta to stabilize the NBD1 region of the CFTR protein. In the PreciSION CF Phase 2a trial it did not reduce sweat chloride versus placebo, and Sionna stopped developing it as an add-on. The company now plans to test SION-451 with SION-2222 as a replacement for Trikafta in AscenSION CF, starting in the first quarter of 2027. It cut about 46% of its workforce, and cash of $268.3 million is expected to last into the second half of 2029.
Thesis checklist
0 risks need attention
Why it is in this state
The evidence, what would weaken it and the source filing
Why it is in this state
The evidence, what would weaken it and the source filing
Why it is in this state
The evidence, what would weaken it and the source filing
Next decision point
Tests: AscenSION CF shows the combination works in patients
Does switching from Trikafta to SION-451 plus SION-2222 keep or improve sweat chloride in F508del patients?
Strong, inconclusive and weak outcomes
What to look for in the result and how each would move the checklist
Price and material events
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Sionna's add-on drug failed; a new two-drug combination starts Phase 2a in 2027
PreciSION CF Phase 2a failed primary endpoint
About this history: every entry shows when the Thesis moved and what it said. The reasoning behind each move (the evidence, the analysis and the source filing) and the earnings write-ups are part of a subscription.
Dates, trials and completed outcomes are open to everyone. What each upcoming milestone hinges on is part of a subscription.
Disease areas: Lung and respiratory diseases
Catalyst calendar · Upcoming FDA decisions · Thesis changes
Competitive landscape
2 peers tracked
Cash: Market-data provider estimate; measurement period unavailable.
Debt: Market-data provider estimate; a complete comparable filing balance is unavailable.
Quarterly burn: Estimated from trailing free cash flow; measurement period unavailable.
Net cash and estimated runway require verified matching measurement periods. Missing debt components are not assumed to be zero.
Runway: No underlying guidance available.