IO Biotech
The business, the turning points, and the decisions behind them.
01 / WHAT IT BUILT
What the company did
IO Biotech was a Copenhagen-based cancer immunotherapy company developing therapeutic cancer vaccines built around its T-win platform, which induces T-cell responses against antigens expressed by immune-suppressive cells in the tumor microenvironment. Its lead asset was Cylembio (IO102-IO103), an off-the-shelf peptide vaccine designed to stimulate T cells against IDO1- and PD-L1-expressing cells alongside checkpoint inhibitors. The company listed on Nasdaq in November 2021, raising approximately $115 million. After the FDA advised against filing for approval in September 2025, IO Biotech ceased operations and filed for Chapter 7 bankruptcy on March 31, 2026.
02 / IO Biotech FAILURE REASONS
Failure factors
IO Biotech's pivotal Phase 3 of Cylembio+Keytruda in advanced melanoma narrowly missed statistical significance (p=0.056); FDA in Sep 2025 advised against a BLA, after which the company cut staff, explored alternatives, and (per SEC 8-K reported in those articles) ceased operations / filed liquidation bankruptcy — primary cause chain is clinical miss + regulatory refusal of approval path.
Phase 3 Cylembio+Keytruda narrowly missed PFS primary endpoint (p=0.056).
FDA advised against filing a biologics license application for Cylembio.
Cash runway (~$31M end-Sep 2025) insufficient after FDA rebuff; strategic alternatives failed.
03 / EVENT HISTORY
Events in the structured record
- Nasdaq IPO
IO Biotech lists its shares on Nasdaq, raising approximately $115 million to fund Phase 3 development of Cylembio in melanoma.
- FDA setback
The FDA advises IO Biotech not to submit Cylembio for approval, after the vaccine narrowly missed its primary endpoint in a Phase 3 melanoma trial versus Keytruda. The company halves its headcount.
- Chapter 7 bankruptcy
After considering strategic alternatives, IO Biotech ceases operations, terminates all employees, and files for Chapter 7 bankruptcy on March 31, 2026; a Delaware court-appointed trustee takes control to liquidate the assets.
04 / CONTEMPORARY REBUILD ASSESSMENT
Difficulty of rebuilding this project today
Material for this section is being gathered and checked. It will appear here once ready.
Overall assessment: Not completed
05 / CAUSAL CHAIN
How the factors connect
- 01
In November 2021 IO Biotech raised approximately $115 million through its Nasdaq IPO, plus a €22.5 million finance contract drawdown from the European Investment Bank (later declared in default).
- 02
On March 31, 2026 the company filed for Chapter 7 bankruptcy; a Delaware bankruptcy court trustee takes control of the assets and liabilities to liquidate them, with proceeds going first to creditors.
- 03
All directors stepped down and all employees were terminated; the company stated it is unlikely that common stockholders will receive any payment following the proceedings.