The FDA advised IO Biotech last year to hold off on filing an approval application for its cancer vaccine Cylembio, pointing to a failed Phase 3 study in frontline advanced melanoma. The biotech has now gone under.
IO Biotech is calling it quits, unable to regain its bearings from an FDA rebuff in September that prevented an approval submission for its investigational cancer vaccine.
The Danish biotech has decided to wind down its operations “after considering all strategic alternatives,” according to a March 31 SEC document. IO has also filed for Chapter 7 bankruptcy, which will allow a Delaware bankruptcy court to appoint a trustee to liquidate all of the company’s assets, with an eye toward paying off debt and other outstanding obligations.
The trustee “will assume control over the assets and liabilities of the Company, effectively eliminating the authority and powers of the Board of Directors,” the regulatory filing reads. “It is unlikely that holders of the Company’s common stock will receive any payment or other distribution on account of those shares following the bankruptcy proceedings.”
As part of its bankruptcy petition, all of IO’s directors stepped down. The biotech also terminated all of its employees, though it remains unclear how many were still working at the company.
In September, IO announced it would halve its headcount, slimming its operations down to around 39 employees, BioSpace estimated at the time. Then, in January, IO implemented another round of cuts that it said would result in a “significant reduction” in force, though it did not specify how many people would be laid off.
The dramatic reductions in staff began when the FDA told IO in September that the company did not have enough evidence to back a biologics license application for its cancer vaccine candidate Cylembio.
IO had been testing Cylembio as a frontline therapy in combination with Merck’s mega-blockbuster Keytruda in a Phase 3 study of advanced melanoma. The trial “narrowly missed” its primary endpoint, IO reported in August 2025. Patients who were given Cylembio plus Keytruda saw a 23% reduction in the risk of disease progression or death as compared with Keytruda monotherapy, an effect that fell short of statistical significance with a p-value of 0.056.
“This is not the outcome we had hoped for,” CEO Mai-Britt Zocca said in a statement in September following the company’s meeting with the FDA. IO at the time said it would continue to engage with the FDA to align on the design of another registrational study for Cylembio. Monday’s closure announcement suggests that the company no longer plans to push forward with those plans.
As of Sept. 30, 2025, IO had $31 million in cash and cash equivalents, which it estimated would last until the first quarter of this year. The company has yet to report full-year 2025 earnings.
