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Firefly Bio
Firefly Bio attaches protein-destroying molecules to antibodies so they are delivered only into cancer cells, a new twist on antibody-drug conjugates. Johnson & Johnson bought the company for about 1 billion dollars in 2026.
Overview
Firefly Bio, incubated by Versant Ventures' Ridgeline Discovery Engine in Basel and based in the San Francisco Bay Area, develops degrader antibody conjugates (DACs): antibody-drug conjugates whose payloads are catalytic targeted protein degraders rather than conventional cytotoxics. Its proprietary Firelink linker is designed to reduce free payload in circulation and uptake by healthy cells, allowing lower doses; preclinical studies reported tumour regressions after single low doses in solid and haematological tumour models. The company emerged from stealth in February 2024 with a USD 94 million Series A co-led by Versant Ventures and MPM BioImpact with Decheng Capital and Eli Lilly. In June 2026 Johnson & Johnson agreed to acquire Firefly for USD 1 billion in cash, and the company reported completion of the acquisition on 29 July 2026.
Headquarters
South San Francisco, CA, US
Funding
All startupsAcquiredAcquired by Johnson & Johnson
Rounds on record
| Round | Year | Amount | Source |
|---|---|---|---|
| Acquisition · USD 1 billion in cash, announced 8 June 2026; completion announced on the company website 29 July 2026 | 2026 | $1B | biopharmadive.com |
| Series A | 2024 | $94M | fireflybiologics.com |
Amounts only where the cited source states them. Rounds without a public source are not listed.
Type
Stage
Acquired
Website
Notes
top- J&J's own press release pages returned an error page to my fetches.
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