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.
Funding
All startups| 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.
Notes
top- J&J's own press release pages returned an error page to my fetches.
Pages like this
not linked directly; found by shared links- CompanyPhotys Therapeutics
Shares MPM BioImpact, PROTACs & molecular glues (targeted protein degradation).
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Shares Degrader-antibody conjugate (DAC), PROTACs & molecular glues (targeted protein degradation).
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Shares Degrader-antibody conjugate (DAC), PROTACs & molecular glues (targeted protein degradation), Antibody-drug conjugate (ADC).
- CompanyPrelude Therapeutics
Shares Degrader-antibody conjugate (DAC), PROTACs & molecular glues (targeted protein degradation).
- IdeaUse antibodies to deliver protein-destroying drugs into the right cells
Shares Degrader-antibody conjugate (DAC), PROTACs & molecular glues (targeted protein degradation), Antibody-drug conjugate (ADC).
- TechnologyAntibody-oligonucleotide conjugates
Shares Degrader-antibody conjugate (DAC), Antibody-drug conjugate (ADC).
- IdeaEfflux-agnostic therapy for mesenchymal TNBC
Shares Degrader-antibody conjugate (DAC), Antibody-drug conjugate (ADC).
- Key paperThe first PROTAC: a chimeric molecule that tags a protein for destruction
Shares Degrader-antibody conjugate (DAC), PROTACs & molecular glues (targeted protein degradation).