# Firefly Bio

Source: https://onco.cc/companies/firefly-bio/  
OnCo record `firefly-bio` (Company). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

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.

## Summary

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.

## Fields

- Kind: Company
- Last checked: 2026-09-10
- HQ: South San Francisco, CA
- Type: biotech
- Website: https://fireflybiologics.com/

## Notes

- J&J's own press release pages returned an error page to my fetches.

## Sources

- Official website: https://fireflybiologics.com/
- Series A press release: https://fireflybiologics.com/press-release-firefly-bio-debuts-with-94-million-series-a-financing/
- BioPharma Dive: J&J to acquire Firefly for $1B: https://www.biopharmadive.com/news/jnj-firefly-acquisition-deal-cancer-degrader-antibody-conjugate/822223/

## Connected records

- collections: [BioPharma Dive](https://onco.cc/collections/src-biopharma-dive/)
- fronts: [Antibody-Drug Conjugates](https://onco.cc/fronts/adcs/), [Targeted Therapy](https://onco.cc/fronts/targeted-therapy/)
- technologies: [Antibody-drug conjugate (ADC)](https://onco.cc/technologies/adc/), [Degrader-antibody conjugate (DAC)](https://onco.cc/technologies/degrader-antibody-conjugate/), [PROTACs & molecular glues (targeted protein degradation)](https://onco.cc/technologies/protac-degrader/)
- companies: [Johnson & Johnson](https://onco.cc/companies/johnson-johnson/), [Lilly Ventures](https://onco.cc/companies/lilly-ventures/), [MPM BioImpact](https://onco.cc/companies/mpm-bioimpact/), [Versant Ventures](https://onco.cc/companies/versant-ventures/)

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JSON: https://onco.cc/api/v1/entities/firefly-bio.json