# Bitterroot Bio

> Bitterroot Bio is a Palo Alto, California clinical-stage biotechnology company pioneering the field of cardio-immunology - the science of how the immune system drives heart disease. Founded by veterans of Forty Seven (the CD47 company Gilead bought for ~$5 billion), Bitterroot is turning the immune-checkpoint playbook from cancer toward atherosclerosis. Its lead candidate, BRB-002, is an immunomodulating protein that blocks the CD47 'don't eat me' signal on arterial plaque, prompting macrophages to clear inflammation and stabilize plaque - a mechanism that works differently from cholesterol-lowering drugs. The company launched out of stealth in June 2023 with a $145 million Series A, which it called the largest-ever round for a preclinical cardiovascular biotech.

- **Founded:** 2021
- **Headquarters:** Palo Alto, California, United States
- **Founders:** Nicholas Leeper (Co-founder; Stanford cardiologist and chief of vascular medicine), Irving L. Weissman (Co-founder; stem cell biologist, founding director of Stanford's Institute for Stem Cell Biology and Regenerative Medicine), Lou Lange (Co-founder; General Partner at Asset Management Ventures, former Chairman & CEO of CV Therapeutics), John C. Martin (Co-founder (late); former Chairman & CEO of Gilead Sciences)
- **Team size:** ~28 employees
- **Products:** BRB-002, Cardio-immunology pipeline
- **Notable:** Closed a $145M Series A in June 2023 - described as the largest-ever round for a preclinical CVD-focused biotech., Founded by veterans of Forty Seven, the CD47 company acquired by Gilead for ~$5 billion., Completed a Phase 1 first-in-human study of BRB-002 with no serious adverse events and 100% CD47 receptor occupancy at top doses, without anemia or thrombocytopenia.

## Products & services

- **BRB-002** — Lead investigational immunomodulating protein therapy that blocks the CD47/SIRP-alpha 'don't eat me' axis on atherosclerotic plaque. By freeing macrophages to clear plaque and dampen vascular inflammation, it aims to reduce plaque burden and the risk of major adverse cardiovascular events (MACE), distinct from lipid-lowering standards of care.
- **Cardio-immunology pipeline** — A broader discovery effort applying immune-modulation science - much of it borrowed from oncology checkpoint biology - to cardiovascular and inflammatory disease.

## Achievements

- Closed a $145M Series A in June 2023 - described as the largest-ever round for a preclinical CVD-focused biotech.
- Founded by veterans of Forty Seven, the CD47 company acquired by Gilead for ~$5 billion.
- Completed a Phase 1 first-in-human study of BRB-002 with no serious adverse events and 100% CD47 receptor occupancy at top doses, without anemia or thrombocytopenia.
- Dosed the first patient in the MATADOR Phase 2a study in atherosclerosis patients (June 2025).
- Presented anti-CD47 cardiovascular research at major cardiology meetings (ACC 2025, AHA 2025).

## Latest updates

- **2025-06** — Dosed the first patient in the MATADOR Phase 2a proof-of-concept study of BRB-002 in atherosclerosis patients in Australia; initial results expected by year-end 2026.
- **2025-03** — Presented detailed Phase 1 results of BRB-002 at the American College of Cardiology Annual Scientific Session 2025.
- **2025-01** — Reported Phase 1 safety and target-engagement data: no serious adverse events and dose-dependent CD47 receptor occupancy reaching 100%.
- **2023-06** — Launched out of stealth with a $145M Series A to develop cardio-immunology medicines.

## Links

- Website: https://bitterrootbio.com
- LinkedIn: http://www.linkedin.com/company/bitterroot-bio
- Twitter/X: https://twitter.com/BitterrootBio
- Facebook: https://facebook.com/profile.php?id=100090938607003

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Profile page: https://yespress.io/bitterroot-bio
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Last updated: 2026-06-29