Caption: A wildflower that survives the dry season, rendered as a logo. The sun clears the ridge - which is roughly what the company wants to do to your arteries.
Cancer doctors learned to point the immune system at tumors. Bitterroot Bio is pointing the same idea at the world's deadliest disease - your heart.
For half a century, the story of heart disease has been a story about cholesterol. Eat less of it, take a statin, lower the number, lower the risk. It worked - up to a point. The inconvenient part is the leftover: people on perfect cholesterol regimens still have heart attacks. Something else is lighting the fire inside the artery wall. Inside a 28-person company on Porter Drive, the suspect has a name, and it is not fat. It is the immune system.
Bitterroot Bio works in a field most people have never heard of - cardio-immunology - which is exactly the kind of phrase that means a discovery is still early. The premise is simple enough to fit on a napkin: the plaque that clogs arteries is not inert sludge. It is a slow, smoldering immune event, patrolled by macrophages that have been told, chemically, to stand down. Bitterroot's whole project is to revoke that order.
If that sounds borrowed from oncology, it is. The people who built this company built another one first.
Tumors survive by hanging out a molecular sign that reads "don't eat me." The protein doing the talking is called CD47, and it tells the immune system's cleanup crew - macrophages - to leave the cell alone. Cancer immunotherapy spent a decade learning to tear that sign down. One of the companies that did it, Forty Seven, was bought by Gilead for roughly $5 billion.
Bitterroot's founders helped write that chapter. Their second act asks an unreasonable-sounding question: what if artery plaque hangs out the same sign? If it does, the same trick - blocking CD47 - might let macrophages do in a blood vessel what they were prevented from doing in a tumor: clean up the mess.
That trick has a name. It is called BRB-002.
Note: BRB-002 is investigational and in clinical trials. Nothing here is an approved therapy or medical advice.
When Bitterroot stepped out of stealth in June 2023, the headline was not just the science - it was the check. A $145 million Series A, before a single dose in a human, is the kind of number that says investors believe the thesis, not just the team. Though they liked the team too.
*Revenue is negligible by design - this is a clinical-stage biotech, not a product company. Backers include ARCH Venture Partners, Deerfield Management, Google Ventures (GV) and Koch Disruptive Technologies.
Bitterroot reads like a who's-who of CD47 and cardiovascular medicine. Two Stanford scientists supplied the biology; seasoned biotech operators supplied the company-building.
For people who do everything right and still carry risk, an anti-inflammatory mechanism could address the part statins leave behind.
If cardio-immunology validates, heart disease joins the list of conditions treated by tuning the immune system - not just biochemistry.
It would show that hard-won cancer-immunotherapy biology can be redirected to the body's most common killer.
A team that exited once via CD47 is testing whether the same target can spawn a second franchise.
Bitterroot Bio launches publicly with a Series A it calls the largest ever for a preclinical CVD biotech, aimed at building cardio-immunology medicines.
First-in-human study of BRB-002 in healthy volunteers shows no serious adverse events and dose-dependent CD47 receptor occupancy reaching 100% - without anemia or thrombocytopenia.
Detailed Phase 1 results presented at the American College of Cardiology Annual Scientific Session 2025; anti-CD47 cardiovascular research also featured at AHA 2025.
First patient dosed in the Phase 2a proof-of-concept study in atherosclerosis patients in Australia, using 18F-FDG-PET/CT imaging to measure plaque inflammation. Initial results expected by year-end 2026.
Why Bitterroot thinks heart disease is partly an immune problem.
How the Forty Seven team reloaded the CD47 idea for hearts.
The "don't eat me" switch that could clean out arteries.
Where cholesterol drugs stop and inflammation begins.
What the Phase 2a trial is actually measuring.
Who wrote the checks - and why, pre-clinic.
The 50-year-old assumption is still standing. Cholesterol still matters; statins still work. But on Porter Drive, a small team has put a second suspect in the room and handed it a drug. By the end of 2026, the MATADOR data will say whether the immune system can be talked into cleaning out a blood vessel. The fire inside the artery wall has been burning quietly for decades. Bitterroot Bio is the first to show up with a hose - and ask the body's own cleanup crew to hold it.