Teaching the body's oldest cellular predators - macrophages - to eat tumors. The drug is PHST001. The target is CD24. The metaphor is, frankly, on the nose.
Forty people. A handful of fume hoods. A clinical trial enrolling patients with ovarian cancer, endometrial cancer, and cholangiocarcinoma. Somewhere in a freezer, vials of an IgG4 monoclonal antibody called PHST001 sit at minus eighty, waiting their turn at the centrifuge. This is what a clinical-stage biotech looks like in 2026 - quieter than the press releases suggest, and busier than the Series A pitch deck implied.
Pheast Therapeutics has been around since 2020. It is not yet a household name. It is, however, the second act of one of the most consequential research lineages in cancer immunology - the same Stanford lab that produced Forty Seven Inc., the CD47 startup Gilead bought for roughly $4.9 billion. The founders are mostly the same. The strategy has changed.
This time the target is CD24. The bet is that the immune system's first responders - macrophages - have been kept on the bench for too long.
CD24 is a protein many cancers crank up to send a chemical message to macrophages: don't eat me. The message lands on a receptor called Siglec-10, and the macrophages politely move on. Tumors stay alive.
An anti-CD24 monoclonal antibody designed to block that handshake. With CD24 silenced, macrophages do what evolution built them to do: phagocytose the cancer cell.
The founders previously discovered CD47's role as a 'don't eat me' signal and built Forty Seven around it. Gilead acquired the company in 2020. CD24 was the second signal Amira Barkal's 2019 Nature paper described.
Phase 1a established tolerability. Phase 1b puts PHST001 next to cytotoxic chemotherapies in ovarian, endometrial, and cholangiocarcinoma - cancers where CD24 is heavily expressed.
Both programs share an underlying conviction: the innate immune system has more to give than oncology has historically asked of it.
"Expanding the landscape of next-generation innate immunotherapies for patients with aggressive cancers who need better treatment options." - Pheast Therapeutics
A founding team that doubles as a chapter in modern cancer immunology textbooks.
Pioneered the discovery of macrophage 'don't eat me' signaling. Co-founder of Forty Seven.
Hematologist-oncologist; co-founder of Forty Seven; central to the CD47 story.
Lead author on the 2019 Nature paper identifying CD24 as a 'don't eat me' signal. Served as interim CEO at Pheast's launch.
The freezers are humming. The vials are still there. But by April 2026 the story attached to them has changed shape: PHST001 is no longer a theoretical antibody whose only credentials are mouse data and a clever name. It is a drug that has been infused into human beings, generated a pharmacokinetic curve someone can graph, and shown the kind of receptor occupancy that medicinal chemists wait years to see.
None of that proves it will work. Phase 1a never does. But the macrophages, in some patients, are getting their first credible invitation to the dinner table in decades of oncology drug development. The forty people in Redwood City are betting that this time, they show up hungry.