In a lab off a side road in Burlingame, a small team is watching B cells disappear. Not slowly. Not partially. In their preclinical work, more than 99% of them are gone, and they are gone fast. The molecule doing the deleting is called HB2198, and in 2026 it crossed the line that separates a promising idea from a real drug: it went into people. Two Phase 1 trials are running now, one in patients living with lupus, one in healthy volunteers. This is Hinge Bio, and it is no longer theoretical.
For a company of roughly twenty people, that is a loud arrival. Hinge Bio does not have a campus or a marketing department or a household name. What it has is a platform with an unusually literal name and a thesis that most of the antibody world has spent decades politely ignoring: that the shape of a drug matters as much as its target.
The Problem They Saw
Antibodies are powerful. They are also stubbornly one-dimensional.
The modern antibody drug is a marvel and a compromise. It finds one target, latches on, and hopes that is enough. Often it is not. In B cell-mediated autoimmune disease - lupus, lupus nephritis, and the long list of conditions where the immune system turns on its own host - the standard antibody approaches leave too many cells behind. Depletion is incomplete. Disease comes back. The patient waits.
There is a more aggressive option. CD19-directed CAR-T cell therapy can wipe out B cells with startling depth, and early results in autoimmune disease have been genuinely exciting. But CAR-T is a production: cells harvested, engineered, re-infused, with a safety profile that demands hospitals and caution. It is a sledgehammer where most patients would prefer a scalpel that still does the job.
That gap - deep enough to matter, simple enough to give in a clinic - is the tension Hinge Bio exists to resolve. Everything the company builds is an answer to one question: how do you make an antibody hit as hard as a cell therapy without becoming one?
The Founders' Bet
If one binding site is good, cooperate.
Hinge Bio was founded in 2015 by Daniel Capon, Carin Mueller Rollins, and Miriam Siekevitz. Capon is not a newcomer to reinventing biology - he is a co-inventor of recombinant Factor VIII, the engineered protein that changed how hemophilia is treated. When someone with that record says antibodies have an unused dimension, it is worth a second look.
The bet is the GEM-DIMER platform. Instead of an antibody that binds one target at one site, GEM-DIMER builds multivalent, multispecific molecules designed to bind their targets cooperatively - several grips at once, reinforcing each other. The result, the company argues, is dramatically enhanced biological activity and functions a conventional antibody simply cannot perform. The name is a wink at the chemistry: a dimer, gem-like, two halves making something sharper than either alone.
What “GEM-DIMER” actually means, minus the jargon
- Multivalent - it grabs in more than one place at once.
- Multispecific - it can grab two different targets (HB2198 goes after CD19 and CD20).
- Cooperative binding - the grips reinforce each other, so the whole hits harder than the sum of its parts.
- The payoff - antibody-style dosing, with a depth the company compares to cell therapy.
In 2023, the founders brought in Harold “Barry” Selick as CEO, formerly UCSF's Vice-Chancellor of Business Development, Innovation, and Partnerships - a signal that the science was ready to meet the clinic, the regulators, and the checkbook.
The Product
HB2198: two targets, one molecule, a lot of missing B cells.
HB2198 is the platform's first proof. It is a B cell-depleting agent that engages both CD19 and CD20 - two markers on the same problem cells - while recruiting natural killer cells to finish the job. In preclinical in vivo studies, it depleted B cells more deeply and more rapidly than has been reported for other antibody-based therapies, clearing more than 99% of them.
B cell depletion: the case for cooperation
Hinge Bio's preclinical claim vs. the conventional ceiling · illustrative
Bars are directional, drawn from company-reported preclinical depth and the general performance gap it cites. CAR-T shown for context, not head-to-head. Read as “the argument,” not a clinical readout.
The pitch is not that HB2198 is the strongest thing ever pointed at a B cell. It is that nothing else delivers this depth in a form you can hang on an IV pole without the apparatus of cell therapy. If the clinic agrees with the mice, that is a genuinely different deal for patients.
The Proof
Money, regulators, and the first patients.
Conviction is cheap in biotech; validation is not. Hinge Bio has been collecting the expensive kind. In January 2025 it closed a $30 million Series A’ led by Point72, with Ridgeback Capital, InVivium Capital, and Lightswitch Capital joining. The proceeds had a single job: get HB2198 into humans.
The road from idea to IV
A milestone timeline · Hinge Bio, Inc.
The regulators followed the money. In October 2025 the FDA cleared the company's Investigational New Drug application for HB2198 in systemic lupus erythematosus and lupus nephritis. Then, in April 2026, the line that matters: first subjects dosed. Hinge Bio is now running one study in lupus patients and one in healthy volunteers - the unglamorous, essential work of finding out whether a beautiful preclinical story survives contact with human biology.
It is also showing its work in public. The platform has been presented at the University of Oxford's Kennedy Institute of Rheumatology and at the American College of Rheumatology's ACR Convergence 2024 - the rooms where rheumatologists are professionally hard to impress.
Who Runs It
A lean room full of people who have done this before.
Barry Selick, PhD
Former UCSF Vice-Chancellor for Business Development, Innovation & Partnerships. Joined 2023.
Daniel Capon, PhD
Co-inventor of recombinant Factor VIII; the scientific architect behind GEM-DIMER.
Carin Mueller Rollins, MBA
Operations lead steering the company from platform to pipeline.
Joshua Carle, MBA
Leads partnerships and business development as programs reach the clinic.
The Mission
Better answers for diseases that have run out of patience.
Hinge Bio frames its purpose plainly: use the GEM-DIMER platform to take on inadequate efficacy, resistance, and side effects across autoimmunity, inflammatory disease, cancer, and beyond. Lupus is the opening act, not the whole show. The same cooperative-binding trick that empties a B cell compartment could, in principle, be pointed at a long list of targets that single-site antibodies have failed to fully engage.
That is the wager hidden inside a clinical-stage biotech: not just that one molecule works, but that the machine that made it can do it again. The Series A bought a shot at the first proof. What happens next decides whether GEM-DIMER is a clever name or a category.
Why It Matters Tomorrow
The scalpel question.
If HB2198 holds up, the people who benefit are not investors or conference audiences. They are the patients currently choosing between treatments that do not go deep enough and treatments that require checking into a hospital. A drug that delivers cell-therapy depth from an IV bag would not be a marginal improvement. It would change the menu.
Back in that Burlingame lab, the B cells are still disappearing - but now the experiment has moved out of the mice and into the people the whole thing was for. The watching is harder now, and the stakes are real. Twenty people, one platform with a pun for a name, and a Phase 1 trial that will, in time, answer the only question that ever mattered: can an antibody finally hit like something bigger than itself? Hinge Bio built its entire existence on betting yes.