Making immunotherapy work
for more patients.
Cancer immunotherapy has been a breakthrough — but it still fails most of the patients who receive it, because tumors build an environment that shuts the immune system down. Oncobiotix is pioneering a new class of medicine: oral drugs that copy the immune signals of a healthy gut microbiome — rather than trying to replace it — so immunotherapy can work for more patients. Our first drug is OBX34.
The biggest breakthrough in cancer in a generation — reaching too few patients.
Immunotherapy changed what was possible in advanced solid tumors: it taught the immune system to recognize cancer, and produced durable remissions where chemotherapy had produced almost none. In advanced melanoma — a disease once measured in months — more than half of patients treated with combination checkpoint therapy were alive five years later. The work behind it won the 2018 Nobel Prize in Medicine.
52% five-year overall survival, nivolumab + ipilimumab · Larkin et al., N Engl J Med 2019 (CheckMate 067)
That is the ceiling, not the average. Checkpoint inhibitors only work when the immune system can actually reach and function within the tumor — and for most patients, it can't.
Who it actually reaches
The real barrier is the tumor's environment — and the microbiome is one of the few levers shown to change it in patients.
Solid tumors surround themselves with an environment that actively suppresses the immune system — crowded with immune cells (called myeloid cells) that hold the attack back. Getting past that barrier is what lets any immunotherapy do its job.
The gut microbiome is one of the most powerful — and best-evidenced — influences on whether that immune response happens. A healthy microbiome switches it on; a disrupted one shuts it down. Oncobiotix delivers that same "switch-on" signal directly, as a defined drug — resetting the tumor's environment so immunotherapy can work.
The immune-priming signals of a healthy gut microbiome — captured in a pill, to help more patients respond to immunotherapy.
This isn't a hunch — the human evidence is already in.
The microbiome is one of the very few immune-response factors shown to change outcomes in real patients, not just in theory.
A stool transplant flips non-responders
When patients who weren't responding to immunotherapy received a gut-microbiome transplant from patients who were, some began responding — in independent clinical trials.
Baruch 2021 · Davar 2021, Science
Disruption has a real cost
Across dozens of studies and tens of thousands of patients, a microbiome disrupted before treatment tracks with clearly worse survival.
Routy 2018 · pooled meta-analyses
And the latest data agrees
A recent randomized trial of microbiome modulation plus immunotherapy reported deep responses in lung cancer and melanoma.
FMT-LUMINate, Nat Med 2026
What none of this gives you is a drug. A stool transplant is challenging and costly to standardize, to combine with other medicines, and to scale. Oncobiotix set out to capture the same biology in a form built for all three — a pill.
Copy the microbiome's signal — don't try to replace the bacteria.
There are two ways to put microbiome biology to work against cancer. Almost everyone is trying to rebuild a patient's gut bacteria. Oncobiotix is pioneering the opposite — and defining the category.
Add living bacteria, and hope they take hold
Stool transplants (FMT) and live-bacteria pills (known as LBPs) introduce living organisms and rely on them settling into the gut.
- Hard to manufacture, standardize, and keep consistent
- Difficult to combine cleanly with other cancer drugs
- Inactivated by antibiotics — exactly when patients need help most
Recreate the signal with a defined molecule
A single, well-characterized small molecule that delivers the microbiome's active immune signal directly — no living organisms required. We call it a synthetic microbiome mimetic.
- Consistent from dose to dose, and stable on a shelf
- Designed to combine with existing immunotherapy regimens
- No live bacteria that need to take hold in the gut
Same underlying biology as a healthy microbiome — delivered as a real drug. Oncobiotix is building this new class from the ground up, with OBX34 as its first medicine.
One approach, many possible medicines — and a first drug to test it.
Because these are defined molecules — not living bacteria — they are designed not to depend on the state of a patient's own gut. OBX34 is the first, and everything below is about how it is designed to work.
Designed to reset the tumor's environment
OBX34 acts on the immune-suppressing cells inside a tumor, through one specific, well-mapped pathway (Gasdermin D / IL-1β).
Effect held when the gut was disrupted
In preclinical models whose gut was disrupted by antibiotics — the closest stand-in for a real disrupted-microbiome patient — OBX34 brought immunotherapy's effect back to a healthy baseline.
A real, buildable drug
An oral tablet — stable at room temperature, made to a defined chemical specification, and designed to be added to any immunotherapy.
We start where the science is strongest — then go broader.
The microbiome shapes the immune response across many cancers, but the human evidence is concentrated in one place: the PD-1 immunotherapies, in lung cancer, backed by the transplant and antibiotic studies above. That's the fastest, lowest-risk way to test OBX34 in people — so it's where we begin.
That's the starting point, not the limit. The same biology should extend to other causes of a disrupted gut, other immunotherapy drugs, and other cancers — widening who immunotherapy can help.
- First: OBX34 added to immunotherapy in lung-cancer patients whose treatment has stopped working — where the evidence is strongest today.
- Then: the wider group of patients whose microbiome is unfavorable, identified by a simple test.
- Beyond: other immunotherapy drugs and cancer types the same biology can reach.
One precise switch inside the tumor.
Most solid tumors are packed with immune cells that suppress the attack. OBX34 turns one specific "danger signal" back up inside them — waking the immune response — through the Gasdermin D / IL-1β pathway.
A pill reaches the tumor
Taken orally, OBX34 reaches the immune cells inside the tumor — with no dependence on the patient's own microbiome.
It flips a molecular switch
Inside those cells it turns up a built-in alarm system (the inflammasome and Gasdermin D), amplifying a signal that's already there.
An immune "call to arms" goes out
That releases messenger molecules like IL-1β — danger signals that summon the immune system to the tumor.
T cells attack the tumor
Killer T cells (CD8⁺) multiply and go after the tumor — restoring the response immunotherapy was meant to produce.
Designed to work alongside every other immunotherapy advance — not against them.
New drugs and combinations keep arriving. OBX34 doesn't compete with them — it targets the tumor environment they all depend on, as a simple oral add-on intended to help more patients respond.
Immunotherapy alone
- Nobel Prize-winning therapy for patients in need
- Leaves most patients without a lasting response
- Doesn't touch the tumor's suppressive environment
Newer combination drugs
- Real gains for fit, selected patients
- Added side effects
- Some patients can't take them
OBX34 + immunotherapy
- Built for the patients immunotherapy leaves behind
- Designed to combine with existing immunotherapy
- An oral tablet, made by standard chemical synthesis
A big idea — with a focused, lower-risk first step.
Oncobiotix is doing the safety and manufacturing work needed to start human trials of OBX34. We welcome conversations with strategic partners across the cancer-immunotherapy field.