Freshly resected tumor slices from lung and ovarian cancer patients landed on the lab bench at Oncomatryx. Scientists kept the tissue alive with each patient’s own immune cells, preserving the original structure and cell mix. Then they introduced OMTX305, a bispecific antibody built to redirect T cells against cancer-associated fibroblasts—the cells that wall off tumors and blunt immune attack.
OMTX305 didn’t go after the cancer cells directly. Instead, it targeted the fibroblasts, aiming to break down the tumor’s protective barrier. The results, published in Science Advances, show a sharp drop in fibroblast numbers—from 38% to 24%—within three days. In several samples, cancer cells near the destroyed fibroblasts died off at higher rates. Surviving tumor cells clustered farther from the targeted fibroblasts. The antibody showed no binding to healthy human tissues in these tests, a detail that matters for safety if the approach moves to the clinic. Researchers also tracked a decrease in PD-L1 expression in cancer cells after OMTX305 exposure, a finding confirmed in the published data but missing from the original press release.
The mechanism of OMTX305 is based on redirecting the patient’s own T cells against fibroblasts surrounding the tumor, rather than directly binding to cancer cells.
Patient responses didn’t line up neatly. Some tumor slices showed more cancer cell death than others. The authors flagged that only clinical trials will reveal which patients stand to gain. The tumor’s immune makeup and, for lung cancer, PD-L1 levels could help predict response, but these markers remain unproven for patient selection. Science Advances notes that OMTX305 is still preclinical, with no patient treatment data or clinical trials yet.
Oncomatryx has spent over fifteen years betting on the tumor microenvironment as a therapeutic target. Myriam Fabre, Chief Scientific Officer, put it plainly: "We have seen in real patient tissue, with its own architecture and immune defenses, that attacking the fibroblasts that protect the tumor also kills the cancer cells around them. These are preclinical results that will need to be confirmed in patients, but they reinforce that the microenvironment is a real route to treating cancer." Laureano Simón, founder and CEO, pointed to the company’s pipeline, which includes OMTX705, now in clinical trials.
The study was led by Meng Dong from the Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology and the University of Tübingen, with Julia Thiel as the first author. The research model preserved the original tumor architecture and cellular diversity, distinguishing it from standard cell cultures.
The research brought together Oncomatryx and German partners: the Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, University of Tübingen, University of Stuttgart, and Robert Bosch Hospital. The full study appears in Science Advances.
Preclinical as they are, these results add weight to the idea that the tumor microenvironment is a legitimate target for therapy. This approach runs counter to treatments that zero in only on malignant cells. It lines up with recent moves in immunotherapy, such as CAR T cell therapy in ovarian cancer, which also leverages the immune system against solid tumors.
Oncomatryx, based in the Basque Country, has built a platform to generate and advance candidates for licensing. The company holds recognition from Spain's Centre for Industrial Technological Development and an EIC Accelerator grant from the European Union. OMTX305’s evidence remains preclinical, with no clinical benefit yet shown. The microenvironment, once a side note, now stands as a battleground for new cancer therapies.
