AMBIGUOUS RESULTS

Nouscom's NOUS-209 shows durable T-cell response, no new polyps at 1 year

Re-treatment data from a 60-patient Lynch Syndrome vaccine trial found no comparator arm, but the sponsor is already citing the result toward a registration-enabling trial.

Nouscom reported Phase 1b/2 data showing NOUS-209 re-treatment was safe and induced durable T-cell responses in Lynch Syndrome carriers, with no new advanced adenomas detected at one year.

By AppliedXLJuly 20, 2026Trial NCT05078866

Executive Summary

A Phase 1/2 cancer-prevention vaccine trial in Lynch Syndrome carriers reported that re-treatment with NOUS-209 was safe, produced durable T-cell responses, and coincided with no new advanced precancerous polyps at one year of follow-up.
The trial ran without a control arm, so the polyp finding describes what happened in treated patients rather than a measured difference against untreated surveillance.
Lynch Syndrome carriers face a high lifetime cancer risk with no approved interception immunotherapy, and Nouscom is using this data, together with a recent FDA Fast Track Designation, to justify moving toward a larger registration-enabling trial.
The finding builds on data already presented at three prior oncology conferences since 2023, making this the fourth public disclosure from the same underlying cohort rather than a new independent readout.

The disclosure

Nouscom said its Phase 1b/2 trial of NOUS-209 in Lynch Syndrome (LS) carriers showed the vaccine was safe upon re-treatment and induced broad, durable T-cell responses that were boosted by annual dosing, with no new advanced adenomas detected one year after treatment. The company said the finding, drawn from data published in Nature Medicine, provides the first clinical evidence of cancer interception in LS carriers. The trial, registered as NCT05078866, enrolled 60 participants under a collaboration between the National Cancer Institute's Cancer Prevention Clinical Trials Network and the iCAN-PREVENT consortium at MD Anderson. Nouscom+1

The design

NOUS-209 is an off-the-shelf immunotherapy designed to induce T-cell responses against frameshift peptide neoantigens found in tumors and precancer lesions carrying mismatch repair deficiency (dMMR) and microsatellite instability (MSI), the two DNA-repair defects that define Lynch Syndrome tumors. The trial is open-label with no masking and no comparator arm, and its primary outcome measure is the rate of immunogenicity following revaccination in a second treatment cohort. Because the study has no control group, the adenoma-surveillance finding describes what was observed in treated patients rather than a measured reduction against a matched untreated population. Nouscom+1

Regulatory context

Nouscom's release ties the results to a recent U.S. Food and Drug Administration Fast Track Designation for NOUS-209 and says the data "reinforces Nouscom's momentum toward initiation of a registration-enabling trial". Chief Executive Officer Marina Udier said the finding is "the fourth oral presentation of data from this trial, following AACR 2025 and SITC 2023 and 2025," and that it "strengthens our conviction and momentum as we advance NOUS-209 into a registration-enabling trial to deliver the first cancer interception immunotherapy for Lynch Syndrome carriers". That framing describes a company's forward plan rather than a regulatory action; no FDA approval action for NOUS-209 was identified. Nouscom

Trial operations

The trial's primary completion date shifted five times between its 2021 registration and 2024, moving from November 2025 to a final date of July 31, 2025, and its enrollment target rose from 45 to 60 participants in March 2024. That amendment pattern is consistent with a multi-year, NCI-sponsored cancer-prevention study and does not itself bear on how the immunogenicity or adenoma findings should be read. The trial remains listed as Recruiting in the registry even as this readout, covering re-treatment and follow-up beyond one year, has already been disclosed. NCT05078866

Next disclosure

Nouscom said it plans to present re-treatment safety, immunogenicity, and long-term follow-up data extending beyond one year in an oral session at the European Society for Medical Oncology (ESMO) Congress 2026, running October 23-27 in Madrid, with the talk to be given by Eduardo Vilar-Sanchez of MD Anderson's Clinical Cancer Prevention program. The company separately maintains an active Phase 1/2 trial of NOUS-209 combined with pembrolizumab in microsatellite-unstable colorectal, gastric, and gastro-esophageal junction tumors, a different population that also carries the dMMR/MSI biomarker. Nouscom

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