On October 13, 2025 Nouscom, a clinical-stage biotech company developing next-generation neoantigen-targeted off-the-shelf and personalized cancer immunotherapies, reported positive results from a completed Phase 2 trial evaluating NOUS-209 in combination with pembrolizumab for patients with microsatellite instability high (MSI-H) metastatic colorectal cancer (mCRC) who are refractory to anti-PD-1 therapy (Press release, NousCom, OCT 13, 2025, View Source;utm_medium=rss&utm_campaign=nouscom-presents-positive-phase-2-results-of-nous-209-immunotherapy-combined-with-pembrolizumab-in-msi-h-metastatic-colorectal-cancer-patients-refractory-to-anti-pd-1-therapy-at-esmo-2025 [SID1234656585]). Results from this Phase 2 trial will be presented in a poster session at the upcoming European Society for Medical Oncology (ESMO) (Free ESMO Whitepaper) Annual Meeting, taking place in Berlin, Germany, from 17 to 21 October 2025.

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Study Highlights:

NOUS-209 is an off-the-shelf viral vector-based immunotherapy targeting frameshift peptides specifically expressed on deficient mismatch repair (dMMR)/MSI-H tumors, thereby harnessing the power of the immune system to recognize and eliminate MSI-H cancer cells.
Anti-PD-1 therapy is the approved first-line standard of care in dMMR/MSI-H mCRC, but resistance or relapse can develop, requiring the development of new treatment options.
In this Phase 2 trial, NOUS-209 combined with pembrolizumab was administered to 20 evaluable patients with dMMR/MSI-H mCRC who had progressed on prior anti-PD-1 treatment (77% had received prior single agent anti-PD-1 therapy, 23% received combination therapy with anti-CTLA-4). The median number of prior lines was 2 (1-7).
The primary endpoint was Objective Response Rate (ORR); secondary endpoints included progression-free survival (PFS) and safety, with immunogenicity as an exploratory endpoint.
Key Results:

ORR was 15% (3 partial responses), with a disease control rate (DCR) of 70% (11 stable disease, 6 progressive disease).
Median progression-free survival (PFS) was 6.4 months.
Safety profile remained favorable, with no emerging findings.
Robust immune activation was detected in 80% of patients.
Seven patients (32%) were retreated with NOUS-209 at 6 months; among those, 86% remained in stable disease and 14% had a partial response, with the latter demonstrating induction of a strong, durable and polytopic T cell immune response with a desired effector memory phenotype and correlating with clinical response.
"There remains a high unmet need for effective therapies that can overcome anti-PD-1 resistance and provide durable disease control. These data are promising in this difficult-to-treat patient population given the modest clinical benefit of approved options in the same setting," said Javier Ros, MD PhD, from Vall d’Hebron University Hospital.

"These clinical data are very encouraging. NOUS-209 combined with pembrolizumab has demonstrated meaningful disease control and immune activation in patients who have exhausted anti-PD-1 therapy," said Dr. Sven Gogov, Chief Medical Officer of Nouscom.

"We are excited by the overall positive clinical dataset emerging from the completed clinical trials of NOUS-209, not only in MSI-H mCRC patients but also the Phase 1b/2 results in Lynch Syndrome carriers that were presented earlier this year at AACR (Free AACR Whitepaper). These results support our commitment to advancing NOUS-209 into a registration-enabling study for cancer interception in Lynch Syndrome carriers," said Dr. Marina Udier, Chief Executive Officer of Nouscom.

Details of the abstract and presentation at ESMO (Free ESMO Whitepaper):

Nous-209 immunotherapy with pembrolizumab for microsatellite instability high (MSI-H) metastatic colorectal cancer, refractory to anti-PD-1: Phase II trial results

Poster Number: 802P
Session: Colorectal Cancer Poster Session
Session Time/ Place: Sunday October 19 / 12:00-12:45 (CEST) / Hall 25
The abstract is available on the ESMO (Free ESMO Whitepaper) website.