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Nouscom Begins Phase II Trial of Neoantigen-Targeted Cancer Vaccine With Checkpoint Inhibitor

NEW YORK – Nouscom on Tuesday said it began a Phase II trial of its cancer vaccine NOUS-209 with Merck's Keytruda (pembrolizumab) in patients with unresectable or metastatic gastric, colorectal, and gastro-esophageal junction tumors characterized by mismatch repair deficiency (dMMR) or high microsatellite instability (MSI-high).

NOUS-209 targets 209 tumor-specific neoantigens tailored to treat dMMR or MSI-high colorectal cancer. According to Basel, Switzerland-based Nouscom, such tumors are ideal for this approach because the insertion and deletion mutations they harbor mainly arise at mononucleotide repeat sequences, leading to frameshift peptides that are highly immunogenic but bear no resemblance to natural protein sequences.

NOUS-209 comprises a priming injection of great ape adenovirus Gad20-209-FSP and three boosts of the modified vaccinia virus Ankara MVA-209-FSP. The recently launched Phase II trial will enroll 115 patients and evaluate the efficacy and safety of the combination regimen. Those eligible for first-line treatment will be randomized to NOUS-209 plus Keytruda or Keytruda alone, while patients who have stopped responding to previous anti-PD-1 and other approved therapies will receive the combination treatment.

The trial will be conducted at sites in Europe and the US and its primary efficacy outcome of interest will be overall response rate over 18 months. The trial will also evaluate safety, tolerability, toxicity, and immunogenicity of the combination.

Nouscom is advancing its cancer vaccine to Phase II studies after NOUS-209 induced neoantigen-specific CD8-positive T cells and those T cells infiltrated metastatic tumors and had anti-tumor activity in its Phase I study. The firm is evaluating another personalized neoantigen cancer vaccine, dubbed NOUS-PEV, also in combination with Keytruda, in a Phase Ib clinical trial involving patients with advanced melanoma and non-small cell lung cancer.