A NEW HER-2 vaccine has demonstrated sustained immunogenicity and therapeutic efficacy when administered alongside monoclonal antibody therapy, supporting its potential integration into existing treatment strategies for HER-2-positive disease.
HER-2 Vaccine Induces Strong Immune Response
The investigational HER-2 vaccine ES2B-C001 represents a new generation of vaccines based on virus-like particles displaying the full extracellular domain of human epidermal growth factor receptor 2. In preclinical models, the HER-2 vaccine elicited strong antibody responses capable of curing human HER-2 transgenic tumours and metastases in mice. In tumour-free mice, treatment with ES2B-C001 resulted in robust production of anti-HER-2 immunoglobulin G, alongside activation of T cell responses.
Importantly, concurrent administration of the anti-HER-2 monoclonal antibody 4D5 did not impair the immunogenicity of the HER-2 vaccine. Antibody responses reached concentrations in the milligram per millilitre range and persisted for more than 6 months following treatment, regardless of prior exposure to monoclonal antibody therapy. These data indicate that the HER-2 vaccine can induce durable immune responses even in the presence of ongoing antibody-based treatment.
HER-2 Vaccine Retains Therapeutic Efficacy
The therapeutic efficacy of the HER-2 vaccine was also evaluated in mice bearing human HER-2 transgenic mammary carcinomas. ES2B-C001 alone resulted in long-term tumour-free survival in 13 out of 20 mice. When combined with 4D5, outcomes were comparable, with 15 out of 20 mice remaining tumour-free over the long term.
These findings demonstrate that the HER-2 vaccine maintains its anti-tumour activity despite concurrent monoclonal antibody therapy. The data are particularly relevant given that early clinical trials may include patients who are already receiving anti-HER-2 treatments.
Clinical Development And Future Implications
The HER-2 vaccine ES2B-C001 has now entered clinical development, and these findings address a clinically important scenario with regard to combination treatment approaches. Preclinical data suggest that co-administration of monoclonal antibodies does not compromise vaccine efficacy or immune activation.
Overall, the HER-2 vaccine shows promise as part of combination strategies, with sustained antibody responses and preserved therapeutic benefit observed in preclinical models. These results support the feasibility of vaccinating patients undergoing established anti-HER-2 therapies such as trastuzumab, potentially expanding treatment options in this setting.
Reference
Semprini MS et al. HER-2 therapeutic vaccine is not hampered by concurrent HER-2 monoclonal antibody. Npj Vaccines. 2026; https://doi.org/10.1038/s41541-026-01462-4.
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