ExpreS2ion Biotech Reports Promising Immune Response Data from HER2-Targeting Cancer Vaccine Phase I Trial
Key Insights
ExpreS2ion Biotech (search) reports that five out of six evaluable patients demonstrated drug-specific immune responses in the ongoing Phase I trial of ES2B-C001, a HER2 (search)-targeting cancer vaccine candidate.
Two patients who completed all scheduled study visits showed sustained elevated anti-HER2 (search) lambda light-chain antibody titers over time, suggesting durability of the immune response.
The vaccine combines ExpreS2ion's ExpreS2 production platform with AdaptVac (search)'s VLP technology to stimulate polyclonal immune responses against HER2 (search)-expressing tumors as a complementary strategy to existing therapies.
ExpreS2ion Biotech (search) has reported encouraging immunogenicity data from its ongoing Phase I clinical trial of ES2B-C001, a HER2 (search)-targeting cancer vaccine candidate. The Danish biotechnology company announced that five out of six evaluable patients demonstrated drug-specific immune responses, defined as an increase from baseline in anti-HER2 lambda light-chain antibody titers following treatment.
Early but Consistent Immune Response Data
The updated assessment includes immunogenicity data available through January 2026 from patients treated in the first dose cohort (50 micrograms plus adjuvant) as well as initial observations from patients in the higher dose cohort (150 micrograms plus adjuvant). The lambda light-chain antibody responses observed are specific to the vaccine-induced immune response.
Notably, two patients who have completed all scheduled study visits continue to show sustained elevated anti-HER2 (search) lambda light-chain immunoglobulin titers over time, suggesting durability of the observed immune response. Additional patients remain on treatment with ongoing follow-up.
"While the dataset remains limited and early, we are encouraged by the consistency of the immune responses observed in patients treated with ES2B-C001," commented Bent U. Frandsen, CEO of ExpreS2ion. "Importantly, we continue to see vaccine-specific antibody responses without any new safety concerns, supporting continued progression of the clinical program."
Clinical Trial Design and Timeline
The ES2B-C001 Phase I trial is an open-label study evaluating the safety, tolerability, and immunogenicity of ES2B-C001 in patients with advanced HER2 (search)-positive or HER2-low breast cancer (search) who have received prior standard-of-care therapy. The study is being conducted at multiple clinical centers in Austria and includes a dose-escalation phase followed by an expansion phase.
Dr. Erik Heegard, Director of Clinical Development, noted that "from a clinical and immunological perspective, the timing and pattern of the observed responses are in line with what we would expect from an active cancer vaccine." However, he emphasized that the small number of patients and heterogeneity of prior and concurrent therapies require careful follow-up and further data before drawing conclusions.
Patient enrollment and screening continue as planned, with sites reporting additional patients available to proceed once dosing is permitted following required safety reviews. Based on current visibility, ExpreS2ion remains on track to complete the dose-escalation portion around mid-2026 and the expansion portion toward the end of 2026.
Novel Vaccine Technology Platform
ES2B-C001 represents an innovative immunotherapy approach developed to treat HER2-expressing cancers (search) by stimulating a patient's own immune system. The vaccine combines ExpreS2ion's ExpreS2 production platform with AdaptVac (search)'s virus-like particle (VLP) technology, both of which have been proven in clinical Phase III trials.
The HER2-VLP vaccine (search) is designed to stimulate a robust and durable polyclonal immune response against HER2 (search)-expressing tumors, offering a complementary strategy to current treatment regimens such as monoclonal antibodies or antibody-drug conjugate therapies. Preclinical studies have demonstrated safety and efficacy across multiple animal models, significantly inhibiting tumor growth and improving survival rates.
ExpreS2ion has developed the ExpreS2 technology platform for fast and efficient development and production of active vaccine materials. The platform, marketed under the brand GlycoX-S2, includes functionally modified glycosylation variants for enhanced immunogenicity and pharmacokinetics. Since 2010, ExpreS2ion has produced more than 500 proteins and virus-like particles in collaboration with leading research institutions and companies.
The company emphasizes that the current dataset remains limited and observations should be interpreted with caution as the study progresses and additional data mature.