Imugene reported updated Phase II results for HER-Vaxx on Monday, saying that adding the experimental B-cell peptide immunotherapy vaccine to chemotherapy led to an overall response rate (ORR) of 50% in certain patients with gastric cancer. The company said the findings, which were presented at the European Society for Medical Oncology (ESMO) World Congress on Gastrointestinal (GI) Cancer, suggest HER-Vaxx "may provide treatment benefits consistent with traditional monoclonal antibodies, with a corresponding adaptive immune response, without added toxicity."

The study involves 39 patients with HER-2/neu-overexpressing, metastatic or advanced adenocarcinoma of the stomach or gastroesophageal junction. Participants were randomised to receive the HER-Vaxx peptide vaccine together with standard chemotherapy, or standard chemotherapy alone. The primary efficacy endpoint is overall survival (OS), while secondary goals included ORR, progression-free survival (PFS) and disease control rate, among others.

Tumour response linked to antibody levels

The findings showed that the proportion of patients who achieved a partial response or better was 50% for the HER-Vaxx group, compared to 29% for those who received chemotherapy alone. The company said the reduction in tumour size was also "substantially higher" in patients who got HER-Vaxx. It noted that tumour response correlated with the amount of HER-2-specific antibodies and that those given HER-Vaxx saw "high levels" early on that were maintained during the treatment and maintenance phase, "with only a few booster injections." Patients with antibody levels over 1050 ng/mL achieved >50% tumour shrinkage, the company said, adding this may serve as a potential biomarker.

In interim analysis data unveiled last November, Imugene said HER-Vaxx plus chemotherapy showed a reduced risk of death of 58.2% compared to chemotherapy alone. Patients achieved a median OS of 14.2 months and 8.8 months, respectively, in the two groups. At the time of the data readout, the independent data monitoring committee recommended that, given the favourable survival outcome, with no added toxicity in the HER-Vaxx arm, a lower number of patients would be required for study completion. Recruitment in the trial wrapped up this past January, and in April, Imugene disclosed that the PFS goal had been met after the statistically significant required number of PFS events occurred.

HER-Vaxx, also known as IMU 131, is a cancer immunotherapy constructed from several B-cell epitopes, and is designed to treat tumours that overexpress the HER-2/neu receptor, such as gastric, breast, ovarian, lung and pancreatic cancers, according to Imugene.