Imugene’s Phase 1b HER-Vaxx cancer trial meets endpoints, reports positive results

Clinical stage immuno-oncology company Imugene (ASX: IMU) has reported positive top-line results from a Phase 1b clinical study of its HER-Vaxx gastric cancer vaccine in patients expressing the HER2 target protein.

The study tested 14 patients at 10, 30 and 50 microgram dose levels of HER-Vaxx in combination with current standard-of-care chemotherapy drugs cisplatin and fluorouracil or capecitabine.

It included three primary endpoints – safety, tolerability, and identification of the optimal dose of HER-Vaxx which will be used for a Phase 2 study based on data collected over the first eight weeks of treatment.

Response rate was also used as an exploratory endpoint in patients who were on study at Day 56 of the tumour assessment visit and deemed evaluable for tumour growth assessment.

Of the 10 evaluable patients, five showed more than 30% decrease in tumour size from baseline scans and four showed “stable disease”, which is where the total tumour burden increases less than 20% and decreases less than 30%.

According to Imugene, all dose levels showed an increased antibody response in patients and the HER-Vaxx was found to be well tolerated.

Managing director Leslie Chong was “cautiously encouraged” by the results, which met all the endpoints of the study in a small sample size.

“With these early results from the HER-Vaxx clinical study, our B-cell active immunotherapy approach is showing positive signs which provides us with further confidence in our B-cell immunotherapy pipeline,” she said.

“This is a promising milestone for patients with advanced gastric cancer who often have very few medical options.”

Phase 2 study

HER2 is a cancer growth signal receptor protein found on the cell surface in breast and gastric cancers.

HER-Vaxx is a B-cell peptide vaccine designed to produce a strong antibody response against tumours which over-express the HER2 receptor such as those in gastric, breast, ovarian, lung and pancreatic cancers.

Based on safety and immunogenicity data from the Phase 1b trial, the study’s Cohort Review Committee has recommended a dose of 50 micrograms for a Phase 2 study in early 2019.

Phase 2 will test the efficacy, safety and immune response in 68 gastric cancer patients with metastatic gastric cancer over-expressing the HER2 protein.

It will be randomised into two arms of either HER-Vaxx plus standard-of-care chemotherapy or standard-of-care alone.

The primary endpoint will be overall survival, with the secondary endpoint being progression-free survival.

The study will be conducted at sites across Asia, Eastern Europe and India where there is a high prevalence of gastric cancer and treatment drugs such as Herceptin and Perjeta are not readily available to patients.

Imugene said activities for Phase 2 preparation have already commenced.

A new clinical batch of HER-Vaxx has been manufactured, delivered and is waiting in storage for distribution to study sites.

At midday, shares in Imugene were trading 4.55% lower at $0.021.