Imugene ‘encouraged’ by data for HER2 vaccine in gastric cancer

Australian biotech Imugene says its HER2 vaccine hit the mark in a phase 1b trial, setting up a phase 2 study that will start recruiting patients in the new year.

The first tranche of data from the 14-patient trial comes from the first 10 evaluable subjects who were given the HER-Vaxx vaccine at three doses on top of standard chemotherapy with cisplatin and fluorouracil or capecitabine.

Of these, five had a partial response—with a 30% decrease or more in tumor size from baseline scans—while four showed disease stabilization. Imugene CEO Leslie Chong said (PDF) she is "cautiously encouraged" by the data, although the phase 1b study is only really intended to give a safety readout. On that score, HER-Vaxx also seemed to be well-tolerated.

"With these early results from the HER-Vaxx clinical study, Imugene’s B-cell active immunotherapy approach is showing positive signs which provides us with further confidence in our … pipeline," she added. The vaccine performed best at the highest dose (50 mcg), which will be taken forward into phase 2.

HER-Vaxx grew out of work at the Medical University of Vienna in Austria and is designed to induce a patient’s own immune system to produce antibodies that can attack tumor cells. Imugene’s hope is that vaccination will be an alternative to regular use of monoclonal antibodies such as Roche’s Herceptin, which made sales of almost $7.5 billion last year.

The vaccine is based on B-cell epitope peptides, which when injected cause patients’ B cells to generate antibodies against HER2 receptors, slowing the growth of HER2-positive cancer cells and causing them to be destroyed by the immune system. HER-Vaxx has previously been shown to stimulate a polyclonal antibody response—based on multiple antibody types—in preclinical studies as well as a phase 1 trial in HER2-positive breast cancer.

The phase 2 gastric cancer study, which is expected to enroll 68 HER2-positive gastric cancer patients, will compare HER-Vaxx plus chemo to chemo alone and be carried out in sites across Asia, Eastern Europe and India, where HER2 treatments such as Herceptin and Roche’s follow-up drug Perjeta are not readily available to patients. Imugene’s HER2 vaccine is seen as the key to showing proof of concept for its B-cell epitope platform, but analysts at Edison think the programs at the company with the greatest potential rewards are its PD-1 (KEY-Vaxx) and combined PD-1/HER2 vaccines.

Imugene has in-house PD-1 candidates in early-stage development but cut two years off its timelines in June after licensing technology from the Ohio State University Wexner Medical Center and Mayo Clinic, according to Edison, which says that deal could be "transformational" for the biotech. Clinical trials of KEY-Vaxx are due next year and if successful could make the vaccine a rival to blockbuster checkpoint inhibitors such as Merck & Co.’s Keytruda and Bristol-Myers Squibb’s Opdivo.

"One of the key appeals of KEY-Vaxx is that if it demonstrates efficacy in clinical studies with acceptable tolerability, then the convenient sub-cutaneous dosing schedule and low cost of goods could make it well suited for use in combination with other therapies in a wide range of cancers," said Edison in a recent research note.

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