ExpreS2ion: At the gates of phase 1

Phase 1 study planned in Austria

ExpreS2ion Biotech has recently filed for starting a first-in-human study of its breast cancer vaccine candidate ES2B-C001 in women with a HER2 positive breast cancer. The application is a major step forward in its proprietary pipeline and the company expects first patient to start study treatment in Q1 next year.

The Clinical Trial Application was submitted to the Austrian Agency for Health and Food Safety, BASG. Assuming no further questions are raised, we understand the agency has 35 calendar days to review the application. Once cleared by the authority and the ethics committee, the study will be conducted at the Medical University of Vienna.

Study will look for signs of efficacy

The study will include an initial number of 18 breast cancer patients. Participants will be tested for toxicities and safety with escalating doses of ES2B-C001. At the highest tolerated dose, it will be possible to expand the study with another 18 patients. As in all phase 1 studies, safety is the main primary endpoint. The vaccine's immunogenicity and its preliminary anti-tumor activity in HER2-positive breast cancer will be assessed as secondary and exploratory endpoints.

The full study is expected to last for 20 months, which should allow a final result by the end of 2026. In the meantime, we expect preliminary results from different stages to be released regularly.

The promise of a potent vaccine candidate

In the phase 1 trial, ES2B-C001 will be studied as a therapeutical agent, not in the preventive setting generally assigned to vaccines. The vaccine antigen is designed to overcome treatment resistance that limits current treatments, mainly monoclonal antibodies, by producing polyclonal antibodies binding to the entire HER2 protein instead of a single epitope.

In the longer run, the vaccine candidate may also show a longer protection to relapsed disease. If these properties can be proven in a phase 3 study by a future partner, we expect sales of ES2B-C001 to surpass USD 3bn.

Fair value raised to SEK 2,4

In our previous report we had a 75 percent likelihood of ES2B-C001 initiating a clinical phase 1 trial early next year. We are raising this likelihood to 90 percent after the recent CTA submission and the successful preparation of GMP batches.

This positive component is trimmed by our calculation of the future number of shares. After the recent new shares issue, we have raised our projected number of new shares by the end of 2026 to 162 mln (152). This base scenario leaves our fair value at SEK 2.4 (2,2).