ExpreS2ion Biotech: Enrolling in phase 1

Swift action by Austrian regulator

The Austrian regulator BASG reacted swiftly to ExpreS2ion Biotechnologies’ request for amending its protocol in the phase 1 trial with ES2B-C001, an immunotherapy for treating HER2 positive breast cancer. The request was filed with the BASG on May 13 and on June 30 ExpreS2ion communicated a positive response.

The first part of the study includes nine patients, which will be evaluated at three different dose levels during a 12-week period, followed by a six-week observation period. So far, two patients are enrolled and a third is being screened for inclusion.

Interim analysis expected by mid-2026

The second part of the study involves an expansion phase at the maximal tolerated dose. The primary study endpoint consists of potential toxicity reactions with a preliminary result expected by mid-2026. By then we anticipate that the safety profile can be established, possibly together with an interim analysis of immune or tumor response to ES2B-C001.

The study will include a total of up to 27 participants with HER2-expressing breast cancer. As in most phase 1 oncology trials, there is no placebo control included. Management expects to conclude the studie within 18 months period, which would imply full recruitment by July-August next year.

Immunotherapy boost for treating breast cancer

ES2B-C001 has the potential to reinforce the patient’s immune response in breast cancer, in combination with standard-of-care, such as antibodies to HER2 or conjugates of antibody and cytotoxic drugs.

Management anticipates that ES2B-C001 will elicit a broader, polyclonal immune response, compared to the monoclonal response of standard-of-care. The market for the treatment of HER2 expressing breast cancer is estimated to reach USD 13bn in a five-year period, with further scope for expansion if an immunotherapy is approved.

Cash-burn lower than expected in Q2

ExpreS2ion’s cash position by the end of Q2 was SEK 48m. Cash burn in the quarter was SEK 9m, half of what we predicted. Including subscription to TO11 in September-October, we expect the company to have a cash runway into Q2 next year. Fair value, given our conservative base scenario, is reiterated at SEK 75.