ExpreS2ion today provided an update on the Phase I trial of ES2B-C001, confirming that all 19 planned patients have been enrolled and started treatment, with seven at 50 µg, six at 150 µg and six at 450 µg.

The last patient’s last visit in the five-dose priming phase is now expected at the end of December 2026, and the primary readout is consequently guided for publication in Q1 2027 rather than end-2026, with database lock in February.

The Phase II initiation target of H2 2027 is unchanged.

Alongside the timing update, the company reported anti-HER2 antibody responses in 12 of 13 evaluable patients at the 5 October data cut-off, with no dose-limiting toxicities and no serious adverse events assessed as related to ES2B-C001 across the 75 doses given.

Completed enrolment is the most substantive operational item here. Recruitment pace and drop-outs have been the standing caveat attached to every timeline the company has communicated since dosing began in June 2025, and with all patients on treatment that risk is now largely behind the programme. The safety picture also remains clean through a fourth consecutive data cut, with no SUSARs reported.

The immunogenicity dataset is holding up. The 12 of 13 responder ratio is identical to the 4 August cut, but the underlying population has matured: nine patients have now completed the full five-dose priming course against five in August, and eight of those nine responded, so the response rate among completers is no longer the 100% reported previously. The median peak increase in antibody titre among completers is reported at eight-fold, against 16-fold among the five completers in August, with a range extending to 81-fold. Medians on single-digit samples move sharply with each added patient, and the company continues to describe the data as preliminary and exploratory with no conclusions on clinical benefit available at this stage, so we would not read the step down as a weakening signal.

The 16-fold reading was one of several observations supporting our argument in the 7 September investment case that ExpreS2ion may justify a probability of success above the oncology average, alongside the cVLP platform’s Phase III validation and the clean safety record, and that argument does not rest on this figure alone. We would also note that the release does not specify whether the eight-fold median covers the eight responders or all nine completers, which limits how precisely it can be compared with the August figure.

The timing shift matters more for the investment case than the data. Since the interim Phase Ia readout was folded into a single consolidated readout, the end-2026 date has been the one anchor that held through successive changes to trial scope and to the Phase II start. It has now moved a quarter, which compresses the window between the readout and the H2 2027 Phase II target and pushes the key value-inflection point further out relative to the funding position.

The Phase II element is the genuinely new strategic information. Following its recent review, the Scientific Advisory Board has suggested evaluating ES2B-C001 together with standard of care in a first-line patient population, where the earlier setting and larger eligible population would be commercially more attractive than later lines. Management states that the review gives a clearer basis for partner discussions, while the design itself remains subject to partner input, regulatory interactions and financing. Scope and cost have not been specified, so we are not drawing conclusions on what this implies for the size of the eventual funding requirement.

For now, our framing from September is unchanged: the pipeline continues to de-risk, and the near-term question remains funding. At a market capitalisation of around SEK 40m against reported cash, the base-case implied probability of success in our model sits close to 1%, against historical benchmarks of roughly 7% at Phase I and 5% in oncology.

We will return to the revised timeline and its funding implications in connection with the Q3 2026 interim report, due on 12 November. Investors who want to hear management on the subject directly can join the live presentation the same day at 10.00, where CEO Bent U. Frandsen and CFO Keith Alexander will present the results and take questions.

Registration is open now, and questions can be submitted in advance without attending live: https://www.inderes.dk/videos/expres2ion-biotech-presentation-of-q3-2026-interim-report

Disclaimer: HC Andersen Capital receives payment from ExpreS2ion Biotech Holding AB for a Digital IR/Corporate Visibility subscription agreement. Michael Friis, 11:20, 23/10-2026