ExpreS2ion: Incremental Phase I data strengthen early biological validation of ES2B-C001
ExpreS2ion today reported updated immunogenicity observations from its ongoing Phase I trial of ES2B-C001, showing that five out of six evaluable patients have demonstrated a vaccine-specific immune response, defined as an increase from baseline in anti-HER2 lambda light-chain antibody titers. The update extends the previously reported dataset, now including patients from both the initial low-dose cohort (50 µg) and early observations from the subsequent higher dose cohort (150 µg), while also providing the first indications of response durability in patients who have completed all scheduled study visits.
Compared with the December update, the current release adds incremental but relevant information. The expansion to six evaluable patients and the consistency of immune responses across patients support the biological rationale of ES2B-C001, while sustained elevated antibody titers in two patients suggest that the induced response may be durable. Importantly, no new safety concerns were reported, and patient enrolment and dose escalation continue broadly in line with the communicated clinical timeline. At the same time, the company appropriately emphasises that the dataset remains limited, heterogeneous, and exploratory, and that further follow-up and additional patients are required before drawing firm conclusions.
From an investment perspective, the update provides continued early biological validation of ES2B-C001 but does not materially alter the overall risk profile of the programme at this stage. This view is broadly consistent with the Redeye report published yesterday, which ascribes substantial long-term value to the HER2 breast cancer indication but also highlights that current valuation remains highly sensitive to clinical progression and funding assumptions. In Redeye’s framework, ES2B-C001 represents the dominant value driver, yet the contribution to present value remains modest at this stage due to the early clinical phase and associated execution risk.
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In HCA current framework, the share price still appears to discount a very low implied probability of success relative to historical benchmarks for Phase I assets. We continue to view this as driven as much by funding risk and limited cash runway as by doubts over the underlying science. While the latest data strengthen the qualitative investment case, we would expect more mature read-outs across additional patients and dose levels before the market is likely to reassess the probability of success it is willing to price into the share.
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Overall, the consistency of immune responses observed across patients and dose levels, together with early indications of durability, reinforces the scientific rationale behind ES2B-C001 and the ExpreS2/AdaptVac platform. If these signals are confirmed and extended through subsequent updates in 2026, they could incrementally de-risk near-term development and improve the basis for a future revaluation. For now, however, the update should be viewed as supportive, but still preliminary.
The new data, FY 2025 results, and whether the latest updates on the Niphah virus projects is changing the case there, will be in focus when the management will present the FY 2025 results on the on 19 February 2026 at 09:30.
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Disclaimer: HC Andersen Capital receives payment from ExpreS2ion Biotechnologies for a Digital IR/Corporate Visibility subscription agreement. Michael Friis, 12.00, d. 03/02-2025