Aprea Therapeutics expands APR-1051 trial to ten sites ahead of Q4 data

Aprea is scaling ACESOT-1051 enrollment to up to ten patients a month and adding combination arms in head and neck cancer and colorectal cancer.

The Biotech Times Editorial Team By The Biotech Times Editorial Team
A bright medical examination room features a white CT scanner with blue accent lights, an attached gray patient examination table, and blurred computer monitors in the background.

Aprea Therapeutics has provided an update on its Phase 1 ACESOT-1051 trial of APR-1051, an oral WEE1 kinase inhibitor, saying active clinical sites have grown from three to ten and that enrolment is expected to reach six to ten patients per month by the fourth quarter of 2026. The Nasdaq-listed company plans to present the next clinical data readout at a medical meeting in Q4 2026, making it a near-term catalyst for the programme.

The update builds on earlier signals from the dose-escalation cohorts, where APR-1051 showed what Aprea describes as early single-agent activity alongside a tolerability profile the company considers favourable. Dose escalation is currently enrolling at the 300 mg cohort, within a protocol range of 10 mg to 500 mg. The trial uses an accelerated titration method at lower dose levels before switching to a Bayesian optimal interval design, with a Part 2 randomisation stage planned to identify the recommended Phase 2 dose across up to 80 patients.

Expanding the indication footprint

Alongside the enrollment acceleration, Aprea is broadening the clinical strategy in two directions. In biomarker-selected solid tumours, the company is targeting at least 50 patients with uterine serous carcinoma or cyclin E-overexpressing, platinum-resistant ovarian cancer, with dose escalation and backfill expansion anticipated to complete in the second quarter of 2027. In parallel, it intends to open new combination arms: APR-1051 paired with immune checkpoint therapy in HPV-positive head and neck squamous cell carcinoma, and with standard-of-care chemotherapy in colorectal cancer. Both combinations are supported by preclinical synergy data, Aprea said.

Chief Medical Advisor Gene Kennedy said that expanding enrolment and adding the combination arms would "broaden the clinical dataset as we advance development of ACESOT-1051," adding that the company looks forward to sharing trial data at a medical meeting later this year.

Market and competitive context

WEE1 inhibition has attracted growing interest in oncology since AstraZeneca's adavosertib demonstrated activity in biomarker-selected populations, though that asset was discontinued after tolerability challenges in later studies. The experience with adavosertib has shaped expectations for the class: selectivity, tolerability and biomarker-driven patient selection are now widely considered the key differentiating factors for any follow-on WEE1 programme. Aprea is positioning APR-1051 precisely on those parameters, citing cyclin E overexpression and CCNE1/CCNE2 alterations as mechanistic rationale for sensitivity.

The indications Aprea is pursuing, particularly platinum-resistant ovarian cancer and uterine serous carcinoma, represent areas of significant unmet need where approved options remain limited. Several other clinical-stage companies are also exploring cell-cycle checkpoint inhibitors across overlapping tumour types, meaning that the Q4 2026 data presentation will be scrutinised for differentiated efficacy and safety signals rather than simply proof of concept for the mechanism.

Aprea's second programme, ATRN-119, an ATR inhibitor, is also in clinical development for solid tumours, giving the company two complementary DNA-damage response assets. How management allocates capital between the two programmes as APR-1051 data matures will be a key question for investors heading into the second half of 2026.

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