On February 18, 2026 Aprea Therapeutics, Inc. (Nasdaq: APRE) ("Aprea" or the "Company"), a clinical-stage biopharmaceutical company developing innovative therapies that exploit cancer-specific vulnerabilities while minimizing damage to healthy cells, reported additional preliminary data from the ongoing Phase 1 ACESOT-1051 trial evaluating its investigational WEE1 kinase inhibitor APR-1051.

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The Company reported a second unconfirmed partial response at first on-treatment scan in a patient with advanced endometrial cancer being treated at the 220 mg dose level (Cohort 8).

At the first on-treatment imaging assessment of single dose daily APR-1051, the responding patient achieved a 50% reduction from baseline in target lesion measurements, consistent with partial response per RECIST v1.1 criteria. In addition, there was a notable decline in the tumor biomarker CA-125, with levels dropping from 362 U/mL at baseline to 47 U/mL (-87%), further supporting the anti-tumor activity of APR-1051. The patient’s tumor harbors a PPP2R1A mutation. To date, the patient had only Grade 1 treatment-emergent adverse effects and continues treatment.

The observed unconfirmed partial responses for both patients with PPP2R1A mutations require confirmation at subsequent imaging assessments to be designated as confirmed responses under standard criteria.

A further update from the trial is expected in the second quarter of 2026.

"We are encouraged to see a second patient in the ongoing ACESOT trial achieve an unconfirmed partial response," said Eugene Kennedy, MD, Chief Medical Advisor at Aprea. "We believe the magnitude of tumor reduction and the substantial drop in CA-125 in this patient provides further evidence of APR-1051’s biologic activity and potential therapeutic impact. Importantly, this patient was refractory to her most recent two prior therapies. The response in a tumor with a PPP2R1A alteration underscores the potential of genomically guided patient selection in our DDR program."

Oren Gilad, Ph.D., President and Chief Executive Officer of Aprea, commented, "We believe the emergence of a second unconfirmed partial response strengthens the clinical trend we are observing as dose escalation progresses. These results reinforce our confidence in the therapeutic potential of WEE1 inhibition in genetically defined difficult-to-treat cancers. In addition, the good safety profile of APR-1051 to date supports our development strategy of a differentiated WEE1 inhibition through a potentially improved therapeutic index (TI), as low TI has been a major hurdle in the development of WEE1 inhibitors. We remain focused on advancing APR-1051 and look forward to providing further updates from this trial."

ACESOT-1051 Trial Key Findings to Date

The ongoing Phase 1 trial is designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of APR-1051 in patients with advanced solid tumors. A total of 22 patients have been treated to date, at doses ranging from 10 mg to 220 mg.

Partial Responses: Two patients have achieved partial responses (unconfirmed) at their first scan, both with endometrial cancer, and with tumors harboring PPP2R1A mutations. These responses were observed at the 150 mg and 220 mg dose levels of APR-1051. Both patients remain on therapy.
Stable Disease: A total of five patients in the trial have had stable disease:
70 mg cohort: HPV-positive head and neck squamous cell carcinoma (HNSCC)
100 mg cohort: FBXW7-mutated colon cancer; KRAS & p53-mutated colon cancer; CCNE1 & TP53 mutated uterine cancer
150 mg cohort: FBXW7-mutated colon cancer
Favorable tolerability: APR-1051 has been generally well tolerated

Taken together, these data support the potential activity of APR-1051 in genomically defined cancers across multiple solid tumor types.

Enrollment in the 220 mg dose cohort continues, and the Company plans to further expand enrollment of PPP2R1A endometrial and HPV-positive HNSCC patients within the study.

About the ACESOT-1051 Trial

ACESOT-1051 is a first-in-human, open-label Phase 1 study evaluating the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of single-agent APR-1051 in patients with advanced solid tumors harboring cancer-associated genetic alterations. The dose-escalation portion of the study is expected to enroll up to 50 patients. APR-1051 is administered orally once daily in continuous 28-day cycles. To date, enrollment has evaluated doses up to 150 mg, with the 220 mg cohort currently enrolling. For more information, visit ClinicalTrials.gov (NCT06260514).

(Press release, Aprea, FEB 18, 2026, View Source [SID1234662747])