DOYLESTOWN, PA — Aprea Therapeutics, Inc. (Nasdaq: APRE) reported a confirmed partial response in its ongoing Phase 1 clinical trial evaluating APR-1051, a WEE1 kinase inhibitor, in patients with biomarker-defined cancers, the company announced.
The confirmed response was observed in a patient with PPP2R1A-mutated endometrial cancer receiving a 220 mg daily dose, with tumor size reduced by more than 50% at initial assessment and an additional 9.5% reduction at follow-up.
The patient also showed a decline in CA-125 levels to 40.2 U/mL from 362 U/mL at baseline, according to the company.
The ACESOT-1051 trial is evaluating the safety, tolerability and preliminary anti-tumor activity of APR-1051 in patients with advanced solid tumors linked to specific genetic mutations.
A total of 24 patients have been treated across dose levels ranging from 10 mg to 220 mg once daily, with two partial responses observed in patients with endometrial cancer, one of which has been confirmed.
Both patients remain on treatment, the company said.
Five additional patients have achieved stable disease, including those with head and neck, colorectal and endometrial cancers.
APR-1051 has been generally well tolerated, with most adverse events reported as Grade 1 or 2, including nausea and fatigue.
“The data emerging from the ACESOT-1051 trial continue to support the clinical potential of APR-1051,” said Eugene Kennedy, chief medical advisor at Aprea, citing evidence of sustained anti-tumor activity and tolerability.
Dose escalation is ongoing, with plans to evaluate a 300 mg daily dose in the second quarter of 2026.
The company said it also plans to enroll additional patients with tumor types and genetic mutations associated with potential response, including uterine serous carcinoma, colorectal cancer and HPV-positive tumors.
Aprea said it expects to provide a further update from the trial in the second quarter of 2026.
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