DOYLESTOWN, PA — Aprea Therapeutics Inc. (Nasdaq: APRE) reported additional preliminary data from its ongoing Phase 1 ACESOT-1051 trial showing a second unconfirmed partial response in a patient with advanced endometrial cancer treated with its investigational WEE1 inhibitor APR-1051.
The company said the response occurred at the 220 mg dose level during the first on-treatment imaging assessment.
According to Aprea, the patient achieved a 50% reduction from baseline in target lesion measurements, consistent with a partial response under RECIST v1.1 criteria. Tumor biomarker CA-125 declined from 362 U/mL at baseline to 47 U/mL, an 87% reduction.
The patient’s tumor harbored a PPP2R1A mutation and experienced only Grade 1 treatment-emergent adverse events to date, the company said. The patient remains on therapy.
Aprea said both observed partial responses in the trial to date have occurred in patients with endometrial cancer and PPP2R1A mutations, at the 150 mg and 220 mg dose levels. The responses remain unconfirmed pending subsequent imaging assessments.
“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. He said the magnitude of tumor reduction and decline in CA-125 “provides further evidence of APR-1051’s biologic activity,” noting the patient had been refractory to her two most recent therapies.
Chief Executive Officer Oren Gilad said the results “strengthen the clinical trend we are observing as dose escalation progresses” and cited what he described as a favorable safety profile to date.
The Phase 1, first-in-human, open-label study is evaluating the safety, pharmacokinetics and preliminary anti-tumor activity of single-agent APR-1051 in patients with advanced solid tumors harboring cancer-associated genetic alterations.
A total of 22 patients have been treated across dose levels ranging from 10 mg to 220 mg, the company said.
In addition to the two unconfirmed partial responses, five patients have achieved stable disease, including patients with head and neck squamous cell carcinoma and colon and uterine cancers with specified genetic mutations.
Enrollment continues in the 220 mg dose cohort, and the company plans to expand enrollment of patients with PPP2R1A-mutated endometrial cancer and HPV-positive head and neck squamous cell carcinoma.
Aprea said it expects to provide a further trial update in the second quarter of 2026. Additional information on the study is available at ClinicalTrials.gov under identifier NCT06260514.
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