Aprea Therapeutics announces additional clinical activity for APR-1051

Aprea Therapeutics (APRE) announced additional preliminary data from the ongoing Phase 1 ACESOT-1051 trial evaluating its investigational WEE1 kinase inhibitor APR-1051. 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. 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, 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.”