On December 2, 2025 Immutep Limited (ASX: IMM; NASDAQ: IMMP) ("Immutep" or "the Company"), a late-stage immunotherapy company targeting cancer and autoimmune diseases, reported new data from the AIPAC-003 trial will be presented at the 2025 San Antonio Breast Cancer Symposium (SABCS) taking place in San Antonio, Texas, from December 9-12, 2025.
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The Phase II study randomised female participants (N=66) with HR+ and HER2-negative/HER2-low metastatic breast cancer (MBC) resistant to endocrine-based therapy (ET) including cyclin-dependent kinase 4/6 (CDK4/6) inhibitors or metastatic triple-negative breast cancer (mTNBC) not eligible for PD-(L)1-based therapy. Patients were randomised 1:1 to receive either 30 or 90 mg eftilagimod alfa (efti) in combination with paclitaxel to determine the optimal biological dose (OBD) consistent with the FDA’s Project Optimus initiative.
Both efti dosing levels on top of weekly paclitaxel in heavily pretreated metastatic breast cancer patients, who received a median of three prior lines of systemic therapy, led to strong objective response rates (ORR) and disease control rates (DCR) of 41.9% and 87.1% (30 mg efti) and 48.5% and 78.8% (90 mg efti), respectively, in the evaluable population (N=64). Time to onset of response (TTR) was comparable at 2.0 months (30 mg) versus 1.9 months (90 mg).
Additionally, both dosing levels elicited the desired pharmacodynamic (PD) response in line with efti’s mechanism of action with substantial increases in immune activation biomarkers including absolute-lymphocyte count (ALC) and interferon-gamma (IFN-γ). Data cut-off date for efficacy results was 15 September 2025.
Dr. Nuhad Ibrahim, Professor, Department of Breast Medical Oncology, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center noted, "Evaluating two biologically active doses allowed us to integrate clinical response data with meaningful pharmacodynamic readouts. In keeping with Project Optimus principles, the study generated rigorous comparative data in heavily pretreated metastatic breast cancer patients showing consistent efficacy measures and immune-activation signals across both arms, reinforcing efti’s novel mechanism of action and the clinical potential of this immunotherapy-chemo combination."
Tolerability at 90 mg was suboptimal including dose-limiting toxicities (DLT) and a higher proportion of local injection site reactions (LISR). In line with FDA guidance/advice and as previously reported on 13 October 2025, 30 mg of efti administered subcutaneously has been defined as the OBD.
(Press release, Immutep, DEC 2, 2025, View Source [SID1234661102])