Immutep Limited announced encouraging efficacy, safety, and pharmacodynamic data from the safety lead-in of the AIPAC-003 Phase II/III trial presented at the European Society for Medical Oncology (ESMO) Breast Cancer 2024 Congress. This lead-in represents the first ever 90mg dosing of efti, a soluble LAG-3 protein and MHC Class II agonist, given in combination with weekly paclitaxel. Efficacy: The poster titled " Testing a higher dose (90 mg s.c.) of efti and paclitaxel, this patient achieved a partial response (PR) that subsequently turned into a CR.

This patient's ongoing CR has been maintained since stopping paclitaxel and being treated with efti monotherapy. The lead-in has also shown that the first-ever 90mg efti dosing in combination with weekly pac litaxel continues to be well tolerated with a favourable safety profile. As of the data cut-off (April 3), no dose-limiting toxicities and no treatment-emergent adverse events of grade 3 or higher severity were recorded.

The 90mg efti dosed leads to a higher maximum concentration of efti in the blood as compared to lower efti dosing in past clinical trials, and efti remains detectable at a pharmacologically active level (>1 ng/mL) up to 96 hours after administration. Pharmacodynamic effects also showed an increase of circulating levels of immune cells such as CD8 & CD4 T cells and plasma Th1 biomarker levels. All patients in the AIPAC-003 safety lead-in had a 1.4-fold change in interferon-gamma (IFN-g) and ~83% had a 1.4- fold change in CXCL10 after a single 90mg efti dose.

This portion of the trial has enrolled 35 patients to date. Importantly, the determination of the optimal dose in AIPAC-003 is directly tied to the FDA's Project Optimus initiative and is relevant for the entire efti program. Further data updates in terms of safety and efficacy from AIPAC-003 are expected in CY2024.

The ESMO Breast 2024 poster will be available on the Posters & Publications section of Immutep's website. Its favourable safety profile enables various combinations, including with anti-PD-[L1 immunotherapy and/or chemotherapy. Efti has received Fast Track Track, and Efti's Phase II portion of the study expected in CY2024.