Immutep (ASX:IMM) will present new clinical results from its AIPAC-003 Phase 2 trial at next week’s San Antonio Breast Cancer Symposium (SABCS), highlighting encouraging response rates and clear signs of immune activation in heavily pretreated metastatic breast cancer patients.
The data mark a significant step in the clinical development of eftilagimod alfa (efti) and confirm the optimal biological dose under the FDA’s Project Optimus framework.
The trial enrolled 66 women with HR-positive/HER2-negative or HER2-low metastatic breast cancer resistant to endocrine therapy, as well as metastatic triple-negative breast cancer not eligible for PD-(L)1 therapy. Participants were randomised to receive either 30 mg or 90 mg of efti in combination with weekly paclitaxel.
Both dosing arms demonstrated notable activity, with objective response rates of 41.9 per cent for 30 mg and 48.5 per cent for 90 mg, and disease control rates of 87.1 per cent and 78.8 per cent, respectively, among the evaluable population. Median time to response was nearly identical across groups at around two months. Substantial increases in immune biomarkers, including absolute lymphocyte count and interferon-gamma, offered further confirmation of efti’s mechanism of action.
Professor Nuhad Ibrahim of MD Anderson Cancer Center said the comparative design was central to meeting the FDA’s modern expectations. “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,” he said.
Tolerability challenges at the higher dose, including dose-limiting toxicities and more frequent injection-site reactions, ultimately supported selecting 30 mg as the optimal biological dose. The FDA has accepted this as the recommended dose across Immutep’s oncology pipeline.
Immutep CEO Marc Voigt said confirmation of the optimal dose marks an important inflection point. “We are pleased to conclude this important phase of efti’s clinical development and are fully committed to advancing this novel immunotherapy to address the needs of cancer patients globally, especially in light of our ongoing Phase III in 1st line NSCLC,” he said. He noted that the findings hold “significant importance” for future combinations, including with antibody-drug conjugates and bispecific antibodies, and for potential future regulatory submissions.
The new findings will be presented during the SABCS poster session on 10 December by Dr Ibrahim.