FDA meeting requested following Phase IIb trial showing median overall survival of 17.6 months without chemotherapy
Immutep Limited (ASX:IMM) has announced impressive overall survival results for its lead immunotherapy candidate eftilagimod alfa (efti) in combination with Merck’s KEYTRUDA® (pembrolizumab) for head and neck cancer patients with low PD-L1 expression, a group with few effective treatment options.
The 17.6-month median overall survival reported in Cohort B of the TACTI-003 (KEYNOTE-C34) Phase IIb trial marks a significant improvement over historical outcomes for patients with a PD-L1 Combined Positive Score (CPS) below 1, who typically see median survival of 7.9 to 11.3 months depending on the treatment regimen.
The study enrolled 31 evaluable patients with recurrent or metastatic head and neck squamous cell carcinoma (1L HNSCC) who received the combination of efti and pembrolizumab as first-line therapy. The data cut-off for the mature results was 31 March 2025.
Patients with CPS <1 are not currently eligible for checkpoint inhibitor monotherapy and must receive chemotherapy. This makes the Immutep results particularly promising, as they suggest a chemotherapy-free option that is both effective and well-tolerated. The company reported no new safety signals.
CEO Marc Voigt highlighted the magnitude of the benefit: “Combining these two complementary immunotherapies has led to a seven-fold increase in response rates and more than doubled median overall survival compared to anti-PD-1 monotherapy.”
The results build on previously reported high overall response rates and multiple complete responses from the same trial cohort. Voigt also noted the lack of competing chemotherapy-free approaches for this subgroup and said the company had requested a meeting with the US Food and Drug Administration to discuss potential paths to approval.
Eftilagimod alfa is Immutep’s proprietary MHC Class II agonist and first-in-class antigen-presenting cell (APC) activator. It is designed to stimulate both the innate and adaptive immune system, enhancing CD8+ T cell and NK cell responses. In addition to head and neck cancer, it is being evaluated for other solid tumours including non-small cell lung cancer and metastatic breast cancer.
Efti has received FDA Fast Track designation for both first-line HNSCC and NSCLC.
Further trial updates are expected later in 2025 as Immutep continues data analysis and regulatory engagement.
