Immutep reports topline results from TACTI-003 Phase 2b trial

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Immutep (ASX:IMM) has announced topline results from the TACTI-003 (KEYNOTE-PNC-34) Phase 2b trial evaluating its eftilagimod alfa (efti) in combination with MSD’s anti-PD-1 therapy KEYTRUDA (pembrolizumab) as first-line treatment of recurrent and metastatic head and neck squamous cell carcinoma (1L HNSCC).

Efti is a novel LAG-3 immunotherapies in development for cancer and autoimmune diseases.

The trial enrolled 171 patients with any PD-L1 expression and negative PD-L1 expression at over 30 centres across the US, Europe, and Australia.

Immutep said that the combination led to higher overall response rates in evaluable patients according to RECIST 1.1 – the study's primary endpoint - across all levels of PD-L1 expression compared to KEYTRUDA monotherapy.

In the overall evaluable trial patient population, the response rate for efti in combination with KEYTRUDA was around 34 per cent regardless of HPV status and PD-L1 expression, including patients with negative PD-L1 expression.

Dr Martin Forster of the UCL Cancer Institute and University College London Hospital NHS Foundation, and TACTI-003 Investigator, said, “It is encouraging to see efti safely drive higher response rates in combination with KEYTRUDA in the first line setting for head and neck squamous cell carcinoma patients, regardless of HPV status and levels of PD-L1. The strong, consistent response rates, irrespective of whether patients have high, low, or negative PD-L1 expression, is intriguing and offers a glimpse into this novel combination’s ability to improve patients’ clinical responses and expand patient populations that benefit from anti-PD-1 therapy.”

Immutep's chief scientific officer, Dr Frédéric Triebel, said, “We are pleased with the quality of responses. Once again, durability is tracking well driven by the complementary nature of these two unique immunotherapies in fighting cancer. Efti’s distinct activation of dendritic cells as an MHC Class II agonist and the resulting engagement of multiple facets of the adaptive and innate immune system has consistently translated into promising duration of responses in combination with immune checkpoint inhibitors across multiple oncology indications.

"From a statistical point of view, given the relatively small number of evaluable patients and the very ambitious differences required to generate significance, coupled with unexpected imbalances leading to unanticipated strength in the control arm among patients with low PD-L1 expression, we are excited to see the ~68% differential in the largest patient segment (CPS >20) in 1L HNSCC in a randomised setting."

“Additionally, the strength of clinical results in patients with negative PD-L1 expression is notable, and we look forward to sharing more data at the ESMO Virtual Plenary session in July,” added Dr Triebel.

Based on the results, the company said it will discuss potential options with regulatory agencies for metastatic 1L HNSCC patients.