Immutep’s eftilagimod alfa linked to improved survival in late-stage cancer pooled analysis

Edited by Robert McTiernan··4 min read

Australia-based Immutep Ltd (ASX: IMM; Nasdaq: IMMP) reported that pooled exploratory analysis suggested that patients with late-stage cancer who mounted an immune response to eftilagimod alfa lived a median of 7.7 months longer — a finding drawn from a pooled analysis of 592 patients across five trials. The news arrives recently after the drug’s Phase III program in lung cancer was shut down for futility.

The exploratory analysis pooled data from five studies — TACTI-mel, TACTI-002, TACTI-003, AIPAC, and AIPAC-003 — spanning non-small cell lung cancer, head and neck squamous cell carcinoma, metastatic breast cancer, and melanoma. All patients received 30 mg subcutaneous eftilagimod alfa plus a standard-of-care backbone, either chemotherapy or a PD-1 antagonist. The central question was whether a measurable pharmacodynamic signal — specifically, an increase in absolute lymphocyte count — translated into a survival benefit.

In the retrospective analysis, an ALC response was associated with longer overall survival. Patients in the efti plus standard-of-care group who showed an ALC response had a median overall survival 7.7 months longer than ALC non-responders (p=0.0017 by log-rank test). No equivalent association between ALC response and survival was observed in the standard-of-care alone group, suggesting the effect was not simply a marker of general immune fitness but was linked specifically to efti’s mechanism. Supporting biomarker data showed rapid increases in circulating TH1-related cytokines and enhanced T-cell function scores on gene expression profiling in responding patients. The effects were consistent across all four tumor types and appeared independent of whether the combination partner was chemotherapy or immunotherapy.

Eftilagimod alfa is a soluble LAG-3–Ig fusion protein that binds MHC class II on antigen-presenting cells, activating dendritic cells and monocytes to enhance downstream T-cell priming — a mechanism positioned upstream of checkpoint blockade rather than in direct competition with it. The data will be presented as a poster at the 2026 American Society of Clinical Oncology Annual Meeting on May 30.

Competitive context

The findings arrive against the backdrop of the failed TACTI-004 Phase III study. In March 2026, the company discontinued TACTI-004, its Phase III trial of eftilagimod alfa in combination with Merck’s Keytruda (pembrolizumab) and chemotherapy in first-line NSCLC, following a recommendation from the Independent Data Monitoring Committee after a planned interim futility analysis. Immune data from TACTI-004 were not included in the current pooled analysis, as collection was incomplete at the time.

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The pooled analysis is explicitly exploratory and retrospective — it identifies a biomarker-outcome correlation across earlier, smaller studies rather than testing a pre-specified hypothesis in a prospective registrational trial. The ALC responder-versus-non-responder comparison within the efti arm is not a randomized comparison, and the 7.7-month median OS difference, while statistically significant by log-rank, reflects a post-hoc subgroup analysis. Cross-trial comparisons are limited by differences in patient populations, lines of therapy, and combination partners across the five included studies.

Nevertheless, the consistency of the ALC-survival association across four distinct tumor types and two different drug classes as combination partners is notable for a biomarker correlation of this kind. The absence of a corresponding ALC-OS association in the standard-of-care-alone arms lends some biological plausibility to the hypothesis that eftilagimod alfa’s immune activation is linked to the survival signal rather than merely reflecting baseline immune fitness.

Whether that signal can be reproduced in a prospective, biomarker-selected trial remains the central unanswered question. Immutep has said it continues to review data from TACTI-004 to understand the factors behind the futility outcome and evaluate implications for the broader eftilagimod alfa development program. The company has not announced a next registrational trial, and the path forward in NSCLC — the indication where the Phase III program failed — remains unclear. TACTI-003 in first-line recurrent or metastatic HNSCC, where efti has received FDA Fast Track designation, represents the most advanced remaining program. Whether the ALC biomarker framework presented at ASCO 2026 informs patient selection in any future trial design will likely be a key question for analysts and investigators reviewing the poster data.

For a drug class that has struggled to demonstrate clean Phase III efficacy signals despite mechanistic differentiation from PD-1 blockade, the pooled analysis does not resolve the core development question. It does, however, offer Immutep a biological rationale to pursue — the possibility that eftilagimod alfa’s benefit is concentrated in patients who mount a measurable immune response, and that identifying those patients prospectively could sharpen the signal that was lost in an unselected Phase III population.

This article was generated with AI assistance and reviewed and edited by the AllSci editorial team Explore more at AllSci News: https://allsci.com/news/