Immutep efti shows 30.9-month mOS in 1L NSCLC despite trial setback
Immutep has reported mature overall survival data from the investigator-initiated INSIGHT-003 Phase I trial, showing a median overall survival (mOS) of 30.9 months in 51 evaluable patients with advanced non-squamous non-small cell lung cancer (NSCLC) receiving eftilagimod alfa (efti) in combination with pembrolizumab and chemotherapy as a first-line regimen.
The data cutoff was 27 March 2026, with a minimum follow-up of 30 months across the cohort. Notably, approximately 92% of enrolled patients had no or low PD-L1 expression (Tumour Proportion Score below 50%), a population for whom checkpoint inhibitor-based regimens have historically delivered more modest outcomes. The mOS of 30.9 months held consistent across this subgroup, and compared favourably to the 22.0-month benchmark reported in the KEYNOTE-189 registrational trial of pembrolizumab plus doublet chemotherapy in non-squamous first-line NSCLC regardless of PD-L1 status. No new safety signals were identified since the previous data cut.
The TACTI-004 discontinuation
The positive INSIGHT-003 update arrives against the backdrop of a significant setback. In March 2026, Immutep announced it would discontinue its Phase III TACTI-004 trial in first-line NSCLC following a recommendation from the Independent Data Monitoring Committee after a planned interim futility analysis. In that analysis (N=173), the objective response rate in patients receiving standard of care plus efti was 42.9%, compared with 55.1% in the placebo-controlled arm. The divergence was observed across both squamous and non-squamous histologies, and efti did not demonstrate superiority in any PD-L1 subgroup, a stark contrast with the 62.7% ORR seen in INSIGHT-003.
Preliminary immune monitoring data from TACTI-004 have since revealed that patients treated with efti in that trial exhibited a markedly different immune activation profile, as assessed by absolute lymphocyte counts and circulating monocyte counts, compared with observations across nearly 600 patients in five earlier studies including AIPAC, TACTI-002 and TACTI-003. This divergence also contrasts with the immune profile observed in INSIGHT-003. Immutep said manufacturing is among the potential factors under investigation, and that its partners Dr. Reddy's and WuXi Biologics are assisting with the root cause analysis. Further results are expected in Q3 2026.
Chief executive Marc Voigt said the mature INSIGHT-003 data reinforce confidence in efti's potential to "enhance anti-tumour immune responses, including in patient populations that have historically experienced less favourable outcomes," while framing the TACTI-004 immune monitoring findings as "valuable insights" for evaluating the asset's path forward.
Market context and regulatory position
Efti is a LAG-3-pathway MHC Class II agonist, a mechanistic class that sits alongside, rather than directly competing with, the established anti-PD-1 and anti-CTLA-4 checkpoint inhibitor franchises. First-line NSCLC remains one of the most competitive segments in oncology, with multiple approved combinations anchored around pembrolizumab. Any future registration programme for efti in this indication will face a high bar for differentiation, particularly among the low PD-L1 population where unmet need is real but comparator data are improving.
Efti holds FDA Fast Track designation in first-line NSCLC and first-line head and neck squamous cell carcinoma. The outcome of the TACTI-004 root cause analysis will be pivotal: if a manufacturing-related anomaly can be identified and corrected, the asset's development rationale may be preserved; if the cause remains unexplained, it will raise questions about reproducibility that no amount of Phase I data can easily address. Investors and clinical partners will be watching the Q3 readout closely.