Key Results from INSIGHT-003 – Data Cutoff – 27 March 2026

Approximately 92% of patients enrolled in INSIGHT-003 had no or low PD-L1 expression (Tumour Proportion Score: TPS <50%), representing a population with significant unmet medical need. With a minimum of 30 months of follow-up, median Overall Survival (mOS) was 30.9 months in the overall population regardless of PD-L1 expression (N=51), with the same mOS observed in patients with TPS <50% (N=47) and 37.8 months in TPS>=50% (N=4).

These mature results continue to compare favourably to the 22.0 month mOS from a registrational trial of anti-PD-1 and doublet chemotherapy in non-squamous 1L NSCLC regardless of PD-L1 expression.1 Notably, patients with TPS <50%, for whom PD-L1 inhibitor-based therapies typically perform suboptimally, were overrepresented in INSIGHT-003 compared with historical benchmarks (~92% versus ~68%1). No new safety signal was identified since the previous data cut-off.

Update on TACTI-004 Root Cause Analysis

In March 2026, following a planned interim futility analysis, Immutep announced that it would discontinue the TACTI-004 Phase III trial in 1st line NSCLC based on a recommendation from the Independent Data Monitoring Committee (IDMC). In the TACTI-004 futility analysis (N=173), the objective response rate (ORR) in the overall patient population receiving standard of care plus efti ("efti arm") was 42.9% compared with 55.1% in patients receiving standard of care plus placebo ("control arm"). The difference was observed across both squamous and non-squamous histologies, and the efti arm did not demonstrate superiority in any TPS subgroup. By comparison, the ORR in INSIGHT-003 has been 62.7%, despite the high proportion of patients with TPS <50%. Pending a final analysis of all patients, to date no new safety signals have been observed in TACTI-004.

Preliminary immune monitoring data generated from TACTI-004 indicate that patients treated with efti exhibited a markedly different immune activation profile compared with that observed in previous studies. This assessment is based on analyses of absolute lymphocyte counts (ALC) and circulating monocyte counts in blood. In particular, these findings contrast with observations from almost 600 patients treated with efti in five earlier studies (AIPAC, AIPAC-003, TACTI-mel, TACTI-002 and TACTI-003), which were presented at ASCO 20262, and also contrast with observations from INSIGHT-003.

The TACTI-004 analysis, which includes all recruited and evaluable patients who received a minimum of 12 weeks of treatment, remains ongoing, with additional results expected in Q3 CY2026. The Company will continue to analyse this data as part of its ongoing root cause analysis of a range of potential factors, including manufacturing, and will share the outcome of that analysis as soon as it becomes available. Immutep is being assisted in this process by its partners, including Dr. Reddy’s and WuXi Biologics.