Immutep Limited announced new data from 1st line NSCLC patients (Part A) of the Phase II TACTI-002 trial evaluating Immutep's lead product candidate, eftilagimod alpha in combination with MSD's anti-PD-1 therapy KEYTRUDA (pembrolizumab) in 114 patients. The data was presented in an Oral Presentation at the American Society of Clinical Oncology's 2022 Annual Meeting. Trial endpoints The primary endpoint was ORR according to iRECIST and local read.

The data announced represents the primary analysis of mature data of this endpoint. Secondary endpoints include ORR by RECIST 1.1., DCR, Duration of Response, PFS, Overall Survival, and Safety assessments. Patient population and condition A total of 114 patients with 1st line NSCLC were enrolled and treated with efti plus pembrolizumab in 6 countries across 19 trial sites throughout Europe, the United States, and Australia.

Importantly, the patients were enrolled without any selection for PD-L1 status (PD-L1 all-comers), a biomarker indicating the likelihood of response to pembrolizumab. The trial was confirmed as a “PD-L1 all-comer trial” with approximately 70% of patients having a Tumour Progression Score of < 50%. 93% of patients had metastatic disease at study entry and the patients had an ECOG performance status of 0 (37.7%) or 1 (62.3%).

Treatment prior to study start included radiotherapy (33%), surgery (20%) and systemic therapy (22%) for non-metastatic disease. The trial reflects a typical patient population for this indication, including a mix of squamous/non-squamous disease and male/female representation. Key Findings from 1st line NSCLC patients in TACTI-002 – data cut-off date 15 April 2022 Primary analysisof primary endpoint by iRECIST– ORR ORR of 38.6% in the intent to treat (ITT) group (44/114 patients) and 42.7% for evaluable patients (44/103) by local read, see Table 1 Responses across all PD-L1 status groups in this all-comer trial (by central lab assessment): ORR of 28.1% (9/32) in PD-L1 negative patients ORR of 41.7% (15/36) in patients with PD-L1 status of 1-49% ORR of 45.5% (25/55) in patients with PD-L1 status of = 1% ORR of 52.6% (10/19) in patients with PD-L1 status of = 50% Comparable ORR in squamous (35%) or non-squamous (38.9%) tumour type RECIST 1.1 results are comparable to the iRECIST results ORR is favourable compared to historical trials of anti-PD-1 monotherapy for all-comer population and PD-L1 status groups1 Analysis by iRECIST – DCR, DoR and PFS Responses are deep, see Chart 1 Responses are also durable, with only 8.6% of confirmed responses having a progression = 6 months and median DoR not yet reached Interim median PFS is 6.9 months Interim median PFS increases to 8.4 months for = 1% PD-L1 status group and to 11.8 months for = 50% PD-L1 status group.

Remains favourable compared to historical trials of anti-PD-1 monotherapy4 DCR of 73.7% (84/114) and 81.6% (84/103) for evaluable patients DCR comparable across all PD-L1 status groups with a range of 68.8-79.0% The combination of efti plus pembrolizumab is safe and well-tolerated, continuing efti's good safety profile to date. Part A reports a low discontinuation rate, with only 9.6% of patients discontinuing due to study treatment related adverse events. The safety profile to date is consistent with that observed in previously reported studies for pembrolizumab monotherapy except for local injection site reactions (erythema).

Conclusion The combination of efti plus pembrolizumab is showing favourable efficacy in 1st line NSCLC in the PD-L1 all-comer population and in all PD-L1 status groups, and with a low treatment discontinuation rate. The data support continued late stage development in this indication.