Immutep Limited announced excellent new clinical data from the TACTI-002 /KEYNOTE-798 Phase II trial evaluating eftilagimod alpha ("efti"), a soluble LAG-3 protein and first-in-class MHC Class II agonist, in combination with MSD's (Merck & Co. Inc., Rahway, NJ., USA) anti-PD-1 therapy KEYTRUDA® (pembrolizumab) as first-line treatment for patients with previously untreated unresectable or metastatic non-small cell lung cancer (NSCLC). The updated TACTI-002 data, with a cut-off date of August 15, 2023 and a median follow up of over 2 years (25.1 months), was presented by Dr. Enric Carcereny, Catalan Institute of Oncology (ICO), Badalona, Spain, during a Mini Oral session (#1312MO) at ESMO Congress 2023 on Saturday, October 21st.

Key takeaways from the oral presentation detailing results from efti in combination with KEYTRUDA® for frontline treatment of advanced or metastatic NSCLC in the TACTI-002 Phase II trial1 include: o Promising Overall Survival (OS), Overall Response Rate (ORR), Progression Free Survival (PFS), and Duration of Response (DOR) are visible across all PD-L1 subgroups (Tumor Proportion Score [TPS] <1%, 1%, 1-49%, and 50%), which clearly differentiates efti in combination with KEYTRUDA® from other chemo-free immuno-oncology (IO) combinations for first-line treatment of NSCLC. o A significant overall survival benefit was achieved, with a 35.5-month median Overall Survival (mOS) in patients with TPS 1%, 23.4-month mOS in TPS 1-49%, and mOS not yet reached in TPS 50%. Notably, the mOS in TPS 1% was attained with central assessment of PD-L1 (N=58) and a larger patient group with central + local assessment of PD-L1 (N=71), and the 35.5-month mOS compares very favourably to standard-of-care IO, IO-IO, IO-chemo, and IO-IO-chemo therapies Exceptional durability and quality of responses are increasingly evident with strong overall survival (OS) and progression free survival (PFS) rates across patients expressing PD-L1.

The 3- year OS rates are 45.6%, 31.0%, and 63.6% in TPS >1%, TPS 1-49%, and TPS >50%, respectively. The 12-month PFS rates are 46.8%, 42.1%, and 55.0% for TPS >1%, TPS 1-49%, and TPS >50%, respectively. The entire patient population regardless of PD-L1 expression (N=114) showed encouraging efficacy with 20.2-month mOS, 21.6-month mDoR, and a 36-month OS rate of 36% despite ~75% of patients having negative or low PD-L1 expression.

In NSCLC patients with >1% PD-L1 expression, a key area for efti's future development where it has FDA Fast Track status, the ORR (48.3%), mPFS (11.2 months), mDOR (24.2 months), and mOS (35.5 months) compare overall favourably to historical results of anti-PD-1 monotherapy, as well as to historical results of approved anti-PD-1 + chemo-containing regimens. Collectively, the breadth of efficacy and safety data from the large number of metastatic NSCLC patients in the Phase II TACTI-002 trial offers compelling evidence of efti's substantial impact in safely stimulating the patients' immune response to fight cancer.