Immatics N.V.

On October 24, 2026, the Company announced updated clinical trial data from its ongoing phase 1b study with IMA402 PRAME TCR bispecific (TCER®) in a heavily pretreated patient population with a median of three prior lines of therapy.

Patient Population. As of the June 1, 2026 data cutoff, 126 heavily pretreated patients across multiple tumor types, primarily melanoma and ovarian cancer, received at least one infusion of IMA402 during the dose escalation or dose expansion part of the ongoing trial (NCT05958121). Patients had received a median of three prior lines of systemic treatment (range: 0 – 7), had a median target lesion sum of diameter of 7.4 cm (range: 1.2 – 39.8) and had a median of four tumor lesions (range: 1 – 15). The efficacy population included 40 patients treated within the recommended Phase 2 dose (RP2D) range of 10 to 45 mg across varying levels of PRAME expression. Within this population, 31 patients exhibited high PRAME expression levels (PRAME-high)1 in their tumors. Of these, all patients with PRAME-high melanoma had received prior systemic treatment with immune checkpoint inhibitors (“ICI”), with a median of 2 prior ICI-regimens and all patients with PRAME-high ovarian cancer were previously treated with platinum-based chemotherapy. Of the 31 patients exhibiting high PRAME expression, 22 were melanoma patients, 20 of which received monotherapy and two received the combination of IMA402 and pembrolizumab.

Safety Data. IMA402 showed favorable tolerability across all doses. The most frequent treatment-related adverse events (“TRAEs”) were expected, transient lymphopenia and low-grade cytokine release syndrome (“CRS”), consistent with the mechanism of action. No cases of Immune Effector Cell-Associated Neurotoxicity Syndrome (“ICANS”) were reported. No IMA402-related Grade 5 events were reported. Tolerability was consistent across all evaluated doses, including the RP2D range, with no additive toxicity observed when combined with an ICI.

The following table shows TRAEs across all indications and dose levels:

1 Patients showed PRAME expression 3-fold higher than the PRAME qPCR threshold, based on an exploratory analysis in the efficacy population. More than 80% of patients with cut. melanoma are estimated to have PRAME-high expression based on Immatics and TCGA RNA seq data.

a TRAEs: All treatment-emergent adverse events at least possibly related to IMA402 with grade 1-2 occurring in at least 9 patients (incidence ≥7.1%), and all events with grade 3-5. One uncoded grade 1 AE (“spotting”) is not included. Abdominal pain incudes “Abdominal Pain” and "Abdominal Pain Upper”; Patients are counted only once per adverse event.

The following table shows TRAEs for IMA402 as monotherapy and IMA402 with pembrolizumab at all dose levels:

a TRAEs: All treatment-emergent adverse events at least possibly related to IMA402 with grade 1-2 occurring in at least 8 patients for monotherapy (incidence ≥7%), and all events with grade 3-5. One uncoded grade 1 AE (“spotting”) is not included. Abdominal pain incudes “Abdominal Pain” and "Abdominal Pain Upper”; Patients are counted only once per adverse event. b Out of 19 patients treated with IMA402 + pembrolizumab, 3 have ongoing early step dosing and did not yet reach their target dose and 6 did not have the opportunity of at least 3 months of follow-up. Of the remaining 10 patients, 3 were treated with IMA402 below 10 mg, 2 were PRAME negative, and 1 had LDH >1.5x ULN. ALT, alanine aminotransferase; AST, aspartate aminotransferase.

The following table shows TRAEs for IMA402 as monotherapy with and without pembrolizumab for the efficacy population:

a TRAEs: All treatment-emergent adverse events at least possibly related to IMA402 with grade 1-2 occurring in at least 4 patients (incidence ≥10%), and all events with grade 3-5. One uncoded grade 1 AE (“spotting”) is not included. Patients are counted only once per adverse event.. ALT, alanine aminotransferase; AST, aspartate aminotransferase.

Anti-Tumor Activity and Durability. IMA402 showed promising anti-tumor activity as monotherapy (n=36) or in combination with an immune checkpoint inhibitor (n=4) in the efficacy population at RP2D range. Treatment with IMA402 demonstrated 10 confirmed responses resulting in an overall confirmed objective response rate (“cORR”) of 25% (10/40) and a disease control rate (DCR) of 63% (25/40). This includes one confirmed complete response in melanoma. The longest ongoing response exceeded 2 years. In the PRAME-high population, cORR was 32% (10/31) across all indications and 32% (7/22) in patients with melanoma. The PRAME-high melanoma population further showed a median duration of response (“mDOR”) of 12.5 months, with a median follow-up time (“mFU”) of 16.8 months. Median overall survival (“mOS”) was not reached (mFU 8.8 months), with 91% of patients alive at 1 year (versus 60% of patients treated below RP2D range), indicating promising overall survival data irrespective of best response. Among 6 patients with PRAME-high ovarian cancer, 3 confirmed responses were reported.

a Includes cutaneous melanoma and one patient with uveal melanoma. b Includes endometrial cancer (n=2), sqNSCLC (n=2), and synovial sarcoma (n=1); BOR, best overall response; BL, baseline; cCR, confirmed complete response; cORR, confirmed objective response rate; DCR, disease control rate; PD, progressive disease; (c)PR, (confirmed) partial response; SD, stable disease.

BOR, best overall response; BL, baseline; cCR, confirmed complete response; cORR, confirmed objective response rate; PD, progressive disease; (c)PR, (confirmed) partial response; SD, stable disease.