IMTX

Business Context and Reporting Period

This Form 6-K filing by Immatics N.V. was submitted on December 11, 2025. The report provides updated dose escalation data from the Phase 1a clinical trial of IMA203CD8, a second-generation PRAME cell therapy, in heavily pre-treated patients with solid tumors. The data cutoff date was October 27, 2025.

Key Clinical Metrics and Financial Status

Clinical Trial Data:

• Enrollment: 78 patients enrolled (median of three prior systemic treatments); 69 patients were efficacy-evaluable.
• Dosing: Median total infused dose was 1.6x10⁹ TCR T cells across seven escalating dose levels.
• Efficacy:
  • Confirmed Objective Response Rate (cORR): 36% (23/64).
  • Objective Response Rate (ORR): 46% (32/69).
  • Tumor Reduction: 78% (54/69).
  • Disease Control Rate (DCR) at week 6: 84% (58/69).
  • Median Duration of Response (mDOR): 9.2 months (median follow-up of 14 months).
• Safety: No Grade 5 IMA203CD8-related adverse events observed. Most frequent TEAEs were anticipated cytopenias. Cytokine release syndrome (CRS) was observed in 95% of patients (mostly Grade 1 and 2). Immune effector cell-associated neurotoxicity syndrome (ICANS) occurred in 7% of patients.

Financial Metrics: The filing text does not provide a clear value for revenue, profit, cash flow, margins, debt, or liquidity. This report focuses exclusively on clinical trial updates.

Material Changes and Subgroup Analysis

The filing highlights specific activity in ovarian carcinoma (n=11), where a dose-dependent signal was observed. Among five patients treated at dose levels ≥DL5, two confirmed partial responses were noted, including one ongoing metabolic complete response at the highest dose (7.1x10⁹ TCR T cells). All responders were resistant to previous platinum-based chemotherapy and did not receive post-infusion low-dose IL-2. The company notes that IMA203CD8 is designed to build on the potential of its lead therapy, anzu-cel (which showed a cORR of 19% in dose escalation), by targeting a broader spectrum of PRAME expression levels and complex tumor microenvironments.

Guidance, Outlook, and Risks

Outlook and Next Steps:

• The company aims to position IMA203CD8 in a tumor-agnostic setting for advanced PRAME cancers beyond melanoma, starting with gynecologic cancers.
• The Phase 1 trial data supports the potential to advance IMA203CD8 without the requirement of post-infusion low-dose IL-2.
• The company is on track to complete Phase 1a dose escalation and determine the Recommended Phase 2 Dose (RP2D) in 2026.

Risks and Contingencies:

• Forward-looking statements regarding trial timing, outcomes, and regulatory filings are subject to risks and uncertainties.
• Scientific and clinical data presented are preliminary and subject to further quality checks and source data verification.
• Actual results may differ materially from expectations due to factors beyond management's control, including general economic conditions and clinical trial risks.

Key Facts for Investor Verification

• Verify the timeline for determining the Recommended Phase 2 Dose (RP2D) in 2026.
• Confirm the durability of responses in the ovarian carcinoma subgroup, specifically the ongoing metabolic complete response.
• Monitor the safety profile regarding CRS and ICANS as dose levels increase to the maximum tolerated dose.
• Assess the company's cash runway and capital requirements, as this filing does not disclose current liquidity or burn rate.
• Review the potential for IMA203CD8 to proceed without post-infusion low-dose IL-2, which could impact manufacturing complexity and cost.