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Immatics Reports Interim Clinical Data from Ongoing Phase 1b Cohort A Monotherapy with ACTengine® IMA203 TCR-T Targeting PRAME

Company to host conference call today, May 2, at 8:30 am EDT / 2:30 pm CEST

  • Update covers data from 11 heavily pre-treated, last-line patients in Phase 1b dose expansion Cohort A treated with IMA203 TCR-T monotherapy against PRAME
  • Objective response rate (ORR): 64% (7/11) initial ORR at week 6 and 67% (6/9) confirmed ORR at month 3
  • Median duration of response not reached at median follow-up time of 8.5 months at data cut-off
  • Objective responses independent of solid tumor type at low, medium and high PRAME expression levels in checkpoint-refractory cutaneous melanoma, platinum-resistant ovarian cancer, uveal melanoma, head and neck cancer and synovial sarcoma
  • Cohort A IMA203 monotherapy TCR-T treatment continues to show manageable tolerability with no high-grade CRS and no ICANS; no dose dependent increase of CRS observed
  • Proprietary rapid manufacturing process with 7 days of manufacturing time; manufacturing success rate of 94% to reach current recommended Phase 2 dose
  • Next data update and pathway towards registration-directed trials planned to be set out in 4Q 2023
  • Company well capitalized with cash position1 of $386m at YE 2022 and reach into 2025 to leverage multi-cancer PRAME opportunity

Houston, Texas and Tuebingen, Germany, May 2, 2023Immatics N.V. (NASDAQ: IMTX, “Immatics”), a clinical-stage biopharmaceutical company active in the discovery and development of T cell-redirecting cancer immunotherapies, today announced an interim clinical data update for 11 patients with recurrent and/or refractory solid cancers treated with ACTengine® IMA203 TCR-T monotherapy in the ongoing Phase 1b dose expansion Cohort A. IMA203 TCR-T cells are directed against an HLA-A*02-presented peptide derived from PRAME, a broadly expressed solid cancer target with clinical proof-of-concept for IMA203 demonstrated by Immatics in 2022. Overall, IMA203 showed a high rate of deep and durable objective responses, with a confirmed objective response rate of 67% (6/9), across multiple tumor types, including two confirmed partial responses (cPR) ongoing at more than 9 months after treatment and three additional partial responses ongoing at data cut-off. IMA203 monotherapy continues to be well tolerated in heavily pre-treated patients at doses of up to approximately 9 billion CD8+ TCR-T cells. No high-grade cytokine release syndrome (CRS) and no immune effector cell associated neurotoxicity syndrome (ICANS) were observed in Cohort A at data cut-off.

The data will be presented by Martin Wermke, MD, Professor at the University Hospital Dresden and Coordinating Investigator of the ACTengine® IMA203 TCR-T trial during a conference call today, May 2, at 8:30 am EDT / 2:30 pm CEST.

“The treatment of solid cancer patients who have exhausted all available standard of care options remains a significant challenge. These patients typically show fast progressing disease with very poor prognosis,” said Martin Wermke, MD, Coordinating Investigator of the ACTengine® IMA203 TCR-T trial. “It is therefore very encouraging to see that IMA203 is able to provide durable, clinically relevant responses in a variety of solid cancer patients.”

“Today marks a significant step in our efforts towards bringing our ACTengine® IMA203 monotherapy to patients with solid tumors, as we present for the first time longer-term clinical data demonstrating deep and durable responses, some of them ongoing beyond 9 months after treatment,” commented Cedrik Britten, MD, Chief Medical Officer at Immatics. “Furthermore, we show that these responses are agnostic of tumor type and that ACTengine® IMA203 achieved objective responses at widely differing PRAME expression levels. These data further increase our confidence in the success and broad potential of targeting PRAME, and our product candidate IMA203. We continue executing and anticipate announcing a potential fast-to-market pathway for the first 1-2 indications by the end of the year.”

Safety data for IMA203 TCR-T monotherapy in Phase 1b Cohort A: Treatment with IMA203 monotherapy continues to show manageable tolerability at doses as high as ~9x109 TCR-T cells.

  • At data cut-off on April 4, 2023, 11 PRAME-positive patients were infused with IMA203 TCR-T cells at dose level (DL) 4 or DL5 with a mean total infused dose of 3.67x109 TCR-T cells (range 1.30-8.84x109 TCR-T cells).
  • Based on data review of 6 patients in the exploratory highest DL5, this DL was cleared by the DSMB (Data and Safety Monitoring Board) for safety, and the updated provisional recommended Phase 2 dose (RP2D) now includes DL4 and DL5. The final RP2D will be defined prior to starting Phase 2.
  • Most frequent treatment-emergent adverse events (TEAEs) were as expected for cell therapies.
  • All 11 patients experienced expected cytopenia (Grade 1-4) associated with lymphodepletion. 10 patients (91%) had a low to moderate (Grade 1-2) cytokine release syndrome (CRS), of which 5 patients (45%) had Grade 1, and 5 patients (45%) had Grade 2 CRS. No high-grade (Grade 3 or higher) CRS and no immune effector cell associated neurotoxicity syndrome (ICANS) were observed in any of these 11 patients. No dose-dependent increase of CRS was observed across Phase 1a and Phase 1b Cohort A (N=38 patients infused with IMA203 in total).
  • No additional dose limiting toxicities (DLT) were observed in Cohort A since the initial Phase 1a dose escalation.

Clinical activity for IMA203 TCR-T monotherapy in Phase 1b Cohort A: IMA203 monotherapy demonstrates a high rate of deep objective responses with ongoing durability of more than 9 months after treatment in some patients.

  • At data cut-off on April 4, 2023, 11 patients were infused with IMA203 TCR-T cells and evaluable for at least one tumor response assessment post treatment.
  • Objective responses were observed in last-line solid cancer patients including cutaneous melanoma, ovarian cancer, uveal melanoma, head and neck cancer, synovial sarcoma.
  • Patients were heavily pre-treated with a mean of ~4 lines of prior systemic treatments and had exhausted all available standard of care treatments.
  • All cutaneous melanoma patients were checkpoint inhibitor-refractory, all ovarian cancer patients were platinum-resistant.
  • Initial objective response rate (ORR) of 64% (7/11) was observed at ~week 6 (partial responses, PR, according to RECIST 1.1).
  • Confirmed ORR of 67% (6/9) was observed at ~month 3; initial responses at week 6 were confirmed for all 6 responders with available subsequent 3-month scan.
  • Median duration of response2 was not reached (min 1.3+ months, max 8.8+ months) at a median follow-up3 of 8.5 months.
  • At data cut-off, 5 of 7 responses remain ongoing:
    • 2 cPRs (cut. & uveal melanoma) ongoing at 9+ months
    • 1 cPR (cut. melanoma) ongoing at 6+ months
    • 1 cPR (ovarian cancer) ongoing at ~3 months
    • 1 PR (synovial sarcoma) ongoing at 6+ weeks
  • Objective responses were observed in patients independent of tumor type at all PRAME expression levels above Immatics’ mass spectrometry-guided RNA threshold including expression levels at or just above this threshold.
  • IMA203 T cells were found in all evaluable tumor tissues and the level of tumor infiltration was associated with objective responses.

Best Overall Response – Phase 1b Cohort A