Immatics (IMTX) Study Update summary

Study design and patient population

• IMA203 targets PRAME and is being evaluated in a phase 1b dose expansion study for PD-1 refractory metastatic melanoma, with a phase III trial planned for late 2024.

• The phase 1b cohort included 28 melanoma patients, all treated at the recommended phase II dose, with a total safety population of 70 patients across all indications.

• Patients were heavily pretreated, last-line, stage IV, with high tumor burden and prior therapies.

• Only cutaneous, acral, and melanoma of unknown origin will be included in phase III; mucosal and uveal melanoma are excluded for homogeneity.

• IMA203 is Immatics' most advanced TCR-based autologous cell therapy, targeting PRAME, a protein highly expressed in various solid tumors.

Efficacy and clinical outcomes

• Confirmed objective response rate in melanoma patients was 54%, with 7 of 14 responses ongoing at data cutoff.

• 88% of patients showed tumor shrinkage, and disease control was achieved in 92% of patients.

• Median duration of response was 12.1 months, with some responses ongoing for over two years.

• Median progression-free survival (PFS) was six months, and median overall survival (OS) was not reached at 8.6 months follow-up.

• Deep responders (≥50% tumor reduction) had median PFS exceeding one year.

Safety and tolerability

• IMA203 was well tolerated, with most adverse events being expected cytopenias from lymphodepletion.

• Mild to moderate cytokine release syndrome (CRS) was most common; 8 of 70 patients had grade III CRS.

• Infrequent ICANS events were observed, all resolved, and no treatment-related deaths occurred.

• Tolerability profile was consistent across melanoma and broader populations at the recommended dose.

• No treatment-related Grade 5 adverse events and mostly mild to moderate side effects.