Immatics announces clinical data on TCER IMA402 targeting PRAME

Immatics (IMTX) is providing the first clinical data update from the ongoing Phase 1 dose escalation trial evaluating its next-generation, half-life extended TCR Bispecific molecule, TCER IMA402 targeting PRAME. Patient Population: As of the data cut-off on November 6, 2024, 33 heavily pretreated patients with recurrent and/or refractory solid tumors have been treated with a dose range from 0.02 mg to 4 mg of IMA402 monotherapy. The treated patient population is composed of patients with a median of three and a maximum of five lines of prior systemic treatments. The safety population includes all 33 patients treated with IMA402, of which 21 patients were evaluable for efficacy analysis and are PRAME-positive or were not tested for PRAME. Of these 21 patients, eight patients received at least one dose of IMA402 at dose level 7, and one patient received IMA402 at dose level 8. Based on preclinical in-vivo data, relevant anti-tumor efficacy was expected starting at ~3 mg human equivalent dose, which aligns with the initial clinical anti-tumor activity reported today. Safety: IMA402 demonstrated a favorable tolerability profile in the 33 patients treated. The most common treatment-related adverse events were mostly mild to moderate cytokine release syndrome and transient lymphopenia. Step dosing has been implemented and dose escalation is ongoing. The maximum tolerated dose has not yet been determined. Pharmacokinetics: Early pharmacokinetic data indicate a median half-life of approximately seven days, potentially enabling bi-weekly dosing. Initial Anti-Tumor Activity: Initial signs of clinical activity have been observed and are associated with PRAME expression and IMA402 dose levels administered. In the PRAME-negative patient population across all doses and indications, only one patient out of seven showed tumor shrinkage of -2.9%. In comparison, in the PRAME-positive or non-tested patients across all indications treated with low dose levels tumor shrinkage was observed in 25% of patients, including one unconfirmed partial response in a cutaneous melanoma patient. Nine patients with tumors that tested PRAME-positive or were not tested for PRAME received a relevant dose. 78% thereof experienced shrinkage of their target lesions, including several patients with significant ongoing tumor shrinkage: one cutaneous melanoma patient with an ongoing confirmed partial response with -40.2% tumor shrinkage treated at DL7; two patients with ongoing stable diseases with significant tumor shrinkage; one ovarian cancer patient with ongoing stable disease and tumor shrinkage of -13% started at DL6 and currently at DL7.