Immatics’ cell therapy has been linked to a 56% objective response rate (ORR) among 32 heavily pretreated patients with metastatic melanoma.
The biotech previously shared progression-free survival (PFS) data for the preferentially expressed antigen in melanoma (PRAME) cell therapy known as IMA203, recording a median PFS of six months.
Now, the German biotech is back to share more phase 1b data from the trial at this year’s American Society of Clinical Oncology conference in Chicago, plus details about the ongoing phase 3 study designed to underpin a potential FDA submission.
The extended phase 1b follow-up included data from 33 patients with PD-1-refractory metastatic melanoma who had a median of two lines of prior treatments. Fourteen of the patients had cutaneous melanoma, while 16 patients had uveal melanoma. Two had mucosal melanoma, and one had melanoma of unknown primary.
Patients received a one-time infusion of the autologous PRAME therapy at the recommended phase 2 dose, which was 1 billion to 10 billion total TCR T cells.
The IMA203 infusion was tied to a confirmed ORR (cORR) for 18 of 32 eligible patients, Immatics said in a May 31 release. One patient with uveal cancer was excluded from the count due to an ongoing unconfirmed partial response.
For the 14 patients with cutaneous melanoma, the cORR was 50%. This compares to a 67% cORR for patients in the uveal melanoma subgroup, which included tebentafusp-refractory patients.
The median duration of response (mDOR) for all 33 patients was 12.1 months at a median follow-up of 13.4 months. For all patients, the median PFS was 6.1 months, and the median overall survival was 15.9 months.
Patients in the cutaneous melanoma subgroup had not reached a mDOR at 16.7 months of follow-up and recorded a median PFS of six months.
Those with uveal melanoma had a mDOR of 11 months at 13.4 months of follow-up and a median PFS of 8.5 months.
Safety data were taken from 74 patients across a phase 1a dose escalation and the phase 1b dose-expansion group.
The most common treatment-emergent adverse events were cytopenias—or low levels of normal blood cells—associated with lymphodepletion, a preparation step before IMA203 infusion.
Cases of cytokine release syndrome (CRS), an adverse event often tied to cell therapies, were mostly mild or moderate, with 37% of patients experiencing grade 1 CRS and 47% with a grade 2 event. Eleven percent of patients experienced a grade 3 CRS, while no grade 4 CRS events occurred. Zero grade 5 events related to IMA203 occurred, according to Immatics.
The biotech said the new data slice demonstrates “favorable tolerability and promising clinical activity with ongoing deep and durable objective responses” in the company release.
IMA203 is currently being evaluated in a phase 3 trial enrolling patients with advanced or metastatic cutaneous melanoma plus a continued phase 1b expansion into uveal melanoma.
The phase 3 study, dubbed SUPRAME, is an open-label, randomized trial testing IMA203 against an investigator’s choice of treatment in about 360 patients who have previously received a checkpoint inhibitor treatment.
The study’s primary endpoint is PFS, with secondary measures including OS, ORR, safety and patient-reported outcomes about quality of life.
Immatics’ TCR-T cell therapy has secured regenerative medicine advanced therapy designation from the FDA, and the biotech plans to submit a full approval request with the FDA in the first quarter of 2027.