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RecruitingNCT06946225Updated Jan 8, 2026

ACTengine® IMA203 Combined With mRNA-4203

A Phase 1 interventional study of IMA203 and mRNA-4203 in Cutaneous Melanoma and Synovial Sarcoma, sponsored by Immatics US, Inc.. Recruiting at 4 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-01-08.

Sponsored by Immatics US, Inc. · Phase 1, Interventional, and Treatment

From the registry’s dates

  • Started Jul 2025; still recruiting 1 year 3 months later.
Phase
Phase 1
Study type
Interventional
Enrollment
15
Allocation
Not applicable
Ages
18 Years and older
Sex
All
01

Study summary

This purpose of this clinical trial is to evaluate the safety, tolerability and anti-tumor activity of IMA203 in combination with different doses of mRNA-4203. The trial includes participants with previously treated unresectable or metastatic cutaneous melanoma (CM) or synovial sarcoma (SS).

Read the detailed description

This clinical trial is a multi-center, open-label, non-comparative Phase 1 a/b trial to assess the safety, tolerability, and anti-tumor activity of the combination of IMA203 and mRNA-4203 in HLA-A*02:01 positive patients with previously treated, unresectable or metastatic cutaneous melanoma (CM) and synovial sarcoma (SS).

02

Conditions studied

  • Cutaneous Melanoma
  • Synovial Sarcoma

Keywords

  • immunotherapy
  • T-cell therapy
  • cutaneous melanoma
  • synovial sarcoma
  • RNA vaccine
  • Immatics
  • Moderna
03

In context

Melanoma

3,370 studies on the registry are indexed under Melanoma; 578 are open to participants now.

This study's planned enrollment of 15 is below the median of 40 across 2,649 interventional studies indexed under Melanoma.

Browse Melanoma studies →

Lead sponsor

Immatics US, Inc. is the lead sponsor of 7 studies on the registry; 3 are open to participants now.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.

Inclusion criteria

  • confirmed and documented cutaneous melanoma (CM) or synovial sarcoma (SS) with unresectable or disease
  • HLA-A*02:01 positive
  • Adequate selected organ function per protocol
  • (ECOG) performance status 0-1
  • according to (RECIST 1.1)
  • more than 5 months
  • CM participants who must have disease progression (resistance, toxicity) on or after at least one inhibitor
  • SS participants must have received (or declined) at least one (including SoC) and are still in need of further systemic therapy.
  • Female participants of must use adequate prior to trial entry until 12 months after the infusion of IMA203 and 15 days after the last mRNA 4203 dose administration

Other protocol defined inclusion criteria could apply

Exclusion criteria

Exclusion Criteria:

  • History of other (except for adequately treated basal or squamous cell carcinoma or carcinoma in situ) within the last 3 years
  • Pregnant or breastfeeding
  • Serious disease
  • History of cardiac conditions as per protocol
  • Prior allogenic stem cell transplantation or solid organ transplantation
  • Concurrent severe and/or uncontrolled medical disease that could compromise participation in the study
  • History of to cyclophosphamide, fludarabine, or IL-2
  • History of hypersensitivity to mRNA-based medicines
  • Positive for infection or with active virus (HBV) or active virus (HCV) infection
  • Any condition contraindicating leukapheresis
  • Participants with lactate dehydrogenase (LDH) greater than threshold allowed per protocol
  • Participants with active prior to lymphodepletion
  • Concurrent treatment in another clinical trial or a device trial that could interfere with the IMA203 treatment
  • Participants with renal impairment AND reduced bone marrow reserve per protocol

Other protocol defined exclusion criteria could apply

Terms in these criteria, in plain language(17)

Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.

Histologically or cytologically confirmed

The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).

Your pathology report is the document that shows this.

Metastases

Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.

ECOG performance status

A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.

0
Fully active, no restrictions.
1
Limited in strenuous activity, but walking and able to do light work, such as housework or office work.
2
Walking and able to look after yourself, but unable to work; up and about more than half of waking hours.
3
Able to look after yourself only in part; in bed or a chair more than half of waking hours.
4
Unable to look after yourself at all; in bed or a chair all day.

Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.

Measurable disease

The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.

The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.

RECIST

The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.

“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.

Life expectancy

The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.

PD-1, PD-L1 and checkpoint inhibitors

PD-1, PD-L1 and CTLA-4 are proteins that act as brakes on the immune system. Checkpoint inhibitors, such as pembrolizumab or nivolumab, block them so the immune system can attack a cancer.

PD-L1 can also be measured in a tumour sample. Some scores count stained tumour cells only (TPS); others also count certain immune cells (CPS). The study names the score and the minimum it uses.

Line of therapy

A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.

“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.

Childbearing potential

Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).

Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.

Contraception

Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.

Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.

Cancer (malignancy)

Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.

Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.

Autoimmune disease

A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.

Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.

Hypersensitivity

An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.

HIV

The human immunodeficiency virus, which weakens the immune system.

Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.

Hepatitis B tests

Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.

Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.

Hepatitis C tests

Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.

After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.

Brain metastases

Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).

Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.

05

Study design

Phase
Phase 1
Primary purpose
Treatment
Allocation
Not applicable
Intervention model
Single group
Masking
None (open label)
Enrollment
15 participants (estimated)

Study arms

  • Experimental
    IMA203 with mRNA-4203 in participants with metastatic cutaneous melanoma or synovial sarcoma

    This is a non-comparative, open-label trial with different cohorts investigating IMA203 in combination with mRNA-4203.

    Biological: IMA203 · Biological: mRNA-4203

Interventions

  • BiologicalIMA203

    Following non-myeloablative chemotherapy for lymphodepletion (LD) with fludarabine (FLU) and cyclophosphamide (CY), participants will receive a single infusion of IMA203 on Day 1 and adjunctive therapy with low dose interleukin (IL)-2 for up to 10 days, starting approximately 24 h after IMA203 infusion.

    Also known as: anzutresgene autoleucel, anzu-cel

  • BiologicalmRNA-4203

    mRNA-4203 will be administered starting on Day 15 after IMA203 infusion at the earliest. mRNA-4203 will be given for 12 cycles (28 day cycle length); during Cycle 1 it will be given on Day 1 and Day 15 and in Cycles 2-12 it will be given on Day 1.

    Also known as: anzu-cel

06

What researchers measure

Primary outcomes

  1. Number of participants with dose-limiting toxicities (DLTs)

    Number of DLTs will be used to determine the maximum tolerated dose (MTD) and/or recommended dose for extension (RDE) after treatment with IMA203 product in combination with mRNA-4203

    Time frame: one year post infusion of IMA203

  2. Number of treatment emergent adverse events (AEs), AEs of special interest, serious AEs (SAEs), changes in laboratory parameters and vital signs, and frequency of dose interruptions, reductions and discontinuations

    Used to evaluate safety and tolerability of treatment with IMA203 in combination with mRNA-4203

    Time frame: one year post infusion of IMA203

Secondary outcomes

  1. Objective response rate (ORR)

    complete response (CR) and partial response (PR) based on best overall response (BOR), locally assessed using Response Evaluation Criteria in Solid Tumors (RECIST) v1.1

    Time frame: one year post infusion of IMA203

  2. Duration of response (DOR)

    CR and PR, locally assessed using RECIST v1.1

    Time frame: one year post infusion of IMA203

  3. Disease control rate (DCR)

    CR, PR and stable disease (SD) lasting 6 or more weeks following the infusion of IMA203, locally assessed using RECIST v1.1

    Time frame: one year post infusion of IMA203

  4. Progression-free survival (PFS)

    locally assessed using RECIST v1.1

    Time frame: one year post infusion of IMA203

  5. Concentration of IMA203 transgene in peripheral blood

    Evaluate the pharmacokinetics of T-cell receptor (TCR) engineered T cells in combination with mRNA-4203

    Time frame: one year post infusion of IMA203

07

Study locations

4 of 4 sites recruiting
08

Timeline

Tracking since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reachedSimilar studies: half by the dot; the band is the middle halfHalf of similar studies reached it by the dot; the band is the middle half, from a quarter to three quarters

Started Jul 2025 (actual). Primary completion is estimated for Aug 2029, 49 months after the start.

Of 225 industry-sponsored phase 1 interventional studies under Melanoma, half reached primary completion within 46 months of starting (the median), counting those still running; a quarter within 28 and three quarters within 66. This study's planned 49 months is close to that.

Counting every sponsor, half of 411 studies reached it within 49 months; a quarter within 31 and three quarters within 76.

How these figures are worked out, and which studies are left out of them.

Registered
Apr 19, 2025
First posted
Apr 27, 2025
StartActual
Jul 25, 2025
Primary completionEst.
Aug 2029
CompletionEst.
Aug 2029
Last update
Jan 8, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
No changes since tracking began. The registry record was last updated on Jan 8, 2026, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
09

Registry details

Key details

Study ID
NCT06946225
Lead sponsor
Immatics US, Inc.
Collaborators
ModernaTX, Inc.
Responsible party
Sponsor
First posted
Apr 27, 2025
Start date
Jul 25, 2025
Primary completion
Aug 2029 (estimated)
Completion
Aug 2029 (estimated)
Last update
Jan 8, 2026

Study contacts

Immatics US, Inc.
Contact
ctgovinquiries@immatics.com
+1 346 204-5400

Oversight

Data monitoring committee
Yes
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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Studies of the drug tested here: Anzutresgene autoleucel

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