Multi-modular Chimeric Antigen Receptor T Cells tarGeting B7-H3 in Children, Teenage & Young Adult Sarcoma

MIGHTY is a multicentre, open label, phase 1 clinical trial of an Advanced Therapy Investigational Medicinal Product (ATIMP) in children, teenagers and young adults aged 1-24 with relapsed or refractory (r/r) rhabdomyosarcoma (RMS), Ewing sarcoma (ES) or desmoplastic small round cell tumour (DSRCT).

The ATIMP for this study (hBRCA84D CAR T cells) are autologous T cells targeting B7-H3 in patients with r/r RMS, ES, or DSRCT.

Patients will undergo an unstimulated leucapheresis for the generation of the ATIMP which will take approximately 15 days to generate.

Patients will receive lymphodepleting (LD) chemotherapy with fludarabine administered over 4 days (Day -6 to Day -3) and cyclophosphamide administered over 2 days (Day -4 and Day-3).

Patients will be treated at one of three dose levels following LD chemotherapy as described above.

The study will evaluate the feasibility of generating the ATIMP, the safety of administering ATIMP, the tolerability of the ATIMP and how effectively the CAR T cells engraft, expand and persist following administration in patients with r/r RMS, ES or DSRCT.

Following infusion of the CAR T cells, patients will be monitored for between 2-4 weeks as an inpatient. Following discharge, patients will enter the interventional follow up phase and be followed up for 1 year. Patients will be seen at 6 weeks post infusion then 3 monthly until 1 year post CAR T cells infusion.

If patients relapse within the first-year post CAR T cell infusion, they will come off the interventional follow up and will be followed up annually until 15 years after the CAR T infusion.

After completing the 1-year interventional phase of the study, all patients, irrespective of whether they progressed or responded to treatment, will enter long term follow up until 15 years post CAR T infusion.

Inclusion criteria

• Age ≥ 1 and ≤ 24 years.
• Tissue diagnosis of RMS, ES or DSRCT
• Expression of B7-H3 in the tumour
• Relapsed or refractory disease after one or multiple lines of previous treatment.
• Measurable disease by cross sectional imaging. Patients with only bone marrow detectable disease (bone marrow aspirate or trephine) are NOT eligible for the study.
• At least 3 weeks or 5 half-lives, whichever is shorter, after treatment with agents on other early phase clinical trial.
• Performance status: Karnofsky (age ≥ 10 years) or Lansky (age < 10) score ≥ 50%.
• Creatinine ≤1.5 x Upper Limit of Normal (ULN) for age, if higher, an estimated (calculated) creatinine clearance must be ≥ 60 ml/min/1.73 m2.
• Left ventricular ejection fraction (LVEF) ≥ 50%
• Absolute lymphocyte count ≥ 0.25 x 109/L.
• Women of childbearing potential (WOCBP) must have a negative pregnancy test and agree to comply with the pregnancy reporting requirements of the protocol (if applicable).
• Written informed consent.

Exclusion criteria

• Patients with only bone marrow detectable disease in the absence of measurable disease by cross sectional imaging.
• Patients with active, inoperative central nervous system (CNS) disease including leptomeningeal disease.
• Active hepatitis B, C or HIV infection.
• Inability to tolerate leukapheresis.
• Clinically significant systemic illness or medical condition (e.g., significant cardiac, pulmonary, hepatic or other organ dysfunction), that in the judgement of the investigator is likely to interfere with assessment of safety or efficacy of the investigational regimen and its requirements.
• Any contraindication to lymphodepletion or to the use of Cyclophosphamide or Fludarabine as per the local SmPC.
• Any contraindication to the use of Anticoagulant Citrate Dextrose Solution.
• Known allergy to albumin, EDTA or DMSO.
• Primary immunodeficiency or history of autoimmune disease (e.g., Crohn's, rheumatoid arthritis, systemic lupus) requiring systemic immunosuppression /systemic disease modifying agents within the last 2 years.
• Prior treatment with investigational or approved gene therapy or cell therapy products.
• Life expectancy <3 months.
• Systemic corticosteroid therapy ≥ 0.05 mg/kg dexamethasone daily (or equivalent) at time of hBRCA84D CAR T cells infusion.
• Women who are pregnant or breastfeeding.
• Patients who have received any live vaccine in the six weeks prior to planned lymphodepletion

Exclusion criteria

for the ATIMP infusion:

• Uncontrolled fungal, bacterial, viral, or other infection. Previously diagnosed infection for which the patient continues to receive antimicrobial therapy is permitted if responding to treatment and clinically stable at the time of scheduled hBRCA84D CAR T cell infusion.
• Systemic corticosteroid therapy ≥ 0.05 mg/kg dexamethasone daily (or equivalent) at time of hBRCA84D CAR T cell infusion.