A Phase 3 Study of T-Cell Receptor Engineered Donor T Cells in Subjects Undergoing Allogeneic Peripheral Blood Stem Cell Transplantation

This is a multicenter, genetically-randomized, controlled, Phase 3 study designed to evaluate the efficacy and safety of TSC-101 in adult participants with AML or MDS undergoing allogeneic peripheral blood stem cell transplantation following reduced-intensity conditioning (RIC). TSC-101 is a donor-derived, genetically engineered T-cell therapy designed to express a therapeutic T-cell receptor recognizing the HA-2 minor histocompatibility antigen presented by HLA-A\*02:01. The study is intended to evaluate whether administration of TSC-101 following transplantation can improve clinical outcomes compared with standard transplantation alone.

Eligible participants are adults with AML or MDS who are candidates for first allogeneic HCT using a haploidentical or mismatched unrelated donor and post-transplant. Participants assigned to the treatment arm must be HLA-A\*02:01 positive, express HA-2, and have a study-eligible HLA-A\*02-negative donor. Participants who are HLA-A\*02:01 positive but do not have a study-eligible donor, as well as participants who are HLA-A\*02:01 negative, may be assigned to the control arm.

Approximately 310 participants will be enrolled, with approximately 155 participants in each study arm. Participants assigned to the treatment arm will receive two infusions of TSC-101 following recovery after transplantation. The first infusion is planned approximately 21 days after HCT (Day +14 to Day +35), and the second infusion is planned approximately 40 days after the first infusion (40 to 68 days after Infusion 1).

All participants will receive SOC transplantation procedures, including one of several protocol-specified RIC regimens followed by peripheral blood stem cell transplantation and post-transplant cyclophosphamide (PTCy)-based graft-versus-host disease (GvHD) prophylaxis.

Safety will be monitored through ongoing review of adverse events, laboratory assessments, and clinical evaluations. An independent Data Safety Monitoring Board (DSMB) will periodically review safety data and study conduct and make recommendations regarding continuation, modification, or termination of the study.

This is an event-driven study. Participants will be followed for up to 3 years after HCT. Participants who receive at least one TSC-101 infusion will subsequently participate in a separate long-term follow-up study for up to 15 years following their final TSC-101 infusion to monitor long-term safety and survival outcomes.