Study to Evaluate Safety and Antitumor Activity of Lete-Cel (GSK3377794) in HLA-A2+ Participants With NY-ESO-1 Positive Previously Treated Advanced (Metastatic or Unresectable) Synovial Sarcoma or Myxoid/Round Cell Liposarcoma

DCR, is defined as the percentage of participants with a confirmed CR, PR, or SD with minimal 12 weeks duration relative to the total number of participants within the analysis population at the time of primary analysis as determined by independent central review per RECIST v1.1. The observed DCR will be reported along with 95% Clopper-Pearson exact confidence interval (CI). DCR will be analyzed based on PEAP and mITT populations.

PFS, is defined as the time from the date of T-cell infusion until the earliest date of radiological PD as assessed by independent central review per RECIST v1.1, or death due to any cause. For the analysis of PFS, if the participant received subsequent anticancer therapy prior to the date of documented events, PFS will be censored at the last adequate disease assessment (e.g., assessment when visit level response was CR, PR, or SD) prior to the initiation of the new anticancer therapy. If a participant does not have an adequate post-baseline disease assessment that is no later than the date of initiation of anti-cancer therapy, PFS will be censored at the date of the T-cell infusion date.

OS is defined as the interval of time between the date of T-cell infusion and the date of death due to any cause. For participants who do not die, time of death will be censored at the date of last contact. The date of death should be taken from that recorded on the Record of Death page. Death on study due to any cause will be included. Survival will be listed and summarized using Kaplan-Meier quartile estimates along with 2-sided 95% CI.

DOR is defined as, in the subset of participants who show a confirmed CR or PR as assessed by independent central review per RECIST v1.1, the time from first documented evidence of CR or PR until the first documented sign of disease progression or death. Duration of response will be summarized descriptively, if data warrant, using Kaplan-Meier medians and quartiles. Censoring: same as PFS censorship table.

TTR is defined as the time from the date of T-cell infusion to initial date of confirmed response (PR or CR) as assessed by independent central review per RECIST v1.1 in the subset of participants who achieved a confirmed PR or CR.

TTR will be listed and summarized descriptively using median and quartiles in the subset of participants with a confirmed response of PR or CR.

Efficacy listings such as BOR, DOR, PFS and OS will be reported for the PEAP and mITT populations.

An AE is any untoward medical occurrence in a clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. SAE is defined as any untoward medical occurrence that, at any dose results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, is a congenital anomaly/birth defect, other situations which involve medical or scientific judgment or is associated with liver injury and impaired liver function.

An AESI may be of scientific and medical concern related to the treatment, monitored, and rapidly communicated by investigator to sponsor. AESIs included cytokine release syndrome (CRS), hematopoietic cytopenias (including pancytopenia and aplastic anemia), graft vs host disease (GVHD), ICANS, Guillain-Barre syndrome, treatment-related inflammatory response at tumor site(s), and neutropenia Grade 4 lasting ≥28 days.

An AE is any untoward medical occurrence in a clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. SAE is defined as any untoward medical occurrence that, at any dose results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, is a congenital anomaly/birth defect, other situations which involve medical or scientific judgment or is associated with liver injury and impaired liver function. AEs and SAEs were graded according to National Cancer Institute-Common Toxicity Criteria for Adverse Events (NCI-CTCAE) version 5.0. Grade 1- Mild; Grade 2- Moderate; Grade 3- Severe or medically significant but not immediately life-threatening; Grade 4- Life-threatening consequences; Grade 5- Death related to AE.

An AESI may be of scientific and medical concern related to the treatment, monitored, and rapidly communicated by investigator to sponsor. AESIs included cytokine release syndrome (CRS), hematopoietic cytopenias (including pancytopenia and aplastic anemia), graft vs host disease (GVHD), ICANS, Guillain-Barre syndrome, treatment-related inflammatory response at tumor site(s), and neutropenia Grade 4 lasting ≥28 days.

RCL was monitored using a polymerase chain reaction (PCR)-based assay that detects and measures copies of the gene coding for the vector's envelope protein, namely vesicular stomatitis virus G protein (VSV-G).

Instances of Insertional Oncogenesis (IO) was summarized descriptively

Cmax was defined as maximum observed persistence, determined directly from the persistence-time data. Blood samples were collected for PK analysis

Tmax was defined as time to reach Cmax, determined directly from the persistence-time data. Blood samples were collected for PK analysis.

Area under the persistence-time curve from time zero to Day 28. Blood samples were collected for PK analysis.