Safety and feasibility of third-party cytotoxic T lymphocytes for high-risk patients with COVID-19

Cytotoxic T lymphocytes (CTLs) destroy virally infected cells and are critical for the elimination of viral infections such as those caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Delayed and dysfunctional adaptive immune responses to SARS-CoV-2 are associated with poor outcomes. Treatment with allogeneic SARS-CoV-2-specific CTLs may enhance cellular immunity in high-risk patients providing a safe, direct mechanism of treatment. Thirty high-risk ambulatory patients with COVID-19 were enrolled in a phase 1 trial assessing the safety of third party, SARS-CoV-2-specific CTLs. Twelve interventional patients, 6 of whom were immunocompromised, matched the HLA-A∗02:01 restriction of the CTLs and received a single infusion of 1 of 4 escalating doses of a product containing 68.5% SARS-CoV-2-specific CD8+ CTLs/total cells. Symptom improvement and resolution in these patients was compared with an observational group of 18 patients lacking HLA-A∗02:01 who could receive standard of care. No dose-limiting toxicities were observed at any dosing level. Nasal swab polymerase chain reaction testing showed ≥88% and >99% viral elimination from baseline in all patients at 4 and 14 days after infusion, respectively. The CTLs did not interfere with the development of endogenous anti-SARS-CoV-2 humoral or cellular responses. T-cell receptor β analysis showed persistence of donor-derived SARS-CoV-2-specific CTLs through the end of the 6-month follow-up period. Interventional patients consistently reported symptomatic improvement 2 to 3 days after infusion, whereas improvement was more variable in observational patients. SARS-CoV-2-specific CTLs are a potentially feasible cellular therapy for COVID-19 illness. This trial was registered at www.clinicaltrials.gov as #NCT04765449.