A Novel CMV-Specific TCR-T Cell Therapy Is Effective and Safe for Refractory CMV Infection after Allogeneic Hematopoietic Stem Cell Transplantation

Background

Cytomegalovirus (CMV) infection is an important infectious complication of allogeneic hematopoietic stem cell transplantation (allo-HSCT) due to the immune-suppressive state of the transplant recipient. Patients are likely to be resistant to traditional antiviral drugs, such as ganciclovir and foscarnet, or have intolerable adverse reactions to these drugs, including bone marrow suppression and nephrotoxicity. CMV-specific CD8 ⁺ and CD4 ⁺ T-cell functional defects are the main reasons for the emergence of refractory CMV infection. Thus, it is possible to cure refractory CMV infection using CMV-specific TCR-T cell therapy via a direct antiviral effect and indirect T cell mediated immune reconstruction.

Objectives and Methods

We conducted a single-arm, open-label, phase I clinical trial (https://clinicaltrials.gov, NCT04153279) at the Hebei Yanda Lu Daopei Hospital. This study was designed to assess the safety and feasibility of CMV-specific TCR-T cell therapy in allo-HSCT patients with refractory CMV viremia or viral disease. We screened multiple TCRs with specificity for CMV-PP65 or IE1 polypeptides restricted by HLA-A*11:01, 24:02 and 02:01, and constructed lentiviral vectors containing CMV-specific TCRs. Peripheral blood (PB) stem cells were obtained from healthy HSCT donors for the TCR-T cell preparation. After stimulation for 24 hours, T-cells were infected with lentivirus carrying HLA-matched CMV TCR, then cultured with medium containing IL-7/IL-15 for a total of 7-9 days before harvest. After infusion, CMV TCR-T cell proliferation and persistence in PB was detected by Q-PCR.

Results

From December 24, 2019 to January 1, 2021, 9 patients were enrolled and as a result 7 patients including 5 with refractory CMV viremia and 2 with CMV disease successfully received the TCR-T therapy. Among the 7 patients who received TCR-T, the median age was 11 years (5-45 years of age) and 5 were male (71.4%). The diagnosis included 5 cases of acute lymphoblastic leukemia (ALL), 1 case of acute myeloid leukemia (AML) and 1 case of mixed phenotype acute leukemia (MPAL) . Patients underwent either haplo-identical transplantation (n=6) or unrelated donor transplantation (n=1). The median time for patients to CMV viremia diagnosis was 28 days (21-231 days). Patients received a median dose of 3 × 10 ⁵ TCR-T cells/kg body weight (1-10 × 10 ⁵ TCR-T cells/kg body weight). The mean proportion of CMV-specific TCR-T in the cultured cell products was 35.5% (18.0-68.9%). Among the 7 patients, successful follow up and data evaluation was available for 6 patients. One patient (P3) withdrew early due to uncontrolled lung infection. The median follow-up time for the entire cohort after HSCT was 199 days (144-479 days). Only 1 patient experienced Grade 1/2 cytokine release syndrome (CRS) with mild hypotension and fever. No immune effector cell-associated neurotoxicity syndrome (ICANS) or TCR-T cell-related graft-versus-host disease (GVHD) occurred in any patient. A total of 6 patients achieved complete response (CMV DNA-negative plasma) after TCR-T cell infusion. The median time from CMV-specific TCR-T infusion to the first CMV clearance was 41 days (19-91 days). The median time for CMV TCR-T cells to reach their first peak was 21 days (10-28 days) with a median copy number of 3.85×10 ⁴ copies/μg genomic DNA (range: 1.93×10 ⁴-7.75×10 ⁴ copies/μg DNA) (Figure 1). CMV TCR T-cells persisted up to 3 months with detectable copy number. The levels of cytokines IL-2, TNF-α, IL-6, IL-8 and IFN-γ in PB were relatively low.

Conclusion

This study demonstrates the safety and feasibility of CMV-specific TCR-T cells for refractory CMV infection after HSCT. We show that adoptive transfer of CMV-specific TCR-T cells can lead to complete CMV clearance in patients who have undergone hematopoietic stem cell transplantation (HSCT) and with good tolerability and safety. Longer-term observation of these patients and larger patient studies are warranted to demonstrate the efficacy and safety of CMV TCR-T cells. Given that immune defect-related CMV infections are common and life threatening for HSCT patients, we see a potential future for CMV-specific TCR-T cell therapy for the treatment and prevention of CMV infection following HSCT or other organ transplantation.

Figure 1

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Figure 1

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