Administration of herpes simplex–thymidine kinase–expressing donor T cells with a T-cell–depleted allogeneic marrow graft

Administration of donor T cells expressing the herpes simplex–thymidine kinase (HS-tk) with a hematopoietic stem cell (HSC) transplantation could allow, if graft-versus-host disease (GVHD) was to occur, a selective in vivo depletion of these T cells by the use of ganciclovir (GCV). The study evaluates the feasibility of such an approach. Escalating numbers of donor HS-tk–expressing CD3+ gene-modified cells (GMCs) are infused with a T-cell–depleted bone marrow transplantation (BMT). Twelve patients with hematological malignancies received 2 × 105(n = 5), 6 × 105 (n = 5), or 20 × 105(n = 2) donor CD3+ GMCs/kg with a BMT from a human leukocyte antigen (HLA)–identical sibling. No acute toxicity was associated with GMC administration. An early increase of circulating GMCs followed by a progressive decrease and long-lasting circulation of GMCs was documented. GCV treatment resulted in significant rapid decrease in circulating GMCs. Three patients developed acute GVHD, with a grade of at least II, while one patient developed chronic GVHD. Treatment with GCV alone was associated with a complete remission (CR) in 2 patients with acute GVHD, while the addition of glucocorticoids was necessary to achieve a CR in the last case. Long-lasting CR occurred with GCV treatment in the patient with chronic GVHD. Unfortunately, Epstein-Barr virus–lymphoproliferative disease occurred in 3 patients. Overall, the administration of low numbers of HS-tk–expressing T cells early following an HLA-identical BMT is associated with no acute toxicity, persistent circulation of the GMCs, and GCV-sensitive GVHD. Such findings open the way to the infusion of higher numbers of gene-modified donor T cells to enhance post-BMT immune competence while preserving GCV-sensitive alloreactivity.