A Prospective Phase II Study to Investigate the Efficacy and Safety of Pre-emptive Cytomegalovirus Adoptive Cellular Therapy in Patients Receiving Allogeneic Haematopoietic Stem Cell Transplant From an Unrelated Donor

As with other herpes viruses, infection with CMV is thought to result primarily from reactivation of latent virus. Transmission of the virus can also occur from donor marrow infusion or from allogeneic red cell, leukocyte or platelet transfusions. However, in immunocompromised bone marrow transplant recipients, CMV is frequently reactivated and disease resulting from the progression of CMV infection is a major cause of infectious morbidity and mortality. CMV infection is a consequence both of the immunosuppression these patients receive and also may reflect delayed immune reconstitution in these patients following transplant. It is of particular concern to recipients of VUD (HLA-Volunteer Unrelated Donor) transplants who often receive lower doses of donor T cells in the transplant and who also require greater post-transplant immunosuppression for GVHD prophylaxis. CMV reactivation is most frequent in this group of transplant recipient.

One approach to improve reconstitution of immunity against viruses following allogeneic HSCT is to adoptively transfer donor-derived virus-specific T lymphocytes, which has been well documented with proven success. Existing evidence suggests that adoptive cellular therapy (ACT) can be an effective approach for treating viral reactivation following allo HSCT, with a minimal risk of inducing GVHD. The major advantage to the patient is likely to be avoidance of extended periods of therapy with antiviral medications that have significant associated morbidities, and sometimes require inpatient care. From a pharmacoeconomic viewpoint this would translate into a reduction of costs associated with standard antiviral therapies compared to the cost of adoptive cellular therapy.

It is anticipated that the use of very small numbers of highly specific T-cells will allow enough CMV-specific T-cells to be obtained in vitro from normal healthy CMV-seropositive donors from the peripheral blood transplant product after a single leucapheresis procedure and that the absence of concurrent lympholytic immunosuppression combined with a profoundly lymphopenic environment should allow for expansion and maintenance of the anti-CMV response in vivo.

This current study is a randomised prospective phase II study of pre-emptive adoptive cellular therapy for CMV following T cell depleted allogeneic HSCT from an unrelated donor. The study is based on earlier phase I-II studies of CMV-specific cellular therapy and our ongoing phase III study of CMV-specific adoptive cellular immunotherapy in immunocompromised recipients of allogeneic sibling donor HSCT based on selection of CMV-specific T cells by two different methodologies (CMV-IMPACT). The proof of safety in the sibling donor setting now strengthens the case for extending the therapy to the unrelated donor setting, where both potential risks and benefits are greater. The current study will investigate the use of CMV-specific T cells selected from mobilised blood collected at the time of stem cell apheresis by the multimer technology in the unrelated donor setting. The selection of CMV-specific T cells selected from a mobilised blood at the time of stem cell apheresis is in contrast to the methodology used in the CMV-IMPACT study where selection is performed on a non-mobilised blood product produced from a second study-dedicated apheresis. Two significant issues remain unresolved for the CMV-ACE/ASPECT study; are these infusions safe in the HLA-matched un-related donor setting and do CMV-reactive T cells derived from the transplant product have equivalent activity in vivo to cells derived from a second apheresis as used in the sibling donor study (CMV-IMPACT study). The study will test the hypothesis that ACT can augment the impaired CMV immune function post-transplant and reduce the requirement for CMV antiviral drug therapy without causing an increase in GVHD; and to determine the efficacy of pre-emptive CMV-specific adoptive cellular therapy following T cell depleted allogeneic HSCT with respect to reconstitution of CMV-reactive T cells. There are multiple methods for T cell depletion available, and differences between them will likely have an effect on immune reconstitution. The study will be restricted to patients receiving alemtuzumab-containing conditioning protocols, where the risk of CMV infection is greatest. ACT will be administered from day 21 post transplant for those receiving ex-vivo T-cell depleted grafts and day 28 for those receiving in vivo T cell depletion, as a single dose immediately upon a single CMV-DNA PCR+ result.

In summary the study is a multicentre, prospective, controlled, open label, randomised (2:1) study of pre-emptive infusion with CMV-specific T cells selected by the multimer selection technique plus standard CMV antiviral therapy versus standard CMV antiviral therapy alone.