Infusion of Donor Lymphocytes Transduced With the Suicide Gene HSV TK in Patients With Haematological Malignancies

Delayed immune-reconstitution remains one of the main limitation of haploidentical stem cell transplantation. The risk of severe infections remains high for several months and CD4+ reconstitution could take more than 10 months. The low number of lymphocytes infused with the graft, the degree of HLA disparity, and a reduced thymic function in adults and differences in host/donor antigen presenting cells are contributing causes.

The infusions of HSV-TK engineered lymphocytes may represent a significant therapeutic improvement in haploidentical haplo-HCT, because it remarkably may enhance both GvL activity, thus reducing the occurrence of disease relapse, and post-transplant immune reconstitution in the absence of chronic immune suppression, thus decreasing the rate of both post-transplant opportunistic infections and transplant-related mortality. Furthermore, the efficient control of GvHD achieved via the suicide mechanism allows also the multiple infusion of HSV-TK-treated donor lymphocytes, when needed, that might further improve post-transplant host immune reconstitution, and, eventually, survival in patients receiving haplo-HCT. Finally, this therapeutic approach, which allows the safe infusion of escalating doses of donor lymphocytes, can become a valuable option for all candidates, including patients with advanced disease and older age.

The proposed clinical trial represents an innovative therapeutic treatment for patients affected by hematological malignancies, who have undergone haploidentical stem cell transplantation.

Inclusion criteria

• Patients >=18 years old affected by hematological malignancies at high risk of relapse based on disease progression or presence of negative prognostic factors, who have received a HCT from donor HLA mismatched (haploidentical) for 2 or 3 loci
• Engraftment documented by >500 neutrophils/µl for three consecutive days in the absence of growth factors
• Mixed chimerism or full donor chimerism confirmed
• AML in 1st or 2nd relapse or primary refractory
• High-risk AML in 1st or subsequent remission
• RAEB and RAEB-T
• CML in 2nd chronic phase, blast crisis or accelerated phase
• Poor prognosis ALL in 1st or subsequent remission
• High grade lymphomas in 3rd or subsequent remission
• Multiple myeloma in advanced stage relapsing or progressing after high dose chemotherapy
• Absence of fully HLA matched or one HLA locus mismatched family donor
• Stable clinical conditions and life expectancy >3 months
• PS Karnofsky >70
• Written donor/patient informed consent

Exclusion criteria

• Infection with cytomegalovirus being treated with ganciclovir
• Presence of GvHD grade > I that requires systemic immunosuppressive therapy (at baseline)
• Ongoing systemic immunosuppressive therapy
• Ongoing acyclovir administration
• Administration after haplo-HCT of G-CSF and cyclosporine A
• CD3+ lymphocytes >100/µl before day +42 after haplo-HCT
• Life-threatening condition or complication other than their basic disease
• CNS disease
• Pregnant or lactating women