In allogeneic stem cell transplantation (SCT) T-cell depletion reduces transplant related mortality by diminishing GVHD. We have investigated a myeloablative regimen for matched unrelated donor SCT using both in vivo and in vitro CAMPATH-1H for effective T-cell depletion, utilising DLI at a later time point for graft versus tumor effect if necessary.
Thirty patients (median age 33 years, range 18–48) were transplanted from January 1997 to June 2002. Diagnoses were: CML CP (n=9), CML AP (n=2), AML/MDS (n=9), ALL (n=8), NHL (n=1) and Fanconi anemia (n=1). Six patients had one HLA mismatch, the others were identical for HLA A, B, C, DR and DQ. Conditioning consisted of CAMPATH-1H 5mg/d on days −8 to −4, TBI 6 Gy on days −8 and −7 and cyclofosfamide 60 mg/kg on days −6 and −5. T-cell depletion was performed by in vitro incubation of the graft with 20 mg CAMPATH-1H for 30 minutes (Campath “in the bag”). Post-transplant GVHD prophylaxis consisted of cyclosporine A and methotrexate. The stem cell source was bone marrow in 19 patients (63%) and peripheral blood in 11 patients.
One graft failure was observed, all other patients had sustained engraftment of donor cells. Acute GVHD was observed in 12 patients (40%), maximally grade I-II skin. No severe acute GVHD (grade III-IV) was experienced. Limited chronic GVHD developed in 2 patients, resolving after treatment. Only in one patient extensive chronic GVHD developed, which did not resolve. CMV reactivation occurred in 23% of patients, one patient developed CMV disease. No EBV disease was observed. Ten patients received donor lymphocyte infusion (DLI) at a median of 17.4 months after SCT (8 patients with relapsed CML, one patient with relapsed ALL, one patient with autoimmune hemolytic anemia). After DLI acute GVHD grade I-II developed in 4 patients, and GVHD grade III-IV in 3. Chronic GVHD developed in 5 patients, of which 2 extensive, resolving in all except one patient. With a median follow up of 37 (range 21–84) months 17 patients are alive (57%). One of the CML patients shows persistence of molecular disease not responding to increasing doses of DLI. All other patients are in CR with the CML patients in molecular remission. Five patients (17%) died because of relapsed disease (2 AML/MDS and 3 ALL). Treatment related mortality was 26% (1 rejection, 2 GVHD, 1 myocardial infarction, 4 infections).
In conclusion, matched unrelated donor SCT following myeloablative conditioning using T-cell depletion with CAMPATH-1H in vivo as well as in vitro results in good engraftment, minimal grade I-II GVHD and an overall survival of 57%. Relapse rate was not increased with this strategy. This regimen appears to be successful for young adults with high-risk malignancies.