Daclizumab Therapy Improves Outcome in Steroid Refractory Acute Graft Versus Host Disease (aGVHD).

Steroid refractory aGVHD following allogeneic stem cell transplant (SCT) is associated with a long-term event-free survival (EFS) of less than 20%. Daclizumab is a humanised monoclonal antibody specific for the Tac subunit of the Interleukin-2 (IL-2) receptor. It inhibits IL-2 binding and is thought to be more specific for alloreactive lymphocytes than pan-T cell antibodies. Limited phase II trials using daclizumab for steroid refractory aGVHD have demonstrated 50–60% complete response (CR) rates, though its safety and efficacy as primary aGVHD treatment has recently been questioned. We examined the Vancouver experience with daclizumab in the management of steroid refractory aGVHD. Between 8/00 and 2/04, 35 patients with steroid refractory aGVHD were treated with daclizumab. Male:female ratio was 1.7:1. Median age was 42 years (17–53). Pretransplant diagnoses were AML (n=7), ALL (n=6), CML (n=6), MDS (n=5), NHL (n=6), MM (n=4) and Myelofibrosis (n=1). One patient with relapsed AML post-SCT developed aGVHD following DLI. Stem cell source was matched unrelated bone marrow (BM) (n=11) or peripheral blood (PB) (n=8), mismatched unrelated BM (n=6) or PB (n=3), matched related BM (n=2) or PB (n=4), and mismatched related BM (n=1). Twenty eight pts were conditioned with Cyclophosphamide/TBI. CSP/MTX aGVHD prophylaxis was used in all pts and initial aGVHD therapy consisted of Methylprednisolone 2 mg/kg IV. Grade I-II aGVHD developed in 18/35 (51%) pts and grade III-IV in 17/35 (49%) pts. Median onset of aGVHD was 18 (6–49) days post transplant. Steroid refractory pts received daclizumab 1 mg/kg IV (maximum dose 100mg) on days 1, 4, 8, 15 and 22 at a median of 40 (18–94) days post transplant. Daclizumab response was assessed at day 42 following its initiation. A CR was defined as a return to stage/grade 0 aGVHD and a PR as a reduction of ≥ 1 aGVHD stage/grade without need for additional therapy. There were no significant infusional complications. One patient died during the response assessment period (regimen related pulmonary toxicity). Overall response rate (ORR) was 25/35 (73%), with 15/25 (44%) achieving a CR and 10/25 (29%) a PR. Response was most likely in pts with skin involvement.

Twenty four (68%) pts developed limited (n=8) or extensive (n=15) chronic GVHD. The 3-year OS and EFS rates were 35% (95% CI 17–53%) and 28% (95% CI 12–47%), respectively. Female patients had a significantly poorer OS (p=0.0064) and EFS (p=0.0112) as did those pts receiving SCT from female donors (p=.0333 / 0.0456). Eleven patients (31%) received antithymocyte globulin (ATG) in addition to daclizumab. In this subgroup, aGVHD response was more likely but ATG treated patients had increased CMV antigenemia rates during the treatment response period (p=0.01), and a significantly lower EFS (p=0.0064) and OS (p=0.0123). Daclizumab is an effective agent for steroid refractory aGVHD especially if limted to the skin. Long-term survival appears to be superior in pts treated with this agent although its use along with ATG may compromise pt outcome.