Introduction: Acute GvHD has, despite established immunosuppressive prophylaxis regimens, significant impact on acute morbidity and mortality following allogeneic stem cell transplantation (SCT). In the unrelated or even non-matched unrelated situation new GvHD-prophylaxis regimens balancing GvHD and graft-versus-leukaemia effect are needed. EC-MPS and mycophenolate mofetil [MMF] are effective immunosuppressants by inhibition of T- and B-cell proliferation. Primary study aims in this ethical board approved, prospective, single-centre, open phase II trial were (1) feasibility of prolongatedly started oral EC-MPS and (2) reduction in the rate of GvHD in unrelated allogeneic SCT.

Patients and Methods: EC-MPS [Myfortic ®] 720 mg twice a day orally starting at day +10 after SCT in addition to standard GvHD prophylaxis, consisting of cyclosporine (CSA) 3 mg/kg continuous intravenous infusion with or without methotrexate (MTX) 15 mg/m2 day +1 and 10 mg/m2 day +3,+6,+11 intravenous push, was evaluated. According to the protocol, EC-MPS was tapered from day +40, if no acute GvHD-signs were present. 54 patients, including 8 patients from a previous pilot trial, with advanced haematological malignancies (n=28) or in first remission of acute leukaemia (n=26) between 8/03 and 12/07 were evaluated. The patients had either a 10/10 HLA-matched (n=32) or a 8-9/10 HLA mismatched unrelated donor (n=22). 32 (59%) patients received 40 mg/kg antithymocyte globulin (ATG), with 8 Gray total body irradiation (TBI) and cyclophosphamide (CY), or with fludarabine 120mg/m2, busulfan 8mg/kg or treosulfan 8–12 mg/kg. 12 or 8 Gray TBI and 120 mg/kg CY followed by MTX i.v. were administered to 22 (41%) patients.

Results: A median of 5.7 (range: 0.9–9.9) unmanipulated G-CSF-mobilized CD-34 positive stem cells per kg were given on day 0. All of the 23 women and 31 men (median age 48 years (range: 20–65)), except one patient, showed a leukocyte engraftment on median day +14 (range: 9–35). Platelet engraftment was observed on median day +17 (range: 9–132). In 12 patients (22%) initially i.v. MMF (1g twice a day) instead of oral study medication was given temporarily, mostly due to severe mucositis. In six patients (11%) EC-MPS (on day +14, 17, 22, 32, 37, 76) had to be discontinued, due to severe nausea (n=2), neurological toxicity (n=2), graft failure (n=1) and protocol violation (n=1). Acute GvHD grade II-IV was observed in 27 (52%) patients, including 8 (15%) with grade III and 4 (7.5%) with grade IV. The incidence of chronic GvHD was 63 % (n=29) [limited chronic GvHD: 54 % (n=15), extended chronic GvHD: 14% (n=4)] of the 46 patients surviving >100 days after SCT. With 10/10 HLA-matched donors GvHD grade II-IV was seen in 44% (n= 14) [grade III and IV n=5 (16%)], whereas with non fully-matched donors the incidence was 59 % (n=13) [grade III and IV n=7 (32%)]. Chronic GvHD incidence was 50% (14/28) in the fully matched donor situation in contrast to 83% (15/18) in the non-fully matched situation. The conditioning regimen with ATG resulted in a GvHD grade II-IV incidence of 39% (n=12) [GvHD grade III/IV: 19% (n=6)], compared to 68% (n=15) [GvHD grade III/IV: 27% (n=6)] without ATG. With a median follow-up of 16 months (range: 1–56) 28 patients (52%) are alive, 18 fully HLA-matched stem cell recipients (56%) and 10 mismatched HLA recipients (45%). Survival with or without ATG was 50% (n=16) and 55% (n=12), respectively. Twenty-six (48%) patients have died; 12 (22%) due to relapse, 10 (19%) due to acute/chronic GvHD, and 4 (7%) due to infection/secondary cancer without GvHD.

Conclusions: EC-MPS with a 10 day prolongated start after transplantation combined with initial standard GvHD prophylaxis in the unrelated stem cell transplantation setting seems to be feasible. Mucositis was the main course for oral intake problems. The toxicity drop-out rate of 7 % should be considered. The analysis of all evaluable patients in the pilot and the prospective trial yielded effectiveness in reducing severe GvHD Grade III/IV, especially in combination with ATG. The MPS application regimen failed to show less incidence of chronic GvHD in the non-fully matched unrelated donor setting. GvHD prevention trials in the future should incorporate new drugs with a different pathway of T-cell inhibition or tolerance induction, respectively.

Disclosures: Sayer:Novartis: Research Funding. Off Label Use: Enteric-coated mycophenolate sodium (EC-MPS, Myfortic (R)); immunosuppressive drug used and approved in solid organ transplantation.

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