Can Addition of GM-CSF in Adult Haplo-Identical Transplant Who Cannot Benefit from NK Alloreactivity Improve the Relapse Rate of Advanced Leukemia: A 3 Step Study.

Haplo-identical transplant is now established as a procedure of choice for patients who lack a compatible donor. It might even be the best choice for AML, provided there is a GvH NK alloreactivity. However, patients are still referred too late, heavily pre-treated, at very advanced stages. We initiated a three-step phase I study trying improve transplant related mortality, relapse rate and immunity: (1): G-CSF + DLI, (2): GM-CSF + DLI, (3): patient and disease adapted strategy. Thirty-four consecutive leukemia patients, aged 18–55, were investigated (20 very poor risk, 11 poor risk and 3 better risk). GvH type NK alloreactivity was chosen when possible (19/34) and balanced across the 3 groups. In the first 9 patients, G-CSF was used pot-transplant and prophylactic DLI were given at month 1, 2 and 3. The use of G-CSF and 1 to 3 DLI (10⁴ CD3/kg) was found safe. It resulted in faster CD4 recovery and a low rate of infections. However, it was insufficient to induce a protective GVL effect. In the next 12 patients, GM-CSF was used plus 1 DLI (10⁴ CD3/kg) at day 30 unless aGVHD (3 pts). The comparison between the 2 first groups can be summarized as follows: G-CSF + DLI: TRM at day 100: 0, RR: 6/9, severe aGVHD:0. GM-CSF + 1 DLI group: RR: 1/12, TRM at day 100: 3, aGVHD grade 2 or more: 9/12; price to pay: GVHD resulting in 5 deaths in total. Median time to relapse in the 21 first patients was 6 months (range 4 to 9). Step 3 (14 patients) consists of a patient adapted strategy: no more aspecific DLI (selected anti-CMV and aspergillus DLI planned in all patients); in myeloid disorders with NK alloreactivity: no GF. In the other cases, GM-CSF (at a reduced total dose of 500 mcg) is given from day 5 to day 9. The follow-up of these 14 patients, although promising (2 relapses), is currently short (median 5 months), compared to the median of relapse in the 2 first groups (6 months) but will be updated for the meeting (10 months and 17 patients). Overall, TRM at day 100 is 3/29, reflecting the good tolerance of the conditioning in a heavily pre-treated population (median age : 43). Overall NR-mortality at one year is 8/26, but was greater in the GM-CSF + DLI group, reflecting the impact of severe aGVHD. In the current group, its is 2/14 at 3 months. We conclude that the third strategy might improve the outcome and the relapse rate without exposing patients to unnecessary severe GVHD.