Assessment of the Effect of Nilotinib (Tasigna) Maintenance Therapy After Allogeneic Stem Cell Transplantation in Patients with Advanced CML and Ph+ ALL On Immune Reconstitution and Lymphocyte Function

Abstract 4478

Allogeneic stem cell transplantation (AlloSCT) is the treatment of choice in advanced chronic myelogenous leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). However, post transplant relapse rate is high and outcome is often poor in this setting. Reduction of tumor mass pre-transplant and maintenance therapy post alloSCT, may improve response rate and reduce relapse rate. We speculated that the second-generation tyrosine-kinase inhibitor (TKI) Nilotinib (Tasigna, Novartis Pharmaceuticals) would be effective in achieving these goals. In the current study Nilotinib, was administered as maintenance therapy post alloSCT in patients (pts) with advanced CML and Ph+ ALL (study CAMN107AIL03T). However, TKIs have been demonstrated in previously published literature to affect T cells proliferation and signal transduction and to potentiate LGL and NK cell activity. Furthermore, in recent studies TKIs have also been demonstrated to ameliorate chronic GVHD. We therefore assessed immunological reconstitution and function including flow analysis of lymphocyte subsets, T-mitogenic response to αCD3 and PHA, thymic activity as determined by the quantification of the T cell receptor excision circles (TREC), TCR repertoire and NK cells cytotoxic activity against K562 cell line. In all, the study included 24 pts. Patients engrafted in a median day +15 (range, 10–38) with 100% donor chimerism. Acute GVHD grade 3/4 was reported in 3 pts (14%) and the rate of extensive chronic GVHD at last follow up was 50%. At 6 months after alloSCT, 11 of 15 pts with advanced CML had attained CCyR, 11 of 15 pts with advanced CML had attained a MMR or better, and 5 of 7 pts with Ph+ ALL attained a CR. The median OS was 16 months, with predicted 1- and 2- year rates of 55% (95% CI, 32% – 72%) and 50% (95% CI, 28% – 68%), respectively. The median PFS was 11 months, with predicted 1- and 2- year rates of 50% (95% CI, 28% – 68%) and 38% (95% CI, 17% – 59%), respectively. Immunological testing was performed pre- and post Nilotinib maintenance therapy in 12 pts (advanced CML-8, Ph+ ALL-4) who received Nilotinib for at least 90 days following alloSCT. The median age was 34.5 years (range, 21–57) and 75% were males. Six pts underwent alloSCT from an HLA-matched sibling donor, 4 from matched unrelated and 2 from an alternative donor (cord blood-1, haploidentical-1). All had myeloablative conditioning. GVHD prophylaxis included CSA and MMF. The relative percentage of T- lymphocyte subsets (assessed by FACS) and total lymphocytes number were stable during Nilotinib maintenance administration after alloSCT, while a 7.8±2.5 fold increase in B cells was noted. T cell mitogenic response with αCD3 and PHA (stimulation index ratio) was sustained (2.5±1.0, vs. 2.8±1.05 and 3.3±1.3 vs. 5.3±2.9 stimulation, pre- and post Nilotinib therapy, respectively). Mean thymic output determined by TREC quantification pre-, during and post Nilotinib administration was 81.8±108, 81.2±90.3 and 142.8±197.4 copies per 0.5ug DNA indicating continuous thymopoiesis. Similarly, no significant change of the TCR repertoire was observed during Nilotinib treatment. Specifically, normal expression of the TCR repertoire was detected in 15.1±5.5 and 15.3±5.6 of the examined TCRs, clonal expression was detected in 2.5±2.2 and 2.9±3 of the examined receptors, while reduced expression was detected only in 6.4±4.3 and 5.8±4.5 of the examined receptors pre-and post Nilotinib treatment, respectively. NK cytotoxic activity against K562 expressed as fold of change from baseline, also remained stable during Nilotinib treatment (2.8±1.1 and 2.3±0.8, respectively). In summary, Nilotinib maintenance therapy post alloSCT in pts with advanced CML and Ph+ALL did not interfere or jeopardized immune reconstitution and function including the number of immune cell subsets, T cell mitogenic response, TCR repertoire, thymic output and NK cytolytic activity post alloSCT. Based on this immunological data we would further recommend Nilotinib maintenance therapy post alloSCT in pts with advanced CML and Ph+ALL.