Ibrutinib in Patients (Pts) with Mantle Cell Lymphoma (MCL) and Chronic Lymphocytic Leukemia (CLL) with Relapsed Disease Post Allogeneic Stem Cell Transplantation (alloSCT)

Background: Ibrutinib has demonstrated efficacy in clinical trials for relapsed and refractory MCL and CLL. There is a paucity of information regarding its safety and efficacy after failing alloSCT. Clinical data suggest that B-cell dysfunction contributes to chronic graft-versus-host-disease (GVHD). It is speculated that this may be due to hyper-responsiveness of the B-cell receptor, which can be abrogated by disrupting the signaling downstream by the use of ibrutinib.

Purpose: To study the safety, toxicity, survival rates and risk of GVHD in patients with CLL and MCL who relapsed post an alloSCT at our center.

Methods: Retrospective review in MCL and CLL pts who received ibrutinib post alloSCT between 12-1-2011 and 12-1-2014. The study was approved by IRB.

Results: We identified 22 pts with CLL (n=16) and MCL (n=6) who failed alloSCT with either nonmyelablative (n=17, 77%) or ablative (n=5, 23%) conditioning. Twelve (55%) received their transplants from HLA-compatible siblings and 10 (45%) from unrelated donors. Median time from alloSCT to progression was 12 months (range, 5-94 months). Ten (45%) failed to respond to donor lymphocyte infusion (DLI). The median time from progression post alloSCT and starting ibrutinib was 17 months (range, 0.5-88 months).When starting ibrutinib, median age was 63 (range, 47-73) years. Ten (43%) pts had bulky disease. Median β2-microglobulin was 4 mg/L (range, 2.7-10). Five (23%) CLL had 17p deletion. Median hemoglobin in CLL pts was 12.3 g/dL (range, 9.2-17.6), median platelets was 109,000/ µL (range, 8000-301,000), median absolute lymphocyte counts were 2,300/µL (range, 310-64,400). All MCL pts had elevated Ki-67 of >30% and 5 (83%) were blastoid. Median % of donor T cell (range, 27-100) and myeloid cells (range, 84-100) was both 100%. The ibrutinib starting dose was 420 mg in 12 (55%) and 560 mg in 10 (45%) pts. With a median follow-up time of 15 (range, 4-38) months, median overall survival (OS) was not reached for CLL, whereas this was of 17 months for MCL pts. Eighteen-month OS rate for CLL and MCL pts were 87% and 33%, respectively (P=0.08) and the 18-month progression-free survival rates were 87% and 33%, respectively (P=0.03). Survival rates were similar in CLL pts with or without 17p deletion. At the time of this analysis, 12 (75%) CLL pts (3 in CR, 4 in PR, 4 in stable disease and one with progressive disease) and 3 (50%) MCL pts (1 in PR, I in stable and 1 with progressive disease) remain alive. Ten episodes of grade 2 infection (3 of which were related to pneumonia) and one septic shock occurred during the course of ibrutinib treatment. Two of these infections occurred in the setting of severe neutropenia. One (5%) pt developed atrial fibrillation that required cardioversion. One (5%) pt experienced bleeding post a tooth extraction that required hospitalization and transfusions. With their prior alloSCT course and DLI, 8 (36%) pts had grade 1-2 acute GVHD, 3 (14%) had acute grade 3-4 GVHD and 7 (32%) had chronic GVHD. At the time ibrutinib was started, all pts were off immunosuppression and 3 had signs of limited chronic GVHD. At ibrutinib initiation, the 3 pts with limited chronic GVGD progressed to extensive GVHD at 43, 105 and 153 days respectively. All 3 had involvement of the mouth, skin (one with severe scleroderma) and 1 had acute gastro-intestinal diarrhea and bleeding. All responded to initiating tacrolimus, systemic steroids and reducing the ibrutinib dose.

Conclusions: Our results show that the use of ibrutinib after alloSCT is safe in pts who do not have active GVHD. The treatment can improve OS especially in CLL pts. This warrants further studies incorporating the drug in an upfront transplant strategy.