In collaboration with Dr. Wiestner, NHLBI, we studied bone marrow changes in patients with chronic lymphocytic leukemia (CLL) and TP53 aberrations enrolled into single-arm phase 2 study of oral agent ibrutinib. Ibrutinib (PCI-32765) is a covalent inhibitor of Bruton's tyrosine kinase (BTK). Once-daily administration causes sustained inactivation of the kinase, resulting in inhibition of B-cell receptor signaling and tumor-microenvironment interactions. Patients with chronic lymphocytic leukemia with TP53 aberrations respond poorly to first-line chemoimmunotherapy, resulting in early relapse and short survival. Eligible adult patients with active CLL with TP53 aberrations received 28-day cycles of ibrutinib 420 mg orally once daily until disease progression or the occurrence of limiting toxicities. 47 patients had CLL with deletion 17p13.1 and four carried a TP53 mutation in the absence of deletion 17p13.1. All patients had active disease requiring therapy. 35 enrolled patients had previously untreated CLL and 16 had relapsed or refractory disease. Median follow-up was 24 months. 33 previously untreated patients and 15 patients with relapsed or refractory CLL were evaluable for response at 24 weeks. Responses were assessed based on IWCLL 2008 criteria, incorporating the recent updates on partial response with lymphocytosis. Clinical response was assessed at each visit. At 2, 6, and 12 months, radiological assessments were done. Bone marrow evaluation was undertaken in 42 patients at 8 weeks, and in 47 patients at 24 weeks. The bone marrow at 8 weeks was omitted in the first patients and one patient refused bone marrow biopsy at 24 weeks. Bone marrow samples were assessed by immunostaining for CD20, CD79a, PAX-5, CD5 and CD3. FISH for deletion 17p13.1 was repeated on blood samples at 24 weeks. 32 (97%; 95% CI 86-100) of 33 previously untreated patients achieved an objective response, including partial response in 18 patients (55%) and partial response with lymphocytosis in 14 (42%). One patient had progressive disease at 0.4 months. 12 (80%; 95% CI 52-96) of the 15 patients with relapsed or refractory CLL had an objective response: six (40%) achieved a partial response and six (40%) a partial response with lymphocytosis; the remaining three (20%) patients had stable disease. Rapid disease control was achieved in all tissue compartments, reaching at least a 50% mean reduction in tumor burden in both spleen and lymph nodes at 8 weeks, with further improvements on continued therapy. Responses in the bone marrow seemed to be somewhat slower than in the spleen and lymph nodes. At 8 weeks, at least a 50% decrease in tumor burden in the bone marrow, lymph node, and spleen was recorded in 16 (44%) of 36, 31 (70%) of 44, and 30 (79%) of 38 patients with complete data, respectively. At the completion of 24 weeks of treatment, the proportion of patients with at least a 50% reduction in tumor burden in bone marrow, lymph node, and spleen was 34 (83%) of 41, 42 (93%) of 45, and 38 (95%) of 40 patients with complete data, respectively. In three patients, no residual CLL infiltrate was detected in the bone marrow by immunohistochemistry. Treatment with ibrutinib was well tolerated. The activity and safety profile of single-agent ibrutinib in CLL with TP53 aberrations is encouraging and supports its consideration as a novel treatment option for patients with this high-risk disease in both first-line and second-line settings. During the course of this trial, we noticed that single-agent ibrutinib treatment decreased CD20 expression in B-cells. We demonstrated that CD20 expression on ibrutinib was rapidly and persistently down-regulated (median reduction 74%, P<0.001) compared to baseline. Concomitantly, CD20 mRNA was decreased concurrent with reduced NF-kappaB signaling. An NF-kappaB binding site in the promoter of MS4A1 (encoding CD20) and down-regulation of CD20 by NF-kappaB inhibitors support a direct transcriptional effect. In addition, tumor cells from patients on ibrutinib were less susceptible to anti-CD20 mAb-mediated complement-dependent cytotoxicity than pre-treatment cells (median reduction 75%, P<0.001); however, opsonization by the complement protein C3d, which targets cells for phagocytosis, was relatively maintained. Expression of decay accelerating factor (CD55) decreased on ibrutinib, providing a likely mechanism for the preserved C3d opsonization. Additionally, ibrutinib significantly inhibited trogocytosis, a major contributor to antigen loss and tumor escape during mAb therapy. The data indicate that ibrutinib promotes both positive and negative interactions with anti-CD20 mAbs, suggesting that successfully harnessing maximal anti-tumor effects of such combinations requires further investigation. In collaboration with Dr. Landgren, we studied bone marrow changes in patients with plasma cell neoplasms treated with carfilzomib-lenalidomide-dexamethasone therapy in newly diagnosed multiple myeloma (NDMM) and high-risk smoldering multiple myeloma (SMM). 45 patients with NDMM and 12 patients with SMM were treated with median follow-up of 17.3 months (NDMM) and 15.9 months (SMM). All patients with SMM achieved at least a very good partial response during the study period. Among the 28 patients with NDMM and the 12 with SMM achieving at least a near-complete response, MRD negativity was found in 28 of 28 (100% 95% CI, 88%-100%), 11 of 12 (92% 95% CI, 62%-100%) (multiparametric flow cytometry), 14 of 21 (67% 95% CI, 43%-85%), and 9 of 12 (75% 95% CI, 43%-94%) (next-generation sequencing), respectively. No patients had neuropathy of grade 3 or greater. The study revealed that carfilzomib-lenalidomide-dexamethasone therapy is tolerable and demonstrates high rates of MRD negativity in NDMM, translating into longer progression-free survival in these patients. In a separate study, treatment responses to pan-KIR2D blockade with IPH2101 humanized monoclonal antibody were assessed. Total of 9 SMM patients were enrolled onto the first stage of the study. After completion of the first stage, the study was terminated due to lack of patients meeting the defined primary objective (50% decline in M-protein). Clinical response rates during the first 6 cycles of IPH2101 yielded 1 of 9 (11%) patients with minimal response (MR), 6 of 9 (66%) patients with stable disease (SD), 1 of 9 (11%) with biochemical progression (BP), and 1 of 9 (11%) patients with clinical progression to symptomatic MM. During the follow-up period (median follow up 32 months, range 837), 2 additional patients progressed to symptomatic MM. IPH2101 infusions were well tolerated with no grade 3 or 4 toxicities reported. Although this study showed no clinical response to single agent IPH2101, KIR blockade given in combination with other agents (e.g. lenalidomide) to bolster NK-cell cytotoxicity or in the setting of adoptive transfer of allogeneic or ex vivo expanded autologous NK cells may generate clinically significant responses in future trials.
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