Daratumumab plus pomalidomide and dexamethasone in relapsed and/or refractory multiple myeloma.

Daratumumab plus pomalidomide and dexamethasone (pom-dex) was evaluated in patients with relapsed/refractory multiple myeloma with ≥2 prior lines of therapy who were refractory to their last treatment. Patients received daratumumab 16 mg/kg at the recommended dosing schedule, pomalidomide 4 mg daily for 21 days of each 28-day cycle, and dexamethasone 40 mg weekly. Safety was the primary end point. Overall response rate (ORR) and minimal residual disease (MRD) by next-generation sequencing were secondary end points. Patients (N = 103) received a median (range) of 4 (1-13) prior therapies; 76% received ≥3 prior therapies. The safety profile of daratumumab plus pom-dex was similar to that of pom-dex alone, with the exception of daratumumab-specific infusion-related reactions (50%) and a higher incidence of neutropenia, although without an increase in infection rate. Common grade ≥3 adverse events were neutropenia (78%), anemia (28%), and leukopenia (24%). ORR was 60% and was generally consistent across subgroups (58% in double-refractory patients). Among patients with a complete response or better, 29% were MRD negative at a threshold of 10-5 Among the 62 responders, median duration of response was not estimable (NE; 95% confidence interval [CI], 13.6-NE). At a median follow-up of 13.1 months, the median progression-free survival was 8.8 (95% CI, 4.6-15.4) months and median overall survival was 17.5 (95% CI, 13.3-NE) months. The estimated 12-month survival rate was 66% (95% CI, 55.6-74.8). Aside from increased neutropenia, the safety profile of daratumumab plus pom-dex was consistent with that of the individual therapies. Deep, durable responses were observed in heavily treated patients. The study was registered at www.clinicaltrials.gov as #NCT01998971.

Phase I study of cladribine, cytarabine (Ara-C), granulocyte colony stimulating factor (G-CSF) (CLAG Regimen) and simultaneous escalating doses of imatinib mesylate (Gleevec) in relapsed/refractory AML.

Receptor activated tyrosine kinases such as c-kit, c-fms and PDGFR are known targets of inhibition by imatinib mesylate (Gleevec) and are expressed on AML blasts. Marrow stromal cells and monocytes express KIT ligand, M-CSF and PDGF and are therefore capable of activating survival pathways in these leukemic cells. Given the synergy in vitro between Ara-C and imatinib mesylate on AML cell growth inhibition, we initiated a Phase I study combining CLAG+imatinib mesylate in AML patients. Patients with relapsed, refractory AML or CML myeloid blast crisis were eligible to receive Cladribine 5mg/m(2) days 3-7, Cytarabine 2gm/m(2) days 3-7, G-CSF 300mcg days 2-7, and escalating doses of imatinib mesylate given on days 1-15. The level 1 Gleevec dose was 400mg, while level 2 was 600mg and the level 3 dose 800mg. A total of 16 patients were enrolled, 15 AML and 1 CML myeloid blast crisis. The dose escalation occurred as planned and there was no clear evidence of added toxicity due to imatinib mesylate. One patient with an extensive cardiac history died of cardiac causes on day 1 of therapy however no other deaths occurred within 30 days of starting therapy. One patient had a Grade 3 skin rash at dose level 2. The most common toxicities encountered during induction therapy were nausea, vomiting, rash and diarrhea that were transient and/or reversible. At the 800mg dose 1 patient developed a decline in cardiac ejection fraction on day 20 who later died of sepsis, so this was considered a dose limiting toxicity. Of 16 evaluable patients 11 achieved a hypocellular marrow after initial induction with 1 additional patient achieving a hypocellular marrow following a second course of the same regimen. Four patients (25%) achieved a complete morphologic response with normal cytogenetics, 2 patients (12.5%) achieved a complete morphologic response only and 1 patient had a complete response in the bone marrow but incomplete blood count recovery. The overall response rate was 43.8%. The median overall survival was 175 days (95% CI 16.24-333.76) and the median relapse free survival was 76 days. The addition of imatinib mesylate to CLAG was well tolerated with acceptable toxicities and response rates comparable to other salvage regimens. To assess the efficacy of imatinib mesylate in combination with CLAG, a larger phase II trial is now planned.

Apoptosis and complement-mediated lysis of myeloma cells by polyclonal rabbit antithymocyte globulin.

Current monoclonal antibody therapies for multiple myeloma have had limited success, perhaps due to narrow target specificity. We have previously described the ability of polyclonal rabbit antithymocyte globulin (rATG) to induce caspase- and cathepsin-mediated apoptosis in human B and plasma cells. We now extend this observation to myeloma cells. Complement independent cell death was measured after addition of rATG (1-1000 microg/mL) to cultures of myeloma cell lines or primary CD138+ isolates from patient bone marrow aspirates. rATG induced significant levels of apoptosis in myeloma cells as assayed by caspase induction, annexin V binding, subdiploid DNA fragmentation, plasma-membrane permeability, and loss of mitochondrial-membrane potential. Addition of complement greatly augmented myeloma-cell death. Binding of rATG to individual myeloma cell-surface proteins, primarily CD38, CD52, CD126, and CD138, was demonstrated by competitive inhibition experiments with targeted monoclonal antibodies. Three pathways of cell death were identified involving caspase activation, cathepsin D, and the genistein sensitive tyrosine kinase pathway. Fab'2 fragments of rATG had reduced proapoptotic activity, which was restored by coincubation with Fc fragments, and anti-CD32 or anti-CD64 antibodies. We conclude that rATG is an effective agent for in vitro induction of apoptosis in multiple myeloma, and that exploratory clinical trials may be warranted.

Donor cell myelodysplastic syndrome after allogeneic stem cell transplantation responding to donor lymphocyte infusion: case report and literature review.

Allogeneic hematopoietic stem cell transplantation (SCT) is a potentially curative treatment for patients with myelodysplastic syndrome (MDS). Relapses after transplantation however, are not uncommon and are usually due to re-emergence of a recipient derived, neoplastic, stem cell clone. We report a unique case of MDS recurring 5 months after non-myeloablative, sibling, allogeneic SCT. Interestingly, chimerism analysis at relapse showed hematopoiesis to be entirely of donor origin confirming donor cell MDS. Donor lymphocyte infusion (DLI) produced a hematological response lasting several months. Our review of the literature shows donor-derived MDS to be very rare, with only four such cases described previously. In this report, we describe the details of our case and discuss putative mechanisms underlying the genesis of donor cell MDS and the observed response to DLI.