Alegria, Victoria

Abstract Therapeutic strategies that target novel pathways are urgently needed for patients with relapsed/refractory multiple myeloma (RRMM). Ibrutinib is an oral covalent inhibitor of Bruton tyrosine kinase, which is overexpressed in MM cells. This phase 1 dose‐escalation study examined various doses of ibrutinib in combination with standard doses of lenalidomide (25 mg) and dexamethasone (40 mg) using a standard 3 + 3 design in RRMM patients. The primary objective was to determine the maximum tolerated dose (MTD) of ibrutinib in combination with lenalidomide and dexamethasone. Patients ( n = 15) had received a median of 4 prior regimens, 53% were triple‐class exposed, 33% were penta‐exposed, and 54% were lenalidomide‐refractory. The MTD of ibrutinib was 840 mg ( n = 6) and only 1 dose‐limiting toxicity; a grade 3 rash possibly related to ibrutinib was noted. The most common ≥ grade 3 adverse events were rash in 2 (13%), lymphopenia in 2 (13%), leukopenia, neutropenia, thrombocytopenia, and anemia all occurring in 3 (20%) patients each. One patient achieved a partial response for an overall response rate of 7%. The clinical benefit rate was 80%. The median time to progression was 3.8 months. Ibrutinib, lenalidomide and dexamethasone appears to be a safe and well‐tolerated regimen with reasonable efficacy in heavily pretreated RRMM patients.

AbstractExtramedullary multiple myeloma is seen in advanced and aggressive disease and occurs due to plasma cell infiltration of sites other than the bone marrow. Myelomatous ascites or pleural effusion is seen in less than 1% of cases and can be differentiated from infectious etiologies based on fluid cytology.

AbstractWaldenström macroglobulinemia (WM)/lymphoplasmacytic lymphoma (LPL) is often differentiated from myeloma based on the presence of lytic bone lesions (LBL). However, WM/LPL can present with LBL, and management is poorly understood. We describe a case of an 81‐year‐old woman with LPL who presented with LBL and was successfully treated with chemoimmunotherapy.

Extramedullary multiple myeloma is defined by the presence of plasma cell infiltration outside of the bone marrow. It is associated with a poor prognosis and resistance to therapy and is often associated with high-risk cytogenetics. Aggressive relapsed and refractory extramedullary multiple myeloma is often treated with salvage infusional chemotherapy to achieve rapid disease control. Commonly used regimens include DCEP, CVAD, and VTD-PACE. While VTD-PACE contains bortezomib and thalidomide which have potent antimyeloma activity, the advent of novel agent therapy with proteasome inhibitors and immunomodulatory agents being used in the first-line setting has resulted in many patients being refractory to bortezomib by the time they are treated with VTD-PACE. Herein, we discuss two cases of aggressive relapsed, high-risk, bortezomib-refractory extramedullary multiple myeloma treated with KRD-PACE and review the available clinical data on salvage chemotherapy regimens used in relapsed refractory myeloma.

AbstractPurpose:CD38 has emerged as a high-impact therapeutic target in multiple myeloma, with the approval of daratumumab (anti-CD38 mAb). The clinical importance of CD38 in patients with chronic lymphocytic leukemia (CLL) has been known for over 2 decades, although it's relevance as a therapeutic target in CLL remains understudied.Experimental Design:We investigated the biological effects and antitumor mechanisms engaged by daratumumab in primary CLL cells. Besides its known immune-effector mechanisms (antibody-dependent cell-mediated cytotoxicity, complement-dependent death, and antibody-dependent cellular phagocytosis), we also measured direct apoptotic effects of daratumumab alone or in combination with ibrutinib. In vivo antileukemic activity was assessed in a partially humanized xenograft model. The influence of CD38 on B-cell receptor (BCR) signaling was measured via immunoblotting of Lyn, Syk, BTK, PLCγ2, ERK1/2, and AKT.Results:In addition to immune-effector mechanisms; daratumumab also induced direct apoptosis of primary CLL cells, which was partially dependent on FcγR cross-linking. For the first time, we demonstrated the influence of CD38 on BCR signaling where interference of CD38 downregulated Syk, BTK, PLCγ2, ERK1/2, and AKT; effects that were further enhanced by addition of ibrutinib. In comparison to single-agent treatment, the combination of ibrutinib and daratumumab resulted in significantly enhanced anti-CLL activity in vitro and significantly decreased tumor growth and prolonged survival in the in vivo CLL xenograft model.Conclusions:Overall, our data demonstrate the antitumor mechanisms of daratumumab in CLL; furthermore, we show how cotargeting BTK and CD38 lead to a robust anti-CLL effect, which has clinical implications.