Bruton tyrosine kinase (BTK) inhibition is an effective treatment approach for patients with Waldenström macroglobulinemia (WM). The phase 3 ASPEN study compared the efficacy and safety of ibrutinib, a first-generation BTK inhibitor, with zanubrutinib, a novel, highly selective BTK inhibitor, in patients with WM. Patients with MYD88L265P disease were randomly assigned 1:1 to treatment with either ibrutinib or zanubrutinib. The primary endpoint was the proportion of patients achieving a complete or very good partial response (CR or VGPR) by independent review. Key secondary endpoints included major response rate (MRR), progression-free survival (PFS), duration of response (DOR), disease burden, and safety. A total of 201 patients were randomized, and 199 received ≥1 dose of study treatment. No patient achieved a CR. Twenty-nine (28%) zanubrutinib and 19 (19%) ibrutinib patients achieved a VGPR, a non-statistically significant difference (P = .09). MRRs were 77% and 78% , respectively. Median DOR and PFS were not reached; 84% and 85% of ibrutinib and zanubrutinib patients were progression-free at 18 months. Incidence of atrial fibrillation, contusion, diarrhea, peripheral edema, hemorrhage, muscle spasms, and pneumonia, as well as adverse events leading to treatment discontinuation, were all lower among zanubrutinib recipients. Incidence of neutropenia was higher with zanubrutinib, although grade ≥3 infection rates were similar in both arms (1.2 and 1.1 events/100 person-months). These results demonstrate that zanubrutinib and ibrutinib are highly effective in the treatment of WM, but zanubrutinib treatment was associated with a trend toward better response quality and less toxicity, particularly cardiovascular toxicity.

Plasma cell leukemia (PCL) is a rare and aggressive variant of myeloma characterized by the presence of circulating plasma cells. It is classified as either primary PCL occurring at diagnosis or as secondary PCL in patients with relapsed/refractory myeloma. Primary PCL is a distinct clinic-pathologic entity with different cytogenetic and molecular findings. The clinical course is aggressive with short remissions and survival duration. The diagnosis is based upon the percentage (≥ 20%) and absolute number (≥ 2 × 10 9/L) of plasma cells in the peripheral blood. It is proposed that the thresholds for diagnosis be reexamined and consensus recommendations are made for diagnosis, as well as, response and progression criteria. Induction therapy needs to begin promptly and have high clinical activity leading to rapid disease control in an effort to minimize the risk of early death. Intensive chemotherapy regimens and bortezomib-based regimens are recommended followed by high-dose therapy with autologous stem-cell transplantation (HDT/ASCT) if feasible. Allogeneic transplantation can be considered in younger patients. Prospective multicenter studies are required to provide revised definitions and better understanding of the pathogenesis of PCL.

We provide an overview on soft-tissue extramedullary plasmacytomas (EMPs) in multiple myeloma (MM). We reviewed the incidence of EMPs in MM, myeloma bone marrow homing, possible mechanisms of extramedullary spread, and prognosis and response to therapy. The incidence of EMPs is 7% to 18% at MM diagnosis and up to 20% at relapse. The current notion that EMPs are more frequent after treatment with novel agents remains to be proven, especially considering that different patterns of disease recurrence can emerge as patients live longer in the era of novel drugs. Bone marrow genetic abnormalities are not associated with extramedullary spread per se, which also suggests that microenvironmental interactions are key. Possible mechanisms of extramedullary spread include decreased adhesion molecule expression and downregulation of chemokine receptors. EMPs usually show plasmablastic morphology with negative CD56 expression. High-dose therapy with autologous stem-cell transplantation (ASCT) can overcome the negative prognostic impact of extramedullary disease in younger selected patients. EMPs do not typically respond to thalidomide alone, but in contrast, responses to bortezomib have been reported. The incidence of EMPs in patients with MM is high and is associated with poor outcome in patients treated conventionally. A potential first-line treatment option seems to be a bortezomib-containing regimen followed by ASCT, whenever possible. Experimental studies on the mechanisms of myeloma cell adhesion, myeloma growth at extramedullary sites, and drug sensitivity are priorities for this area of continuing therapeutic challenge.

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Early clinical results of chimeric antigen receptor (CAR) T cell therapy targeting B cell maturation antigen (BCMA) for multiple myeloma (MM) appear promising, but relapses associated with residual low-to-negative BCMA-expressing MM cells have been reported, necessitating identification of additional targets. The orphan G protein–coupled receptor, class C group 5 member D (GPRC5D), normally expressed only in the hair follicle, was previously identified as expressed by mRNA in marrow aspirates from patients with MM, but confirmation of protein expression remained elusive. Using quantitative immunofluorescence, we determined that GPRC5D protein is expressed on CD138+ MM cells from primary marrow samples with a distribution that was similar to, but independent of, BCMA. Panning a human B cell–derived phage display library identified seven GPRC5D-specific single-chain variable fragments (scFvs). Incorporation of these into multiple CAR formats yielded 42 different constructs, which were screened for antigen-specific and antigen-independent (tonic) signaling using a Nur77-based reporter system. Nur77 reporter screen results were confirmed in vivo using a marrow-tropic MM xenograft in mice. CAR T cells incorporating GPRC5D-targeted scFv clone 109 eradicated MM and enabled long-term survival, including in a BCMA antigen escape model. GPRC5D(109) is specific for GPRC5D and resulted in MM cell line and primary MM cytotoxicity, cytokine release, and in vivo activity comparable to anti-BCMA CAR T cells. Murine and cynomolgus cross-reactive CAR T cells did not cause alopecia or other signs of GPRC5D-mediated toxicity in these species. Thus, GPRC5D(109) CAR T cell therapy shows potential for the treatment of advanced MM irrespective of previous BCMA-targeted therapy.

Smoldering multiple myeloma (SMM) is an asymptomatic precursor state of multiple myeloma (MM). Recently, MM was redefined to include biomarkers predicting a high risk of progression from SMM, thus necessitating a redefinition of SMM and its risk stratification. We assembled a large cohort of SMM patients meeting the revised IMWG criteria to develop a new risk stratification system. We included 1996 patients, and using stepwise selection and multivariable analysis, we identified three independent factors predicting progression risk at 2 years: serum M-protein >2 g/dL (HR: 2.1), involved to uninvolved free light-chain ratio >20 (HR: 2.7), and marrow plasma cell infiltration >20% (HR: 2.4). This translates into 3 categories with increasing 2-year progression risk: 6% for low risk (38%; no risk factors, HR: 1); 18% for intermediate risk (33%; 1 factor; HR: 3.0), and 44% for high risk (29%; 2–3 factors). Addition of cytogenetic abnormalities (t(4;14), t(14;16), +1q, and/or del13q) allowed separation into 4 groups (low risk with 0, low intermediate risk with 1, intermediate risk with 2, and high risk with ≥3 risk factors) with 6, 23, 46, and 63% risk of progression in 2 years, respectively. The 2/20/20 risk stratification model can be easily implemented to identify high-risk SMM for clinical research and routine practice and will be widely applicable.

Engraftment syndrome (ES) is increasingly observed in patients who receive auto-SCT. To investigate this fact, validate the clinical criteria for ES diagnosis and analyze the risk factors for this complication, we reviewed 328 consecutive peripheral blood auto-SCT performed during the past 7 years. A total of 43 patients presented with clinical or biological data suggestive of ES. Of the total, 41 (95%) and 22 (51%) could be diagnosed with ES using the Maiolino criteria (MC) and the Spitzer criteria (SC), respectively. The SC were less sensitive as they do not consider some relevant clinical data and limit the observation time after engraftment. All ES cases had high C-reactive protein (CRP) values not observed in the remaining patients at engraftment (median ± s.d.: 17.5 ± 7.3 vs 2.4 ± 3.4 mg per 100 ml; P ¼ 0.0001). Multivariate analysis showed a higher risk of ES in SCT performed in recent years (relative risk (RR) 2.3, 95% confidence interval (CI 1.0-4.7), female patients (RR 2.5, 95% CI 1.2-5.2), and absence of intensive chemotherapy before SCT (RR 8.8,). All patients except one improved after treatment with corticosteroids. The MC seem to be the best tool to establish a diagnosis of ES. In doubtful cases, the diagnosis could be confirmed by evaluating CRP. Auto-SCT in patients not receiving previous chemotherapy could explain the increasing incidence of ES in the past years.

Key Points• The first wide, prospective report on the role of IEM in the differential diagnosis of systemic amyloidosis.• IEM allows for the correct characterization of the amyloid protein in virtually all cases and represents a viable alternative to mass spectrometry.Accurate diagnosis of systemic amyloidosis is necessary both for assessing the prognosis and for delineating the appropriate treatment. It is based on histologic evidence of amyloid deposits and characterization of the amyloidogenic protein. We prospectively evaluated the diagnostic performance of immunoelectron microscopy (IEM) of abdominal fat aspirates from 745 consecutive patients with suspected systemic amyloidoses. All cases were extensively investigated with clinical and laboratory data, with a follow-up of at least 18 months. The 423 (56.8%) cases with confirmed systemic forms were used to estimate the diagnostic performance of IEM. Compared with Congo-red-based light microscopy, IEM was equally sensitive (75% to 80%) but significantly more specific (100% vs 80%; P < .001). In amyloid light-chain (AL) amyloidosis, k cases were more difficult to diagnose (sensitivity 71%), whereas the analysis of abdominal aspirate was informative in only 40% of patients with transthyretin amyloidosis. We found a high prevalence (20%) of a monoclonal component in patients with non-AL amyloidosis, highlighting the risk of misdiagnosis and the need for unequivocal amyloid typing. Notably, IEM identified correctly the specific form of amyloidosis in >99% of the cases. IEM of abdominal fat aspirates is an effective tool in the routine diagnosis of systemic amyloidoses. (Blood. 2015;125(14):2239-2244) IntroductionAmyloidosis is a heterogeneous group of diseases that share the deposition of amyloid fibrils in organs and tissues, with the same characteristic cross-b-sheet secondary structure, independently of their protein primary structure.1 More than 30 unrelated autologous proteins can produce systemic amyloidoses, 2-5 either localized or systemic. The various forms differ in pathogenesis and prognosis, but they usually show overlapping clinical manifestations, making their differentiation on clinical grounds very difficult. Precise amyloid typing is crucial for the adequate treatment of patients because the various forms require different approaches, which can range from autologous stem cell transplantation in amyloid light-chain (AL) amyloidosis to liver transplantation in transthyretin (TTR) amyloidosis (ATTR). 2,4,5 Diagnosis and classification are based on histologic demonstration of amyloid deposits and characterization of the amyloid precursor. Abdominal subcutaneous fat aspiration with a fine needle is fast and harmless and is the most common diagnostic tool when a systemic form is suspected, 6 offering a convenient alternative to organ biopsy. The resulting tissue smear is examined by polarized light microscopy (LM) after Congo red staining in order to detect the presence of amyloid. The second step is to identify the amyloidogenic protein in order to u...