Henk M. Lokhorst

PURPOSE: The clinical outcome of multiple myeloma (MM) is heterogeneous. A simple and reliable tool is needed to stratify patients with MM. We combined the International Staging System (ISS) with chromosomal abnormalities (CA) detected by interphase fluorescent in situ hybridization after CD138 plasma cell purification and serum lactate dehydrogenase (LDH) to evaluate their prognostic value in newly diagnosed MM (NDMM). PATIENTS AND METHODS: Clinical and laboratory data from 4,445 patients with NDMM enrolled onto 11 international trials were pooled together. The K-adaptive partitioning algorithm was used to define the most appropriate subgroups with homogeneous survival. RESULTS: ISS, CA, and LDH data were simultaneously available in 3,060 of 4,445 patients. We defined the following three groups: revised ISS (R-ISS) I (n = 871), including ISS stage I (serum β2-microglobulin level < 3.5 mg/L and serum albumin level ≥ 3.5 g/dL), no high-risk CA [del(17p) and/or t(4;14) and/or t(14;16)], and normal LDH level (less than the upper limit of normal range); R-ISS III (n = 295), including ISS stage III (serum β2-microglobulin level > 5.5 mg/L) and high-risk CA or high LDH level; and R-ISS II (n = 1,894), including all the other possible combinations. At a median follow-up of 46 months, the 5-year OS rate was 82% in the R-ISS I, 62% in the R-ISS II, and 40% in the R-ISS III groups; the 5-year PFS rates were 55%, 36%, and 24%, respectively. CONCLUSION: The R-ISS is a simple and powerful prognostic staging system, and we recommend its use in future clinical studies to stratify patients with NDMM effectively with respect to the relative risk to their survival.

BACKGROUND: Multiple myeloma cells uniformly overexpress CD38. We studied daratumumab, a CD38-targeting, human IgG1κ monoclonal antibody, in a phase 1-2 trial involving patients with relapsed myeloma or relapsed myeloma that was refractory to two or more prior lines of therapy. METHODS: In part 1, the dose-escalation phase, we administered daratumumab at doses of 0.005 to 24 mg per kilogram of body weight. In part 2, the dose-expansion phase, 30 patients received 8 mg per kilogram of daratumumab and 42 received 16 mg per kilogram, administered once weekly (8 doses), twice monthly (8 doses), and monthly for up to 24 months. End points included safety, efficacy, and pharmacokinetics. RESULTS: No maximum tolerated dose was identified in part 1. In part 2, the median time since diagnosis was 5.7 years. Patients had received a median of four prior treatments; 79% of the patients had disease that was refractory to the last therapy received (64% had disease refractory to proteasome inhibitors and immunomodulatory drugs and 64% had disease refractory to bortezomib and lenalidomide), and 76% had received autologous stem-cell transplants. Infusion-related reactions in part 2 were mild (71% of patients had an event of any grade, and 1% had an event of grade 3), with no dose-dependent adverse events. The most common adverse events of grade 3 or 4 (in ≥ 5% of patients) were pneumonia and thrombocytopenia. The overall response rate was 36% in the cohort that received 16 mg per kilogram (15 patients had a partial response or better, including 2 with a complete response and 2 with a very good partial response) and 10% in the cohort that received 8 mg per kilogram (3 had a partial response). In the cohort that received 16 mg per kilogram, the median progression-free survival was 5.6 months (95% confidence interval [CI], 4.2 to 8.1), and 65% (95% CI, 28 to 86) of the patients who had a response did not have progression at 12 months. CONCLUSIONS: Daratumumab monotherapy had a favorable safety profile and encouraging efficacy in patients with heavily pretreated and refractory myeloma. (Funded by Janssen Research and Development and Genmab; ClinicalTrials.gov number, NCT00574288.).

CD38, a type II transmembrane glycoprotein highly expressed in hematological malignancies including multiple myeloma (MM), represents a promising target for mAb-based immunotherapy. In this study, we describe the cytotoxic mechanisms of action of daratumumab, a novel, high-affinity, therapeutic human mAb against a unique CD38 epitope. Daratumumab induced potent Ab-dependent cellular cytotoxicity in CD38-expressing lymphoma- and MM-derived cell lines as well as in patient MM cells, both with autologous and allogeneic effector cells. Daratumumab stood out from other CD38 mAbs in its strong ability to induce complement-dependent cytotoxicity in patient MM cells. Importantly, daratumumab-induced Ab-dependent cellular cytotoxicity and complement-dependent cytotoxicity were not affected by the presence of bone marrow stromal cells, indicating that daratumumab can effectively kill MM tumor cells in a tumor-preserving bone marrow microenvironment. In vivo, daratumumab was highly active and interrupted xenograft tumor growth at low dosing. Collectively, our results show the versatility of daratumumab to effectively kill CD38-expressing tumor cells, including patient MM cells, via diverse cytotoxic mechanisms. These findings support clinical development of daratumumab for the treatment of CD38-positive MM tumors.

Daratumumab targets CD38-expressing myeloma cells through a variety of immune-mediated mechanisms (complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, and antibody-dependent cellular phagocytosis) and direct apoptosis with crosslinking. These mechanisms may also target nonplasma cells that express CD38, which prompted evaluation of daratumumab's effects on CD38-positive immune subpopulations. Peripheral blood (PB) and bone marrow (BM) from patients with relapsed/refractory myeloma from 2 daratumumab monotherapy studies were analyzed before and during therapy and at relapse. Regulatory B cells and myeloid-derived suppressor cells, previously shown to express CD38, were evaluated for immunosuppressive activity and daratumumab sensitivity in the myeloma setting. A novel subpopulation of regulatory T cells (Tregs) expressing CD38 was identified. These Tregs were more immunosuppressive in vitro than CD38-negative Tregs and were reduced in daratumumab-treated patients. In parallel, daratumumab induced robust increases in helper and cytotoxic T-cell absolute counts. In PB and BM, daratumumab induced significant increases in CD8(+):CD4(+) and CD8(+):Treg ratios, and increased memory T cells while decreasing naïve T cells. The majority of patients demonstrated these broad T-cell changes, although patients with a partial response or better showed greater maximum effector and helper T-cell increases, elevated antiviral and alloreactive functional responses, and significantly greater increases in T-cell clonality as measured by T-cell receptor (TCR) sequencing. Increased TCR clonality positively correlated with increased CD8(+) PB T-cell counts. Depletion of CD38(+) immunosuppressive cells, which is associated with an increase in T-helper cells, cytotoxic T cells, T-cell functional response, and TCR clonality, represents possible additional mechanisms of action for daratumumab and deserves further exploration.

PURPOSE: We investigated whether bortezomib during induction and maintenance improves survival in newly diagnosed multiple myeloma (MM). PATIENTS AND METHODS: In all, 827 eligible patients with newly diagnosed symptomatic MM were randomly assigned to receive induction therapy with vincristine, doxorubicin, and dexamethasone (VAD) or bortezomib, doxorubicin, and dexamethasone (PAD) followed by high-dose melphalan and autologous stem-cell transplantation. Maintenance consisted of thalidomide 50 mg (VAD) once per day or bortezomib 1.3 mg/m(2) (PAD) once every 2 weeks for 2 years. The primary analysis was progression-free survival (PFS) adjusted for International Staging System (ISS) stage. RESULTS: Complete response (CR), including near CR, was superior after PAD induction (15% v 31%; P < .001) and bortezomib maintenance (34% v 49%; P < .001). After a median follow-up of 41 months, PFS was superior in the PAD arm (median of 28 months v 35 months; hazard ratio [HR], 0.75; 95% CI, 0.62 to 0.90; P = .002). In multivariate analysis, overall survival (OS) was better in the PAD arm (HR, 0.77; 95% CI, 0.60 to 1.00; P = .049). In high-risk patients presenting with increased creatinine more than 2 mg/dL, bortezomib significantly improved PFS from a median of 13 months to 30 months (HR, 0.45; 95% CI, 0.26 to 0.78; P = .004) and OS from a median of 21 months to 54 months (HR, 0.33; 95% CI, 0.16 to 0.65; P < .001). A benefit was also observed in patients with deletion 17p13 (median PFS, 12 v 22 months; HR, 0.47; 95% CI, 0.26 to 0.86; P = .01; median OS, 24 months v not reached at 54 months; HR, 0.36; 95% CI, 0.18 to 0.74; P = .003). CONCLUSION: Bortezomib during induction and maintenance improves CR and achieves superior PFS and OS.