Phase II Clinical and Pharmacokinetic Study of Plitidepsin 3-Hour Infusion Every Two Weeks Alone or with Dexamethasone in Relapsed and Refractory Multiple Myeloma

Purpose: This trial evaluated the antitumor activity and safety of the marine-derived cyclodepsipeptide plitidepsin in patients with relapsed/refractory multiple myeloma. Experimental Design: This was a prospective, multicenter, open-label, single-arm, phase II trial with plitidepsin at 5 mg/m2 as a 3-hour i.v. infusion every two weeks. The protocol was amended to allow patients with suboptimal response to single-agent plitidepsin to add 20 mg/day on days 1 to 4 of oral dexamethasone every two weeks. Results: Fifty-one patients started treatment with plitidepsin and 47 were evaluable for efficacy. The overall response rate (complete response plus partial response plus minimal response) was 13% with plitidepsin alone and 22% in the cohort of patients with the addition of dexamethasone (n = 19, 18 evaluable). Both plitidepsin alone and with dexamethasone were feasible and well tolerated. Anemia (29%) and thrombocytopenia (18%) were the most frequent grade 3/4 hematologic toxicities. Fatigue (16%), muscular toxicity (6%), and transient alanine aminotransferase/aspartate aminotransferase (27%) and creatine phosphokinase (23%) increases were the most relevant nonhematologic side effects. A prolonged plasma half-life was observed in responding patients as compared with nonresponding patients (P = 0.009). Conclusions: Single-agent plitidepsin has limited but reproducible activity in relapsed/refractory multiple myeloma patients. Activity observed after dexamethasone addition merits further study. Both regimens were well tolerated in this heavily pretreated population

Phase II Clinical and Pharmacokinetic Study of Plitidepsin 3-Hour Infusion Every Two Weeks Alone or with Dexamethasone in Relapsed and Refractory Multiple Myeloma

Purpose: This trial evaluated the antitumor activity and safety of the marine-derived cyclodepsipeptide plitidepsin in patients with relapsed/refractory multiple myeloma. Experimental Design: This was a prospective, multicenter, open-label, single-arm, phase II trial with plitidepsin at 5 mg/m2 as a 3-hour i.v. infusion every two weeks. The protocol was amended to allow patients with suboptimal response to single-agent plitidepsin to add 20 mg/day on days 1 to 4 of oral dexamethasone every two weeks. Results: Fifty-one patients started treatment with plitidepsin and 47 were evaluable for efficacy. The overall response rate (complete response plus partial response plus minimal response) was 13% with plitidepsin alone and 22% in the cohort of patients with the addition of dexamethasone (n = 19, 18 evaluable). Both plitidepsin alone and with dexamethasone were feasible and well tolerated. Anemia (29%) and thrombocytopenia (18%) were the most frequent grade 3/4 hematologic toxicities. Fatigue (16%), muscular toxicity (6%), and transient alanine aminotransferase/aspartate aminotransferase (27%) and creatine phosphokinase (23%) increases were the most relevant nonhematologic side effects. A prolonged plasma half-life was observed in responding patients as compared with nonresponding patients (P = 0.009). Conclusions: Single-agent plitidepsin has limited but reproducible activity in relapsed/refractory multiple myeloma patients. Activity observed after dexamethasone addition merits further study. Both regimens were well tolerated in this heavily pretreated population

Chromatin activation as a unifying principle underlying pathogenic mechanisms in multiple myeloma

Multiple myeloma (MM) is a plasma cell neoplasm associated with a broad variety of genetic lesions. In spite of this genetic heterogeneity, MMs share a characteristic malignant phenotype whose underlying molecular basis remains poorly characterized. In the present study, we examined plasma cells from MM using a multi-epigenomics approach and demonstrated that, when compared to normal B cells, malignant plasma cells showed an extensive activation of regulatory elements, in part affecting coregulated adjacent genes. Among target genes up-regulated by this process, we found members of the NOTCH, NF-kB, MTOR signaling, and TP53 signaling pathways. Other activated genes included sets involved in osteoblast differentiation and response to oxidative stress, all of which have been shown to be associated with the MM phenotype and clinical behavior. We functionally characterized MM-specific active distant enhancers controlling the expression of thioredoxin (TXN), a major regulator of cellular redox status and, in addition, identified PRDM5 as a novel essential gene for MM. Collectively, our data indicate that aberrant chromatin activation is a unifying feature underlying the malignant plasma cell phenotype