Evidence-based treatment decisions in Waldenström's macroglobulinemia now rely mainly on small-scale, single-armed trials. Patients with this disease should be treated in the setting of a clinical trial if possible. Trials aimed at improving the quality of treatment for other IgM-associated diseases, such as IgM neuropathies and cold agglutinin disease, would also be desirable.

Homeobox genes are key regulators in normal and malignant hematopoiesis. The human Vent-like homeobox gene VENTX, a putative homolog of the Xenopus laevis Xvent-2 gene, was shown to be highly expressed in normal myeloid cells and in patients with acute myeloid leukemia. We now demonstrate that constitutive expression of VENTX suppresses expression of genes responsible for terminal erythroid differentiation in normal CD34+ stem and progenitor cells. Transplantation of bone marrow progenitor cells retrovirally engineered to express VENTX caused massive expansion of primitive erythroid cells and partly acute erythroleukemia in transplanted mice. The leukemogenic potential of VENTX was confirmed in the AML1-ETO transplantation model, as in contrast to AML1-ETO alone co-expression of AML1-ETO and VENTX induced acute myeloid leukemia, partly expressing erythroid markers, in all transplanted mice. VENTX was highly expressed in patients with primary human erythroleukemias and knockdown of VENTX in the erythroleukemic HEL cell line significantly blocked cell growth. In summary, these data indicate that VENTX is able to perturb erythroid differentiation and to contribute to myeloid leukemogenesis when co-expressed with appropriate AML oncogenes and point to its potential significance as a novel therapeutic target in AML.

Background: Rituximab/chemotherapy is still one of the cornerstones of treatment for patients with Waldenström's macroglobulinemia (WM) despite the emergence of BTK inhibitors. Beside Rituximab-Bendamustine the combination Dexamethasone, Rituximab and Cyclophospamide (DRC) is the most widely recommended immunochemotherapy in national and international guidelines based on its low myelotoxicity and anti-lymphoma activity in WM. In addition, the proteasome inhibitor Bortezomib (B) has shown significant activity in WM as single agent or combined with Rituximab and/or Dexamethasone. This study aimed at evaluating the efficacy and toxicity of Bortezomib-DRC (B-DRC) as first line treatment in WM. Methods: In this prospective randomized multicenter European phase II study, patients with the diagnosis of WM confirmed by reference pathology and in need of treatment were randomized 1:1 to DRC (Dexamethasone 20 mg orally d1, Rituximab 375 mg/m2 IV d1 cycle 1 and 1400 mg SC d1 cycle 2-6, Cyclophosphamide 100 mg/m2 x 2 orally d1-5) or to B-DRC (DRC plus Bortezomib SC 1,6mg/m2 day 1, 8, 15) for 6 cycles (28d interval). Primary endpoint was progression free survival (PFS). Secondary endpoints included response rates, overall survival (OS), and toxicity. Results: Of 204 registered patients, 2 patients were excluded due to incorrect randomization. Median follow-up was 27.5 months at the time of the data cut. Median age was 68 years (range 34-89) in both arms. According to the ISSWM prognostic score 14 % of patients were at low, 73 % at intermediate and 13 % at high risk in both treatment arms. Median baseline hemoglobin for B-DRC and DRC was 10.0 and 9.8 g/dl and median baseline IgM 31.7 and 31.9 g/dl, respectively. Mutational status was available for 72 patients: in the B-DCR vs DRC treatment arm 26 and 16 patients were MYD88 mutated (MYD88MT) and CXCR4 wildtype (CXCR4WT), 8 and 12 patients were MYD88MT/CXCR4MT and 5 and 5 patients MYD88WT/CXCR4WT, respectively. Median PFS has not been reached in the B-DRC arm (95% CI: 33.5; --) compared to 50.1 months in the DRC arm (95% CI: 31.1; --) with an estimated PFS at 24 months of 80.6 % (95% CI: 69.5; 88.0) and 72.8 % (95% CI: 61.3; 81.3), respectively (p=0.32). Median OS has not been reached in either treatment arm with 5 deaths and 6 deaths in the B-DRC and DRC arm, respectively. At the end of treatment B-DRC induced major responses (at least PR) in 79.1 % of patients (vs 68.9% for DRC) and a CR/VGPR in 18.7 % of patients (vs 11.1 % for DRC) with an overall response of 91.2 compared to 86.7 % for DRC. Compared to baseline IgM decreased by 79 % and 73 % and Hb increased by 28 % and 32 % in the B-DRC and DRC arm, respectively. Responses and PFS were independent of the mutational status in both treatment arms. B-DRC and DRC were well tolerated: grade ≥3 AEs occurred in 48% of all patients (B-DRC 48%, DRC 47%). Most common grade ≥3 AEs included neutropenia (25%), anemia (6%), and thrombocytopenia (5%). Overall, 16 pts (8%) developed infections (1% grade ≥3). Serious AEs occurred in 40 pts (20%) (DRC: 26 (26%), B-DRC: 14 (14%)). Peripheral sensory neuropathy occurred in 18 patients treated with B-DRC (2 patients with grade 3, 16 patients grade 1-2) and in 3 patients treated with DRC (all grade 1 and 2). Conclusions: This is the first and largest prospective randomized trial to evaluate bortezomib in combination with standard immunochemotherapy, demonstrating that B-DRC is a well-tolerated regimen which induces a high rate of major responses including deep remissions after 6 months of treatment with a 2-year PFS of 81%, independently of the mutational status of MYD88 and CXCR4. At this time point of analysis, adding Bortezomib to DRC did not induce significant differences in PFS compared to DRC alone. Future trials will have to compare chemotherapy-free approaches such as continuous treatment with BTK inhibitors with fixed duration treatments exemplified by B-DRC to understand which of the two treatment approaches offers the highest long - term sustained clinical benefit to WM patients. Disclosures Buske: Roche, Janssen, Bayer, MSD: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; Roche, Janssen, AbbVie, Pfizer, Celltrion: Honoraria, Speakers Bureau. Dimopoulos:Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Research Funding, Speakers Bureau; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Personal fees, Speakers Bureau. Kastritis:Genesis Pharma: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding. Tomowiak:Roche: Research Funding; Gilead: Research Funding; Janssen: Honoraria; AbbVie: Honoraria; Beigene: Honoraria; Takeda: Honoraria. Hajek:Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Consultancy, Honoraria; PharmaMar: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Research Funding; Oncopeptides: Consultancy. Viardot:Roche: Honoraria, Other: advisory board; Kite/Gilead: Honoraria, Other: advisory board; Novartis: Honoraria, Other: advisory board; Amgen: Honoraria, Other: advisory board. Aurran:Janssen: Honoraria. Lepretre:Gilead: Honoraria; Astra Zeneca: Honoraria; AbbVie: Honoraria; Janssen: Honoraria. Leblond:AbbVie: Honoraria; Gilead: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees; Lilly: Honoraria; Janssen: Honoraria; Roche: Honoraria; Astra Zeneca: Honoraria; Amgen: Honoraria; Gilead: Honoraria; Beigene: Honoraria; Beigene: Membership on an entity's Board of Directors or advisory committees. de Guibert:Gilead Sciences: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. Garcia-Sanz:Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria; Gilead: Honoraria, Research Funding; Incyte: Research Funding; Janssen: Honoraria, Research Funding; Novartis: Honoraria; Pharmacyclics: Honoraria; Takeda: Consultancy, Research Funding. Gomes da Silva:roche: Consultancy; abbvie: Consultancy; BMS: Consultancy; MSD: Consultancy; Janssen: Consultancy; Gilead: Consultancy. Morel:Janssen: Honoraria. OffLabel Disclosure: Bortezomib in combination with DRC in Waldenström's Macroglobulinemia

PURPOSE Rituximab/chemotherapy is a cornerstone of treatment for Waldenström's macroglobulinemia (WM). In addition, bortezomib has shown significant activity in WM. This study evaluated the efficacy and safety of dexamethasone, rituximab, and cyclophosphamide (DRC) as first-line treatment in WM. METHODS In this European study, treatment-naïve patients were randomly assigned to DRC or bortezomib-DRC B-DRC for six cycles. The primary end point was progression-free survival. Secondary end points included response rates, overall survival, and safety. RESULTS Two hundred four patients were registered. After a median follow-up of 27.5 months, the estimated 24-month progression-free survival was 80.6% (95% CI, 69.5 to 88.0) for B-DRC and 72.8% (95% CI, 61.3 to 81.3) for DRC ( P = .32). At the end of treatment, B-DRC and DRC induced major responses in 80.6% versus 69.9% and a complete response/very good partial response in 17.2% versus 9.6% of patients, respectively. The median time to first response was shorter for B-DRC with 3.0 (95% CI, 2.8 to 3.2) versus 5.5 (95% CI, 2.9 to 5.8) months for DRC. This resulted in higher major response rates (57.0% v 32.5%; P < .01) after three cycles of B-DRC compared with DRC. At best response, the complete response/very good partial response increased to 32.6% for B-DRC. Both treatments were well tolerated: grade ≥ 3 adverse events occurred in 49.2% of all patients (B-DRC, 49.5%; DRC, 49.0%). Peripheral sensory neuropathy grade 3 occurred in two patients treated with B-DRC and in none with DRC. CONCLUSION This large randomized study illustrates that B-DRC is highly effective and well tolerated in WM. The data demonstrate that fixed duration immunochemotherapy remains an important pillar in the clinical management of WM.

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