ALBERT

Description: Abstract 1945 Background Prognosis of patients with multiple myeloma (MM) has significantly improved by the introduction of autologous (auto) stem cell transplantation (SCT). The “novel drugs” which have shown activity in relapsed MM are increasingly used in first-line therapy aiming at maximized response prior to SCT. Whether allogeneic (allo) SCT adds to further disease control remains a matter of debate. Our group has shown the RAD regimen (lenalidomide, adriamycin and dexamethasone) to be highly effective and relatively well tolerated in relapsed and refractory MM. Therefore, we decided to explore RAD in the up-front management. Patients and Methods The current phase-II trial (DSMM XII) was designed to include patients (pts) up to the age of 65 years with newly diagnosed MM requiring treatment. We chose four cycles of RAD (lenalidomide 25 mg d-21; infusional adriamycin 9 mg/m2 per day d1-4; dexamethasone 40 mg d1-4 and 17–20; pegfilgrastim 6 mg d 6) every 4 weeks for induction followed by chemomobilization of peripheral blood stem cells. Low molecular weight heparin is mandatory during RAD treatment for thromboprophylaxis. All pts are to undergo one cycle of melphalan 200 mg/m2 followed by auto SCT. A subsequent allo SCT after reduced intensity conditioning (treosulfan/fludarabin) is scheduled for pts featuring at least one previously identified (cytogenetic or serologic) risk factor. Those with very favourable risk are to proceed to a second auto SCT. All patients will receive 12 months of lenalidomide maintenance (10 mg per day) on a continuous basis. Here, we present results of a planned safety analysis. Results 75 pts with a median age of 57 (range, 35–66) years have been enrolled by 11 German centers between 9/2009 and 7/2010. Currently, 51 pts are evaluable for toxicity during RAD induction: In all, 25 severe adverse events (SAEs) were reported for 16 subjects (31%). 68% of SAEs were assessed to be drug-related. Most frequent events were venous thrombosis (VTE; n=4), pyrexia (n=3) and syncope (n=2). Neutropenia, extravasation, pleural effusion, and allergic dermatitis accounted for one SAE each. 17 patients, 10 of whom (59%) had ISS stage II/III disease, are evaluable for post-induction response. Ten subjects (59%) achieved VGPR or better: 6 pts had VGPR and 2 patients each CR and stringent CR as assessed by the investigator. Conclusions Our preliminary results suggest RAD to be a well tolerated and effective novel induction protocol in up-front treatment of MM. Notably, incidence of severe hematotoxicity observed so far is significantly lower than was in our previous study in relapsed/refractory pts. Incidence of VTE was acceptable while no neurotoxicity occurred. Updated results will be presented. Disclosures: Knop: Celgene Germany: Consultancy, Honoraria. Off Label Use: Lenalidomide in combination with doxorubicin in myeloma first-line therapy. Reichle:Celgene Germany: Research Funding. Einsele:Celgene Germany: Consultancy, Honoraria. Bargou:Celgene Germany: Consultancy, Research Funding.

Description: Introduction: In the past decade, substantial progress has been made in the understanding of multiple myeloma (MM) cell biology and its interaction with the bone marrow microenvironment (BMM). Binding of MM cells to BM stroma cells (BMSCs) alters the expression of SDF-1α and its receptor CXCR4, leading to the secretion of anti-apoptotic cytokines, promoting tumor growth, drug resistance and migration. MM cancer stem cells migrate to endosteal BM niches, where they escape therapies in a quiescent state causing relapse in the course of the disease. The development of novel agents that aim to target the MM and BMM interaction includes drugs as promising as 2nd and 3rdgeneration IMIDs or proteasome inhibitors. Despite these profound advances, the failure rate of preclinically proven cytotoxic single substances is sizeable, as preclinical models often lack the biological, genetic, etiological and immunological properties of the disease (Schüler, Expert. Opin. Biol. Ther. 2013; Kortüm. CLML 2014; Rongvaux. Annu Rev Immunol 2013). Methods & Results: We have previously demonstrated that BM interaction and homing to niches, mediated by the adhesion molecules CXCR4, CD49d and CD44, protect MM cell lines (MMCL) and primary plasma cells (PC) from the cytotoxic effect of anti-MM agents, such as bortezomib (Bor), vorinostat (Vor) and pomalidomide (Pom). Our in vitro and in vivo observed cytotoxic effects from Bor, Vor and Pom confirmed their potent cytotoxicity, whereas cocultivation with M2-10B4 substantially reduced apoptosis and induced tumor protective effects. Additional treatment with the CXCR4 inhibitor AMD3100 blocked CXCR4 in coculture, but left CD49d, CD44 and CD11a widely unchanged. Toxic or therapeutic effects from AMD3100 monotherapy were excluded for the doses used. Comparison of the CXCR4 antibody (ab)-clones 12G5, 44717 and 4G10 revealed that AMD3100 treatment of U266 cells reduced CXCR4 expression with use of 12G5 and 44717, whereas binding of both FITC- and PE-coupled 4G10 was not influenced, making the latter the most reliable for CXCR4 analysis. Use of image cytometry (IC) allowed accurate visualization of co-localisation of CXCR4 expression both on the cell surface and within the cytoplasm of MM cells. IC correlated with flow cytometry-determined CXCR4 expression and allowed the detailed assessment of treatment studies with and without anti-MM agents and AMD3100. Of note, AMD3100 resensitized MM cells to Bor, Vor and Pom (Waldschmidt. Blood 2012:2450), whereas carfilzomib (Cfz) reduced CXCR4 expression in MMCL and could not be antagonized by stroma coculture. Cfz sensitivity was not increased by adding AMD3100 (Simon. Blood 2013:3851). These preclinical studies need additional adaptation to the clinical setting in order to surpass prior drug failure rates, and there is a need to develop more broadly available and better predictive preclinical systems. Therefore, we are currently assessing a 3D co-culture MM model composed of agarose matrix interlayers, based on a novel liquid overlay technique. This model has been specifically adapted to MM cell and BM component interactions as described (Udi. BJH 2013; Zlei. Exp Hematol 2007; Schüler. EOBT 2013). MM cells are cultivated in conical microwells of a non-adherent agarose matrix after BMSCs were plated on the bottom of each plate, allowing the diffusion of soluble cytokines but no direct contact between BMSC and MMCL. Therein, we are presently testing novel anti-MM substances in comparison to our standard-coculture system. Conclusion: Targeting microenvironmental mediators, like SDF-1α and CXCR4, is a promising approach to expand the choice of antimyeloma agents and amplify the effects of established antimyeloma drugs, as previously shown by us and others for the combination of AMD3100 and Bor or Pom. However, as our knowledge on MM and its BMM has dramatically increased a great effort has been made in the preclinical testing of promising new anti-MM agents, and more complex high-throughput in vitro models are urgently needed to better predict the potency of these substances in order to reduce dropouts in clinical trials. We hereby provide a novel approach which better reflects the spatial growth of human MM samples in BMSC coculture, and more closely mimics the growth and proliferation of human MM clones in vivo. Disclosures No relevant conflicts of interest to declare.

Description: Deletion of the tumor suppressor gene TP53is significantly associated with an unfavorable clinical course of Multiple Myeloma (MM). In addition, point mutations that abrogate p53 function similarly shorten survival. Most recently 'double hit', bi-allelic TP53inactivated MM was identified as an ultimate high risk feature of MM, affecting 3.7% of newly diagnosed MM patients (NDMM, Walker et al., Leukemia 2018). For TP53genetic analysis we combined data from two targeted sequencing M3P cohorts with targeted sequencing and FISH data, one of NDMM (n=142, Kortüm et al. Blood Cancer J. 2016), and one of multirefractory patients (rMM, n=40; Kortüm et al. Blood 2016). We also included two independent cohorts with paired NDMM and rMM, one with mutational data (n=43; Corre J et al 2017) and one with paired FISH analysis (Merz M et al. Haematologica 2017). We confirmed an increase of mutations in TP53 (8% NDMM / 16.9% rrMM), as well as del17p (12.6% / 22%). Similarly, mono- (12.7% / 22.5%) and bi-allelic events (5.6% / 17.5%) both demonstrated a significant increase over time (Figure, top). Importantly we observed deletion after mutation and vice versa in our cohorts. Next we established an AMO-1 MM cell line model (TP53+/+) mimicking mono and bi-allelic TP53-inativation. After CRISPR/Cas9-mediated TP53destruction, we introduced a modified Sleeping Beauty (SB) vector with two separate expression cassettes (p53 wt / wt and mutant p53 (R282W or R175H). Functionality of the p53 system was confirmed using nutlin-3, as inhibitor of MDM2-p53 interaction, as described elsewhere. Results: Doxorubicin and Melphalan are commonly used compounds in the treatment of MM. The IC50 of Melphalan in AMO1 naïve cells was 5µM and 5.5 µM after the reintroduction of 2 copies of wt TP53 in the KO model, with cell viability at 10µM of 30% and 31% respectively, measured by AlamarBlue Assay. Strikingly, we observed significant resistance induction in our hemizygous systems (del/wt p53; cell viability at 10µM 60% and mut/wt (62%). This furthermore increased within our homozygous models (TP53 del/del (85%); TP53 mut/del 80%) (Figure, bottom). Similar results were observed under doxorubicin treatment. Remarkably, this effect was absent against proteasome inhibition. Conclusions Here we present first evidence of TP53 inactivation impacting drug response to Melphalan and Doxorubicin, which might lead to the clonal selection of MM subclones harboring increased risk. The fact, that response to proteasome inhibition was not affected in our model might, at least in part, might explain their ability to confine high risk in MM. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

Description: We have recently shown that Hsp90 is overexpressed in multiple myeloma (MM) and critically contributes to tumor cell survival. Pharmacologic blockade of Hsp90 has consistently been shown to induce MM cell death. However, most data have been obtained with MM cell lines whereas knowledge about the molecular effects of pharmacologic Hsp90 blockade in primary tumor cells is lacking. Furthermore, these investigations have so far exclusively relied on geldanamycin derivatives. Here, we analyzed the anti-tumor effects of a novel diarylisoxazole-based Hsp90 inhibitor (NVP-AUY922) in a large set of primary MM samples and in MM cell lines. The majority of cell lines (n = 8), as well as most primary samples (n = 20), displayed profound apoptotic responses and steep dose-effect curves with EC50 values in the range of 5–15 nM and EC90 values between 8 and 25 nM. This effect was not attenuated in coculture with cells from the bone marrow microenvironment. Some cell lines and about a quarter of primary MM samples displayed greater resilience to drug treatment, with EC50 values but not EC90 values reached at concentrations up to 50 nM. Sensitivity of MM cells to the Hsp90 inhibitor was not correlated with TP53 mutation or Hsp70 induction levels. Western analyses of MM cell lines and flow cytometric analyses of antibody-stained Hsp90 client proteins in primary tumor cells showed that NVP-AUY922-treatment entailed molecular effects and pharmacodynamic properties consistent with abrogation of Hsp90 function. Consequently, downregulation of multiple signaling and survival pathways was detectable through, for example, decreases in the phosphorylated (activated) forms of extracellular signal-regulated kinase (ERK) 1 and 2, signal transducer and activator of transcription (STAT) 3 and glycogen synthase kinase-3beta. All samples treated displayed strong upregulation of Hsp70. Importantly, peripheral blood mononuclear cells as well as primary bone marrow stromal cells were much less affected by high (50–100 nM) concentrations of NVP-AUY922, showing that a therapeutic window might be established for the treatment of multiple myeloma. Taken together, NVP-AUY922 could be a promising new drug for the treatment of a majority of myeloma patients.