Aftab, Blake T.

Abstract Hematological malignancies such as multiple myeloma (MM) have an increased reliance on the ubiquitin proteasome system (UPS) presumably as a consequence of their high protein synthetic and secretory burden. Chemical agents that target the proteasome, such as bortezomib and carfilzomib, have been successful in treating multiple myeloma; however patients treated with these drugs ultimately relapse. The AAA-ATPase p97/VCP (p97) facilitates ATP-dependent extraction and degradation of ubiquitinated proteins destined for proteasomal elimination. In addition to ubiquitin-dependent protein degradation, p97 is also closely involved in other aspects of protein homeostasis, including endoplasmic reticulum-associated degradation (ERAD) and autophagy. Pharmacologic inhibition of p97 provides a compelling therapeutic approach for hematological malignancies that rely on tight regulation of protein homeostasis as a component of their survival. CB-5083 is a novel small molecule inhibitor of p97 ATPase activity with nanomolar enzymatic and cellular potency. Treatment of cancer cells with CB-5083 causes a dramatic increase in poly-ubiquitinated proteins as well as an accumulation of substrates of the UPS and ERAD. CB-5083 causes a profound induction of the unfolded protein response (UPR) with consequent activation of the DR5 death receptor, caspase 8, caspase 3/7 and ultimately cell death. Induction of the UPR occurs to a greater magnitude with CB-5083 when compared to the proteasome inhibitor, bortezomib, suggesting the potential for increased efficacy in cancers with sensitivity to UPR-mediated cell death. In addition, activation of apoptosis and cell death occur more rapidly with CB-5083 than with bortezomib. Sequencing of cell lines made resistant to CB-5083 reveals missense mutations mapping to the D2 ATPase site in p97, supporting on-target association with cytotoxicity. In an expanded panel of MM cell lines there is no correlation between the cytotoxic sensitivity to CB-5083 and the cytotoxic sensitivity to proteasome inhibitors, suggesting differential mechanisms of cytotoxicity and potential activity of CB-5083 in proteasome inhibitor resistant settings. Compared to myeloma cell lines, CB-5083 has reduced cytotoxic potency in immortalized stromal cell lines and in patient-derived CD138-negative bone marrow mononuclear cells. Furthermore, unlike the reduced potency demonstrated by carfilzomib in the context of MM cell-bone marrow stromal cell (BMSC) interactions, the cyto-reductive potential of CB-5083 is unaffected in co-cultures of MM cells with patient-derived BMSCs or immortalized BMSCs from healthy donors. In vivo, CB-5083 is orally bioavailable, shows a pharmacodynamic effect in tumor tissue (as measured by poly-ubiquitin accumulation) and demonstrates robust anti-tumor activity across several MM models. CB-5083 treatment of mice bearing subcutaneous xenografts leads to tumor stasis and regression in RPMI8226 and AMO1 MM models, respectively. In advanced models of disseminated, ortho-metastatic disease, intermittent oral administration of CB-5083 demonstrates significant inhibition of myeloma burden and improves survival, with an overall efficacy profile that compares favorably to that of clinically approved proteasome inhibitors. Furthermore, in the Vk*Myc genetically engineered mouse model of MM, treatment with CB-5083 results in a significant reduction in M-spike by 55%. Combination treatment of mice bearing the RPMI8226 subcutaneous xenograft model with CB-5083, dexamethasone and lenalidomide results in tumor regression. Taken together, these data demonstrate that CB-5083 is a potent and selective inhibitor of the p97 ATPase with robust activity in vitro and in vivo in numerous MM models and strongly support clinical evaluation. Based on these observations, a phase 1 dose-escalation trial has recently been initiated and is currently underway in patients with relapsed/refractory multiple myeloma. Disclosures Anderson: Cleave Biosciences: Employment. Le Moigne:Cleave Biosciences: Employment. Djakovic:Cleave Biosciences: Employment. Rice:Cleave Biosciences: Employment. Wong:Cleave Biosciences: Employment. Kumar:Cleave Biosciences: Employment. Valle:Cleave Biosciences: Employment. Menon:Cleave Biosciences: Employment. Kiss von Soly:Cleave Biosciences: Employment. Wang:Cleave Biosciences: Employment. Yao:Cleave Biosciences: Employment. Soriano:Cleave Biosciences: Employment. Bergsagel:ONYX: Consultancy; Janssen: Consultancy; BMS: Consultancy; Novartis: Research Funding. Yakes:Cleave Biosciences: Employment. Zhou:Cleave Biosciences: Employment. Wustrow:Cleave Biosciences: Employment. Rolfe:Cleave Biosciences: Employment.

Abstract Inhibition of the AAA ATPase, p97, was recently shown to be a novel method for targeting the ubiquitin proteasome system, and CB-5083, a first-in-class inhibitor of p97, has demonstrated broad antitumor activity in a range of both hematologic and solid tumor models. Here, we show that CB-5083 has robust activity against multiple myeloma cell lines and a number of in vivo multiple myeloma models. Treatment with CB-5083 is associated with accumulation of ubiquitinated proteins, induction of the unfolded protein response, and apoptosis. CB-5083 decreases viability in multiple myeloma cell lines and patient-derived multiple myeloma cells, including those with background proteasome inhibitor (PI) resistance. CB-5083 has a unique mechanism of action that combines well with PIs, which is likely owing to the p97-dependent retro-translocation of the transcription factor, Nrf1, which transcribes proteasome subunit genes following exposure to a PI. In vivo studies using clinically relevant multiple myeloma models demonstrate that single-agent CB-5083 inhibits tumor growth and combines well with multiple myeloma standard-of-care agents. Our preclinical data demonstrate the efficacy of CB-5083 in several multiple myeloma disease models and provide the rationale for clinical evaluation as monotherapy and in combination in multiple myeloma. Mol Cancer Ther; 16(11); 2375–86. ©2017 AACR.

Abstract Background: Genome wide association studies (GWAS) have recently identified 8 loci identified with multiple myeloma (MM) susceptibility. We hypothesized that germ line genetic variants may also affect MM progression. We performed the first GWAS of MM survival, by conducting a meta-analysis of two existing studies at University of California San Francisco (UCSF) and the Mayo Clinic, and replicating findings in the International Multiple Myeloma rESEarch (IMMEnSE) consortium. Methods: The UCSF study included 353 MM patients genotyped on an Illumina Omni5 and Illumina 660 array. The Mayo clinic study included 239 MM patients genotyped on an Affymetrix 6.0 array. We imputed missing genotypes using the 1000 Genomes dataset and performed a GWAS for survival using proportional hazards models adjusting for age and gender and genetic ancestry using principal components analysis. We conducted a meta-analysis of the results from the two GWAS. We replicated the top SNPs in the IMMEnSE cohort which included 772 patients with survival data from 7 European countries and one North American site. We used the dataset from Grundberg et al (Nat Genetics 2012) to test for an association between SNPs associated with survival and gene expression in immortalized lymphocytes. We used gene expression data from Zhan et al (Blood 2006) to analyze the association between expression and survival. Results: In meta-analysis, we found a genome wide significant association between SNPs on a region at 16p13 and survival (rs72773978; p=2.9x10e-10). Patients with the minor allele were at increased risk for mortality (HR 2.73; 95% CI: 1.99 - 3.73). The top associated SNPs were all in strong linkage disequilibrium and were centered over the gene FOPNL. We replicated the association in the IMMEnSE cohort and found a significant association between the top SNP from the discovery dataset (rs72773978 p=0.037). We used previously published data to determine the association between gene expression and the top associated SNPs from the GWAS. The top SNP (rs72773978) was not in previously published eQTL databases, so we used rs7201759 which was also associated with survival in our data (p=3.8x10e-10) as a proxy. The minor allele for this SNP was associated with increased levels of expression of FOPNL (p=9x10e-5), but not with expression of any other genes within a 1 megabase region. Finally, we also observed an association between increased expression of FOPNL and shorter survival (HR: 2.62 per standard deviation.; 95% CI: 1.08 - 6.32). Conclusion: Germ line variants at 16p13 near the FOPNL gene are associated with survival among MM patients. FOPNL is thought to be involved in centrosomal function, and centrosomal activity has previously been associated with survival in MM patients. Our results support this previous observation. Furthermore, they suggest that germ line variants could also be useful in assessing prognosis for patients with MM. Citation Format: Elad Ziv, Eric Dean, Donglei Hu, Alessandro Martino, Daniel Serie, Daniele Campa, Blake Aftab, Paige Bracci, Gabriele Buda, Jennifer Caswell, Charles Dumontet, Marek Dudziński, Laura Fejerman, Alexandra Greenberg, Scott Hunstman, Artur Jurczyszyn, Krzysztof Jamroziak, Shaji Kumar, Herlander Marques, Thomas Martin, Joaquin Martinez-Lopez, Vincent Rajkumar, Juan Sainz, Annette Juul Vangsted, Marzena Watek, Jeffrey Wolf, Susan Slager, Federico Canzian, Celine Vachon. Genome wide association study identifies variants at 16p13 associated with survival in multiple myeloma patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5078. doi:10.1158/1538-7445.AM2014-5078