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Metastatic prostate cancer/PCa is the second leading cause of cancer deaths in US men. Most early-stage PCa are dependent on overexpression of the androgen receptor (AR) and, therefore, androgen deprivation therapies/ADT-sensitive. However, eventual resistance to standard medical castration (AR-inhibitors) and secondary chemotherapies (taxanes) is nearly universal. Further, the presence of cancer stem-like cells (EMT/epithelial-to-mesenchymal transdifferentiation) and neuroendocrine PCa (NEPC) subtypes significantly contribute to aggressive/lethal/advanced variants of PCa (AVPC). In this study, we introduced a pharmacogenomics data-driven optimization-regularization-based computational prediction algorithm (“secDrugs”) to predict novel drugs against lethal PCa. Integrating secDrug with single-cell RNA-sequencing/scRNAseq as a ‘Double-Hit’ drug screening tool, we demonstrated that single-cells representing drug-resistant and stem-cell-like cells showed high expression of the NAMPT pathway genes, indicating potential efficacy of the secDrug FK866 which targets NAMPT. Next, using several cell-based assays, we showed substantial impact of FK866 on clinically advanced PCa as a single agent and in combination with taxanes or AR-inhibitors. Bulk-RNAseq and scRNAseq revealed that, in addition to NAMPT inhibition, FK866 regulates tumor metastasis, cell migration, invasion, DNA repair machinery, redox homeostasis, autophagy, as well as cancer stemness–related genes, HES1 and CD44. Further, we combined a microfluidic chip-based cell migration assay with a traditional cell migration/‘scratch’ assay and demonstrated that FK866 reduces cancer cell invasion and motility, indicating abrogation of metastasis. Finally, using PCa patient datasets, we showed that FK866 is potentially capable of reversing the expression of several genes associated with biochemical recurrence, including IFITM3 and LTB4R. Thus, using FK866 as a proof-of-concept candidate for drug repurposing, we introduced a novel, universally applicable preclinical drug development pipeline to circumvent subclonal aggressiveness, drug resistance, and stemness in lethal PCa.

Metastatic prostate cancer is the second leading cause of cancer deaths in US men. Resistance to standard medical castration and secondary taxane-based chemotherapy is nearly universal. Further, presence of cancer stem-like cells (EMT/epithelial to mesenchymal transdifferentiation) and neuroendocrine PCa (NEPC) subtypes significantly contribute to aggressive/advanced/lethal variants of PCa (AVPC).In this study, first we used single-cell RNA sequencing (scRNAseq) analysis to demonstrate that ARlow PCa cells in metastatic prostate cancer, including castration-sensitive tumors, harbored signatures of EMT, and ‘cancer stemness’. Next, we introduced a novel pharmacogenomics data-driven computational approach and identified several potential agents that can be re-purposed as novel secondary drugs (“secDrugs”) to treat advance variants of Prostate cancer. Using scRNAseq as a biomarker-based drug screen, we demonstrated that a majority of the single-cell subclones in mCRPC and mCSPC cell lines also showed significantly high expression of the NAMPT pathway genes, indicating that the secDrug FK866, which targets NAMPT, is potentially effective against drug-resistant and stem-cell-like subpopulation cluster. Next, we showed significant in vitro cytotoxicity of FK866 as single-agent and in combination with the taxanes or Enzalutamide against models of clinically-advanced PCa. We performed bulk- and single-cell RNAseq to identify several pathways underlining FK866 mechanism of action and found that in addition to NAMPT inhibition, FK866 regulates tumor metastasis, cell migration, invasion, DNA repair machinery, redox homeostasis, autophagy, as well as cancer stemness–related genes HES1 and CD44. Further, we performed a microfluidic chip-based cell migration assay that demonstrated that FK866 reduces cancer cell invasion and motility, indicating abrogation of metastasis. Finally, using multiple PCa patient datasets, we showed that FK866 is potentially capable of reversing expression of several genes associated with biochemical recurrence and inter-ethnic differences, including IFITM3 and LTB4R.Thus, using FK866 as a proof-of-concept drug, we introduced a novel, universally applicable preclinical drug development pipeline to circumvent subclonal aggressiveness, drug resistance, and stemness in lethal PCa.

Multiple myeloma (MM) is an incurable plasma cell malignancy with dose-limiting toxicities and inter-individual variation in response/resistance to the standard-of-care/primary drugs, proteasome inhibitors (PIs), and immunomodulatory derivatives (IMiDs). Although newer therapeutic options are potentially highly efficacious, their costs outweigh the effectiveness. Previously, we have established that clofazimine (CLF) activates peroxisome proliferator-activated receptor-γ, synergizes with primary therapies, and targets cancer stem-like cells (CSCs) in drug-resistant chronic myeloid leukemia (CML) patients. In this study, we used a panel of human myeloma cell lines as in vitro model systems representing drug-sensitive, innate/refractory, and clonally-derived acquired/relapsed PI- and cereblon (CRBN)-negative IMiD-resistant myeloma and bone marrow-derived CD138+ primary myeloma cells obtained from patients as ex vivo models to demonstrate that CLF shows significant cytotoxicity against drug-resistant myeloma as single-agent and in combination with PIs and IMiDs. Next, using genome-wide transcriptome analysis (RNA-sequencing), single-cell proteomics (CyTOF; Cytometry by time-of-flight), and ingenuity pathway analysis (IPA), we identified novel pathways associated with CLF efficacy, including induction of ER stress, autophagy, mitochondrial dysfunction, oxidative phosphorylation, enhancement of downstream cascade of p65-NFkB-IRF4-Myc downregulation, and ROS-dependent apoptotic cell death in myeloma. Further, we also showed that CLF is effective in killing rare refractory subclones like side populations that have been referred to as myeloma stem-like cells. Since CLF is an FDA-approved drug and also on WHO’s list of safe and effective essential medicines, it has strong potential to be rapidly re-purposed as a safe and cost-effective anti-myeloma drug.

Mantle cell lymphoma (MCL) is an aggressive lymphoid neoplasm that develops from malignant B-lymphocytes in the outer edge or mantle zone of a lymph node. This is a sub-type of B-cell non-Hodgkin lymphoma characterized by rapid clinical progression and poor response rate to conventional chemotherapeutic drugs with recurrent relapse resulting in a short estimated 5-year overall survival (OS) of 2-5 years depending on the clinical risk. Combination therapies such as R-CHOP, R-DHAP, Hyper-CVAD, VcR-CAP constitute the front-line chemotherapeutic treatment landscape for MCL. Despite good initial response to the combination regimens, all patients develop resistance over time. The Bruton's tyrosine kinase inhibitor (BTKi) Ibrutinib and the proteasome inhibitor (PI) Bortezomib are FDA-approved therapies for refractory or relapsed (R/R) MCL with demonstrated high initial response rate in clinical trials. However, highly variable treatment response along with dose-limiting toxicities has limited the efficacy in real-world settings with the median progression-free survival (PFS) of Thus, the identification of novel drugs that function either alone or as combination to curb the oncogenic progression as well as to reduce drug-associated toxicities is of high clinical significance. We have designed a novel optimization-regularization-based computational prediction algorithm called "secDrug" that uses large-scale pharmacogenomics databases like the GDSC1000 to identify novel secondary drugs for the management of treatment-resistant B-cell malignancies. We hypothesize that combination of our predicted secDrugs with BTKi/ PI will be useful in curbing oncogenic progressions of R/R MCL and abrogate drug resistance through simultaneous inhibition of multiple oncogenic factors/pathways. When applied to BTKi/PI-resistant R/R MCL, the top predicted secondary drugs (secDrugs) were YM155 (Survivin inhibitor) and S63845 (selective MCL-1 inhibitor). Interestingly, both Survivin and MCL-1 are reported to be over-expressed in MCL, and their expression is strongly correlated with the oncogenic progression and survivability of the patients. To validate our in-silico predictions, we performed in vitro cytotoxicity assays with the top predicted secDrugs (YM155 and S63845) as single agents (IC50 for YM155 4.87±0.66 nM, for S63845 0.9±1.1 uM) as well as in combination with BTKi/PI against a panel of MCL cell lines representing PI/BTKi sensitive, innate resistant (representing refractory MCL) and clonally-derived acquired resistant (representing relapsed MCL). Our results showed that the YM155 and S63845 exhibited significant synergistic cell killing activities (Combination index/ CI value of 0.31±0.49 as calculated using Chou-Talalay's CI theorem, C.I>1 depicts synergism) alone and in combination with Bortezomib (PI) and Ibrutinib (BTKi), especially in R/R MCL cell lines. Further, our results also showed that both YM155 and S63845 in combination with BTKi/PI were able to significantly lower the effective dose of both BTKi/PI required to achieve desired therapeutic response by >12 times (Dose Reduction Index or DRI for YM155 in combination is 15.87±4.93; DRI for S63845 in combination is 12.34±2.67), thereby making the cell lines relatively more BTKi/PI sensitive. Next, we performed next-generation RNA sequencing analysis to identify mechanisms of secDrug action and synergy. Our Gene expression profiling and Ingenuity pathway analysis of the RNAseq data among YM155-treated MCL cell lines revealed eIF4-p70S6K signaling and mTOR signaling as the top canonical pathways. Our study thus identified YM155 and S63845 as potential novel candidates for repurposing as secondary drugs in combination with BTKi/PI for the treatment of R/R MCL. Currently, we are exploring the probable subclonal molecular mechanisms governing the synergistic drug action by using single-cell transcriptomics analysis. As both YM155 and S63845 have reported activity against cancer stem-ness, we will further investigate the effect of our novel drugs on the cancer stem-like cells in MCL, which have a potential role in treatment resistance. The secDrug algorithm promises to serve as a universal prototype for the discovery of novel drug combination regimens for treatment outcomes in any cancer type by enhancing sensitivity or overcoming resistance to standard of care drugs. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Multiple myeloma (MM) is the second-most common hematological malignancy in the US. MM is an incurable, age-dependent plasma cell neoplasm with a 5-year survival rate of less than 50%. Extensive inter-individual variation in response to standard-of-care drugs like proteasome inhibitors (PIs) and immunomodulatory drugs (IMiDs), drug resistance, and dose-limiting toxicities are critical problems for the treatment of MM. Clinical success in anti-myeloma treatment, therefore, warrants continuous development of novel combination therapy strategies with the explicit goal to improve the therapeutic efficacy by concomitantly targeting multiple signaling pathways. Previously, we have reported the development of an in-house computational pipeline called secDrug that applies greedy algorithm-based set-covering computational optimization method followed by a regularization technique to predict secondary drugs that can be repurposed as novel synergistic partners of standard-of-care drugs for the management of refractory/ resistant MM. Top among these secondary drugs (secDrugs) were the HSP90 inhibitor 17-AAG. In this study, we used 17-AAG as a proof of principle to establish a pipeline that integrates our in silico predictions with in vitro and ex vivo validation as well as multi-omics technologies to identify, validate, and characterize therapeutic agents that could be used either alone or in combination with standard-of-care drugs for the treatment of R/R MM patients (Figure 1). To screen and validate our in silico prediction results, we performed in vitro cytotoxicity assays using 17-AAG on a panel of human myeloma cell lines (HMCLs; in vitro model systems) that captures a wide range of biological and genetic heterogeneity representing the complexities encountered in clinical settings. These cell lines include HMCLs representing innate sensitive/resistance, >10 pairs of parental and clonally-derived PI- and IMiD-resistant pairs (P vs VR or LenR; representing acquired/emerging resistance/relapse), NRAS mutants which leads to the constitutive activation of oncogenic Ras signaling, and CRISPR-edited HSP90 knockdown cell line. Our results showed that 17-AAG has high synergistic activity in combination with PI in inducing apoptosis even in innate and acquired PI-resistant HMCLs and significantly reduces the effective dose of PI required to achieve IC 50 (Chou-Talalay's Dose Reduction Index or DRI 7±1.4). Moreover, 17-AAG+IMiD showed synergistic cell killing activity in clonally-derived IMiD resistant HMCL. Further, 17-AAG induced cell death was comparable with Hsp90 knockdown as evident from the cytotoxicity assay using PI and 17-AAG in combination in RPMI8226-wild type and RPMI-HSP90AA1 knocked down cell line. Notably, 17-AAG was strikingly effective against the NRAS-mutant cell line indicating an additional niche (NRas mutant myeloma) where 17-AAG could be most effective. Next, we performed RNA sequencing to elucidate the molecular mechanisms behind 17-AAG drug action, drug synergy, 17-AAG-induced cell death. Our gene expression profiling (GEP) followed by Ingenuity Pathway Analysis (IPA) analysis revealed protein ubiquitination, aryl hydrocarbon receptor signalling pathway as the top canonical pathways. 17-AAG induced apoptosis via mitochondrial mediated pathway in myeloma. 17-AAG exerts its cytotoxic effect by activating intrinsic pathway of apoptosis which we further confirmed through the increase in reactive oxygen species generation and decrease in mitochondrial membrane potential. 17-AAG was also effective in reducing the expression of hallmarks of MM such as p65/NF-kB, IRF4, c-Myc. Finally, we performed mass cytometry (CyTOF; Cytometry by time of flight) on primary bone-marrow cells (PMCs) from myeloma patients for further validation of proteomic signatures at the single-cell level. CyTOF analysis confirmed 17-AAG-induced cell death and key changes in MM-specific proteomic markers. 17-AAG treated PMCs showed elevated cleaved caspase levels and down-regulation of IRF4 and phospho-STAT3. GEP and CyTOF results were confirmed using immunoblotting assays. Together, our study demonstrates a unique pipeline for drug repositioning that has the potential to revolutionize clinical decision-making by minimizing the number of drugs required for discovering successful combination chemotherapy regimens against drug-resistant myeloma. Figure 1 Figure 1. Disclosures Kumar: BMS: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Tenebio: Research Funding; Beigene: Consultancy; Oncopeptides: Consultancy; Antengene: Consultancy, Honoraria; Carsgen: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Roche-Genentech: Consultancy, Research Funding; Bluebird Bio: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding.

Mantle Cell Lymphoma (MCL) is a difficult to cure, highly heterogeneous, and aggressive form of non-Hodgkin lymphoma comprising roughly 7% of all cases with a high recurrence rate and poor long-term prognosis. The reported progression-free survival is about 1-2 years, and median overall survival/OS Previously, we have demonstrated that Clofazimine (CLF), an anti-leprosy drug, could potentially be repurposed for the treatment of chronic myeloid leukemia and PI/IMiD resistant multiple myeloma that also targets subclones representing putative stem-like-cells (CSCs). Notably, using single-cell analysis and high dimensional immunophenotyping or CyTOF (Cytometry Time of Flight), we have also identified molecular networks underpinning CLF+PI synergy. We hypothesize that CLF has strong potential to be repurposed as a novel anti-MCL drug, particularly in a relapsed/refractory setting. For this purpose, we used MCL cell lines representing drug-sensitive (JEKO1, MINO), innate PI/BTKi-resistance (Z138; representing refractory patients), and clonally-derived acquired PI/BTKi-resistance (MINO-R; representing relapse patients) as in vitro model systems and showed i) the efficacy of CLF as a single agent (IC 50= 6.9±3.6 uM) and ii) in combination with PIs (Bz) and BTKis (Ibrutinib, Acalabrutinib) against innate and acquired resistant MCL (Fig.1), as well as iii) the unique targeting of putative CSCs by CLF. Remarkably, CLF+BTKi/PI combination lowered the effective BTKi and PI doses required to achieve desired therapeutic response by >10-folds (estimated dose reduction index for BTKi and PI were 12.43 and 10.99, respectively). Further, mRNA-sequencing followed by differential gene expression analysis using DESeq2 and EdgeR revealed that the top significantly upregulated genes following PI+CLF treatment were GSR, DAP3, and DOK1, which have reported anti-tumorigenic activity. The top significantly downregulated genes EHD1, CBX8, DDX17, SOX12, and COMMD3 have reported pro-survival function. Ingenuity pathway analysis revealed protein ubiquitination pathway and cell cycle arrest at the G2/M phase as the top canonical pathways. Causal network analysis showed synergistic drug action significantly elevated the levels of oxidative stress and unfolded protein response. Additionally, PI+CLF combination potentiated AMPK mediated down-regulation of the mTOR signaling pathway, which further led to direct reduction of Cyclin D1 (aberrantly expressed in MCL) and the downregulation of eIF4-p70S6K signaling. The synergistic drug activity also led to the downregulation of oncogenic pathways like p38 MAPK and NF-kB signaling. Recent studies have indicated that intra-tumor heterogeneity due to the presence of stem-like cells in MCL (MCL-CSCs), including CD45+CD19- MCL-initiating cells (MCL-ICs), relatively quiescent-highly clonogenic aldehyde dehydrogenase (ALDH)+ cells and side populations (SP) may drive drug resistance and disease relapse. Notably, we found that several of the differentially regulated genes are critical for the maintenance and functioning of CSCs. For example, PI+CLF combination downregulates Wnt/β catenin signaling, which is found to be frequently overexpressed in MCL-ICs. HIPPO, another signaling pathway involved in the maintenance of cancer stem-ness and emergence of drug resistance, was also down-regulated. Currently, we are validating the specific targeting of putative MCL-CSCs by CLF. Next, we plan to replicate our findings using PDX models of MCL. CLF is an FDA-approved drug as well as on WHO's List of Essential Medicines. Thus, our study introduces CLF as a novel, safe, and inexpensive therapeutic option for the management of R/R MCL. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

// Arijit Bhowmik 1 , Sayak Chakravarti 1, * , Aparajita Ghosh 2, * , Rajni Shaw 1, * , Suman Bhandary 2 , Satyaranjan Bhattacharyya 3 , Parimal C. Sen 2 and Mrinal K. Ghosh 1 1 Signal Transduction in Cancer and Stem Cells Laboratory, Translational Research Unit of Excellence (TRUE), Division of Cancer Biology and Inflammatory Disorder, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), Kolkata 700091, India 2 Division of Molecular Medicine, Bose Institute, Centenary Campus, Kolkata 700054, India 3 Division of Surface Physics, Saha Institute of Nuclear Physics, Kolkata 700064, India * These authors have contributed equally to this work Correspondence to: Mrinal K. Ghosh, email: mrinal.res@gmail.com Keywords: glioma, blood brain barrier, 3,3’-diindolylmethane encapsulated nanoparticle, somatostatin receptor 2 peptide, epidermal growth factor receptor Received: November 22, 2016 Accepted: May 22, 2017 Published: June 27, 2017 ABSTRACT Current therapy for Glioblastoma is insufficient because of the presence of blood brain barrier. It limits the transport of essential drugs to the tumor sites. To overcome this limitation we strategized the delivery of an anticancer compound 3,3’-diindolylmethane by encapsulation in poly (lactic-co-glycolic acid) nanoparticles. These nanoparticles were tagged with a novel peptide against somatostatin receptor 2 (SSTR2), a potential target in glioma. The nanoformulation (27-87nm) had loading and encapsulation efficiency of 7.2% and 70% respectively. It was successfully internalized inside the glioma cells resulting in apoptosis. Furthermore, an in vivo bio-distribution study revealed the selective accumulation of the nanoformulation into rat brain tumor sites by crossing the blood brain barrier. This resulted in abrogation of epidermal growth factor receptor pathway activation in glioma cells. Our novel nanopreparation therefore shows great promise to serve as a template for targeted delivery of other therapeutics in treating GBM.

Metastatic castration resistant prostate cancer (mCRPC) is the most advanced and lethal stage of prostate cancer. A subset of advanced CRPC patients eventually develop an aggressive variant of prostate cancer (AVPCa), a rapidly progressive disease state with lack of AR expression (AR-ve mCRPC) and limited or no therapeutic options. To address this outstanding issue, we have previously reported using a novel computational algorithm (‘secDrug') and in vitro chemosensitivity and phenotypic assays to identify TAK715-a p38MAPK inhibitor as a synergistic partner for Taxanes/TX in treating AVPCa. Notably, in CRPC, MAPK pathway is involved in sustaining AR-independent cell proliferation. In this study, we investigated the genes, networks and molecular pathways underlining TX+TAK715 drug synergy in AVPCa. Gene expression profiling (mRNA sequencing) followed by Ingenuity pathway analysis (IPA) revealed upregulation of mitochondrial dysfunction and oxidative phosphorylation (OXPHOS) as the top dysregulated pathways following single-agent and combination treatment, which were confirmed by immunoblotting. In vitro ROS generation assay and Mitochondrial membrane potential measurement following combination treatment confirmed elevated intra-cellular ROS level (≈7 folds; indicating oxidative stress) and membrane depolarization (indicating mitochondrial dysfunction), respectively, in mCRPC lines. Furthermore, our IPA causal network analysis predicted significant upregulation of microRNA-132 and downregulation of miR-21 in response to combination treatment. Using in silico analysis on multiple GEO PCa datasets, we found low expression level of miR-132 was associated with poor clinical prognosis, transition from androgen dependent (AD) to independent (AI) stage and metastasis. miRNA 21 was significantly up regulated in the GEO PCa datasets. miRNA 21 is an AR-regulated miRNA that plays key role in nullifying the effect of castration, drive progression to AI stage, TX resistance and cellular invasiveness through down-regulation of tumor suppressor PTEN. Finally, using single-cell transcriptomic analysis we showed that cell subpopulations expressing the PCa stemness marker CD44, or drug resistant markers (CXCL8, CDK1), or epithelial-to-mesenchymal transition markers (Vimentin, TGFB1) were also very high expressors of TAK715 target genes (CSNK1D, MAPK14, MAP4K4) indicating TAK715 is potentially effective against treatment-refractory and stem-cell like subclones.Together, we conclude that TAK715+Taxane combination may be useful in curbing oncogenic progressions in AVPCa through simultaneous inhibition of multiple oncogenic factors/pathways. Currently, we are performing functional analysis of microRNA signatures of drug synergy as well as in vivo validation of the drug combinations using mouse xenograft models. Citation Format: Sayak Chakravarti, Suman Mazumder, Farnaz Hemmati, Farshad Amiri, Taraswi Mitra Ghosh, Ujjal Kumar Mukherjee, Panagiotis Mistriotis, Timothy Moore, Robert Arnold, Clayton Yates, Amit Kumar Mitra. Deciphering the functional basis of synergy between taxanes and TAK715: A novel repurposed drug candidate in treatment-refractory aggressive prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1354.

Drug resistance is a major cause of concern in cancer chemotherapy that not only reduces efficacy but also causes toxicity through overdosing. For example, Ixazomib, an oral proteasome inhibitor, has proven to remarkably improve myeloma patient outcomes but is associated with dose limiting toxicities and drug resistance. Therefore, new combination treatment regimens are urgently needed for the treatment of cancers, including multiple myeloma, which can lower the required dose of standard-of-care drug without compromising on treatment efficacy. We will present an optimization-regularization based computational prediction method called secDrug that uses large-scale pharmacogenomics databases to identify novel secondary drug combinations to reverse drug resistance. In this study, we applied secDrug to Ixazomib-resistant cell lines (>100) in the Genomics of Drug Sensitivity in Cancer (GDSC) database and predicted that the following FDA-approved drug classes can be best combined with Ixazomib to overcome resistance in MM: nicotinamide phospho ribosyl transferase or Nampt inhibitor (FK866), HDAC inhibitors (Panobinostat, SAHA), neddylation inhibitor (MLN4924), Raf inhibitor (PLX-4720) and HSP90 inhibitor (17-AAG). Our results corroborate with earlier studies that have indicated these drugs could potentially be used in MM, alone or in combination. To validate our prediction results, we treated our panel of >50 human multiple myeloma cell lines (Ix-sensitive and Ix-resistant HMCLs) with the top predicted drug combination - FK866 + Ixazomib. The results, based on combination index theorem, show that this combination works highly synergistically where the IC50 of ixazomib in MM cells was significantly reduced in presence of FK866. Similar results were obtained for the other top predicted combination regimens. Our findings provide a strong case for using secDrug for predicting secondary drugs in cancers resistant to the standard-of-care therapy. Furthermore, this provides additional evidence in support of combining FK866 with ixazomib to enhance sensitivity or overcome resistance to ixazomib and thereby improve patient outcome. Our future aim is to investigate the mechanism behind the synergism between proteasome inhibitors and the top drugs identified by our algorithm as candidates for secondary combination therapies using next-gen transcriptomics and single-cell approaches. Citation Format: Harish Kumar, Ujjal Kumar Mukherjee, Sayak Chakravarti, Li Chen, Brian Van ness, Amit Kumar Mitra. A novel computational combination-therapy prediction algorithm (secDrug) identifies the Nampt inhibitor FK866 reverses PI-resistant multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-266.