Kinesin Spindle Protein Inhibitor Research Articles

Development of Half-Sandwich Ru, Os, Rh, and Ir Complexes Bearing the Pyridine-2-ylmethanimine Bidentate Ligand Derived from 7-Chloroquinazolin-4(3H)-one with Enhanced Antiproliferative Activity.

Kinesin spindle protein (KSP) inhibitors are one of the most promising anticancer agents developed in recent years. Herein, we report the synthesis of ispinesib-core pyridine derivative conjugates, which are potent KSP inhibitors, with half-sandwich complexes of ruthenium, osmium, rhodium, and iridium. Conjugation of 7-chloroquinazolin-4(3H)-one with the pyridine-2-ylmethylimine group and the organometallic moiety resulted in up to a 36-fold increased cytotoxicity with IC50 values in the micromolar and nanomolar range also toward drug-resistant cells. All studied conjugates increased the percentage of cells in the G2/M phase, simultaneously decreasing the number of cells in the G1/G0 phase, suggesting mitotic arrest. Additionally, ruthenium derivatives were able to generate reactive oxygen species (ROS); however, no significant influence of the organometallic moiety on KSP inhibition was observed, which suggests that conjugation of a KSP inhibitor with the organometallic moiety modulates its mechanism of action.

Identifying and characterising promising small molecule inhibitors of kinesin spindle protein using ligand-based virtual screening, molecular docking, molecular dynamics and MM‑GBSA calculations

The kinesin spindle protein (Eg5) is a mitotic protein that plays an essential role in the formation of the bipolar spindles during the mitotic phase. Eg5 protein controls the segregation of the chromosomes in mitosis which renders it a vital target for cancer treatment. In this study our approach to identifying novel scaffold for Eg5 inhibitors is based on targeting the novel allosteric pocket (α4/α6/L11). Extensive computational techniques were applied using ligand-based virtual screening and molecular docking by two approaches, MOE and AutoDock, to screen a library of commercial compounds. We identified compound 8-(3-(1H-imidazol-1-ylpropylamino)-3-methyl-7-((naphthalen-3-yl)methyl)-1H-purine-2, 6 (3H,7H)-dione (compound 5) as a novel scaffold for Eg5 inhibitors. This compound inhibited cancer cell Eg5 ATPase at 2.37 ± 0.15 µM. The molecular dynamics simulations revealed that the identified compound formed stable interactions in the allosteric pocket (α4/α6/L11) of the receptor, indicating its potential as a novel Eg5 inhibitor.Graphical

Abstract 3197: Addressing drug metabolism and pharmacokinetics (DMPK) challenges of small molecule-drug conjugates (SMDCs)

Abstract Background: SMDCs are gaining momentum with potential advantages over antibody-drug conjugates (ADCs), eg, better tumor penetration and lack of immunogenicity. We have developed a novel platform technology with tailored solutions for ADCs and SMDCs with intracellular and extracellular cleavage options. Key features of the SMDC technology comprise of a small molecule ligand such as an αvβ3 integrin binder showing efficient tumor homing and a linker extracellularly cleaved by neutrophil elastase (NE) in the tumor microenvironment allowing for seamless release of different payload classes.1 Our lead SMDC VIP2362 is currently in a Phase 1 clinical trial for the treatment of advanced solid tumors (NCT05712889). SMDCs often have a shorter half-life compared with ADCs, which may result in more frequent dosing schedules. Here we show significant reduction of clearance and drastic prolongation of half-life of SMDCs achieved by adding a second binding moiety. Methods: Payloads such as kinesin spindle protein inhibitors (KSPi), cyclin-dependent kinase 9 inhibitors (CDK9i), and monomethyl auristatin E (MMAE) have been linked via elastase-cleavable linkers to one or, via a branched linker, to two αvβ3 integrin binding moieties. Cytotoxicity of SMDCs was measured in cell lines with or without NE. Monovalent and bivalent SMDCs were investigated in DMPK studies in rats while monitoring the conjugate and the released payload. Results: Payloads were coupled to the NE-cleavable peptides via different linkages. MMAE was conjugated via sterically hindered ester bonds, CDK9i was conjugated via sulfoximide bonds, and KSPi payloads were coupled via amide bonds. Each of these SMDCs was highly stable in plasma and buffer. Without NE, in vitro cytotoxicity of SMDCs in each cell line was poor with IC50 in the micromolar range. In contrast, in the presence of NE, potency increased, and cytotoxicity (IC50) was in the low nanomolar to picomolar range depending on the cell line and payload. In each case, the SMDCs reached similar potency as the free payload indicating efficient cleavage of the SMDC by NE. In DMPK studies of SMDCs in rat, none or trace levels of free payload (<0.1% as compared to the respective conjugates) was measured. With each of the SMDCs and independent of the conjugated payloads, a remarkable impact on exposure was observed when attaching a second binding ligand. The SMDCs with two ligands showed a 37- to 81-fold reduced plasma clearance as compared with the respective monovalent SMDCs, which parallels a 12- to 57-fold increase in half-life (eg, 2.1 h and 28 h for mono and bivalent MMAE SMDCs respectively). Initial in vivo studies in a cell line-derived xenograft model showed efficacy of bivalent SMDCs with once weekly dosing. Conclusion: Our technology platform comprises NE-cleavable SMDCs with promising options to tune the DMPK profile for a longer half-life. 1. Lerchen et al, AACR (2023). 2. Lerchen et al, Cancers (2023). Citation Format: Anne-Sophie Rebstock, Hans-Georg Lerchen, Harvey Wong, Beatrix Stelte-Ludwig, Mareike Wiedmann, Amy J. Johnson, Raquel Izumi, Ahmed Hamdy. Addressing drug metabolism and pharmacokinetics (DMPK) challenges of small molecule-drug conjugates (SMDCs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3197.

Abstract 629: Activity of VIP943 on AML patient-derived leukemic blasts and healthy donor-derived bone marrow hematopoietic stem cells

Abstract Introduction: In patients with acute myeloid leukemia (AML), CD123 has been shown to have high expression on blast cells and leukemic stem cells (LSC) compared with normal hematopoietic stem cells (HSCs) and other more mature CD34+ subsets (Zhou J, World J Stem Cells 2014). LSCs are inherently resistant to standard of care chemotherapeutics and LSC persistence after chemotherapy is associated with disease relapse. VIP943 is an ADC consisting of an anti-CD123 antibody, a unique linker cleaved intracellularly by legumain which is required for release, and activation of a novel kinesin spindle protein inhibitor (KSPi) payload that accumulates inside the cell. Herein, we evaluated the potential of VIP943 to target LSC and progenitor cells. Methods: Cytotoxicity assay: Bone marrow aspirates (BMA) and peripheral blood from previously untreated patients with primary or transformed from myelodysplastic syndrome AML were used in this experiment. Cells were treated with VIP943 (66 nM or 330 nM). After the end of the 48 h or 72 h incubation, the CD123+ cells and the CD34+CD38- LSC were detected by flow cytometry. Characterization of progenitor cell population: Fresh BM samples from healthy volunteers (HVBM) were stained with specific monoclonal antibodies to identify progenitor cell populations. Depletion assay: The effect of VIP943 on HVBM was evaluated by measuring the depletion of CD34+ progenitor cell populations in comparison to the anti-CD33-ADC, gemtuzumab ozogamicin (gem-oz). At the end of the incubation time, red blood cells were lysed; the remaining cells were stained with a cocktail of antibodies to discriminate between progenitor cells and analyzed by flow cytometry. Results: Treatment of patient-derived CD123+ leukemic blasts with VIP943 resulted in a 50% reduction after 48 h and up to 80% at 72 h. A reduction of >70% of CD123+CD34+CD38- LSCs derived from BM aspirates of untreated patients with AML was achieved after incubation with VIP943 up to 72h. In addition, HVBM samples derived from five healthy volunteers were treated with VIP943 or gem-oz in a depletion assay, where gem-oz was toxic to CD34+ cells with an EC50 of 0.16 µM in contrast to VIP943 with an EC50 value of 8.83 µM. Conclusions: In this in vitro analysis of primary samples from patients with AML, activity of VIP943 is observed in AML patient-derived CD123+ blasts as well as chemoresistant LSCs. At anticipated pharmacologic levels, VIP943 shows no adverse effects on HSCs unlike gem-oz suggesting an improved therapeutic index. In the ongoing first-in-human dose-escalation study in subjects with advanced CD123+ hematologic malignancies, VIP943 demonstrates a promising safety profile (NCT06034275). Citation Format: Beatrix Stelte-Ludwig, Tibor Schomber, Melanie M. Frigault, Joseph Birkett, Amy J. Johnson, Anne-Sophie Rebstock, Sebastian Ludwig, Raquel Izumi, Ahmed Hamdy. Activity of VIP943 on AML patient-derived leukemic blasts and healthy donor-derived bone marrow hematopoietic stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 629.

Abstract 2051: Innovations in ADC technology platform with legumain-cleavable KSP-inhibitor payloads adaptable to various aspects of cancer biology

Abstract Despite recent advances in the antibody-drug conjugate (ADC) field it remains challenging to achieve a sufficient therapeutic window. To address key issues of current ADCs such as aggregate formation and payload-related toxicities, we have developed a platform technology with tailored solutions for ADCs and small molecule-drug conjugates (SMDCs). Key features of the ADC technology comprise of kinesin spindle protein inhibitors (KSPi) as a novel payload class, a unique linker selectively cleaved by the tumor-associated protease legumain, and a CellTrapper® modification of the KSPi payload to reduce membrane permeability and provide accumulation in tumor cells beneficial for efficacy and safety1,2. Our advanced ADC VIP943 is targeting CD123 for the treatment of AML and MDS and is currently in Phase 1 clinical trial (NCT06034275). Here we show the extension and applicability of the platform in combination with various antibodies. Two case studies demonstrate how the payload-linker optimization increases the selectivity for tumor over healthy cells and potentially overcomes transporter-mediated drug resistance. Tuning the cleavable linker of cetuximab-ADCs for a higher challenge of legumain-mediated payload release resulted in a 52-fold improved selectivity of cytotoxicity against tumor cells versus HaCaT skin cells. A trastuzumab-ADC using a KSPi payload modified with the CellTrapper, shows low nanomolar potency against JIMT-1 cells resistant to trastuzumab-deruxtecan and thus may overcome resistance. An increased potency was not observed with an ADC releasing a permeable KSPi without CellTrapper. To address heterogenous target expression in solid tumors, novel antibody-2-drug conjugates (A2DCs) were synthesized to combine the advantages of intracellular accumulation of non-permeable payloads with the release of a second, membrane permeable KSPi payload. In vitro studies comparing the A2DCs with their respective mono-drug ADCs on 4 different targets shows the highest cytotoxicity achieved with A2DCs independent of the efficacy driver in mono ADCs. Lastly, synthesis of homogenous KSPi ADCs with a drug to antibody ratio of ~8 is compatible with different antibodies without significant aggregate formation. Furthermore, an easy and efficient process for ring-opening of the thiosuccinimide ring after conjugation was developed and shown to successfully avoid ADC de-conjugation via retro-Michael reaction. Selected examples of each of these subclasses were coupled to trastuzumab; all conjugates were highly efficacious and resulted in tumor regressions in the SKOV-3 model similar to trastuzumab-deruxtecan. Conclusion: Our technology platform offers options for efficient and safe cancer treatments and allows for versatile adaptations to the various aspects of cancer biology. 1. Kirchhoff et al, Cancers (2020). 2. Lerchen et al, Bioconj Chem. (2020). Citation Format: Hans-Georg Lerchen, Anne-Sophie Rebstock, Mareike Wiedmann, Beatrix Stelte-Ludwig, Amy J. Johnson, Raquel Izumi, Ahmed Hamdy. Innovations in ADC technology platform with legumain-cleavable KSP-inhibitor payloads adaptable to various aspects of cancer biology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2051.

Abstract 647: FDA approved library screen revealed Ewing and clear cell sarcomas have increased sensitivity to filanesib over other cancer types

Abstract There is a compelling need for the development of more effective and less toxic therapies for patients with Ewing Sarcoma (ES) and Clear Cell Sarcoma (CCS). ES and CCS are characterized by chromosomal translocations which result in two distinct fusion proteins: EWS-ATF1 (t(12;22)(q13;q12)) in CCS and EWS-FLI1 (t(11;22)(q24;q12)) in ES. There is a strong premise that targeting the fusion proteins or their key downstream signaling pathways will be disease modifying and improve outcomes for patients. Preliminary high throughput screening studies using an FDA approved small molecule compound library identified filanesib, a kinesin spindle protein (KIF11) inhibitor, as having potent anti-proliferative activity in ES and CCS cells over other cancer subtypes. The mechanism linking the fusion proteins with KIF11 and the tumorigenic role of KIF11 in ES and CCS has yet to be described. Previous studies have shown that the EWS-ATF1 fusion protein forms a heterodimer with transcription factors to target the promoters of its downstream genes. In breast cancer, the knockdown of KIF11 has been shown to significantly reduce the phosphorylation of these transcription factors. Additionally, KIF11 has been shown to directly interact with p300/CBP-associated factor (PCAF), a histone acetyltransferase (HAT). HATs are necessary for EWS-FLI1-induced chromatin remodeling. We hypothesize that the fusion proteins, EWS-FLI1 and EWS-ATF1, form a complex with KIF11 that regulates the activity of co-transcription factors during chromatin remodeling. The target of filanesib, KIF11, has essential roles in maintaining cell cycle progression through mitosis and its inhibition results in mitotic arrest and subsequent cell death. We used ImageStream to assess the effects of filanesib on the cell cycle. ImageStream allows both a quantitative and qualitative analysis of the cell cycle by measuring the population of cells that are positive for a given marker as well as imaging each cell by microscopy. Results demonstrate that filanesib promotes an increase in cells arrested in prophase with dramatically altered spindle formation. We are currently addressing the role of KIF11 in regulating the expression levels of the fusion proteins’ associated transcriptional coactivators and downstream target genes. By completing these studies, we aim to, i) outline the mechanism underpinning the relationship between KIF11 and the oncogenic fusion proteins in ES and CCS cells, and ii) gain an understanding of why ES and CCS cells are particularly vulnerable to KIF11 inhibition. This work has been supported in part by the Flow Cytometry and the Molecular Genomics Cores at the H. Lee Moffitt Cancer Center & Research Institute, a comprehensive cancer center designated by the National Cancer Institute and funded in part by Moffitt’s Cancer Center Support Grant (P30-CA076292) Citation Format: Hannah L. Walker-Mimms, Nicole Londono, Yi Liao, Neelkamal Chaudhary, Dessiree Pena Gomez, Yonghong Zhang, Mingxiang Teng, Uwe Rix, Derek R. Duckett. FDA approved library screen revealed Ewing and clear cell sarcomas have increased sensitivity to filanesib over other cancer types [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 647.

Neutrophil elastase as a versatile cleavage enzyme for activation of αvβ3 integrin-targeted small molecule drug conjugates with different payload classes in the tumor microenvironment.

Introduction: The development of bioconjugates for the targeted delivery of anticancer agents is gaining momentum after recent success of antibody drug conjugates (ADCs) in the clinic. Smaller format conjugates may have several advantages including better tumor penetration; however, cellular uptake and trafficking may be substantially different from ADCs. To fully leverage the potential of small molecule drug conjugates (SMDCs) with potent binding molecules mediating tumor homing, novel linker chemistries susceptible for efficient extracellular activation and payload release in the tumor microenvironment (TME) need to be explored. Methods: We designed a novel class of SMDCs, which target αvβ3 integrins for tumor homing and are cleaved by neutrophil elastase (NE), a serine protease active in the TME. A peptidomimetic αvβ3 ligand was attached via optimized linkers composed of substrate peptide sequences of NE connected to different functional groups of various payload classes, such as camptothecins, monomethyl auristatin E, kinesin spindle protein inhibitors (KSPi) and cyclin-dependent kinase 9 inhibitors (CDK-9i). Results: NE-mediated cleavage was found compatible with the diverse linker attachments via hindered ester bonds, amide bonds and sulfoximide bonds. Efficient and traceless release of the respective payloads was demonstrated in biochemical assays. The newly designed SMDCs were highly stable in buffer as well as in rat and human plasma. Cytotoxicity of the SMDCs in cancer cell lines was clearly dependent on NE. IC50 values were in the nanomolar or sub-nanomolar range across several cancer cell lines reaching similar potencies as compared to the respective payloads only in the presence of NE. In vivo pharmacokinetics evaluating SMDC and free payload exposures in rat and particularly the robust efficacy with good tolerability in triple negative breast and small cell lung cancer murine models demonstrate the utility of this approach for selective delivery of payloads to the tumor. Discussion: These results highlight the broad scope of potential payloads and suitable conjugation chemistries paving the way for future SMDCs harnessing the safety features of targeted delivery approaches in combination with NE cleavage in the TME.

Comparison of the CXCR5-Antibody Drug Conjugate (ADC; VIP924) to a CD19-ADC and a CD79b-ADC in a Humanized Rec-1 Mantle Cell Lymphoma (MCL) Mouse Model

Introduction The chemokine receptor CXCR5 is highly expressed in MCL, which is a rare subtype of non-Hodgkin lymphoma. VIP924 is a first-in-class CXCR5-targeting ADC composed of a legumain-cleavable linker and a kinesin spindle protein inhibitor (KSPi) payload. We compared VIP924 with a CD19- and a CD79b- targeting ADC in a humanized mouse model of MCL. Methods Expression of CXCR5 and the B-cell targets CD19 and CD79b were analyzed on tumor samples from patients with MCL using immunohistochemistry. Slides were examined by a pathologist and scored for expression. NSG-SGM3 mice were transplanted with human hematopoietic stem cells from 4 different donors and after engraftment transplanted subcutaneously with REC-1 MCL cells into their flanks. When subcutaneous tumors reached a size of 100 mm 3, mice were randomized into 5 groups and treated with 10 mg/kg of an isotype control ADC, 3 mg/kg polatuzumab vedotin, 0.66 mg/kg loncastuximab teserine, 3 mg/kg VIP924, or 10 mg/kg VIP924 every 5 days for 4 doses. Immunophenotyping of peripheral blood was performed by flow cytometry before starting treatment (Day 0) and on Day 5 and Day 18 during the treatment. At the end of the experiment, immunophenotyping was also done on tumors, spleen, and bone marrow. Complete blood count was analyzed based on single cell evaluation (Drew Scientific HemaVet 950FS Auto Blood Analyzer). Results By immunohistochemistry CXCR5 and CD19 showed comparable high expression on patient samples, whereas CD79b expression was moderate. Treatment of humanized mice bearing REC-1 tumors with VIP924 at 10 mg/kg reduced tumor growth effectively (p<0.0001 vs. isotype control on Day 10), while treatment with polatuzumab vedotin and loncastuximab teserine showed no effects on tumor growth. This outcome was also reflected in the median survival rates for the different groups with 17 days for isotype control and polatuzumab vedotin, 14 days for loncastuximab teserine and not reached for the 10-mg/kg VIP924 group. However, polatuzumab vedotin treatment significantly reduced hCD45+ cells in peripheral blood and spleen, while loncastuximab teserine treatment showed a clear trend for reduction. VIP924 treatment in both arms had no effect on peripheral or splenic hCD45+ cells. All tested ADCs reduced the CD19+ and more mature CD19+/CXCR5+ B-cells in peripheral blood and spleen, with polatuzumab vedotin and loncastuximab teserine showing significant (p<0.0001 vs. isotype control on Day 18) effects on CD19+ cell reductions, while VIP924 treatment showed a milder reduction in CD19+ cells (p= 0.0051 for 3 mg/kg and p= 0.0407 for 10 mg/kg VIP924). Loncastuximab teserine treatment increased the amount of myeloid derived suppressor cells in the peripheral blood significantly (p= 0.0467). In contrast, VIP924 led to a significant (p< 0.0001) increase in peripheral regulatory T-cells compared with isotype control. Complete blood counts from treated mice showed a reduction of white blood cells (WBC), absolute lymphocyte count, and absolute monocyte count in loncastuximab teserine-treated animals. Loncastuximab teserine treatment also reduced red blood cell count and hemoglobin values. In VIP924-treated animals, no effects on WBC, red blood cell count, or hemoglobin values were observed. All treatments showed no detrimental effects on body weights of the mice. Conclusion CXCR5 is a highly attractive target in B-cell malignancies such as diffuse large B-cell lymphoma and MCL due to high CXCR5 surface expression. VIP924, a CXCR5-targeting ADC, showed high potency and superiority to other B-cell-targeted ADCs in a humanized mouse model of MCL. In this MCL model in humanized mice, VIP924 at 10 mg/kg treatment showed a significant reduction in tumor growth and improvement in survival, while polatuzumab vedotin and loncastuximab teserine had no effect on tumor growth or survival. Interestingly, VIP924 was the only ADC to cause a significant increase in peripheral T regulatory cells, which may enhance tumor growth inhibition. Loncastuximab teserine had a deleterious effect on several hematologic parameters, which was not observed with VIP924 or polatuzumab vedotin. The efficacy and tolerability observed in this study with VIP924 suggests further testing in human clinical trials is warranted.

Selectivity and Safety of VIP943: A Novel CD123-Targeting Antibody-Drug Conjugate (ADC) Using a Proprietary Linker and Payload Class

Introduction ADCs afford high efficacy though often have shortcomings in their safety profile. Most ADC payloads are cytotoxic agents that can inhibit general processes of cellular homeostasis, including microtubule polymerization or DNA damage repair. While these are good targets for cytotoxicity, they have the drawback of being nonselective for dividing cancer cells. Here, we report the potent, on-target activity and selectivity of our novel CD123-targeting ADC VIP943, which uses a kinesin spindle protein (KSP; also known as KIF11 or Eg5) inhibitor as the payload (VIP716). The kinesin superfamily (KIF) is comprised of motor-proteins involved in various cellular mechanisms, including formation of the bipolar mitotic spindle during cell division. Targeting KSP selectively inhibits dividing cells, while sparing nondividing, differentiated cells thereby increasing the therapeutic index of VIP943. Methods VIP716 selectivity and potency: The motor domain of the human KSP and the other KIF family members were incubated with stabilized microtubules in a biochemical assay. The freshly prepared mixture was then incubated VIP716 and ispinesib, a clinical stage KSPi. ATPase activity was directly analyzed by measuring the formed inorganic phosphate. VIP943 selectivity: The binding of VIP943 to 6,019 human plasma membrane proteins expressed on HEK cells was evaluated (Retrogenix cell microarray). Cell cycle/death analysis: The effect of VIP943 on the 3 phases of the cell cycle (G0/G1- S- G2/M) was measured with DNA staining and flow cytometry in MOLM-13 and MV-4-11 cell lines. In addition, cell death was measured by flow cytometry after a 4 h incubation with VIP943 in MOLM-13 cells. Isotype ADC was used as a control. In vitro cytotoxicity: 56 hematologic cell lines were treated in vitro with VIP331 (cell permeable analog of VIP716). IC 50 results were matched with the DNA/RNA profile of relevant oncogenes to determine correlations. Nonhuman primate safety and toxicokinetics: VIP943 was intravenously administered to Cynomolgus monkeys at 1, 3, or 9 mg/kg once weekly for 4 weeks in a Good Laboratory Practice (GLP) toxicology study. Serial plasma samples were collected on Day 1 and Day 22. Total antibody from VIP943 (as a surrogate for VIP943) and VIP716 concentrations were measured by LC/MS/MS. Toxicokinetics (TK) were assessed using noncompartmental methods. Results In a biochemical assay, VIP716 (payload), achieved comparable potency to ispinesib with IC 50 values of 1.4 and 1.6 nM, respectively, for KSP. VIP716 did not inhibit any of the 11 other KIF family members up to 10 µM. In the Retrogenix assay, VIP943 (ADC) had no interaction with any of the analyzed human cell surface proteins except for CD123. Cell cycle analysis in AML cells showed a dose- and time-dependent increase in G2/M arrest with VIP943 treatment, but not with isotype control. An increase in cell death with VIP943 treatment was also observed after a 4-hour incubation. In a broad hematologic cell line panel, the median cytotoxicity IC 50 for VIP331 (cell permeable KSPi) was 2.49 nM. Of note, no genomic alterations correlated with sensitivity, suggesting VIP943 may be effective even in hard-to-treat hematologic malignancies. VIP943 was well tolerated in the GLP monkey toxicology study. No mortality occurred in any monkeys. No neutropenia, thrombocytopenia or anemia were observed. VIP943 and VIP716 exposures increased with increasing dose in a dose-proportional or greater than dose-proportional manner. No consistent differences in TK were observed with sex. Based on area under the concentration curve (AUC), no accumulation was observed. Payload to parent ratios were consistent with a low level of non-specific release of VIP716 from VIP943. Conclusion High on-target activity of VIP716, the payload of our new CD123-targeting ADC, VIP943, was demonstrated in a biochemical assay and selectivity against other KIF family members was confirmed. This activity translated into cell cycle arrest in the G2/M phase and subsequent cell death in a dose- and time-dependent manner. Additionally, toxicology in non-human primates and in vivo TK studies confirm safety, favorable drug exposures, and little non-specific release of the payload. Based on these data, evaluation of VIP943 in human clinical trials is warranted.

A novel antibody-KSP inhibitor conjugate improves KSP inhibitor efficacy in vitro and in vivo

Many clinical trials of kinesin spindle protein (KSP) inhibitors have failed due to issues such as high toxicity and a short circulation half-life in vivo. To address the limitations of current KSP inhibitors and thus broad its use in antitumor therapy, this study applied antibody–drug conjugate (ADC) technology to the KSP inhibitor SB-743921, which was coupled with the HER2-specific antibody trastuzumab using a cathepsin B-dependent valine–alanine (Val–Ala, VA) dipeptide-type linker to generate H2-921. Ex vivo and in vivo analyses of H2-921 showed an increased half-life of SB-743921 and prolonged contact time with tumor cells. Furthermore, H2-921 induced apoptosis and incomplete autophagy in HER2-positive cells. In the in vivo analyses, H2-921 had significant tumor-targeting properties, and tumor inhibition by H2-921 was greater than that by traditional KSP inhibitors but similar to that by the positive control drug T-DM1. In conclusion, this study describes a novel application of ADC technology that enhances the antitumor effects of a KSP inhibitor and thus may effectively address the poor clinical efficacy of KSP inhibitors.

Abstract 6294: CXCR5 is a very promising drug target for the development of antibody-drug conjugates to treat patients with lymphoma

Abstract Introduction: The chemokine receptor CXCR5 is highly expressed in tumor cells from different lymphoma types and represents a viable drug target for the development of antibody-drug conjugates (ADC) to treat patients with lymphoma.   Methods: Immunohistochemistry of human tissues of different lymphoma types were stained using antibodies against human CXCR5, CD20, CD70 and CD79b. Slides were examined by a pathologist and scored for expression. CXCR5 expression on tumor cell lines was analyzed by flow cytometry. Cell surface receptor density was analyzed by Quantibrite ™ PE-beads. Evaluation of antibody internalization was performed using the Operetta High Content Imaging System. NOD/SCID mice were transplanted subcutaneously with lymphoma patient-derived (PDX) tumor specimens and treated with 2mg/kg or 10mg/kg VIP924 CXCR5-ADC or isotype control. Results: CXCR5 reveals very low to no expression in most tissues except for lymph nodes. Expression of CXCR5 and other B-cell targets like CD19, CD20, CD70 and CD79b was analyzed on patient-derived tumor samples. High expression of CXCR5 was found on naïve and previously treated diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL), mantle cell lymphoma (MCL), and chronic lymphocytic leukemia (CLL) samples. Based on these results, we developed a CXCR5 targeted ADC with a novel, highly potent kinesin spindle protein inhibitor (KSPi) payload linked via a legumain-cleavable linker (VIP924). To compare the performance of KSPi ADCs, the same effector chemistry was attached to antibodies against other B-cell targets and tested in cytotoxicity assays in various cell lines. CXCR5-targeted ADC demonstrates significantly higher activity compared to the other ADCs tested except for the CD79b ADC with equal potency. VIP924 was then tested in vivo in different PDX tumor mouse models with different levels of CXCR5 expression. In the LY2264 and HBL-1 DLBCL models, we obtained a tumor growth inhibition of 68% and 100% respectively compared to isotype control. The median survival time for the isotype control group was 29 days and median survival time for the mice treated with 10mg/kg VIP924 could not be determined as all mice survived until the end of the study (Day 37). No effect on body weight or any adverse effects in the VIP924 treated mice were observed. Conclusions: CXCR5 is a highly attractive target in hematological malignancies such as DLBCL, MCL, and FL due to high protein expression and almost no expression in healthy tissues. CXCR5-targeting ADC with KSPi payload showed high potency and superiority to other B-cell-targeted ADCs in vitro on a broad range of lymphoma cell lines. VIP924 with a novel legumain-cleavable linker showed activity in in vivo PDX models from lymphoma patients. Due to the high CXCR5 expression found in relapsed DLBCL patients, VIP924 may bring promising new treatment options for previously treated patients with lymphoma. Citation Format: Tibor Schomber, Beatrix Stelte-Ludwig, Amy J. Johnson, Oliver von Ahsen, Christoph Schatz, Raquel Izumi, Ahmed Hamdy, Hans-Georg Lerchen. CXCR5 is a very promising drug target for the development of antibody-drug conjugates to treat patients with lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6294.

Recent Advances in the Applications of Small Molecules in the Treatment of Multiple Myeloma.

Therapy for multiple myeloma (MM), a hematologic neoplasm of plasma cells, has undergone remarkable changes over the past 25 years. Small molecules (molecular weight of less than one kDa), together with newer immunotherapies that include monoclonal antibodies, antibody-drug conjugates, and most recently, chimeric antigen receptor (CAR) T-cells, have combined to double the disease's five-year survival rate to over 50% during the past few decades. Despite these advances, the disease is still considered incurable, and its treatment continues to pose substantial challenges, since therapeutic refractoriness and patient relapse are exceedingly common. This review focuses on the current pipeline, along with the contemporary roles and future prospects for small molecules in MM therapy. While small molecules offer prospective benefits in terms of oral bioavailability, cellular penetration, simplicity of preparation, and improved cost-benefit considerations, they also pose problems of toxicity due to off-target effects. Highlighted in the discussion are recent developments in the applications of alkylating agents, immunomodulators, proteasome inhibitors, apoptosis inducers, kinesin spindle protein inhibitors, blockers of nuclear transport, and drugs that affect various kinases involved in intracellular signaling pathways. Molecular and cellular targets are described for each class of agents in relation to their roles as drivers of MM.

Organometallic Ru, Os, Rh and Ir half-sandwich conjugates of ispinesib - impact of the organometallic group on the antimitotic activity.

Antimitotic agents are among the most important drugs used in anticancer therapy. Kinesin spindle protein (KSP) was proposed as a promising target for new antimitotic drugs. Herein, we report the synthesis of Ru, Os, Rh, and Ir half-sandwich complexes with the KSP inhibitor ispinesib and its (S)-enantiomer. Conjugation of the organometallic moiety with ispinesib and its (S)-enantiomer resulted in a significantly increased cytotoxicity of up to 5.6-fold compared to the parent compounds, with IC50 values in the nanomolar range. The most active derivatives were the ispinesib Ru and Rh conjugates which were able to generate reactive oxygen species (ROS), which may at least partially explain their high cytotoxicity. At the same time, the Os and Ir derivatives acted as KSP inhibitors with no effects on ROS generation.

VIP943 Is a Novel CD123 Antibody Drug Conjugate with in Vitro and In Vivo Efficacy in Acute Myeloid Leukemia (AML) Models

Background: Current treatment options (cytarabine with anthracyclines) for patients with acute myeloid leukemia (AML) are often associated with severe and barely tolerable toxicities. In patients who tolerate induction therapy, the complete remission rate is 60%-80%; however, 50% of patients relapse due to the presence of leukemic stem cells (LSC). Antibody-drug conjugates (ADCs) are putatively designed to deliver potent drugs directly to cancer cells while sparing normal tissue; however, first-generation ADCs are associated with severe bone marrow and liver toxicity. VIP943 is a CD123-targeting ADC which uses a kinesin spindle protein inhibitor (KSPi) as a new payload class and a unique legumain linker designed to overcome liabilities of currently approved ADC therapies. The payload is delivered with a drug-antibody ratio of 6. It consists of the KSPi warhead which is modified with a CellTrapperTM moiety so it accumulates within the CD123-targeted tumor cell and cannot enter normal cells. Non-human primate toxicology studies demonstrated a highly favorable and differentiated safety profile for VIP943 (Kirchhoff et al, Cancers 2020). Here we characterize VIP943 in various patient-derived AML models. Methods: For co-localization experiments, MOLM-13 AML cell line was stained with labelled anti-CD123 antibody or isotype control and CytoPainter LysoGreen indicator reagent and analyzed by imaging flow cytometry. AML primary patient mononuclear cells from blood and bone marrow were treated with VIP943 for 24, 48, and 72 hours. Flow cytometry immunophenotyping for AML blasts and CD34+/CD38- LSCs was used to analyze these populations. An in vivo patient-derived AML PDX mouse model was treated with VIP943 (5 mg/kg IV every 7 days) or in combination with 5-azacytidine (2.5 mg/kg SC days 1-5 x 3) and venetoclax (50 mg/kg PO days 1-5 x 3). Cytokine release syndrome was analyzed comparing VIP943 to isotype control ADC, anti-CD123 antibody, and positive comparator antibodies by in vitro cytokine release assays (CRA) in two different assay formats using whole blood and isolated mononuclear cells from 10 healthy donors. Flow cytometric lymphocyte and leukemic immunophenotyping was performed from blood of non-human primates. A leukemia cell line panel drug screen with VIP943 was evaluated and baseline genomic features were correlated with response. Results: Co-localization studies confirm specific internalization and efficient intracellular trafficking to the lysosome of VIP943. In vitro treatment with VIP943 (66 nM, continuous exposure) delivers blast reductions of 37% after a 24h incubation with VIP943, 45% after 48h incubation and 83% after an 72h incubation. In the CD34+/CD38- cell population, a reduction of 71% was achieved. In a patient-derived AML model, VIP943 with 5-azacytidine and venetoclax led to complete tumor growth inhibition after 21 days showing superiority of this triplet therapy (complete regression: 8/9 mice) with high tolerability (maximum body weight loss -4.8 %). The immunotoxicological evaluation in both CRA formats and with the tested antibody concentrations (100µg, 10µg, 1µg) exerts no induction of cytokines by VIP943 compared to controls. Immunophenotyping demonstrates no impact of VIP943 treatment on lymphocytic subpopulations, whereas the CD123-positive basophils are reduced after 24h followed by an almost complete recovery. VIP943 IC50 ranges from 0.1nM-300nM in a leukemia cell line panel screen and features associated with sensitivity are investigated. Conclusions: VIP943 is a next-generation ADC with a differentiated safety profile from currently approved ADCs, including lack of in vitro cytokine release. In vitro and in vivo studies using patient-derived AML cells show VIP943 has favorable monotherapy and combination efficacy including targeting of leukemic stem cells, which drive relapse. These findings warrant evaluating VIP943 in clinical trials.

Kinesin spindle protein inhibitor exacerbates cisplatin-induced hair cell damage

There is emerging evidence indicating that Kinesin family, plays vital roles in influencing the growth of axons, interference with the progression of tumor. However, the function of Kinesin member in the auditory organs remains unknown. SB743921, a kinesin spindle protein (KSP) inhibitor, was applied in mouse organ of Corti and House Ear Institute-Organ of Corti 1 (HEI-OC1) cell line to examine the role of KSP in auditory system with and without cisplatin damage. Cell Counting Kit-8 (CCK-8) and Lactase dehydrogenase (LDH) release assay were conducted to evaluate cell activity and toxicity. Pretreatment with SB743921 increased the sensitivity of HEI-OC1 cells to cisplatin ototoxicity through promoting cell apoptosis and deteriorating superoxide generation mediated damage from cisplatin. SB743921 also enhanced cisplatin induced hair cell damage in explants of mouse cochleae in vitro. Furthermore, the combined N-acetylcysteine (NAC) treatment with cisplatin or with cisplatin and SB743921 both completely rescued the reduced number of hair cells impaired by cisplatin, confirming the strengthening function of superoxide accumulation by SB743921 after cisplatin treatment. Inhibition of kinesin spindle protein enhanced the susceptibility of hair cells to cisplatin induced damage in mouse cochlear explants and HEI-OC1 cells, indicating that kinesin spindle protein might be an unprecedented target to weaken the ototoxicity of platinum medicaments.

The therapeutic effect of KSP inhibitors in preclinical models of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an epithelial malignancy with a dismal prognosis owing to limited treatment options. Here, we identified several compound candidates against CCA using a high-throughput drug screen with approved or emerging oncology drugs, among which kinesin spindle protein (KSP) inhibitors showed potent cytotoxic effects on CCA cells. Treatment with KSP inhibitors SB743921 and ARRY520 caused significant tumor suppression in CCA xenograft models in vivo. Mechanistically, KSP inhibitors led to the formation of abnormal monopolar spindles, which further resulted in the mitotic arrest and cell death of CCA cells both in vivo and in vitro. KEGG pathway analysis of transcriptional data confirmed this finding. Moreover, our clinical data as well as the TCGA database showed KIF11 expression was abundant in most CCA tumor specimens and associated with poor outcomes of CCA patients. Our results demonstrate that the therapeutic regimen of KSP inhibitors could be a promising treatment strategy in CCA.

Role of KSP Inhibitors as Anti-cancer Therapeutics: An Update.

Regardless of the growing discovery of anticancer treatments targeting cancer-specific pathways, cytotoxic therapy still maintained its abundant clinical significance because tumours harbor a greater population of actively dividing cells than normal tissues. Conventional anti-mitotic agents or microtubule poisons acting on the major mitotic spindle protein tubulin have been effectively used in clinical settings for cancer chemotherapy over the last three decades. However, the use of these drugs is associated with limited clinical utility due to serious side effects such as debilitating and dose-limiting peripheral neuropathy, myelosuppression, drug resistance, and allergic reactions. Therefore, research initiatives have been undertaken to develop novel microtubule motor proteins inhibitors that can potentially circumvent the limitations associated with conventional microtubule poisons. Kinesin spindle proteins (KSP) belonging to the kinesin-5 family play a crucial role during mitosis and unregulated cell proliferation. Evidence from preclinical studies and different phases of clinical trials have presented kinesin spindle protein as a promising target for cancer therapeutics. Kinesin spindle protein inhibitors causing mitosis disruption without interfering with microtubule dynamics in non-dividing cells offer a potential therapeutic alternative for the management of several major cancer types and are devoid of side effects associated with classical anti-mitotic drugs. This review summarizes recent data highlighting progress in the discovery of targeted KSP inhibitors and presents the development of scaffolds, structure-activity relationships, and outcomes of biological and enzyme inhibition studies. We reviewed the recent literature reports published over the last decade, using various electronic database searches such as PubMed, Embase, Medline, Web of Science, and Google Scholar. Clinical trial data till 2021 was retrieved from ClinicalTrial.gov. Major chemical classes developed as selective KSP inhibitors include dihydropyrimidines, β-carbolines, carbazoles, benzimidazoles, fused aryl derivatives, pyrimidines, fused pyrimidines, quinazolines, quinolones, thiadiazolines, spiropyran, and azobenzenes. Drugs such as filanesib, litronesib, ispinesib have entered clinical trials; the most advanced phase explored is Phase II. KSP inhibitors have exhibited promising results; however, continued exploration is greatly required to establish the clinical potential of KSP inhibitors.

Abstract 3892: High-throughput combination screen for identifying novel therapies against high-risk neuroblastoma

Abstract Neuroblastoma is a childhood solid tumor commonly located in the adrenal gland. High-risk neuroblastoma patients undergo multidrug and multi-interventional treatment but despite these efforts many patients develop resistance to chemotherapy and eventually relapse. Neuroblastoma patients face an urgent need of novel therapeutic strategies that could effectively combat the disease. In a recent study we identified kinesin spindle protein (KSP) as a highly effective target in high-risk neuroblastoma. Pharmacological inhibition of KSP resulted in complete regression of a subset of neuroblastoma subcutaneous PDX tumors and tumor growth delay in orthotopic PDXs (Hansson, Radke et al, Sci. Transl. Med 2020). The purpose of the present study is to identify novel synergistic drug combinations effective against neuroblastoma and investigate their translational potential. We designed, optimized, and performed a high-throughput combination screen using 3D tumor organoids that represent three MYCN-amplified neuroblastoma tumors. KSP inhibition was tested in combination with the FIMM drug set of 527 approved and investigational drugs. Screening was performed stepwise: • Step 1: High-throughput drug screening 527 drug combinations and machine learning prediction (DECREASE tool) of drug combination synergy based on minimal required input. • Step 2: Screening of 6x6 dose-response matrices of top 26 predicted hits in high-risk neuroblastoma models. • Step 3: Screening of 6x6 dose-response matrices of top 26 hits in CD34+ cord blood controls to identify compounds that have low toxicity towards proliferating fraction of hematopoietic cells. Overall, we identified seven drug candidates (P1-P7). They classify as: kinase inhibitors, differentiating modifiers, and one hormone therapy. Screened combinations were chosen based on selective efficacy (difference between anti-neuroblastoma efficacy and efficacy towards CD34+ cord blood controls). Identified drug combinations are common among three high-risk neuroblastoma models and have most synergistic area score (MSA) over five. We further plan to validate seven hits in neuroblastoma models in vitro, investigate MOA of the most promising combination and test it in PDX models in vivo. Citation Format: Katarzyna Radke, Karin Hansson, Jani Saarela, Aleksandr Ianevski, Philipp Ianevski, Aurélie Baudet, Mattias Magnusson, Daniel Bexell. High-throughput combination screen for identifying novel therapies against high-risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3892.

Kinesin spindle protein inhibitors in cancer: from high throughput screening to novel therapeutic strategies.

Bringing to a halt the cell cycle in mitosis and interfering with its normal progression is one of the most successful anti-cancer strategies used nowadays. Classically, several kinds of anti-cancer drugs like taxanes and vinca alkaloids directly inhibit microtubules during cell division. These drugs exhibit serious side effects, most importantly, severe peripheral neuropathies. Alternatively, KSP inhibitors are grasping a lot of research attention as less toxic mitotic inhibitors. In this review, we track the medicinal chemistry developmental stages of KSP inhibitors. Moreover, we address the challenges that are faced during the development of KSP inhibitor therapy for cancer and future insights for the latest advances in research that are directed to find active KSP inhibitor drugs.

Antibody–drug conjugates harboring a kinesin spindle protein inhibitor with immunostimulatory properties

ABSTRACT Antibody–drug conjugates (ADCs) are used to target cancer cells by means of antibodies directed to tumor-associated antigens, causing the incorporation of a cytotoxic payload into target cells. Here, we characterized the mode of action of ADC costing of a TWEAKR-specific monoclonal antibody conjugated to a small molecule kinesin spindle protein (KSP) inhibitor (KSPi). These TWEAKR-KSPi-ADCs showed strong efficacy in a TWEAKR expressing CT26 colon cancer model in mice. TWEAKR-KSPi-ADCs controlled the growth of CT26 colon cancers in immunodeficient as well as in immunocompetent mice. However, when treated with suboptimal doses, TWEAKR-KSPi-ADCs were still active in immunocompetent but not in immunodeficient mice, indicating that TWEAKR-KSPi-ADCs act – in addition to the cytotoxic mode of action – through an immunological mechanism. Indeed, in vitro experiments performed with a cell-permeable small molecule KSPi closely related to the active payload released from the TWEAKR-KSPi-ADCs revealed that KSPi was capable of stimulating several hallmarks of immunogenic cell death (ICD) on three different human cancer cell lines: cellular release of adenosine triphosphate (ATP) and high mobility group B1 protein (HMGB1), exposure of calreticulin on the cell surface as well as a transcriptional type-I interferon response. Further, in vivo experiments confirmed that treatment with TWEAKR-KSPi-ADCs activated immune responses via enhancing the infiltration of CD4+ and CD8+ T lymphocytes in tumors and the local production of interferon-γ, interleukin-2, and tumor necrosis factor-α. In conclusion, the antineoplastic effects of TWEAKR-KSPi-ADCs can partly be attributed to its ICD-stimulatory properties.