Kinesin Spindle Protein Inhibitor Research Articles

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.

Safety and Efficacy of Filanesib in Combination with Pomalidomide and Dexamethasone in Refractory MM Patients. Phase Ib/II Pomdefil Clinical Trial Conducted By the Spanish MM Group

Safety and Efficacy of Filanesib in Combination with Pomalidomide and Dexamethasone in Refractory MM Patients. Phase Ib/II Pomdefil Clinical Trial Conducted By the Spanish MM Group

Design, synthesis, and evaluation of a novel prodrug, a S-trityl-l-cysteine derivative targeting kinesin spindle protein.

Kinesin spindle protein (KSP) is expressed only in cells undergoing cell division, and hence represents an attractive target for the treatment of cancer. Several KSP inhibitors have been developed and undergone clinical trial, but their clinical use is limited by their toxicity to rapidly proliferating non-cancerous cells. To create new KSP inhibitors that are highly selective for cancer cells, we optimized the amino acid moiety of S-trityl-l-cysteine (STLC) derivative 1 using in silico modeling. Molecular docking and molecular dynamics simulation were performed to investigate the binding mode of 1 with KSP. Consistent with the structure activity relationship studies, we found that a cysteine amino moiety plays an important role in stabilizing the interaction. Based on these findings and the structure of GSH, a substrate of γ-glutamyltransferase (GGT), we designed and synthesized the prodrug N-γ-glutamylated STLC derivative 9, which could be hydrolyzed by GGT to produce 1. The KSP ATPase inhibitory activity of 9 was lower than that of 1, and LC-MS analysis indicated that 9 was converted to 1 only in the presence of GGT invitro. In addition, the cytotoxic activity of 9 was significantly attenuated in GGT-knockdown A549cells. Since GGT is overexpressed on the cell membrane of various cancer cells, these results suggest that compound 9 could be a promising prodrug that selectively inhibits the proliferation of GGT-expressing cancer cells.

IL3RA-Targeting Antibody-Drug Conjugate BAY-943 with a Kinesin Spindle Protein Inhibitor Payload Shows Efficacy in Preclinical Models of Hematologic Malignancies.

Simple SummaryIL3RA (alpha subunit of the interleukin 3 receptor) is a cell membrane protein frequently expressed in acute myeloid leukemia (AML) and Hodgkin lymphoma; therefore, it is a promising therapeutic target for cancer treatment. Here, we introduce BAY-943, a novel IL3RA-targeting antibody–drug conjugate that shows potent and selective efficacy in IL3RA-positive AML and Hodgkin lymphoma cell lines. In IL3RA-positive AML mouse models, BAY-943 improved survival and reduced tumor burden. Impressively, treatment with BAY-943 induced complete tumor remission in 12 out of 13 mice in an IL3RA-positive HL model. BAY-943 showed a favorable safety profile without any signs of toxicity in rats and monkeys. Overall, these preclinical results support the further development of BAY-943 for the treatment of IL3RA-positive hematologic malignancies.IL3RA (CD123) is the alpha subunit of the interleukin 3 (IL-3) receptor, which regulates the proliferation, survival, and differentiation of hematopoietic cells. IL3RA is frequently expressed in acute myeloid leukemia (AML) and classical Hodgkin lymphoma (HL), presenting an opportunity to treat AML and HL with an IL3RA-directed antibody–drug conjugate (ADC). Here, we describe BAY-943 (IL3RA-ADC), a novel IL3RA-targeting ADC consisting of a humanized anti-IL3RA antibody conjugated to a potent proprietary kinesin spindle protein inhibitor (KSPi). In vitro, IL3RA-ADC showed potent and selective antiproliferative efficacy in a panel of IL3RA-expressing AML and HL cell lines. In vivo, IL3RA-ADC improved survival and reduced tumor burden in IL3RA-positive human AML cell line-derived (MOLM-13 and MV-4-11) as well as in patient-derived xenograft (PDX) models (AM7577 and AML11655) in mice. Furthermore, IL3RA-ADC induced complete tumor remission in 12 out of 13 mice in an IL3RA-positive HL cell line-derived xenograft model (HDLM-2). IL3RA-ADC was well-tolerated and showed no signs of thrombocytopenia, neutropenia, or liver toxicity in rats, or in cynomolgus monkeys when dosed up to 20 mg/kg. Overall, the preclinical results support the further development of BAY-943 as an innovative approach for the treatment of IL3RA-positive hematologic malignancies.

A Phase 1 Dose-Escalation Study of LH031, a Kinesin Spindle Protein Inhibitor, in Patients with Refractory/Resistance Multiple Myeloma

PURPOSE: Kinesin spindle protein is an attractive target for cancer treatment since it plays an important role in mitosis without directly affecting microtubules. LH031 is a highly selective inhibitor of kinesin spindle protein, which has demonstrated preclinical antimyeloma activity.. This phase 1 study was conducted to evaluated dose limiting toxicities (DLTs) and determined a maximum tolerated dose (MTD) for LH031 in Chinese patients with Refractory/Resistance Multiple Myeloma (RRMM).The pharmacokinetics (PK) and preliminary efficacy of LH031 were also evaluated. METHODS: A non-randomized, single-center, open-label, dose-escalation phase 1 trial was conducted to evaluate the safety, tolerability, pharmacokinetics and efficacy of single or multiple escalation dose (20 mg, 30 mg, 40 mg, 50 mg) of LH031 given as schedule of oral once a day. LH031 was administered on Day 1~5 of each week for 3 weeks (21 days) per cycle. A standard 3+3 dose escalation design was employed. An expansion cohort was conducted at the MTD. Pharmacokinetics was evaluated in plasma. A major efficacy evaluation was performed at the end of each treatment cycle. RESULTS: The study is still on going, at present there are 6 patients received LH031 and completion of all visits, divided equally into 20mg and 30mg cohort. Patients in each cohort had received a median of 6 prior therapies. DLTs reported in two patients dosed at 30mg. Both of the DLTs were neutropenia. The most commonly reported treatment-related AEs were hematological toxicity (e.g. neutropenia, lymphocytopenia, leukocytopenia) that were similar to other Eg5 inhibitors. The main severe adverse events (CTCAE grade 3 or 4) in the 20mg and 30 mg dose groups were leukocytopenia and neutropenia, and they were all reversible. Neurotoxicity related to LH031 was not observed. Efficacy data demonstrated that the best response was Stable Disease(SD) and Disease Control Rate (DCR, ≥SD[≥8 weeks]) was 50%. The longest treatment time was 177 days, even though PFS was determined according to the last tumor evaluation before the COVID period (D88). The PK data shows that T1/2 are approximately 20h in Chinese patients, which is longer than Caucasian (10h); Chinese AUC for 20mg is also higher than that of Caucasian (1996 h*ng/ml vs. 476 h*ng/ml) ; the exposure at 20mg dose group is close to that at 50 mg dose in Caucasian. These PK parameter indicates that the elimination of LH031 is slower in Chinese patients compared with Caucasian. CONCLUSIONS: The current phase 1 study showed that LH031 was an accepted safety profile at 20mg. DLTs was expected and reversible. MTD is to be determined by recruiting 3 more subjects at 20mg dose. It demonstrated that the elimination rate of LH031 in Chinese patients was slower than Caucasian. The monotherapy showed some benefit to RRMM, Phase 2 clinical trials are being planned to include various combination therapies with existing treatments (e.g. lenalidomide, dexamethasone, bortezomib) for MM to benefit more potential refractory/resistance MM patients. Disclosures Song: Link Health Group: Current Employment.

Pharmacologic profiling of patient-derived xenograft models of primary treatment-na\xefve triple-negative breast cancer

Triple-negative breast cancer (TNBC) accounts for 15–20% of breast cancer cases in the United States, lacks targeted therapeutic options, and is associated with a 40–80% risk of recurrence. Thus, identifying actionable targets in treatment-naïve and chemoresistant TNBC is a critical unmet medical need. To address this need, we performed high-throughput drug viability screens on human tumor cells isolated from 16 patient-derived xenograft models of treatment-naïve primary TNBC. The models span a range of TNBC subtypes and exhibit a diverse set of putative driver mutations, thus providing a unique patient-derived, molecularly annotated pharmacologic resource that is reflective of TNBC. We identified therapeutically actionable targets including kinesin spindle protein (KSP). The KSP inhibitor targets the mitotic spindle through mechanisms independent of microtubule stability and showed efficacy in models that were resistant to microtubule inhibitors used as part of the current standard of care for TNBC. We also observed subtype selectivity of Prima-1Met, which showed higher levels of efficacy in the mesenchymal subtype. Coupling pharmacologic data with genomic and transcriptomic information, we showed that Prima-1Met activity was independent of its canonical target, mutant p53, and was better associated with glutathione metabolism, providing an alternate molecularly defined biomarker for this drug.

Metal-Dependent Cytotoxic and Kinesin Spindle Protein Inhibitory Activity of Ru, Os, Rh, and Ir Half-Sandwich Complexes of Ispinesib-Derived Ligands

Ispinesib is a potent inhibitor of kinesin spindle protein (KSP), which has been identified as a promising target for antimitotic anticancer drugs. Herein, we report the synthesis of half-sandwich complexes of Ru, Os, Rh, and Ir bearing the ispinesib-derived N,N-bidentate ligands (R)- and (S)-2-(1-amino-2-methylpropyl)-3-benzyl-7-chloroquinazolin-4(3H)-one and studies on their chemical and biological properties. Using the enantiomerically pure (R)- and (S)-forms of the ligand, depending on the organometallic moiety, either the SM,R or RM,S diastereomers, respectively, were observed in the molecular structures of the Ru- and Os(cym) (cym = η6-p-cymene) compounds, whereas the RM,R or SM,S diastereomers were found for the Rh- and Ir(Cp*) (Cp* = η5-pentamethylcyclopentadienyl) derivatives. However, density functional theory (DFT) calculations suggest that the energy difference between the diastereomers is very small, and therefore a mixture of both will be present in solution. The organometallics exhibited varying antiproliferative activity in a series of human cancer cell lines, with the complexes featuring the (R)-enantiomer of the ligand being more potent than the (S)-configured counterparts. Notably, the Rh and Ir complexes demonstrated high KSP inhibitory activity, even at 1 nM concentration, which was independent of the chirality of the ligand, whereas the Ru and especially the Os derivatives were much less active.

Abstract 1807: Anti-tumor activity of a novel structural class of NAMPT inhibitor-based ADCs in models of hematologic and solid tumor indications

Abstract Nicotinamide phosphoribosyl-transferase (NAMPT) is the rate-limiting enzyme in the salvage pathway, generating nicotinamide adenine dinucleotide (NAD) from nicotinamide (NAM). Inhibition of intracellular NAMPT activity represents a differentiated mode-of-action for tumor-targeting antibody-drug conjugates (ADCs) as it is not dependent on cell proliferation. Thus, NAMPT inhibitor-based ADCs have the potential to target both proliferating and resting tumor cells. We therefore developed a novel structural class of NAMPT inhibitors (NAMPTi) as a potent ADC payload class and characterized NAMPTi and NAMPTi-ADCs in vitro and in vivo in preclinical tumor models. We profiled the small molecule NAMPTi BAY-346 in comparison to the kinesin spindle protein inhibitor (KSPi) BAY-331 on a panel of 350 cancer cell lines from various tumor indications showing a differential sensitivity profile of BAY-346 vs BAY-331, with cell lines characterized by low NAMPT mRNA levels as being very sensitive to BAY-346. NAMPTi BAY-346, but not KSPi BAY-331, reduced the viability of quiescent HaCat cells as well as of serum starved non-proliferating NCI-N87 cells. In vitro treatment with NAMPTi BAY-346, which bears a pyridine warhead that can be phosphoribosylated by NAMPT, resulted in IC50 values in the nanomolar to subnanomolar range (2.8 nM to 0.01 nM) in cell lines derived from solid and hematologic tumor indications (e.g., THP-1, MV-4-11, U-251, NCI-H292, MDA-MB-453, LoVo, KPL4, HT1197 and BxPC3). BAY-346 was 100-fold more potent than the small molecule NAMPTi BAY-248, which cannot be phosphoribosylated. A BAY-346 derived NAMPTi was conjugated as a payload to a series of antibodies targeting different tumor-associated antigens: C4.4a (LYPD3), HER2, B7H3 (CD276), and TWEAKR (Fn14/ TNFRSF10A). The resulting NAMPTi-ADCs were tested in proliferation and cellular mechanistic in vitro assays. NAMPTi-ADCs depleted NAD+ in tumor cells and showed potent growth inhibitory activity with IC50 values in the subnanomolar- to nanomolar range in a target-dependent manner. A C4.4a-NAMPTi-ADC and a HER2-NAMPTi-ADC were tested In the C4.4a- and HER2-expressing MDA-MB-453 cell line derived subcutaneous breast cancer model xenografted on NOD/SCID mice. Both NAMPTi-ADCs showed highly potent anti-tumor Efficacy: The C4.4a-NAMPTi-ADC induced complete responses (in 3 of 8 mice) and stable diseases (in 5 of 8 mice) and the HER2-NAMPTi-ADC achieved complete tumor regression in all treated animals. In addition, in the THP-1 acute myeloid leukemia (AML) subcutaneous in vivo model, a B7H3-NAMPTi-ADC induced complete tumor responses in 7 of 8 treated animals. Taken together, we identified a new series of NAMPT inhibitors as a novel class of ADC payloads exhibiting strong in vivo efficacy in various preclinical xenograft models. Citation Format: Anette Sommer, Stefanie Hammer, Sandra Berndt, Antje M. Wengner, Niels Boehnke, Markus Berger, Nils Griebenow, Andreas Steffen, Beatrix Stelte-Ludwig, Christoph Mahlert, Simone Greven, Lisa Dietz, Hannah Joerissen, Anja Giese, Maria Quanz, Zhengzheng Bao, Xiuli Wu, Hilmar Weinmann, Lars Linden, Bertolt Kreft, Dominik Mumberg. Anti-tumor activity of a novel structural class of NAMPT inhibitor-based ADCs in models of hematologic and solid tumor indications [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1807.

Design, synthesis, and molecular docking study of new monastrol analogues as kinesin spindle protein inhibitors.

Lung, colorectal, and breast cancers are the top three types of cancer by incidence and are responsible for one-third of the cancer incidence and mortality. A series of 18 3,4-dihydropyrimidine analogues bearing a 1,2-methylenedioxybenzene component at position 4 with diverse side chains at positions 5 and 6 was designed and synthesized as inhibitors of the Eg5 kinesin enzyme. Target compounds were screened for their anticancer activity according to the NCI-USA protocol toward a panel of 60 cancer cell lines. Compounds 12a and 12b displayed the best antiproliferation activity against many cell lines. Interestingly, compound 12a displayed lethal effects against non-small-cell lung cancer NCI-H522 cells (-42.26%) and MDA-MB-468 breast cancer cells (-1.10%) at a single-dose assay concentration of 10-5 M. Compounds 11c, 11d, 11g, 12a-d, 13, 15, and 18a were assayed against the kinesin enzyme, with IC50 values ranging from 1.2 to 18.71 μM, which were more potent compared with monastrol (IC50 = 20 μM). Cell cycle analysis of NCI-H522 cells treated with compound 12a showed cell cycle arrest at the G2/M phase. Furthermore, the expression levels of active caspase-3 and -9 were measured. A molecular docking study was performed for some demonstrative compounds as well as monastrol docked into the allosteric binding site of the kinesin spindle protein.

KSP siRNA/paclitaxel-loaded PEGylated cationic liposomes for overcoming resistance to KSP inhibitors: Synergistic antitumor effects in drug-resistant ovarian cancer

Despite the promising anticancer effects of kinesin spindle protein (KSP) inhibition, functional plasticity of kinesins induced resistance against KSP inhibitors in a variety of cancers, leading to clinical failure. Additionally, paclitaxel is a widely used anticancer agent, but drug resistance has limited its use in the recurrent cancers. To overcome resistance against KSP inhibitors, we paired KSP inhibition with microtubule stabilization using KSP siRNA and paclitaxel. To enable temporal co-localization of both drugs in tumor cells in vivo, we exploited PEGylated cationic liposomes carrying both simultaneously. Drug synergism study shows that resistance against KSP inhibition can be suppressed by the action of microtubule-stabilizing paclitaxel, because microtubule stabilization prevents a different kinesin Kif15 from replacing all essential functions of KSP when KSP is inhibited. Our combination therapy showed more effective antiproliferative activity in vitro and in vivo than either paclitaxel or KSP siRNA alone. Ultimately, we could observe significantly improved therapeutic effects in the drug-resistant in vivo models, including cell line and patient-derived xenografts. Taken together, our combination therapy provides a potential anticancer strategy to overcome resistance against KSP inhibitors. Particularly, this strategy also provides an efficient approach to improve the therapeutic effects of paclitaxel in the drug-resistant cancers.

Filanesib for the treatment of multiple myeloma

ABSTRACTIntroduction: Kinesin spindle protein (KSP) is indispensable for the proper separation of spindle poles during mitosis. Importantly, this protein is expressed only in cells undergoing cell division and hence represents an appealing target for the treatment of cancer. Many KSP inhibitors have demonstrated a strong antitumoral effect in vitro, however, they have exhibited only limited activity in clinical trials. By contrast, the KSP inhibitor filanesib has demonstrated clinical efficacy in patients with multiple myeloma (MM).Areas covered: This article provides a comprehensive overview about the progress to date in the preclinical and clinical development of filanesib for the treatment of cancer, and particularly, MM.Expert opinion: Responses observed with filanesib alone or in combination with dexamethasone were encouraging in MM. However, the subsequent appearance of highly effective novel agents such as monoclonal antibodies, has hindered the development of agents such as filanesib that exhibit a more limited activity. Nevertheless, filanesib has shown interesting results for some patients when combined with carfilzomib and pomalidomide. Most importantly, the availability of a biomarker of response such as alpha 1-acid glycoprotein (AAG), could be key to the identification of patients that could benefit most from these combinations.

Antibody-drug Conjugates with Novel Kinesin Spindle Protein Inhibitor Payloads and a Tailor-made Linker Chemistry

With the approval of meanwhile five ADCs and more than 80 ADCs in clinical trials, the ADC landscape has developed rapidly during the last decade. However, as indicated also by the large number of ADCs which failed in the clinic, it remains challenging to achieve a sufficiently large therapeutic window in cancer patients. Furthermore, the identification of ADC payload classes with a novel mode of action would increase therapeutic options and potentially help to overcome resistance. Inhibitors of kinesin spindle protein (KSP/Eg5) have raised great interest because of their high antitumor potency which, however, could not be transferred into highly efficient clinical regimens due to dose limiting side effects such as neutropenia and mucositis.

Design, synthesis, and bioactivity of dihydropyrimidine derivatives as kinesin spindle protein inhibitors

A series of twenty-one 3,4-dihydropyrimidine derivatives bearing the heterocyclic 1,3-benzodioxole at position 4 in addition to different substituents at positions 2, 3 and 5 were designed and synthesized as monastrol analogs. The novel synthesized compounds were screened for their cytotoxic activity towards 60 cancer cell lines according to NCI (USA) protocol. Compounds 10b and 15 showed the best antitumor activity against most cell lines. Compound 15 was subsequently tested in 5-doses mode and displayed high selectivity towards CNS, prostate and leukemia subpanel with selectivity ratios of 22.30, 15.38 and 12.56, respectively at GI50 level. The IC50 of compounds 9d, 10b, 12, 15 and 16 against kinesin enzyme were 3.86 ± 0.12, 10.70 ± 0.35, 3.95 ± 0.12, 4.36 ± 0.14, and 14.07 ± 0.45 μM respectively, while the prototype compound, monastrol, reported IC50 value of 20 ± 0.42 μM. The safest compound among test compounds against normal cell line (HEK 293) is 10b with IC50 value of 62.02 ± 2.42 µM/ml in comparison to doxorubicin (IC50 = 11.34 ± 0.44 µM/ml). Cell cycle analysis of SNB-75 cells treated with compound 15 showed cell cycle arrest at G2/M phase. Further, the assay of levels of active caspase-3 and caspase-9 was investigated. Moreover, Molecular docking of compounds, 9d, 10b, 12, 15, 16, monastrol and mon-97 was performed to study the interaction between inhibitors and the kinesin spindle protein allosteric binding site.

A High-Throughput Screen of a Library of Therapeutics Identifies Cytotoxic Substrates of P-glycoprotein.

The ATP-binding cassette transporter P-glycoprotein (P-gp) is known to limit both brain penetration and oral bioavailability of many chemotherapy drugs. Although US Food and Drug Administration guidelines require that potential interactions of investigational drugs with P-gp be explored, often this information does not enter the literature. In response, we developed a high-throughput screen to identify substrates of P-gp from a series of chemical libraries, testing a total of 10,804 compounds, most of which have known mechanisms of action. We used the CellTiter-Glo viability assay to test library compounds against parental KB-3-1 human cervical adenocarcinoma cells and the colchicine-selected subline KB-8-5-11 that overexpresses P-gp. KB-8-5-11 cells were also tested in the presence of a P-gp inhibitor (tariquidar) to assess reversibility of transporter-mediated resistance. Of the tested compounds, a total of 90 P-gp substrates were identified, including 55 newly identified compounds. Substrates were confirmed using an orthogonal killing assay against human embryonic kidney-293 cells overexpressing P-gp. We confirmed that AT7159 (cyclin-dependent kinase inhibitor), AT9283, (Janus kinase 2/3 inhibitor), ispinesib (kinesin spindle protein inhibitor), gedatolisib (PKI-587, phosphoinositide 3-kinase/mammalian target of rampamycin inhibitor), GSK-690693 (AKT inhibitor), and KW-2478 (heat-shock protein 90 inhibitor) were substrates. In addition, we assessed direct ATPase stimulation. ABCG2 was also found to confer high levels of resistance to AT9283, GSK-690693, and gedatolisib, whereas ispinesib, AT7519, and KW-2478 were weaker substrates. Combinations of P-gp substrates and inhibitors were assessed to demonstrate on-target synergistic cell killing. These data identified compounds whose oral bioavailability or brain penetration may be affected by P-gp. SIGNIFICANCE STATEMENT: The ATP-binding cassette transporter P-glycoprotein (P-gp) is known to be expressed at barrier sites, where it acts to limit oral bioavailability and brain penetration of substrates. In order to identify novel compounds that are transported by P-gp, we developed a high-throughput screen using the KB-3-1 cancer cell line and its colchicine-selected subline KB-8-5-11. We screened the Mechanism Interrogation Plate (MIPE) library, the National Center for Advancing Translational Science (NCATS) pharmaceutical collection (NPC), the NCATS Pharmacologically Active Chemical Toolbox (NPACT), and a kinase inhibitor library comprising 977 compounds, for a total of 10,804 compounds. Of the 10,804 compounds screened, a total of 90 substrates were identified of which 55 were novel. P-gp expression may adversely affect the oral bioavailability or brain penetration of these compounds.

Abstract 4825: Preclinical characterization of BAY-924, a first in class ADC targeting CXCR5-positive B-cell malignancies, with a KSP inhibitor as novel payload

Abstract Despite recent progress in the treatment of B-cell malignancies, patients are still in need of innovative therapeutic approaches. CXCR5 is a chemokine receptor expressed in a majority of B-cell malignancies including diffuse large B-cell lymphoma (DLBCL), Mantle cell lymphoma (MCL), follicular lymphoma and chronic lymphocytic leukemia. Evaluation of tumor biopsies from relapsed DLBCL patients shows that CXCR5 staining remains high, suggesting altogether that it could be a relevant target to explore for the treatment of non-Hodgkin lymphoma. BAY-924 is a novel first-in-class antibody drug conjugate (ADC) consisting of a humanized anti-CXCR5 IgG1 antibody (Ab) linked to a potent proprietary kinesin spindle protein inhibitor (KSPi). Of importance, the structure of the ADC is optimized for a specific metabolism, matching the KSPi mode of action and enabling a maximal retention of the payload within the tumor cells (Lerchen HG et al.; Angew. Chem. Int. Ed, 2018). Surface plasmon resonance assay showed a high binding affinity of the Ab to CXCR5 (2.5 nM). Affinities of 0.8 to 10 nM were measured by flow cytometry for the ADC in different CXCR5+ lymphoma cell lines. In vitro, BAY 924 had high and selective anti-proliferative activity in a panel of tumor cell lines with different levels of CXCR5 expression (<0.03 - 2 nM IC50). Efficient internalization and lysosomal co-localization of the Ab was observed in a variety of cell lines including the CXCR5+ MCL REC-1 cells. In vivo, BAY-924 was highly active in several CXCR5+ lymphoma models with a specific accumulation of the payload in tumor versus liver, spleen and kidney and almost undetectable levels in plasma. In the REC-1 model implanted subcutaneously (SC) in mice and treated at large tumor size (500 mm3), long lasting tumor regression was observed after 2 intravenous injections of BAY 0924 at 10 mg/kg, Q7D, whereas the model was insensitive to ibrutinib, a current standard of care (SoC) for the MCL indication. In the advanced ABC DLBCL model OCI-LY1 (SC), a single injection of BAY-924 at 10 mg/kg induced complete responses in 10/10 mice (up to day 95 post-treatment). In this model, head-to-head comparison showed superior activity of BAY-924 compared to the SoCs rituximab (R)-CHOP, R/bendamustine and R/lenalidomide. Also, BAY-924 induced potent antitumor effect with a 4% ΔT/ΔC (day 55) in the ABC DLBCL OCI-Ly3-2b model, expressing weak to moderate levels of CXCR5 in vivo. Given its unique structure, and based on supportive data from other projects, it is anticipated that BAY-924 shows a favorable safety profile, due to the high stability of the ADC and a non-cell permeable free payload which is trapped inside the tumor cells. Overall, these results support further development of BAY-924 as an innovative approach for the treatment of CXCR5+ non-Hodgkin lymphoma. Citation Format: Sarah Johannes, Stefanie Hammer, Stephan Maersch, Hans-Georg Lerchen, Beatrix Stelte-Ludwig, Hannah Joerissen, Oliver von Ahsen, Christoph Schatz, Simone Greven, Christoph Mahlert, Dominik Mumberg, Pascale Lejeune. Preclinical characterization of BAY-924, a first in class ADC targeting CXCR5-positive B-cell malignancies, with a KSP inhibitor as novel payload [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 4825.

Abstract 4828: Anti-tumor activity of BAY-943, an anti-IL3RA ADC with a novel KSP inhibitor payload, in CDX and PDX AML models

Abstract Despite recent progress in the treatment of AML, clinical outcomes have improved only minimally over the past three decades. Therefore, novel therapeutic agents with a high therapeutic window and a favorable tolerability profile are urgently needed to improve the therapeutic outcome for AML patients. IL3RA (CD123) is the alpha subunit of the interleukin 3 (IL-3) receptor which regulates proliferation, survival and differentiation of hematopoietic cells. IL3RA is expressed at high frequency, with ~84% of AML cases and 59% of classical Hodgkin lymphoma (cHL) cases being positive. IL3RA is expressed in AML blast and leukemic stem cells (LSCs) but not in hematopoietic stem cells (HSCs). In healthy individuals, the IL3RA expression is restricted to myeloid progenitor cells, plasmacytoid dendritic cells (pDCs), basophils and - at low levels - monocytes and B-lymphocyte subsets. This expression pattern suggests that IL3RA could be a clinically relevant target for an antibody-drug conjugate (ADC) approach in treatment of AML, cHL, and MDS. BAY-943 is a novel antibody-drug conjugate (ADC) consisting of a humanized internalizing anti-IL3RA IgG1 antibody (Ab, EC50 on IL3RA-positive tumor cells in flow cytometry: 2-5 nM) conjugated via lysine residues to a potent proprietary kinesin spindle protein inhibitor (KSPi). The kinesin spindle protein (KSP/Eg5/KIF11) is essential for the proper segregation of duplicated centrosomes during spindle formation in the G2/M phase of the cell cycle, as such it is only active in proliferating cells. In vitro, in a panel of IL3RA-positive AML and HL cell lines, BAY-943 showed potency in the nano- to subnanomolar range. In IL3RA-positive cell line derived (CDX) AML xenograft models (MOLM-13 and MV4-11) and patient-derived xenograft (PDX) models, BAY-943 dosed at 10 mg/kg given Q7Dx increased survival compared to vehicle treated mice. Tumor burden (percentage of human CD45 positive AML cells) was significantly reduced compared to vehicle treated mice. In the subcutaneous IL3RA-positive cHL CDX model HDLM-2, BAY-943 dosed at 5 and 10 mg/kg Q7Dx2 induced complete tumor remission in 12 out of 13 mice. In safety studies in Cynomolgus monkeys, BAY-943 (which is cross-reactive with Cynomolgus IL3RA), up to 20 mg/kg single or 10 mg/kg repeat (QWx3) dose were well tolerated with no signs of thrombocytopenia, neutropenia and no liver toxicity, i.e. adverse events observed with ADCs containing other payload classes. As expected, a transient reduction of IL3RA expressing cell types (basophils, pDCs) was observed. In summary, IL3RA-KSPi-ADC BAY-943 shows efficacy in IL3RA-positive AML and HL models and has a favorable safety profile in monkey repeat dose studies. Overall, the preclinical results support further development of BAY-943 as an innovative approach for the treatment of IL3RA-positive AML. Citation Format: Anette Sommer, Dennis Kirchhoff, Antje M. Wengner, Beatrix Stelte-Ludwig, Hans-Georg Lerchen, Anne-Sophie Rebstock, Oliver von Ahsen, Lisa Dietz, Pascale Buchmann, Sandra Johanssen, Dominik Mumberg, Bertolt Kreft. Anti-tumor activity of BAY-943, an anti-IL3RA ADC with a novel KSP inhibitor payload, in CDX and PDX AML models [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 4828.

Abstract 228: KSPi-ADCs: ADCs with novel kinesin spindle protein inhibitor payloads and a tailor-made linker chemistry

Abstract Inhibitors of kinesin spindle protein (KSP/Eg5) have raised great interest because of their high antitumor potency which, however, could not be transferred into highly efficient clinical regimens due to dose limiting side effects such as neutropenia. We have developed a new, highly potent pyrrole subclass of KSPis as a novel payload class in ADCs. To increase the therapeutic window, a tailor-made effector chemistry has been designed. The tumor associated protease legumain (LGMN) is utilized for ADC cleavage to provide active metabolites with high and long-lasting exposure in tumors, thus matching the KSPi mode of action. LGMN is a lysosomal asparaginyl endopeptidase overexpressed in solid tumors which is associated with invasion, metastasis and poor survival. In our studies, we show an efficient LGMN mediated linker cleavage and payload release from different ADCs. In addition, the unique LGMN substrate sequence allows for high cleavage specificity and discrimination versus other proteases such as elastase, which has been associated with an undesired extracellular cleavage of e.g. vc-MMAE ADCs resulting in neutropenia. Variations of the linker chemistry were performed to retain high potency of the KSPi-ADCs against tumor cells while decreasing the activation of KSPi-ADCs in cells of healthy organs such as the liver. From this approach, highly potent KSPi-ADCs with improved tumor/organ ratios of active metabolites were obtained. In conclusion, ADC metabolism under legumain control is a versatile strategy to provide KSPi-ADCs with high potency and an improved safety profile. Citation Format: Hans-Georg Lerchen, Beatrix Stelte-Ludwig, Anette Sommer, Sandra Berndt, Anne-Sophie Rebstock, Sarah Johannes, Leo Marx, Christoph Mahlert, Simone Greven, Lisa Dietz, Hannah Joerissen, Hilmar Weinmann. KSPi-ADCs: ADCs with novel kinesin spindle protein inhibitor payloads and a tailor-made linker chemistry [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 228.

Rigorous Free Energy Perturbation Approach to Estimating Relative Binding Affinities between Ligands with Multiple Protonation and Tautomeric States.

Accurate prediction of ligand binding affinities is of key importance in small molecule lead optimization and a central task in computational medicinal chemistry. Over the years, advances in both computer hardware and computational methodologies have established free energy perturbation (FEP) methods as among the most reliable and rigorous approaches to compute protein-ligand binding free energies. However, accurate description of ionization and tautomerism of ligands is still a major challenge in structure-based prediction of binding affinities. Druglike molecules are often weak acid or bases with multiple accessible protonation and tautomeric states that can contribute significantly to the binding process. To address this issue, we introduce in this work the p Ka and tautomeric state correction approach. This approach is based on free energy perturbation formalism and provides a rigorous treatment of the ionization and tautomeric equilibria of ligands in solution and in the protein complexes. A series of Kinesin Spindle Protein (KSP) and Factor Xa inhibitor molecules were used as test cases. Our results demonstrate that the p Ka and tautomeric state correction approach is able to rigorously and accurately incorporate multiple protonation and tautomeric states in the binding affinity calculations.

Antibody-Drug Conjugates with Pyrrole-Based KSP Inhibitors as the Payload Class.

The number of cytotoxic payload classes successfully employed in antibody-drug conjugates (ADCs) is still rather limited. The identification of ADC payloads with a novel mode of action will increase therapeutic options and potentially increase the therapeutic window. Herein, we describe the utilization of kinesin spindle protein inhibitors (KSPi) as a novel payload class providing highly potent ADCs against different targets, for instance HER-2 or TWEAKR/Fn14. Aspects of technical optimization include the development of different linker attachment sites, the stabilization of ADC linkage to avoid payload deconjugation and finally, the tailor-made design of active metabolites with a long lasting intracellular exposure in the tumor matching the mode of action of KSP inhibition. These KSPi-ADCs are highly potent and selective in vitro and demonstrate in vivo efficacy in a broad panel of tumor models including complete regressions in a patient-derived urothelial cancer model.