Incorporation of Hydrophilic Macrocycles Into Drug-Linker Reagents Produces Antibody-Drug Conjugates With Enhanced in vivo Performance.

Antibody-drug conjugates (ADCs) have begun to fulfil their promise as targeted cancer therapeutics with ten clinical approvals to date. As the field matures, much attention has focused upon the key factors required to produce safe and efficacious ADCs. Recently the role that linker-payload reagent design has on the properties of ADCs has been highlighted as an important consideration for developers. We have investigated the effect of incorporating hydrophilic macrocycles into reagent structures on the in vitro and in vivo behavior of ADCs. Bis-sulfone based disulfide rebridging reagents bearing Val-Cit-PABC-MMAE linker-payloads were synthesized with a panel of cyclodextrins and crown ethers integrated into their structures via a glutamic acid branching point. Brentuximab was selected as a model antibody and ten ADCs with a drug-to-antibody ratio (DAR) of 4 were prepared for biological evaluation. In vitro, the ADCs prepared showed broadly similar potency (range: 16-34 pM) and were comparable to Adcetris® (16 pM). In vivo, the cyclodextrin containing ADCs showed greater efficacy than Adcetris® and the most efficacious variant (incorporating a 3'-amino-α-cyclodextrin component) matched a 24-unit poly(ethylene glycol) (PEG) containing comparator. The ADCs bearing crown ethers also displayed enhanced in vivo efficacy compared to Adcetris®, the most active variant (containing a 1-aza-42-crown-14 macrocycle) was superior to an analogous ADC with a larger 24-unit PEG chain. In summary, we have demonstrated that hydrophilic macrocycles can be effectively incorporated into ADC reagent design and offer the potential for enhanced alternatives to established drug-linker architectures.

Targeted clearance of senescent cells using an antibody-drug conjugate against a specific membrane marker.

A wide range of diseases have been shown to be influenced by the accumulation of senescent cells, from fibrosis to diabetes, cancer, Alzheimer's and other age-related pathologies. Consistent with this, clearance of senescent cells can prolong healthspan and lifespan in in vivo models. This provided a rationale for developing a new class of drugs, called senolytics, designed to selectively eliminate senescent cells in human tissues. The senolytics tested so far lack specificity and have significant off-target effects, suggesting that a targeted approach could be more clinically relevant. Here, we propose to use an extracellular epitope of B2M, a recently identified membrane marker of senescence, as a target for the specific delivery of toxic drugs into senescent cells. We show that an antibody-drug conjugate (ADC) against B2M clears senescent cells by releasing duocarmycin into them, while an isotype control ADC was not toxic for these cells. This effect was dependent on p53 expression and therefore more evident in stress-induced senescence. Non-senescent cells were not affected by either antibody, confirming the specificity of the treatment. Our results provide a proof-of-principle assessment of a novel approach for the specific elimination of senescent cells using a second generation targeted senolytic against proteins of their surfaceome, which could have clinical applications in pathological ageing and associated diseases.

Stability of Maleimide-PEG and Mono-Sulfone-PEG Conjugation to a Novel Engineered Cysteine in the Human Hemoglobin Alpha Subunit.

In order to use a Hemoglobin Based Oxygen Carrier as an oxygen therapeutic or blood substitute, it is necessary to increase the size of the hemoglobin molecule to prevent rapid renal clearance. A common method uses maleimide PEGylation of sulfhydryls created by the reaction of 2-iminothiolane at surface lysines. However, this creates highly heterogenous mixtures of molecules. We recently engineered a hemoglobin with a single novel, reactive cysteine residue on the surface of the alpha subunit creating a single PEGylation site (ßCys93Ala/αAla19Cys). This enabled homogenous PEGylation by maleimide-PEG with >80% efficiency and no discernible effect on protein function. However, maleimide-PEG adducts are subject to deconjugation via retro-Michael reactions and cross-conjugation to endogenous thiol species in vivo. We therefore compared our maleimide-PEG adduct with one created using a mono-sulfone-PEG less susceptible to deconjugation. Mono-sulfone-PEG underwent reaction at αAla19Cys hemoglobin with > 80% efficiency, although some side reactions were observed at higher PEG:hemoglobin ratios; the adduct bound oxygen with similar affinity and cooperativity as wild type hemoglobin. When directly compared to maleimide-PEG, the mono-sulfone-PEG adduct was significantly more stable when incubated at 37°C for seven days in the presence of 1 mM reduced glutathione. Hemoglobin treated with mono-sulfone-PEG retained > 90% of its conjugation, whereas for maleimide-PEG < 70% of the maleimide-PEG conjugate remained intact. Although maleimide-PEGylation is certainly stable enough for acute therapeutic use as an oxygen therapeutic, for pharmaceuticals intended for longer vascular retention (weeks-months), reagents such as mono-sulfone-PEG may be more appropriate.

Engineering hemoglobin to enable homogenous PEGylation without modifying protein functionality.

In order to infuse hemoglobin into the vasculature as an oxygen therapeutic or blood substitute, it is necessary to increase the size of the molecule to enhance vascular retention. This aim can be achieved by PEGylation. However, using non-specific conjugation methods creates heterogenous mixtures and alters protein function. Site-specific PEGylation at the naturally reactive thiol on human hemoglobin (ßCys93) alters hemoglobin oxygen binding affinity and increases its autooxidation rate. In order to avoid this issue, new reactive thiol residues were therefore engineered at sites distant to the heme group and the α/ß dimer/dimer interface. The two mutants were ßCys93Ala/αAla19Cys and ßCys93Ala/ßAla13Cys. Gel electrophoresis, size exclusion chromatography and mass spectrometry revealed efficient PEGylation at both αAla19Cys and ßAla13Cys, with over 80% of the thiols PEGylated in the case of αAla19Cys. For both mutants there was no significant effect on the oxygen affinity or the cooperativity of oxygen binding. PEGylation at αAla19Cys had the additional benefit of decreasing the rates of autoxidation and heme release, properties that have been considered contributory factors to the adverse clinical side effects exhibited by previous hemoglobin based oxygen carriers. PEGylation at αAla19Cys may therefore be a useful component of future clinical products.

Targeting Thioredoxin System with an Organosulfur Compound, Diallyl Trisulfide (DATS), Attenuates Progression and Metastasis of Triple-Negative Breast Cancer (TNBC).

BACKGROUND/AIMS: Metastasis is the leading cause resulting in high mortality in triple negative breast cancer (TNBC) patients. Cancer cells are skilled at utilizing thioredoxin (Trx) system as an efficient antioxidant system to counteract oxidative damage, facilitating the occurrence of metastasis. Here, we identified an organosulfur compound named DATS isolated from garlic, that inhibits the expression of Trx-1 and the enzyme activity of Trx reductase in breast cancer cells. METHODS: Tissue microarray of breast cancer patients and immunohistochemical method were used to analyze the role of Trx-1 in breast cancer metastasis. Spotaneous metastasis model and experimental metastasis model combined with HE staining, immunohistochemistry were used to verify in vivo anti-metastatic effect of DATS as well as its regulation on thioredoxin. Western blot, immunofluorescence, redox state assessment and detection of enzyme activity were employed to determine the effect of DATS on thioredoxin system. Trx-1 siRNA interference was used to investigate the conclusive evidence that Trx-1 was the target of DATS. RESULTS: In agreement with reduced Trx-1 nuclear translocation from cytoplasm by DATS, the production of reduced form of Trx-1 was dramatically decreased. Furthermore, in vivo, DATS administration was observed to significantly suppress spontaneous and experimental metastasis in nude mice. Delivery of DATS also resulted in decreased expression of Trx-1 as the direct target, as well as expression of NF-κB and MMP2/9 in primary tumor and lung tissue. Notably, the effects of DATS on the expression of downstream metastasis-associated genes were mediated by Trx-1, as demonstrated by the combination use of DATS and Trx-1 siRNA. CONCLUSION: Collectively, this present study indicates that targeting Trx system with DATS may provide a promising strategy for treating metastasis of TNBC.

Suppressive role of diallyl trisulfide in the activated platelet-mediated hematogenous metastasis of MDA-MB-231 human breast cancer cells.

Accumulating evidence has indicated that garlic consumption may reduce the risk of developing several types of cancer, and extensive studies have revealed the effects of its bioactive component, diallyl trisulfide (DATS), on the proliferation and apoptosis of tumor cells. The present study was undertaken to examine whether DATS affects hematogenous metastasis. In view of the dynamic crosstalk interplayed by tumor cells and platelets in hematogenous metastasis, we attempted to demonstrate the role of DATS in the metastatic behavior of MDA-MB-231 human breast cancer cells, which were co-incubated with activated platelets. Indeed, our data indicated that DATS significantly blocked platelet activation and aggregation induced by platelet-activating factor (PAF), and decreased the production of thromboxane B2 (TXB2). It was also found that DATS suppressed the migration and invasion of MDA-MB-231 cells in the presence of platelets activated by PAF in vitro in a dose-dependent manner. Furthermore, our results revealed thaat the release of activated TGF-ß1 in the platelet-tumor cell system was markedly attenuated by DATS. Therefore, our findings strongly suggest that the diverse pharmacological activities of DATS are at least partially reflected by the interruption of the activated platelets-mediated metastasis of breast cancer cells.

Modulation of drug-linker design to enhance in vivo potency of homogeneous antibody-drug conjugates.

Antibody-drug conjugates (ADCs) are a promising class of anticancer agents which have undergone substantial development over the past decade and are now achieving clinical success. The development of novel site-specific conjugation technologies enables the systematic study of architectural features within the antibody conjugated drug linker that may affect overall therapeutic indices. Here we describe the results of a systematic study investigating the impact of drug-linker design on the in vivo properties of a series of homogeneous ADCs with a conserved site of conjugation, a monodisperse drug loading, a lysosomal release functionality and monomethyl auristatin E as a cytotoxic payload. The ADCs, which differed only in the relative position of certain drug-linker elements within the reagent, were first evaluated in vitro using anti-proliferation assays and in vivo using mouse pharmacokinetics (PK). Regardless of the position of a discrete polymer unit, the ADCs showed comparable in vitro potencies, but the in vivo PK properties varied widely. The best performing drug-linker design was further used to prepare ADCs with different drug loadings of 4, 6 and 8 drugs per antibody and compared to Adcetris® in a Karpas-299 mouse xenograft model. The most efficacious ADC showed complete tumor regression and 10/10 tumor free survivors at a single 0.5mg/kg dose. This study revealed drug-linker design as a critical parameter in ADC development, with the potential to enhance ADC in vivo potency for producing more efficacious ADCs.

Xanthatin anti-tumor cytotoxicity is mediated via glycogen synthase kinase-3ß and ß-catenin.

Xanthatin, a xanthanolide sesquiterpene lactone isolated from Xanthium strumarium L. (Asteraceae), has prominent anti-tumor activity. Initial mechanism of action studies suggested xanthatin triggered activation of Wnt/ß-catenin. We examined the effects of xanthatin on signaling pathways in A459 lung cancer cells and mouse embryonic fibroblasts to ascertain requirements for xanthatin-induced cell death and tumor growth in xenografts. Genetic inactivation of GSK-3ß, but not the related isoform GSK-3α, compromised xanthatin cytotoxicity while inactivation of ß-catenin enhanced xanthatin-mediated cell death. These data provide insight into how xanthatin and related molecules could be effectively targeted toward certain tumors.

Cryptotanshinone, a novel tumor angiogenesis inhibitor, destabilizes tumor necrosis factor-α mRNA via decreasing nuclear-cytoplasmic translocation of RNA-binding protein HuR.

Cryptotanshinone (CT), one major lipophilic component isolated from Salvia miltiorrhiza Bunge, has shown to possess chemopreventive properties against various types of cancer cells. In this study, CT was shown to be a potent anti-angiogenic agent in zebrafish, and mouse models and could limit tumor growth by inhibiting tumor angiogenesis. We further found that CT could inhibit the proliferation, migration, angiogenic sprouting, and tube formation of HUVECs. In addition, we demonstrated that CT could lower the level of TNF-α due to the destabilization of TNF-α mRNA, which associated with regulating 3'-untranslated region (3'-UTR) of TNF-α and preventing the translocation of RNA binding protein, HuR, from the nucleus to the cytoplasm. Moreover, the underlying mechanism responsible for the regulation in angiogenesis by CT was partially related to the suppression of NF-κB, and STAT3 activity. Based on the abilities of CT in targeting tumor cells, inhibiting angiogenesis, and destroying tumor vasculature, CT is worthy of further investigation for preventive, and therapeutic purposes in cancer. © 2015 Wiley Periodicals, Inc.

Paeonol inhibits B16F10 melanoma metastasis in vitro and in vivo via disrupting proinflammatory cytokines-mediated NF-κB and STAT3 pathways.

Cancer related inflammation (CRI) is now recognized as the seventh hallmark in the pathogenesis of many types of malignancies. Paeonol, a natural phenolic component isolated from the root bark of Paeonia moutan, has significant anti-inflammatory activity. Recently, accumulating body of research has revealed potent anti-tumor effects mediated by paeonol. However, little is known about its anticancer mechanism on the basis of CRI. In this study, we observed that paeonol exerted direct anticancer activity through inhibition of cell proliferation, induction of apoptosis, and evident anti-inflammatory effects by reducing proinflammatory cytokines secretion (TNF-α, IL-1ß, IL-6, and TGF-ß) in the conditioned medium of B16F10 mouse melanoma cells. Interestingly, we found that paeonol significantly reversed motility phenotypes in TNF-α- or IL-6-induced B16F10 singe cell and collective migration and invasion in vitro, which were related to affecting epithelial-to-mesenchymal transition (EMT) makers and MMPs expression. In particular, paeonol disrupted both TNF-α-activated NF-κB and IL-6-activated STAT3 signaling pathways in B16F10 cells. EMSA and luciferase assays showed that paeonol abrogated NF-κB binding and NF-κB-driven promoter activity in the presence of TNF-α. Finally, we showed that paeonol attenuated B16F10 spontaneous lung metastases in C57/BL6J mice with down-regulated levels of serum proinflammatory cytokines. Therefore, paeonol possessed antitumor activity in melanoma cells and mice model by interruption of the aggressive feedback through proinflammatory cytokines mediated NF-κB and STAT3 signaling activation. These findings provide a novel treatment strategy that paeonol might be a promising versatile adjuvant therapy for cancer related inflammation.

Antimetastatic Therapies of the Polysulfide Diallyl Trisulfide against Triple-Negative Breast Cancer (TNBC) via Suppressing MMP2/9 by Blocking NF-κB and ERK/MAPK Signaling Pathways.

BACKGROUND: Migration and invasion are two crucial steps of tumor metastasis. Blockage of these steps may be an effective strategy to reduce the risk. The objective of the present study was to investigate the effects of diallyl trisulfide (DATS), a natural organosulfuric compound with most sulfur atoms found in garlic, on migration and invasion in triple negative breast cancer (TNBC) cells. Molecular mechanisms underlying the anticancer effects of DATS were further investigated. METHODS AND RESULTS: MDA-MB-231 cells and HS 578t breast cancer cells were treated with different concentrations of DATS. DATS obviously suppressed the migration and invasion of two cell lines and changed the morphological. Moreover, DATS inhibited the mRNA/protein/ enzymes activities of MMP2/9 via attenuating the NF-κB pathway. DATS also inhibited ERK/MAPK rather than p38 and JNK. CONCLUSION: DATS inhibits MMP2/9 activity and the metastasis of TNBC cells, and emerges as a potential anti-cancer agent. The inhibitory effects are associated with down-regulation of the transcriptional activities of NF-κB and ERK/MAPK signaling pathways.

In Vitro and In Vivo Evaluation of Cysteine Rebridged Trastuzumab-MMAE Antibody Drug Conjugates with Defined Drug-to-Antibody Ratios.

The conjugation of monomethyl auristatin E (MMAE) to trastuzumab using a reduction bis-alkylation approach that is capable of rebridging reduced (native) antibody interchain disulfide bonds has been previously shown to produce a homogeneous and stable conjugate with a drug-to-antibody ratio (DAR) of 4 as the major product. Here, we further investigate the potency of the DAR 4 conjugates prepared by bis-alkylation by comparing to lower drug loaded variants to maleimide linker based conjugates possessing typical mixed DAR profiles. Serum stability, HER2 receptor binding, internalization, in vitro potency, and in vivo efficacy were all evaluated. Greater stability compared with maleimide conjugation was observed with no significant decrease in receptor/FcRn binding. A clear dose-response was obtained based on drug loading (DAR) with the DAR 4 conjugate showing the highest potency in vitro and a much higher efficacy in vivo compared with the lower DAR conjugates. Finally, the DAR 4 conjugate demonstrated superior efficacy compared to trastuzumab-DM1 (T-DM1, Kadcyla), as evaluated in a low HER2 expressing JIMT-1 xenograft model.

Phenolcarboxylic acids from medicinal herbs exert anticancer effects through disruption of COX-2 activity.

Integrated research of herbs and formulas characterized by functions of promoting blood circulation and removing blood stasis is one of the most active fields in traditional Chinese medicine. This paper strives to demonstrate the roles of a homologous series of phenolcarboxylic acids from these medicinal herbs in cancer treatment via targeting cyclooxygenase-2 (COX-2), a well-recognized mediator in tumorigenesis. We selected thirteen typical phenolcarboxylic acids (benzoic acid derivatives, cinnamic acid derivatives and their dehydration-condensation products), and found gallic acid, caffeic acid, danshensu, rosmarinic acid and salvianolic acid B showed 50% inhibitory effects on hCOX-2 activity and A549 cells proliferation. 2D-quantitative method was introduced to describe the potential structural features that contributed to certain bioactivities. We also found these compounds underwent responsible hydrogen bonding to Arg120 and Ser353 in COX-2 active site residues. We further extensively focused on danshensu [d-(+)-ß-(3,4-dihydoxy-phenylalanine)] or DSS, which exerted COX-2 dependent anticancer manner. Both genetic and pharmacological inhibition of COX-2 could enhance the ability of DSS inhibiting A549 cells growth. Additionally, COX-2/PGE2/ERK signaling axis was essential for the anticancer effect of DSS. Furthermore, combined treatment with DSS and celecoxib could produce stronger anticancer effects in experimental lung metastasis of A549 cells in vivo. All these findings indicated that phenolcarboxylic acids might possess anticancer effects through jointly targeting COX-2 activity in cancer cells and provided strong evidence in cancer prevention and therapy for the herbs characterized by blood-activating and stasis-resolving functions in clinic.

Bridging disulfides for stable and defined antibody drug conjugates.

To improve both the homogeneity and the stability of ADCs, we have developed site-specific drug-conjugating reagents that covalently rebridge reduced disulfide bonds. The new reagents comprise a drug, a linker, and a bis-reactive conjugating moiety that is capable of undergoing reaction with both sulfur atoms derived from a reduced disulfide bond in antibodies and antibody fragments. A disulfide rebridging reagent comprising monomethyl auristatin E (MMAE) was prepared and conjugated to trastuzumab (TRA). A 78% conversion of antibody to ADC with a drug to antibody ratio (DAR) of 4 was achieved with no unconjugated antibody remaining. The MMAE rebridging reagent was also conjugated to the interchain disulfide of a Fab derived from proteolytic digestion of TRA, to give a homogeneous single drug conjugated product. The resulting conjugates retained antigen-binding, were stable in serum, and demonstrated potent and antigen-selective cell killing in in vitro and in vivo cancer models. Disulfide rebridging conjugation is a general approach to prepare stable ADCs, which does not require the antibody to be recombinantly re-engineered for site-specific conjugation.

Concerted suppression of STAT3 and GSK3ß is involved in growth inhibition of non-small cell lung cancer by Xanthatin.

Xanthatin, a sesquiterpene lactone purified from Xanthium strumarium L., possesses prominent anticancer activity. We found that disruption of GSK3ß activity was essential for xanthatin to exert its anticancer properties in non-small cell lung cancer (NSCLC), concurrent with preferable suppression of constitutive activation of STAT3. Interestingly, inactivation of the two signals are two mutually exclusive events in xanthatin-induced cell death. Moreover, we surprisingly found that exposure of xanthatin failed to trigger the presumable side effect of canonical Wnt/ß-Catenin followed by GSK3ß inactivation. We further observed that the downregulation of STAT3 was required for xanthatin to fine-tune the risk. Thus, the discovery of xanthatin, which has ability to simultaneously orchestrate two independent signaling cascades, may have important implications for screening promising drugs in cancer therapies.