Abstract 4054: Development of a new site-specific sulfomaleimide rebridging platform for the generation of homogeneous, stable, potent and safe antibody drug conjugates

There are currently 5 antibody drug conjugates (ADC) on the market and over 80 other ADCs evaluated in the clinic. The major drawbacks of the commonly employed bioconjugation methods based on nucleophilic coupling to lysine and cysteine are the non-selectivity and the in vivo instability. These limitations may be overcome by using alternative bioconjugation chemistries. To avoid the need for antibody engineering, disulfide-bridging linkers have recently emerged for the generation of homogeneous and stable ADCs.

Here, we report a novel maleimide-based linker for site-selective bioconjugation of drugs via covalent re-bridging of reduced interchain disulfide bonds on native IgG1 antibodies. After optimization of the maleimide and linker parts, as well as of the coupling process, the sulfomaleimide re-bridging (SMR) platform was used to conjugate tubulin and DNA-targeting cytotoxic agents to model antibodies. Compared to conventional maleimide (MC)-ADCs, the SMR-ADCs were highly homogeneous by HIC-HPLC and LC-MS analysis, with DAR 4 species as the major product, and highly stable in vitro, with no deconjugation observed after incubation in different types of serum. Then, IGF-1R-targeting SMR-ADCs were synthesized with Auristatin and PNU-159682 derivatives and evaluated in in vitro and in vivo models. These ADCs exhibited potent cytotoxicity and anti-tumoral activity in 2+ and 3+ IGF-1R-expressing models at different doses (0.3 to 3 mg/kg) and schedules of administration (Q1W to Q3W, i.v.). Significant differences in in vivo efficacy were observed between SMR- and MC-ADCS constructed with Auristatin derivatives. While they were comparable in a 3+ xenograft model (MCF-7), complete regressions were indeed obtained in the 2+ CaOV3 and NCI-H2122 models after single injections of the Auristatin-based SMR-ADC, whereas the corresponding MC-ADC induced only partial responses in the same conditions. To compare their in vivo stability and tolerability, these ADCs were injected in mice at doses of 3-30 mg/kg (Q2W, i.v.). No mortality and clinical signs were observed. Body weight evolution was not affected whatever the treatment. From a histopathological perspective, no difference between both constructs could be highlighted at this point. Toxicokinetic analyses carried out from satellite animals demonstrated that there was no major difference between both ADCs and that animal exposure increased proportionally with the dose. Nevertheless, serum exposure to the payload was 2-to-7-fold higher for MC-ADC than for SMR-ADC.

Our results demonstrate that the SMR platform can be applied to native IgG1 antibodies, without antibody engineering, to yield highly homogeneous and stable ADCs via cysteine cross-linking. The resulting ADCs demonstrate a therapeutic index benefit compared to analogous conventional heterogeneous ADCs.

Citation Format: Jean-Francois Haeuw, Frederic Marion, Cyrille Dreyfus, Barbara Akla, Laurence Zanna, Marie-Claire Janin, Charlotte Beau-Larvor, Marion Millet, Martine Farrie, Alain Batton, Celine Thuilliez, Alain Beck, Sarah Cianferani, Thierry Clerc, Philippe Maillos, Nathalie Corvaia. Development of a new site-specific sulfomaleimide rebridging platform for the generation of homogeneous, stable, potent and safe antibody drug conjugates [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 4054.

Cerebrovascular β-amyloid deposition and associated microhemorrhages in a Tg2576 Alzheimer mouse model are reduced with a DHA-enriched diet

Cerebral amyloid angiopathy (CAA) is a major contributor to Alzheimer's disease (AD) pathogenesis. Like AD, CAA is often accompanied by marked inflammation, aggravating associated vasculopathies. No evidence-based prevention or treatment strategies are available. Here, we evaluate the possible beneficial effect of a diet enriched with docosahexaenoic acid (DHA), which is known to attenuate inflammation in CAA. Tg2576 mice, a transgenic model of AD/CAA, were fed a DHA-enriched diet starting at 2 mo of age and ending at 10, 14, or 18 mo of age. β-Amyloid (Aβ)-peptide deposition and bleeding were visualized by immunohistochemistry or histochemistry on coronal sections of the brain. DHA, arachidonic acid, and eicosanoid levels were measured by liquid chromatography/mass spectrometry or GC-MS. DHA-enriched diet throughout aging limits the accumulation of vascular Aβ peptide deposits as well as the likelihood of microhemorrhages. There is a strong correlation between systemic 12-hydroxyeicosatetraenoic acid (HETE) levels and the size of the area affected by both vascular amyloid deposits and hemorrhages. The lowest levels of 12-HETE, a lipid-derived proinflammatory product of 12-lipoxygenase (LOX), were found in DHA-fed mice. In vitro experiments performed on amyloid vascular smooth muscle cells showed that a 12-LOX inhibitor almost completely blocked the Aβ_1-40 peptide-induced apoptosis of these cells. This study yet again highlights the important role of inflammation in CAA pathogenesis and identifies potential new targets for preventive care.-Hur, J., Mateo, V., Amalric, N., Babiak, M., Béréziat, G., Kanony-Truc, C., Clerc, T., Blaise, R., Limon, I. Cerebrovascular β-amyloid deposition and associated microhemorrhages in a Tg2576 Alzheimer mouse model are reduced with a DHA-enriched diet.

V0162 a new long-acting bronchodilator for treatment of chronic obstructive lung diseases: preclinical and clinical results

Background

Long acting bronchodilators are the standard of care in the management of chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate the efficacy and safety of V0162, a novel anticholinergic agent with bronchodilator properties, in preclinical models and in patients with COPD.

Methods

Guinea pigs were used to evaluate the impact of V0162 on the acetylcholine or histamine-induced bronchoconstriction. V0162 was also investigated in an allergic asthma model on ovalbumin-sensitized guinea pig. For clinical investigations, healthy volunteers were included in a dose-escalation, randomized, placebo-controlled phase I study to determine the maximal tolerated dose, followed by a randomized, placebo-controlled, cross-over phase II study in patients with COPD. V0162 was given via inhalation route. The objectives of the phase I/II study were to assess the safety and efficacy of V0162, in terms of bronchodilation and reduction in hyperinflation.

Results

Preclinical results showed that V0162 was able to prevent bronchoconstriction induced either by acetylcholine or histamine. V0162 reversed the bronchoconstriction and airway inflammation caused by ovalbumin challenge in sensitized guinea pigs. In the healthy volunteers study, 88 subjects were enrolled: 66 received V0162 and 22 received placebo. No particular safety concerns were raised. The maximal tolerated dose was not reached and the dose escalation was stopped at 2400 μg. A total of 20 patients with COPD were then enrolled. All patients received a single-dose of V0162 1600 μg and of placebo in two alternating periods. In COPD patients, V0162 demonstrated a significant increase in FEV₁ compared with placebo (148 ± 137 ml vs. 36 ± 151 ml, p = 0.003). This bronchodilatory effect was corroborated by a reduction in hyperinflation. There was a trend toward dyspnea relief (change in visual analog scale at 22 h, −15.1 ± 26.0 mm vs.- 5.3 ± 28.8 mm with placebo, p = 0.054). No serious adverse events (AEs) were reported. Most common AEs were productive and non-productive cough, dyspnea and pruritus.

Conclusions

V0162 improved pulmonary function and tended to improve dyspnea in patients with COPD over more than 24 h. The slight plasmatic exposure observed might support the good safety profile.

Trial registration

ClinicalTrials.gov identifier: NCT01348555

In vitro and in vivo methotrexate disposition in alveolar macrophages: comparison of pharmacokinetic parameters of two formulations

MTX-liposomes, prepared with a polymerised core (LSP), were administered in anaesthetised rats by pulmonary instillation versus free drug. No toxicological effects were macroscopically observed. After each time point: 15, 30, 60 and 90 min, animals were humanely killed and analyses of radio-signal were done. This approach allowed recovery of MTX or breakdown products within biological samples. Previously, kinetics of MTX cellular uptake was performed to identify the cytotoxic concentration of drug formulation for human macrophage. Flow cytometry was set-up to characterise liposomal uptake by ex vivo pulmonary macrophage. Cells were isolated by bronchioloalveolar washes from animals. Results have shown clear different pharmacokinetic parameters between free MTX and the liposomal form of MTX. Unlike classical liposomes, which are mainly taken up by the reticulo-endothelial system, LSP-MTX was not targeted to spleen or kidney. The route of administration could be an explanation of this phenomenon. In addition, LSP-MTX was more retained by the lung tissue. Moreover, free form of the drug reaches easily lymph node. This latest result should be taken into consideration for neoplasic disease and more specifically when lymph nodes are a way for pulmonary metastasis. Finally, LSP-MTX should be tested in physio-pathological model of lung cancer to evaluate the influence of the variation of liposomal formulation pharmacokinetic parameters on the drug efficacy.

Colloidal anticancer drugs bioavailabilities in oral administration models

Liposomes have been prepared with a polymerised core. Drug release and gastrointestinal (GI) degradation of liposomes with this polymerised core was slightly less important than those of classical liposomes. Vincristine, 5-fluorouracil (5-FU), and methotrexate (MTX) have been incorporated into the liposomes, and studies carried out using the differentiated cell lines Caco-2 and TC7, and with 150 histologically normal sections of human colon. Encapsulation of the drugs in liposomes had variable effects, depending on the test system and the drug used. For 5-FU and MTX calculated to be in a therapeutic range, liposomal formulation enhanced drug permeation, but not for the other drugs tested. In the excised human colon model, the treatment history of the patients can affect bioavailability: pre-operative radiation increased the drug tissue uptake. Transmucosal transport of ions was modified by prior chemotherapy. These results should be taken into account in the design of oral anticancer treatments both at the level of nutritional and pharmacological considerations.

Synthesis of new covalently bound kappa-carrageenan-AZT conjugates with improved anti-HIV activities

This paper describes the first covalent synthesis of kappa-carrageenan-3'-azido-3'-deoxythymidine (AZT) conjugates. A succinate diester spacer was used to covalently couple AZT onto kappa-carrageenan, resulting in a tripartite prodrug. Two methods (UV and radioactive counting) are described and validated to determine the AZT loading onto the kappa-carrageenan carrier. This polymeric carrier, through its own intrinsic anti-HIV activity, is expected to act not only as a drug delivery agent but also as an anti-HIV agent. Synergism between the two drugs (kappa-carrageenan and AZT) was demonstrated when MT-4 cells were preincubated with the kappa-carrageenan-AZT conjugate prior to HIV-1-infection. A threshold of AZT loaded onto the kappa-carrageenan was required to achieve this synergistic effect. Such kappa-carrageenan-AZT conjugates could be of great therapeutic interest because these conjugates, which contain a low AZT concentration, present improved anti-HIV activities relative to free AZT. Moreover, kappa-carrageenan is a well-tolerated biopolymer, already used in the food industry.

New 3'-azido-3'-deoxythymidin-5'-yl O-(4-hydroxyalkyl or -alkenyl or -alkylepoxide) carbonate prodrugs: synthesis and anti-HIV evaluation

New 5'-O-carbonate prodrugs of zidovudine (AZT) have been synthesized in order to enhance its uptake by HIV-1 infected cells, to improve its anti-HIV potency, and to optimize the intramolecular cyclic rearrangement process related to the 5'-O-(4-hydroxybutyl) carbonate moiety. Evidence of this prodrug rearrangement was confirmed by comparison of the serum half-lives of the 3'-azido-3'-deoxythymidin-5'-yl O-(4-hydroxyalkyl or -alkenyl or -alkylepoxide) carbonate prodrugs with our thermodynamic predictions. Interestingly, these 5'-O-carbonate prodrug series show increased anti-HIV potencies in conjunction with, or without, reduced cytotoxicity as compared to AZT that lead to a gain in selectivity indexes. The cytotoxicity of AZT could be reduced with these 5'-O-carbonate prodrug series by delaying the 5'-O-glucuronidation of AZT, which is one of the major limitations of AZT.

New 3'-azido-3'-deoxythymidin-5'-yl O-(omega-hydroxyalkyl) carbonate prodrugs: synthesis and anti-HIV evaluation

Prodrugs of zidovudine (AZT) have been synthesized in an effort to enhance its uptake by HIV-1 infected cells and its anti-HIV activity. The 5'-OH function of AZT was functionalized with various enzymatically labile alkyl groups using specific procedures. The prodrug moieties included 5'-O-carbonate, 5'-O-carbamate, and 5'-O-ester. Analogues of the 3'-azido-3'-deoxythymidin-5'-yl O-(omega-hydroxyalkyl) carbonate series were particularly interesting since they were rearranged through an intramolecular cyclic process during their enzymatic hydrolysis. Evidence of this prodrug rearrangement was confirmed by comparison of the serum half-lives of 5'-O-carbonate prodrugs with their corresponding 5'-O-ester- and 5'-O-carbamate-AZT prodrugs. Interestingly, the anti-HIV-1 activities (EC(50)) of 3'-azido-3'-deoxythymidin-5'-yl O-(4-hydroxybutyl) carbonate 10 in acutely infected MT-4 cells and in peripheral blood mononuclear cells (PBMCs) were 0.5 nM and 0.78 nM, respectively. Compound 10 was 30 to 50 times more potent than its parent drug AZT. Our results suggest that the specific intramolecular rearrangement associated with the 3'-azido-3'-deoxythymidin-5'-yl O-(omega-hydroxyalkyl) carbonate prodrugs could explain the remarkable anti-HIV-1 activity of this series of AZT prodrugs. Prodrug 10 may therefore have better clinical potential than AZT for the treatment of AIDS.

Effects of dexamethasone and linoleic acid on hepatic secretion of biliary lipids and anionic polypeptide factor: In vivo and in vitro studies

Synthetic glucocorticoids, such as dexamethasone, and diets enriched with unsaturated fatty acids have been shown to stimulate hepatic bile salt synthesis. This fact led us to investigate the effects of dexamethasone and linoleic acid supplementation on bile secretion. Cholesterol (Ch) and phospholipid secretions are bile acid dependent. Ch and phospholipid in bile are also highly bound to a small apoprotein, the anionic polypeptide factor (APF). In bile, APF may play a physiological role in stabilizing cholesterol:phospholipid vesicles and might also be important in the regulatory process of bile lipid secretion. In order to study the factors influencing bile secretion, the biliary secretion rates of bile lipids and APF were experimentally modulated in perfused rat liver (PRL) and HepG2 cells. As expected, dexamethasone induced an increase in the biliary secretion rate of bile salts (BS) in the two models (PRL: 34 up to 67 nmol/l/min/g liver; HepG2 cells: 234% vs. 100% in controls). The bile secretion rates for phospholipids (PRL: from 5 down to 1.5 nmol/l/min/g liver; HepG2 cells: 93 vs. 100% in controls) and APF (PRL: from 0.34 down to 0.12 microg/l/min/g liver; cells: 86 vs. 100% in controls) rapidly decreased independently from those of BS. The data from experimental cell models supplemented with linoleic acid indicated a correlation between the BS and APF levels (APF: 71 and 63%; BS: 161 and 197% vs. 100% in controls). The phospholipid level was regulated independently from that of APF and BS and increased (106 and 111% vs. 100% in controls), while Ch remained nevertheless unchanged. Our data showed that dexamethasone induced changes in bile and that linoleic acid clearly impaired the regulation exerted by the dexamethasone on bile lipids.

Differences in hypolipidaemic effects of two statins on Hep G2 cells or human hepatocytes in primary culture

1. The objective of this study was to compare in cultured human hepatocytes or Hep G2 cells, changes in the fate of unesterified low density lipoprotein (LDL)-cholesterol induced by crilvastatin, a new cholesterol lowering drug and a reference statin, simvastatin. 2. The experiments were carried out for 20 h, each well contained 4.2 x 10(5)/cm2 Hep G2 cells or 0.5 x 10(5)/Cm2 human hepatocytes, 130 microM ursodeoxycholate, 0.68 microCi or 1.59 microCi unesterified human [14C]-LDL-cholesterol, crilvastatin or simvastatin at 0 or 50 microM (both cell types) or 300 microM (Hep-G2 cells). Incubation with the two drugs resulted in increased amounts of unesterified [14C]-LDL-cholesterol taken by the two cell types, compared to control. 3. Crilvastatin 50 microM led to significantly higher quantities of [14C]-glyco-tauro-conjugated bile salts, compared to simvastatin. Statins reduced the apo B100 level secreted by the two cell types (simvastatin) or human hepatocytes (crilvastatin). Crilvastatin enhanced both the level of apo A1 secreted by the Hep G2 cells and the level of APF, a high density lipoprotein (HDL) and biliary apoprotein. 4. Crilvastatin not only acts by stimulating LDL-cholesterol uptake by hepatocytes, but also by enhancing the catabolism of LDL-cholesterol in bile salts and probably by stimulating HDL and/or bile component secretion. Such a mechanism was not previously described for HMG CoA reductase inhibitors. Our results on APF show that this apoprotein could be considered also as an indicator of changes in bile and/or HDL compartments. 5. The human hepatocyte model appeared to be a suitable and relevant model in the pharmacological-metabolic experiments carried out in this study. It led to more consistent data than those obtained with Hep G2 cells.

Activation of thick targets by energetic heavy ions and the resultant radiation levels

This study completes data collected for thick targets exposed to carbon and oxygen ions accelerated at 86 MeV/u. The radioactivity induced in carbon and tungsten targets bombarded by argon projectiles at 95 MeV/u has been studied in order to assess the relative contributions of the incoming heavy ion and the mass number of the bombarded nuclei to the consequent radiation hazards related to the production of radioactive ion beams. Induced radioactivity measurements are only rarely made under controlled irradiation conditions, in order to derive from the measured activities the dose rates after beam bombardment and a prediction of radiation protection constraints.

Effect of crilvastatin, a new cholesterol lowering agent, on unesterified LDL-cholesterol metabolism into bile salts by rat isolated hepatocytes

1. The aim of these experiments was to determine the effect of crilvastatin, a new cholesterol lowering agent, on the metabolism of unesterified low density lipoprotein (LDL)-cholesterol by rat freshly isolated hepatocytes. This preclinical model was developed as an alternative to in vivo experiments, to mimic the metabolic effects of a molecule on its target cells and to define optimal conditions for future experimentation on human hepatocytes. 2. Cells were obtained from normolipidaemic or hypercholesterolaemic rats, hypercholesterolaemia was nutritionally induced. Incubations were performed in a medium containing 600 microM taurocholate and 50 microM or 300 microM crilvastatin. 3. This molecule was shown in vitro to be carried by physiological transporters, i.e., albumin-bile salt micellar associations and LDL. Crilvastatin induced a significance increase in the synthesis and secretion by hepatocytes of bile salts resulting from the metabolism of unesterified LDL-cholesterol in both normolipidaemic and hypercholesterolaemic rats. Stimulation involved non-conjugated as well as tauro- and glyco-conjugated bile salts. These findings corroborate preliminary studies showing in vivo that crilvastatin enhances the secretion of bile acids by stimulating the uptake and incorporation of LDL-cholesterol by the liver.

Bile salt secretion by hepatocytes incubated with bile salts and liposomes or low density lipoproteins

The purpose of this work was to determine the effect of exogenous unesterified cholesterol provided in either artificial liposomes or LDL on bile salt synthesis by isolated rat hepatocytes. Rates of de novo synthesis were determined in the presence of 300 or 600 microM taurocholate, 600 microM taurodehydrocholate, cholate, deoxycholate or chenodeoxycholate. There was no significant difference between the cholesterol uptake by hepatocytes when the degree of hydrophobicity of the bile salts changed (cholate vs deoxycholate or chenodeoxycholate). Compared to taurocholate, taurodehydrocholate lowered the hepatic incorporation of unesterified cholesterol for the first 60 minutes; compared to control, taurocholate stimulated the cholesterol incorporation for the first 20 minutes. A possible explanation for this finding would be an interaction between bile salts and exogenous cholesterol, depending on the kind of conjugated bile salt. Taurocholate increased the exchange of cholesterol between liposomes or LDL and hepatocyte membranes. It resulted in a significant increase of bile salt synthesis and secretion. This phenomenon was not observed with taurodehydrocholate.

Importance of high-density lipoprotein-phosphatidylcholine in secretion of phospholipid and cholesterol in bile

The purpose of this work was to evaluate biliary phosphatidylcholine (PC) secretion after intravenous infusion of high density lipoprotein (HDL)-[3H]phosphatidylcholine (HDL-[3H]PC) in rats and to study the effect of infusion of dehydrocholic and cholic acids, which, respectively, inhibit and stimulate biliary secretion of PC. The data obtained in this study showed that, in the basal state, HDL-PC accounted for 38% of biliary PC. Dehydrocholic acid infusion caused only a "residual" secretion of HDL-PC in the bile; however, cholic acid infusion stimulated the secretion of HDL-PC as well as PC from intrahepatic microsomes. The low level of radioactivity of HDL-PC in intrahepatic compartments suggests that HDL-PC taken up by the liver is predestined for the bile secretion. The correlation between the kinetics of bile secretion of HDL-cholesterol and HDL-[3H]PC suggests the importance of HDL-PC in reverse transport of cholesterol to the liver and its transport to the bile. The differences between the effects of dehydrocholic acid and cholic acid infusions can be explained by the differences in bile salts binding to the surface of HDL.

Mechanisms of action in the liver of crilvastatin, a new hydroxymethylglutaryl-coenzyme A reductase inhibitor

Crilvastatin is a drug from the pyrrolidone family that had been shown to induce non-competitive inhibition of rat hydroxymethylglutaryl-coenzyme A reductase activity in vitro. The aim of this study was to evaluate the activity of crilvastatin on the hepatic metabolism of cholesterol in rats. Crilvastatin increased low density lipoprotein (LDL)-cholesterol uptake by the liver more than high density lipoprotein (HDL) uptake, thus increasing by up 30% the clearance of excess plasma cholesterol. In normolipidemic rats, crilvastatin significantly enhanced acyl coenzyme A:cholesterol acyl transferase and cholesterol 7 alpha-hydroxylase activity. In rats with a previous high cholesterolemia, crilvastatin also enhanced cholesterol 7 alpha-hydroxylase activity and did not increase liver acyl coenzyme A:cholesterol acyl transferase activity. These findings suggest that a drug such as crilvastatin could have a hypocholesterolemic effect by a mechanism other than the sole inhibition of cholesterol synthesis, possibly by stimulating cholesterol and bile salt secretion via the biliary tract in previously hypercholesterolemic rats.