Antibody and antibody fragments site-specific conjugation using new Q-tag substrate of bacterial transglutaminase

During the last few years Antibody-Drug Conjugates (ADCs) have become one of the most active and very promising therapeutic weapons. Lessons learned from the traditional chemical conjugations (via lysine or cysteine residues of the antibodies) and the clinical studies of the developed ADCs have recently paved the way to the improvement of the conjugation technologies. Use of site-specific conjugation is considered as the promising path for improving the design and development of homogeneous ADCs with controlled Drug-Antibody ratio (DAR). Moreover, some of these conjugations can be applied to antibody fragments such as Fab, scfv and VHH for which random and chemical conjugation showed significant limitations. In this study, we identified a novel small peptide substrate (Q-tag) with high affinity and specificity of bacterial transglutaminase which can be genetically fused to different formats of antibodies of interest for the development of enzymatic site-specific conjugation we named "CovIsolink" platform. We describe the synthesis of chemically defined drugs conjugation in which the site and stoichiometry of conjugation are controlled using a genetically encoded Q-tag peptide with specific amino acids which serves as a substrate of bacterial transglutaminase. This approach has enabled the generation of homogeneous conjugates with DAR 1,7 for full IgG and 0,8 drug ratio for Fab, scfv and VHH antibody fragments without the presence of significant amounts of unconjugated antibody and fragments. As a proof of concept, Q-tagged anti Her-2 (human IgG1 (Trastuzumab) and the corresponding fragments (Fab, scfv and VHH) were engineered and conjugated with different aminated-payloads. The corresponding Cov-ADCs were evaluated in series of in vitro and in vivo assays, demonstrating similar tumor cell killing potency as Trastuzumab emtansine (Kadcyla®) even with lower drug-to-antibody ratio (DAR).

Optimised methods (SDS/PAGE and LC-MS) reveal deamidation in all examined transglutaminase-mediated reactions

Transglutaminases (TGs) are a family of structurally and functionally related enzymes that catalyse calcium‐dependent post‐translational modifications of proteins through protein–protein crosslinking, amine incorporation, or deamidation. For many years deamidation mediated by TGs was considered to be a side reaction, but recently substrate‐specific deamidations have been reported. Here we describe an optimised SDS/PAGE assay for the easy and rapid monitoring of the TG reaction with small peptides. The relative proportion of deamidation to transamidation was evaluated by densitometric analysis and confirmed by nano‐liquid chromatography–nano‐electrospray ionisation MS. We further investigated the effect of reaction conditions on transamidation and deamidation of TG1, TG2 and blood coagulation factor XIII A‐subunit (FXIII‐A) enzymes using a panel of glutamine‐containing peptide substrates. The ratio of transamidation to deamidation was enhanced at high excess of the acyl‐acceptor substrate and increasing pH. In addition, it was influenced by peptide substrates as well. Whereas deamidation was favoured at low cadaverine concentrations and acidic pH, no significant effect of calcium was observed on the ratio of transamidation/deamidation. Under our experimental conditions, deamidation always occurred in vitro even at high excess of the acyl‐acceptor substrate, and the reaction outcome was shifted to deamidation at neutral pH. Our results provide clear evidence of the deamidation in the TG reaction, and may serve as an important approach for in vivo analysis of deamidation to better understand the role of TGs in biological events.

Abstract 752: CovisoLinK: New bacterial transglutaminase Q-Tag substrate for the development of site specific antibody-drug conjugates

CovIsoLink™ (Covalently Isopeptide crosslinking) relates to methods for enzymatic covalently coupling drugs and other compounds through transglutaminase site specific generated in the targeted proteins including, polypeptides, proteins and immunoglobulins (patent pending1). Transglutaminases (TGases) catalyze covalent cross- linking of specific glutamine residues to the primary amine of peptide-bound lysine residues or primary amines of other compounds such as polyamines2. Using an in house peptide library and the transglutaminase colorometric assay3, we identified several amino acid sequences that were recognized as glutamine donor substrates. The optimum peptide sequences were selected and we further confirmed that these sequences have improved affinity compared with the conventional small peptides Z-QG. In different experiments we engineered Fc-containing polypeptide at the C-terminal domain and showed that mTG incorporates with high efficiency several types of amine donors to the engineered antibodies. CovIsoLink™ is now used to develop new antibody drug conjugates (ADCs) since the major advantage of this method is to obtain a homogenous immunoconjugate with uniform stoichiometry. We developed and characterized different recombinant anti Her2 IgG1 Mab carrying optimized enzymatic substrates (tag) by genetic insertion in the coding sequence of MAb. We then evaluated the best linkers and conformation to incorporate different compounds through bacterial Transglutaminase (mTG) enzymatic reaction. We set up experimental conditions, production, purification, HPLC/MS analysis and control of the immunoreactivity of CovIsoLink™ Her2-ADC. Using mTG, we obtained site specific conjugation of different modified drugs with optimized linker on the anti Her2 IgG1 antibody. By HIC analysis, we validated a specific and reproducible DAR reaching DAR2 depending on drugs and experimental conditions. In vitro and In vivo characterization and dose response studies of CovIsolink-ADC specificity and reactivity are currently performed in Her2 positive models demonstrating an improved efficacy by comparison with Kadcyla (T-DM1).1) PCT/EP2014/0792278, 2) El Alaoui S et al, Int J Cancer, 1991; 3) Perez AM et al, Anal Biochem, 2009.

Citation Format: Eva Sivado, Vincent Thomas, Meddy El Alaoui, Anne-Catherine Jallas, Mike R. Dyson, John McCafferty, Said El Alaoui, Sandrine Valsesia-Wittmann. CovisoLinK: New bacterial transglutaminase Q-Tag substrate for the development of site specific antibody-drug conjugates [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 752.

A continuous spectrophotometric assay that distinguishes between phospholipase A1 and A2 activities

A new spectrophotometric assay was developed to measure, continuously and specifically, phospholipase A1 (PLA1) or phospholipase A2 (PLA2) activities using synthetic glycerophosphatidylcholines (PCs) containing α-eleostearic acid, either at the sn-1 position [1-α-eleostearoyl-2-octadecyl-rac-glycero-3-phosphocholine (EOPC)] or at the sn-2 position [1-octadecyl-2-α-eleostearoyl-rac-glycero-3-phosphocholine (OEPC)]. The substrates were coated onto the wells of microtiter plates. A nonhydrolyzable ether bond, with a non-UV-absorbing alkyl chain, was introduced at the other sn position to prevent acyl chain migration during lipolysis. Upon enzyme action, α-eleostearic acid is liberated and then solubilized into the micellar phase. The PLA1 or PLA2 activity was measured by the increase in absorbance at 272 nm due to the transition of α-eleostearic acid from the adsorbed to the soluble state. EOPC and OEPC differentiate, with excellent accuracy, between PLA1 and PLA2 activity. Lecitase(®), guinea pig pancreatic lipase-related protein 2 (known to be a PLA1 enzyme), bee venom PLA2, and porcine pancreatic PLA2 were all used to validate the assay. Compared with current assays used for continuously measuring PLA1 or PLA2 activities and/or their inhibitors, the development of this sensitive enzymatic method, using coated PC substrate analogs to natural lipids and based on the UV spectroscopic properties of α-eleostearic acid, is a significant improvement.

Glycoxidized HDL, HDL enriched with oxidized phospholipids and HDL from diabetic patients inhibit platelet function

CONTEXT

High-density lipoproteins (HDL) possess atheroprotective properties including anti-thrombotic and antioxidant effects. Very few studies relate to the functional effects of oxidized HDL on platelets in type 2 diabetes (T2D).

OBJECTIVE

The objective of our study was to investigate the effects of in vitro glycoxidized HDL and HDL from patients with T2D on platelet aggregation and arachidonic acid signaling cascade. At the same time, the contents of hydroxylated fatty acids were assessed in HDL.

RESULTS

Compared with control HDL, in vitro glycoxidized HDL had decreased proportions of linoleic (LA) and arachidonic (AA) acids in phospholipids and cholesteryl esters, and increased concentrations of hydroxy-octadecadienoic acids (9-HODE and 13-HODE) and 15-hydroxy-eicosatetraenoic acid (15-HETE), derived from LA and AA respectively, especially hydroxy derivatives esterified in phospholipids. Glycoxidized HDL dose-dependently decreased collagen-induced platelet aggregation by binding to scavenger receptor BI (SR-BI). Glycoxidized HDL prevented collagen-induced increased phosphorylation of platelet p38 MAPK and cytosolic phospholipase A2, as well as intracellular calcium mobilization. HDL enriched with oxidized phosphatidylcholine (PC), namely PC(16:0/13-HODE) dose-dependently inhibited platelet aggregation. Increased concentrations of 9-HODE, 13-HODE, and 15-HETE in phospholipids (2.1-, 2.1-, and 2.4-fold increase, respectively) were found in HDL from patients with T2D, and these HDL also inhibited platelet aggregation via SR-BI.

CONCLUSIONS

Our results suggest that in vitro glycoxidized HDL as well as HDL from patients with T2D inhibit platelet aggregation, and suggest that oxidized LA-containing phospholipids may contribute to the anti-aggregatory effects of glycoxidized HDL and HDL from patients with T2D.

Development of a high-throughput assay for measuring phospholipase A activity using synthetic 1,2-α-eleostearoyl-sn-glycero-3-phosphocholine coated on microtiter plates

To date, several sensitive methods, based on radiolabeled elements or sterically hindered fluorochrome groups, are usually employed to screen phospholipase A (PLA) activities. With the aim of developing a convenient, specific, sensitive, and continuous new ultraviolet (UV) spectrophotometric assay for PLA, we have synthesized a specific glycerophosphatidylcholine (PC) esterified at the sn-1 and sn-2 positions, with α-eleostearic acid (9Z, 11E, 13E-octadecatrienoic acid) purified from Aleurites fordii seed oil. The conjugated triene present in α-eleostearic acid constitutes an intrinsic chromophore and, consequently, confers the strong UV absorption properties of this free fatty acid as well as of the glycerophospholipids harboring it. This coated PC film cannot be desorbed by the various buffers used during PLA assays. Following the action of PLA at the oil-water interface, α-eleostearic acid is freed and desorbed from the film and then solubilized with β-cyclodextrin. The UV absorbance of the α-eleostearic acid is considerably enhanced due to the transformation from an adsorbed to a water-soluble state. The PLA activity can be measured continuously by recording the variations with time of the UV absorption spectra. The rate of lipolysis was monitored by measuring the increase of absorption at 272 nm, which was found to be linear with time and proportional to the amount of added PLA. This continuous high-throughput PLA assay could be used to screen new PLA and/or PLA inhibitors present in various biological samples.

[Heller's operation in the treatment of idiopathic megaesophagus. Apropos of 35 cases]

The authors report 35 cases of idiopathic megaoesophagus in adult. They underline its clinical latency, often the patients come belatedey the insist upon the interest of Heller's procedure giving the best functional results.