Therapeutic Potential of MF-TTZ-MMAE, a Site-Specifically Conjugated Antibody-Drug Conjugate, for the Treatment of HER2-Overexpressing Breast Cancer.

With three clinically approved antibody-drug conjugates targeting HER2, this target is clearly identified to be of interest in oncology. Moreover, the advent of new bioconjugation technologies producing site-specific homogenous conjugates led to the opportunity of developing new medicines linking antibodies and payloads. Here, a new relevant HER2-targeting ADC was obtained by the conjugation of monomethyl auristatin E onto trastuzumab using McSAF Inside bioconjugation technology. The antibody-drug conjugate formed presented an average drug-to-antibody ratio of 4 with a high homogeneity and an excellent stability especially when incubated with human serum albumin or in human plasma. Moreover, it demonstrated a strong efficacy in an HER2 xenograft tumor model in mice, superior to the clinically approved antibody-drug conjugate ado-trastuzumab emtansine, with a complete tumor regression observed both macroscopically and microscopically demonstrating its therapeutic potential.

Innovative Bioconjugation Technology for Antibody-Drug Conjugates: Proof of Concept in a CD30-Positive Lymphoma Mouse Model.

To overcome stability and heterogeneity issues of antibody-drug conjugates (ADCs) produced with existing bioconjugation technologies incorporating a maleimide motif, we developed McSAF Inside, a new technology based on a trifunctionalized di(bromomethyl)pyridine scaffold. Our solution allows the conjugation of a linker-payload to previously reduced interchain cysteines of a native antibody, resulting in disulfide rebridging. This leads to highly stable and homogeneous ADCs with control over the drug-to-antibody ratio (DAR) and the linker-payload position. Using our technology, we synthesized an ADC, MF-BTX-MMAE, built from anti-CD30 antibody cAC10 (brentuximab), and compared it to Adcetris, the first line treatment against CD30-positive lymphoma, in a CD30-positive lymphoma model. MF-BTX-MMAE displayed improved DAR homogeneity, with a solid batch-to-batch reproducibility, as well as enhanced stability in thermal stress conditions or in the presence of a free thiol-containing protein, such as human serum albumin (HSA). MF-BTX-MMAE showed antigen-binding, in vitro cytotoxicity, in vivo efficacy, and tolerability similar to Adcetris. Therefore, in accordance with current regulatory expectations for the development of new ADCs, McSAF Inside technology gives access to relevant ADCs with improved characteristics and stability.

Cytotoxicity of the Urokinase-Plasminogen Activator Inhibitor Carbamimidothioic Acid (4-Boronophenyl) Methyl Ester Hydrobromide (BC-11) on Triple-Negative MDA-MB231 Breast Cancer Cells.

BC-11 is an easily synthesized simple thiouronium-substituted phenylboronic acid, which has been shown to be cytotoxic on triple negative MDA-MB231 breast cancer cells by inducing a perturbation of cell cycle when administered at a concentration equal to its ED50 at 72 h (117 µM). Exposure of cells to BC-11, either pre-absorbed with a soluble preparation of the N-terminal fragment of urokinase-plasminogen activator (uPa), or in co-treatment with two different EGFR inhibitors, indicated that: (i) BC-11 acts via binding to the N-terminus of the enzyme where uPa- and EGF receptor-recognizing sites are present, thereby abrogating the growth-sustaining effect resulting from receptor binding; and (ii) the co-presence of the EGFR inhibitor PD153035 potentiates BC-11's cytotoxicity. Exposure of cells to a higher concentration of BC-11 corresponding to its ED75 at 72 h (250 µM) caused additional impairment of mitochondrial activity, the production of reactive oxygen species and promotion of apoptosis. Therefore, BC-11 treatment appears to show potential for the development of this class of compounds in the prevention and/or therapy of "aggressive" breast carcinoma.

Impact of Maleimide Disubstitution on Chemical and Biological Characteristics of HER2 Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) are the spearhead of targeted therapies. According to the technology used, the conjugation of a cytotoxic drug to an antibody can produce suboptimal heterogeneous species, impacting the overall efficacy. Herein, we describe the synthesis of HER2-targeting ADCs with three disulfide rebridging heads, allowing homogeneous and site-specific bioconjugation: dibromomaleimide (DBM), dithiomaleimide (DTM), and hybrid thio-bromomaleimide (TBM) chemical bricks to combine the properties of both previously used heads. The primary purpose of this study was to compare the reactivity of these three chemical bricks in the bioconjugation process. Then, the resulting ADCs were evaluated in terms of physicochemical stability, binding, and biological activity. We have demonstrated that the higher percentage of a drug-to-antibody ratio of 4 was obtained with TBM. Additionally, the reaction time was drastically reduced with TBM in comparison to DTM. The three ADCs showed good binding to HER2 and in vitro cytotoxicity, which validate the TBM structure as an attractive alternative scaffold for rebridging bioconjugation.

Synthesis, biological evaluation and molecular modeling of a novel series of 7-azaindole based tri-heterocyclic compounds as potent CDK2/Cyclin E inhibitors.

From four molecules, inspired by the structural features of fascaplysin, with an interesting potential to inhibit cyclin-dependent kinases (CDKs), we designed a new series of tri-heterocyclic derivatives based on 1H-pyrrolo[2,3-b]pyridine (7-azaindole) and triazole heterocycles. Using a Huisgen type [3 + 2] cycloaddition as the convergent key step, 24 derivatives were synthesized and their biological activities were evaluated. Comparative molecular field analysis (CoMFA), based on three-dimensional quantitative structure-activity relationship (3D-QSAR) studies, was conducted on a series of 30 compounds from the literature with high to low known inhibitory activity towards CDK2/cyclin E and was validated by a test set of 5 compounds giving satisfactory predictive r(2) value of 0.92. Remarkably, it also gave a good prediction of pIC50 for our tri-heterocyclic series which reinforce the validation of this model for the pIC50 prediction of external set compounds. The most promising compound, 43, showed a micro-molar range inhibitory activity against CDK2/cyclin E and also an antiproliferative and proapoptotic activity against a panel of cancer cell lines.

A synthetic, catalytic and theoretical investigation of an unsymmetrical SCN pincer palladacycle.

The SCN ligand 2-{3-[(methylsulfanyl)methyl]phenyl}pyridine, 1, has been synthesized starting from an initial Suzuki-Miyaura (SM) coupling between 3-((hydroxymethyl)phenyl)boronic acid and 2-bromopyridine. The C-H activation of 1 with in situ formed Pd(MeCN)4(BF4)2 has been studied and leads to a mixture of palladacycles, which were characterized by X-ray crystallography. The monomeric palladacycle LPdCl 6, where L-H = 1, has been synthesized, and tested in SM couplings of aryl bromides, where it showed moderate activity. Density functional theory and the atoms in molecules (AIM) method have been used to investigate the formation and bonding of 6, revealing a difference in the nature of the Pd-S and Pd-N bonds. It was found that S-coordination to the metal in the rate determining C-H bond activation step leads to better stabilization of the Pd(II) centre (by 13-28 kJ mol(-1)) than with N-coordination. This is attributed to the electron donating ability of the donor atoms determined by Bader charges. The AIM analysis also revealed that the Pd-N bonds are stronger than the Pd-S bonds influencing the stability of key intermediates in the palladacycle formation reaction pathway.

Microwave-mediated synthesis of an arylboronate library.

A series of arylboronates has been synthesized from the reaction of 2-(2-, (3-, or (4-(bromomethyl)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane 1{1-3} respectively with a range of N-, S-, and O-nucleophiles, using microwave-mediated chemistry. For the synthesis of N- and S-substituted boronates, a supported base, PS-NMM, was employed, and many reactions were complete within 15 min. With O-nucleophiles, a mixture of tetrabutylammonium bromide, potassium carbonate, and sodium hydroxide was employed. The resulting aminomethyl, mercaptomethyl, or alkoxy-/phenoxymethyl-arylboronates were subjected to microwave-mediated Suzuki Miyaura coupling reactions to afford a range of biaryls in moderate to good yields. The X-ray structures of five boronates were determined.