François Clerc

Identification of the main epitope on human cytochrome P450 IID6 recognized by anti-liver kidney microsome antibody.

Antibodies present in the sera of a group of children with autoimmune hepatitis react with human cytochrome P450 IID6. cDNA constructions of various fragments of human P450 IID6 were made and expressed and the resulting peptides were tested in immunoblot with patients sera. These allowed identification of at least two antigenic sites on the P450 molecule. The main one, recognized by all sera tested, is located between amino acids 239 and 271. Synthesis of three peptides covering this area of the molecule allowed identification of a sequence of three amino acids (tyrosine-tryptophane-asparagine) located at position 261-263 that constitutes the essential part of the epitope. A protein sequence data-base search revealed homologies between this region of human P450 and proteins from Salmonella typhimurium, from human T lymphotropic virus types 1 and 2 and Herpes simplex virus type 1.

Synthesis of azepane scaffolds on solid support for combinatorial chemistry

Abstract Enantiopure C 2 -symmetric azepanes have been synthesized on solid support as scaffolds for the synthesis of peptidomimetics in combinatorial chemistry. The key step involves Rink resin as a formal equivalent of ammonia in the nucleophilic opening of L-iditol bis-epoxide.

Primary structure control of recombinant proteins using high-performance liquid chromatography, mass spectrometry and microsequencing.

The conformity of two recombinant proteins (a von Willbrand factor fragment and human serum albumin, consisting of respectively 289 and 585 amino acids) has been examined by HPLC combined with mass spectrometry and microsequencing, on both intact material and fragment peptides obtained by proteolytic cleavage. These studies confirmed that the primary structure of the recombinant proteins corresponds to that predicted from their gene, particularly the integrity of their N and C termini, and, in the case of albumin, the agreement between the observed disulfide bond pattern and the published model. Furthermore, the structure of an albumin-related compound could be elucidated. Application of LC-MS for batch-to-batch quality control is also under discussion.

Local constrained shifty pseudopeptides inhibitors of rasfarnesyl transferase

Abstract Pseudopeptide analogues related to the C-terminal tetrapeptide of ras-protein (Cys-Val-X-Met) were synthesized and evaluated for inhibition of ras farnesyl transferase (FTase). We demonstrate that the introduction of a shifty amino acid related to Cys instead of Cys-Val and a tetrahydroisoquinoline carboxylic acid (TIC) instead of Phe lead to potent inhibitors of FTase on isolated enzyme or on cell based tests. One of the pseudopeptides, conceived as a prodrug, suppressed specifically the ability of ras transformed cells to form colonies in soft agar.

Synthesis and conformational analysis of peptide inhibitors of farnesyltransferase

Farnesylation of the ras oncogene product by Farnesyl Transferase (FTase) is known to be a critical step in cell transformation leading to uncontrolled proliferation. The peptide CysValTicMet is a potent FTase inhibitor, but its degradation by amino-peptidases and its only weak internalization into cells make it a bad candidate for a future cancer drug. We have prepared improved CysValTicMet analogues using several approaches: (i) amino terminal modifications or introduction of pseudopeptides or non-natural amino acids to increase proteolytic stability, (ii) introduction of hydrophobic aliphatic chains to increase cell internalization and metabolic stability and (iii) transformation into prodrugs. Additionally, we have carried out comparative conformational analysis studies by molecular dynamics of some of the here presented peptides and of our recently described peptidomimetic inhibitors of FTase.

Abstract LB-053: Towards new cryptophycins as promising payloads for ADC

Cryptophycins are a class of macrocyclic depsipeptides produced as secondary metabolites by cyanobacteria of the genus Nostoc and were found to bind to microtubules at the vinca site. The natural product C-1 isolated in 1990 and the synthetic derivative C-52 displayed potent in vitro and in vivo antitumor activity in preclinical models. Cryptophycin C-52 (LY355703) produced marginal antitumor activity at MTD in two phase II lung cancer trials and was therefore discontinued. Considering its higher potency versus other tubulin binders such as maytansine and auristatin, this chemical series was selected for an ADC approach. Several conjugates were evaluated in vitro and in vivo based on the conjugation of C52 derivatized at the para-benzylic position of the macrocycle. As described in this study, this optimization led to the discovery of cryptophycin ADC which displayed potent antitumor activity in vivo. However, these conjugates were found unstable in mice plasma while being stable in the plasma of non-rodent species. This species-dependent instability was shown to be the result of a mice plasmatic metabolization of C52 macrocycle once conjugated to the antibody. We therefore designed and synthesized new cryptophycin ADC which exhibited improved plasmatic stability when tested in mice and enhanced therapeutic index in comparison with C52 ADC. In conclusion, these data demonstrated the potent in vitro and in vivo antitumor activity of these new cryptophycin ADC and warrant further development of this cytotoxic payload for an ADC approach. Citation Format: Marie-Priscille Brun, Herve Bouchard, Francois Clerc, Jidong Zhang, Pierre-Yves Abecassis, Celine Amara, Eric Beys, Florence Efremenko, Celine Nicolazzi, Marie-Helene Pascual, Olivier Pasquier, Alain Krick, Pierre-Francois Berne, Laurence Gauzy, Nathalie Karst, Sylvain Huille, Christophe Henry, Anne-Marie Lefebvre, Ingrid Sassoon. Towards new cryptophycins as promising payloads for ADC. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-053.