MI130004, a Novel Antibody-Drug Conjugate Combining Trastuzumab with a Molecule of Marine Origin, Shows Outstanding In Vivo Activity against HER2-Expressing Tumors.

In the search for novel payloads to design new antibody-drug conjugates (ADC), marine compounds represent an interesting opportunity given their unique chemical features. PM050489 is a marine compound that binds ß-tubulin at a new site and disrupts the microtubule network, hence leading to mitotic aberrations and cell death. PM050489 has been conjugated to trastuzumab via Cys residues through a noncleavable linker, and the resulting ADC, named MI130004, has been studied. Analysis of MI130004 delivered data consistent with the presence of two molecules of PM050489 per antibody molecule, likely bound to both sides of the intermolecular disulfide bond connecting the antibody light and heavy chains. The antitumor activity of MI130004 was analyzed in vitro and in vivo in different cell lines of diverse tumor origin (breast, ovary, and gastric cancer) expressing different levels of HER2. MI130004 showed very high in vitro potency and good selectivity for tumor cells that overexpressed HER2. At the cellular level, MI130004 impaired tubulin polymerization, causing disorganization and disintegration of the microtubule network, which ultimately led to mitotic failure, mirroring the effect of its payload. Treatment with MI130004 in mice carrying histologically diverse tumors expressing HER2 induced a long-lasting antitumor effect with statistically significant inhibition of tumor growth coupled with increases in median survival time compared with vehicle or trastuzumab. These results strongly suggest that MI130004 is endowed with remarkable anticancer activity and confirm the extraordinary potential of marine compounds for the design of new ADCs. Mol Cancer Ther; 17(4); 786-94. ©2018 AACR.

Stellatolides, a new cyclodepsipeptide family from the sponge Ecionemia acervus: isolation, solid-phase total synthesis, and full structural assignment of stellatolide A.

The marine environment is a rich source of metabolites with potential therapeutic properties and applications for humans. Here we describe the first isolation, solid-phase total synthesis, and full structural assignment of a new class of cyclodepsipeptides from the Madagascan sponge Ecionemia acervus that shows in vitro cytotoxic activities at submicromolar concentrations. Seven structures belonging to a new family of compounds, given the general name stellatolides, were characterized. The sequence and stereochemistry of all the amino acids in these molecules were established by a combination of spectroscopic analysis, chemical degradation, and derivatization studies. Furthermore, the complete structure of stellatolide A was confirmed by an efficient solid-phase method for the first total synthesis and the full structural assignment of this molecule, including the asymmetric synthesis of the unique ß-hydroxy acid moiety (Z)-3-hydroxy-6,8-dimethylnon-4-enoic acid.

Stolonoxides E and F, cytotoxic metabolites from the marine ascidian Stolonica socialis.

Two new members of the stolonoxide family, stolonoxides E (1) and F (2), were isolated from samples of the marine ascidian Stolonica socialis collected in Cádiz (Spain). Their structures were determined by a combination of techniques, including (+)-HRESIMS, 1D and 2D NMR spectroscopy, and comparison with published data for the structurally related stolonoxides A-D (3-6). Both compounds displayed cytotoxicity against a panel of three human tumor cell lines.

Efficient entry to diversely functionalized spirocyclic oxindoles from isatins through carbonyl-addition/cyclization reaction sequences.

A novel approach to diversely functionalized spirocyclic oxindoles has been developed by using different metal-mediated carbonyl-addition/cyclization reaction sequences. Spirocyclization precursors, 2-indolinone-tethered homoallylic alcohols, (buta-1,3-dien-2-yl)methanols, and alpha-allenols have been obtained by regioselective addition of stabilized organoindium reagents to isatins in aqueous environment. Ruthenium-, silver-, and palladium-catalyzed reactions of the above unsaturated alcohol derivatives provided oxaspiro oxindoles.

Pd-Cu bimetallic catalyzed domino cyclization of alpha-allenols followed by a coupling reaction: new sequence leading to functionalized spirolactams.

A novel regioselective metal-catalyzed spirocyclization of alpha-allenols-cross coupling (Heck, Sonogashira, and Suzuki) reaction sequence, leading to potentially bioactive spirocyclic lactam derivatives has been developed. Precursors for the tandem spirocyclization-coupling reaction, alpha-allenols 2 a-d were obtained starting from alpha-oxolactams 1 a-c via indium-mediated Barbier-type carbonyl-allenylation reaction in aqueous media by using our previously described methodologies.

Metal-mediated entry to functionalized 3-substituted 3-hydroxyindolin-2-ones via regiocontrolled carbonylallylation, bromoallylation, 1,3-butadien-2-ylation, propargylation, or allenylation reactions of isatins in aqueous media.

Reactions of 2,3-indolinediones (isatins) with stabilized organometallic reagents were investigated in aqueous media. Isatins and a variety of stabilized organic halides undergo coupling under Barbier-type conditions in the presence of different metals (indium, tin, zinc) and additives (ammonium chloride, hydrobromic acid, bismuth(III) chloride, hafnium(IV) chloride). The regiochemistry of the processes (carbonylallylation, bromoallylation, 1,3-butadien-2-ylation, propargylation, or allenylation reactions) were generally excellent. On this basis, simple and fast protocols for the synthesis of the potentially bioactive 3-substituted 3-hydroxyoxindole moiety were developed.

Novel carbonyl bromoallylation/Heck reaction sequence. Stereocontrolled access to bicyclic beta-lactams.

[reaction: see text] The reaction of 2,3-dibromopropene with racemic as well as enantiopure 4-oxoazetidine-2-carbaldehydes 1 in aqueous media was promoted by tin in the presence of several additives to afford the corresponding bromohomoallyl alcohols 2 in high diastereoselectivities. However, indium or zinc were unable to promote the bromoallylation reaction of aldehydes 1 under similar Barbier-type conditions. Vinyl bromides 2 bearing an extra alkene tether were used for the preparation of differently sized, fused bicyclic beta-lactams of nonconventional structure via Heck cyclization.

Straightforward asymmetric entry to highly functionalized 3-substituted 3-hydroxy-beta-lactams via Baylis-Hillman or bromoallylation reactions.

The reaction of various activated vinyl systems, including 2-cyclopenten-1-one, with enantiopure azetidine-2,3-diones 1 was promoted by DABCO to afford the corresponding optically pure Baylis-Hillman adducts 2 without detectable epimerization. However, the reaction of alpha-keto lactams 1 with but-3-yn-2-one was not as successful, giving the corresponding beta-halo Baylis-Hillman adduct in low yield. Metal-mediated bromoallylation reaction between 2,3-dibromopropene and azetidine-2,3-diones 1 was investigated in aqueous media. Surprisingly, indium was unable to promote the bromoallylation reaction of alpha-keto lactams 1, but the Sn-Hf(4)Cl-promoted bromoallylation of ketones 1 proceeded efficiently to achieve bromohomoallyl alcohols 5 as single diastereomers. On this basis, simple and fast protocols for the asymmetric synthesis of the potentially bioactive 3-substituted 3-hydroxy-beta-lactam moiety were developed.

Metal-mediated carbonyl-1,3-butadien-2-ylation by 1,4-bis(methanesulfonyl)-2-butyne or 1,4-dibromo-2-butyne in aqueous media: asymmetric synthesis of 3-substituted 3-hydroxy-beta-lactams.

Metal-mediated 1,3-butadien-2-ylation reactions between 1,4-dibromo-2-butyne or 1,4-bis(methanesulfonyl)-2-butyne and optically pure azetidine-2,3-diones were investigated in aqueous media, offering a convenient asymmetric entry to the potentially bioactive 3-substituted 3-hydroxy-beta-lactam moiety. The diastereoselectivity of the addition reaction was controlled by the bulky chiral auxiliary at C4. However, while the regioselectivity of the process was full, the chemical yield of the addition was a function of the nature of both the metal reagent and the system solvent as well. In addition, 2-azetidinone-tethered 1,3-butadienes can easily be transformed into other functionalities via Diels-Alder reaction.