31 research outputs found
Abstract 2186: Peptide-cleavable maytansinoid (ADCs) induce high bystander killing leading to improved anti-tumor activity <i>in vivo</i>
No full textAbstract
Antibodies targeting surface antigens on cancer cells typically have progressively lower access to tumor cells that are further removed from blood vessels. Also, the antibody will not bind to cells in the tumor mass that do not express antigen, including stromal cells of the tumor, many of which reportedly aid in the survival or metastasis of cancer cells.
ADCs can bind to antigen positive cancer cells, after which they are internalized and catabolized to release one or more cytotoxic metabolite(s) that can kill the targeted cell. Metabolites that are membrane permeable may also diffuse into and kill neighboring cells, often called bystander cells, that would normally be less accessible.
The goal of this work was to design ADCs that would have increased bystander activity, which could result in greater killing of cancer cells and stromal cells in the tumor environment. We have prepared a new type of peptide-cleavable immolative ADC (PCI-ADC) that efficiently releases membrane permeable cytotoxic maytansinoid metabolites upon cleavage of the peptide linker, followed by immolation. Several PCI-ADCs were prepared that release metabolites having different degrees of hydrophobicity. As the hydrophobicity of the metabolite increased, the PCI-ADCs’ bystander activity also increased. The lead PCI-ADC generally displayed a similar degree of in vitro cytotoxicity as maytansinoid ADCs that utilize disulfide linkers, however the PCI-ADC induced significantly more bystander killing. In mice bearing large tumor xenografts (250 mm3) or tumor xenografts that express the target antigen heterogeneously, PCI-ADCs were found to be more efficacious than maytansinoid ADCs that use disulfide linkers, as well as our recently reported peptide-para-anilino maytansinoid ADCs. The nature of the amino acid residues in the peptide linker of the PCI-ADC was also altered so that the tolerability of the ADCs in mice could be increased without impeding efficacy.
In conclusion, we have developed a promising new type of maytansinoid ADC, one that provides a high degree of bystander killing, improved activity in homogeneous and heterogeneous tumor models in vivo, and has a different mechanism of metabolite release than current maytansinoid based ADCs.
Citation Format: Wayne C. Widdison, Juliet A. Costoplus, Jose F. Ponte, Leanne Lanieri, Yulius Setiady, Ling Dong, Anna Skaletskaya, Rui Wu, Qifeng Qiu, Yelena Kovtun, Ravi V. Chari. Peptide-cleavable maytansinoid (ADCs) induce high bystander killing leading to improved anti-tumor activity in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2186. doi:10.1158/1538-7445.AM2017-2186</jats:p
Abstract 2668: Detoxification of metabolites from antibody-maytansinoid conjugates by human liver microsomes
No full textAbstract
Six antibody-maytansinoid conjugates (AMCs) consisting of the cytotoxic maytansinoid, DM1 or DM4, linked to a tumor-targeting monoclonal antibody are undergoing clinical evaluation, with the most advanced in Phase III testing. In these AMCs, the maytansinoid is attached through its C3 side chain to the antibody via a thioether or disulfide bond. The antibody moiety of the conjugate binds specifically to a tumor cell after which the conjugate is internalized and processed to release one or more maytansinoid metabolites (MMs) which kill the cell. Some of these MMs are hydrophobic and highly potent against both the forming cell and neighboring dividing cells, while others are charged or polar compounds that are highly toxic to the cell that intracellularly released them, but have a relatively low toxicity to adjacent cells due to poor membrane permeability. Similar MMs are formed from AMCs inside cells of the reticulo-endothelial system (RES), the primary route of elimination of proteinaceous therapeutics such as AMCs. We have previously reported, from studies with radiolabeled MMs in mice, that the primary elimination route of RES-formed MMs is via the liver, and entails biliary excretion of relatively low potency charged or polar maytansinoids. It would be desirable to know if MMs generated from AMCs in the RES systems of patients can be inactivated by the oxidative processes of the human liver. To model this, MMs and other maytansinoids were synthesized and then exposed in vitro to human liver microsomes. The resulting microsomal metabolites were identified by HPLC/MS and their cytotoxicities were determined. In general, the major metabolites formed from microsome exposure occurred via oxidation on the C3 side chain, with only minimal microsome-dependent alterations noted in the macrocycle. Non-charged hydrophobic maytansinoids containing at least one sulfur atom were oxidized on the sulfur atom(s) to yield one or more products which were significantly less cytotoxic than the substrate. For example, the highly cytotoxic tumor cell metabolite, S-methyl DM4, was converted to its sulfoxide and sulfone analogues, which were more than 20-fold less potent than S-methyl DM4. Charged maytansinoids containing an amino acid or a carboxylic acid were poorly metabolized by the human liver microsomes even when these maytansinoids contained one or more sulfur atoms. These data suggest that the highly potent, non-charged MMs formed in the tumor cells or the RES systems of patients would be rendered less toxic through oxidation in the liver prior to biliary elimination. Furthermore, the less potent, charged MMs likely would not be further processed by liver in a way that would increase their systemic toxicity.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2668.</jats:p
Abstract 538: LC-MS based catabolite identification study of an ADC with DM21-C, a novel maytansinoid linker-payload
No full textAbstract 538: LC-MS based catabolite identification study of an ADC with DM21-C, a novel maytansinoid linker-payload
No full textAbstract 645: Stability and efficacy comparison of site-specific and lysine-linked maytansinoid antibody-drug conjugates
No full textTumor Delivery and In Vivo Processing of Disulfide-Linked and Thioether-Linked Antibody−Maytansinoid Conjugates
No full textAntibody−drug conjugates (ADCs) are designed to eradicate cancer cells that express the target antigen on their cell surface. A key component of an ADC is the linker that covalently connects the cytotoxic agent to the antibody. Several antibody−maytansinoid conjugates prepared with disulfide-based linkers such as those targeting the CanAg antigen have been shown to display more activity in preclinical mouse xenograft models than corresponding conjugates prepared with uncleavable thioether-based linkers. To investigate how the linker influences delivery and activation of antibody−maytansinoid conjugates, we isolated and characterized the [3H]maytansinoids from CanAg-positive tumor tissues following a single intravenous administration of 300 μg/kg (based on maytansinoid dose) of anti-CanAg antibody (huC242)-3H-maytansinoid conjugates prepared with cleavable disulfide linkers and an uncleavable thioether linker. We identified three target-dependent tumor metabolites of the disulfide-linked huC242-SPDB-DM4, namely, lysine-Nε-SPDB-DM4, DM4, and S-methyl-DM4. We found similar metabolites for the less hindered disulfide-linked huC242-SPP-DM1 conjugate with the exception that no S-methyl-DM1 was detected. The sole metabolite of the uncleavable thioether-linked huC242-SMCC-DM1 was lysine-Nε-SMCC-DM1. The AUC for the metabolites of huC242-SMCC-DM1 at the tumor over 7 d was about 2-fold greater than the corresponding AUC for the metabolites of the disulfide-linked conjugates. The lipophilic metabolites of the disulfide-linked conjugates were found to be nearly 1000 times more cytotoxic than the more hydrophilic lysine-Nε-linker-maytansinoids in cell-based viability assays when added extracellularly. The cell killing properties associated with the lipophilic metabolites of the disulfide-linked conjugates (DM4 and S-methyl-DM4, and DM1) provide an explanation for the superior in vivo efficacy that is often observed with antibody−maytansinoid conjugates prepared with disulfide-based linkers in xenograft mouse models
