47 research outputs found
Young readers and parental guidance
No full textTwo books in the Children\u27s collection of the Josephine Community Libraries were challenged as inappropriate for this collection in the past year. One book was moved from Children\u27s to the Young Adult area, the other decision is pending. Author discusses banned books, reasons for book challenges, and the local library\u27s process for reviewing challenged materials
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 71: Bystander activity and <i>in vivo</i> efficacy of a folate receptor α (FRα)-targeting antibody-drug conjugate with a novel peptide linker
No full textAbstract
Folate receptor α (FRα) is an antigen that is overexpressed on the cell surface of solid tumors including ovarian cancer. The differential expression on cancer cells makes FRα an attractive target for antibody-drug conjugates (ADCs), and an ADC targeting FRα, Mirvetuximab soravtansine, has demonstrated promising activity and safety profiles in the clinic. Here, we employed a new linker (NL) to enhance the bystander activity of ADCs, which is the ability of ADCs to generate cell-permeable catabolites that can diffuse into and kill proximal cancer cells with little or no target expression. With the goal of improving the potency of anti-FRα ADC in solid tumors with heterogeneous FRα expression, we constructed the M9346A-NL-DM. M9346A-NL-DM is a conjugate of the tubulin-disrupting maytansinoid (DM), linked via a novel linker to M9346A, a humanized antibody that binds FRα with high affinity. After cellular uptake and catabolism of the ADC, the new linker undergoes lysosomal cleavage followed by self-immolation to generate free DM that can readily penetrate neighboring cancer cells. Correspondingly, M9346A-NL-DM showed enhanced bystander cytotoxic activity against proximal antigen-negative cells in vitro. In the xenograft tumor models in vivo, M9346A-NL-DM demonstrated enhanced efficacy against tumors with heterogeneous expression of FRα. Interestingly, M9346A-NL-DM also showed improved antitumor activity against a tumor model with homogeneous expression of FRα, possibly due to better tumor penetration of the cell-permeable catabolite. In summary, M9346A-NL-DM is a novel ADC with enhanced bystander activity and antitumor activity that can target tumors with heterogeneous expression of FRα.
Citation Format: Qifeng Qiu, Rui Wu, Leanne Lanieri, Erin Maloney, Anna Skaletskaya, Shan Jin, Lintao Wang, Olga Ab, Joe Ponte, Yulius Setiady, Wayne Widdison, Thomas Keating, Ravi Chari, Richard Gregory, Erica Hong. Bystander activity and in vivo efficacy of a folate receptor α (FRα)-targeting antibody-drug conjugate with a novel peptide linker [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 71. doi:10.1158/1538-7445.AM2017-71</jats:p
Abstract 3898: Preclinical evaluation of DM21, a next-generation maytansinoid payload with a stable peptide linker
No full textMaytansine and Cellular Metabolites of Antibody-Maytansinoid Conjugates Strongly Suppress Microtubule Dynamics by Binding to Microtubules
No full textAbstract
Maytansine is a potent microtubule-targeted compound that induces mitotic arrest and kills tumor cells at subnanomolar concentrations. However, its side effects and lack of tumor specificity have prevented successful clinical use. Recently, antibody-conjugated maytansine derivatives have been developed to overcome these drawbacks. Several conjugates show promising early clinical results. We evaluated the effects on microtubule polymerization and dynamic instability of maytansine and two cellular metabolites (S-methyl-DM1 and S-methyl-DM4) of antibody-maytansinoid conjugates that are potent in cells at picomolar levels and that are active in tumor-bearing mice. Although S-methyl-DM1 and S-methyl-DM4 inhibited polymerization more weakly than maytansine, at 100 nmol/L they suppressed dynamic instability more strongly than maytansine (by 84% and 73%, respectively, compared with 45% for maytansine). However, unlike maytansine, S-methyl-DM1 and S-methyl-DM4 induced tubulin aggregates detectable by electron microscopy at concentrations ≥2 μmol/L, with S-methyl-DM4 showing more extensive aggregate formation than S-methyl-DM1. Both maytansine and S-methyl-DM1 bound to tubulin with similar KD values (0.86 ± 0.2 and 0.93 ± 0.2 μmol/L, respectively). Tritiated S-methyl-DM1 bound to 37 high-affinity sites per microtubule (KD, 0.1 ± 0.05 μmol/L). Thus, S-methyl-DM1 binds to high-affinity sites on microtubules 20-fold more strongly than vinblastine. The high-affinity binding is likely at microtubule ends and is responsible for suppression of microtubule dynamic instability. Also, at higher concentrations, S-methyl-DM1 showed low-affinity binding either to a larger number of sites on microtubules or to sedimentable tubulin aggregates. Overall, the maytansine derivatives that result from cellular metabolism of the antibody conjugates are themselves potent microtubule poisons, interacting with microtubules as effectively as or more effectively than the parent molecule. Mol Cancer Ther; 9(10); 2689–99. ©2010 AACR.</jats:p
Abstract 3898: Preclinical evaluation of DM21, a next-generation maytansinoid payload with a stable peptide linker
No full text
