Antibody drug conjugates (ADCs) charged with HDAC inhibitor for targeted epigenetic modulation

We describe here two novel antibody-drug conjugates loaded with the HDAC inhibitor ST7612AA1 (IC50equal to 0.07 μM on NCI-H460 cells), a thiol-based molecule with a moderate toxicity in vivo. Two payloads were prepared using cleavable and non-cleavable linkers. After anchoring to cetuximab through amide bond with lysines, the resulting HDAC inhibitor-antibody conjugates showed ability to recognize EGFR and efficient internalization in tumor cells. Both ADCs induced sensible increment of histones 3 and 4 and alpha-tubulin acetylation. Animal models of human solid tumors showed high anti-tumor efficacy of the conjugates without the toxicity generally observed with traditional ADCs delivering highly potent cytotoxic drugs. These compounds, the first ADCs charged with not highly cytotoxic warheads, are potentially suitable for epigenetic modulation, extending the ADC strategy to the targeted delivery of HDAC inhibitors with many possible therapeutic applications beyond cancer

Antibody drug conjugates with hydroxamic acid cargos for histone deacetylase (HDAC) inhibition.

The bioconjugation of hydroxamic acids to antibodies has been made possible through a non-cleavable linker based on the p-mercaptobenzyl alcohol structure that releases hydroxamates in the cells

In water alkylation of amines with alcohols through a borrowing hydrogen process catalysed by ruthenium nanoparticles

A simple and environmentally benign procedure for the synthesis of secondary amines in water has been developed. Combining Ru3(CO)12, tetraphenylcyclopentadienone and a small quantity of TGPS-750-M surfactant, primary and secondary alcohols were alkylated at N employing equimolar amounts of aromatic amines in water. The reaction occurs under microwave (MW) dielectric heating with high conversion and high yield. When required, the use of biomass-derived 2-MeTHF or GVL as a co-solvent is possible. Under the influence of MWs, a Ru nanoparticle–nanomicelle combination was formed acting as an effective and recyclable catalyst. This protocol was also employed for “in water” cyclisation to synthesise biologically relevant pyrrolobenzodiazepines (PBDs).

ErbB2 Targeted Epigenetic Modulation: Anti-tumor Efficacy of the ADC Trastuzumab-HDACi ST8176AA1

Targeted therapy using monoclonal antibodies conjugated to toxins is gaining space in the treatment of cancer. Here, we report the anti-tumor effect of a new antibody drug conjugate (ADC) delivering a HDAC inhibitor to ErbB2+ solid tumors. Trastuzumab was partially reduced with tris [2-carboxyethyl] phosphine (TCEP) and conjugated to ST7464AA1, the active form of the prodrug HDAC inhibitor ST7612AA1, through a maleimide-thiol linker to obtain the Antibody Drug Conjugate (ADC) ST8176AA1. The average drug/antibody ratio (DAR) was 4.5 as measured by hydrophobic interaction chromatography (HIC). Binding of ST8176AA1 to ErbB2 receptor and internalization in tumor cells were investigated by enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR), cytofluorimetry, and High Content Screening (HCS) Imaging. The biological activity of the ADC was evaluated in vitro and in vivo by measuring cell proliferation/cell cycle, apoptosis/DNA damage, tubulin, and histone acetylation and modulation of Epithelial/Mesenchymal Transition (EMT) markers. Receptor binding and internalization of ST8176AA1 were confirmed to be similar to trastuzumab. Higher anti-tumor activity of ST8176AA1 compared to trastuzumab was observed in vitro in tumor cell lines. Such higher activity correlated with increased acetylation of histones and alfa-tubulin as a consequence of HDAC inhibitor-mediated epigenetic modulation that also induced increased expression of ErbB2 and estrogen receptor in triple negative breast cancer cells. Consistently with in vitro data, ST8176AA1 exhibited higher tumor growth inhibition than trastuzumab in xenograft models of ovary and colon carcinoma and in two patient-derived xenograft (PDX) models of pancreatic carcinoma. Immunohistochemistry analysis of tumor masses showed lower expression of the proliferation marker Ki67 and higher expression of cleaved caspase-3 in mice treated with the ADC compared to those treated with trastuzumab and results correlated with increased acetylation of both histones and tubulin. Collectively, present data indicate that ADC ST8176AA1 can target epigenetic modulation to ErbB2+ tumors. Interestingly, the amount of HDACi estimated to be delivered at the ST8176AA1 effective dose would correspond to ~1/1,000 of ST7612AA1 effective dose. Therefore, ST8176AA1 is an attractive new therapeutic candidate because it exhibits increased anti-tumor potency compared to trastuzumab by exerting epigenetic modulation at a much safer dose compared to standard HDACi-based therapeutic protocols