Development of Stabilized Peptide-Based PROTACs against Estrogen Receptor α

Abstract

Peptide modulators targeting protein-protein interactions (PPIs) exhibit greater potential than small-molecule drugs in several important aspects including facile modification and relative large contact surface area. Stabilized peptides constructed by variable chemistry methods exhibit improved peptide stability and cell permeability compared to that of the linears. Herein, we designed a stabilized peptide-based proteolysis-targeting chimera (PROTAC) targeting estrogen receptor α (ERα) by tethering an N-terminal aspartic acid cross-linked stabilized peptide ERα modulator (TD-PERM) with a pentapeptide that binds the Von Hippel-Lindau (VHL) E3 ubiquitin ligase complex. The resulting heterobifunctional peptide (TD-PROTAC) selectively recruits ERα to the VHL E3 ligase complex, leading to the degradation of ERα in a proteasome-dependent manner. Compared with the control peptides, TD-PROTAC shows significantly enhanced activities in reducing the transcription of the ERα-downstream genes and inhibiting the proliferation of ERα-positive breast cancer cells. In addition, in vivo experiments indicate that TD-PROTAC leads to tumor regression in the MCF-7 mouse xenograft model. This work is a successful attempt to construct PROTACs based on cell-permeable stabilized peptides, which significantly broadens the chemical space of PROTACs and stabilized peptides.

The PROTAC technology in drug development

“…Therefore, researchers named this PROTAC peptide-based PROTAC. 39 However, the activity of these peptide-based PROTACs was low and remained at the micromolar range. However, the problem for these peptide-based PROTCs was due to their difficulty to permeate the cell membrane.…”

“…38 The peptide-based PROTAC against ERα was further designed effectively in a MCF-7 mouse xenograft model. 39 However, the activity of these peptide-based PROTACs was low and remained at the micromolar range. The main obstacle may be the poor cell permeability.…”

A critical evaluation of the approaches to targeted protein degradation for drug discovery

“…The application of endogenous tagging methods to directly monitor ternary complex formation and target protein depletion in living cells promises to increase the speed and efficiency of the optimisation of the heterobifunctional species for cellular activity [29] . Using systematic approaches, heterobifunctional molecules suitable for in vivo studies have been generated [19] , [22] , [31] , [30] , [41] , [42] , [26] , [65] , [66] , notably for molecules targeting degradation of nuclear receptors for the treatment of cancer. A clinical candidate heterobifunctional molecule (ARV-110, [43] that redirects E3 ligase activity to induce androgen receptor degradation has been recently announced ( http://ir.arvinas.com/news-releases/news-release-details/arvinas-receives-authorization-proceed-its-ind-application ; accessed 03.02.2019).…”

Stabilized Peptide HDAC Inhibitors Derived from HDAC1 Substrate H3K56 for the Treatment of Cancer Stem–Like Cells In Vivo

“…Tumor-bearing mice were treated with peptides 16cyc-HxA, 16lin-HxA, 16KA, SAHA, or vehicle (5 mice/group, 50 mg/kg, every other day, intraperitoneal injection) for a duration of 3 weeks. We chose this route of administration as it is a common practice for peptide therapeutics referred to previous reports (25,43). In the PA-1 and NTERA-2 xenograft animal model, in contrast to the vehicle-treated group, peptide 16cyc-HxA resulted in significant inhibition of tumor, at a rate of over 80% ( Fig.…”

“…Recently, our group has developed several efficient helical stabilization methodologies including the N-terminal helix nucleating template (TD strategy) and the in-tether chiral center induced peptide helicity (CIH strategy) based on the concept that a precisely tuned in-tether chiral center could dominate the peptide's secondary structure and its biological functions (23,24). Peptides constructed with these methods are successfully utilized to target ERa-coactivator interaction and p53-MDM2/MDMX interaction (25,26). Inspired by the previous success of FK228 and our own experience in stabilized peptides, we hypothesized that peptide substrate analogues with large binding surfaces could achieve enhanced efficiency and reduced toxicity through effectively disrupting the interaction between HDACs and their substrates.…”