Effective Non-Invasive Delivery of Epigenetic Drugs Using Functionalized Accessory Unit Conjugates

Epigenetics involves heritable changes in gene expression—such as DNA methylation (5-methylcytosine; 5mC), histone modifications, and regulation by non-coding RNAs at the mRNA translation level—without altering the underlying DNA sequence. As targeting these mechanisms enables intervention at the root cause of disease rather than the symptoms alone, epigenetics has become a rapidly advancing field in pharmaceutical sciences. Various epigenetic modulators, including histone deacetylase (HDAC) inhibitors, histone acetyltransferase (HAT) inhibitors, DNA methyltransferase (DNMT) inhibitors, and microRNAs (miRNAs), have been developed, and some have already been approved for cancer therapy. However, these agents often face significant challenges such as poor membrane permeability, enzymatic instability, and suboptimal biodistribution. Incorporating functionalized accessory units—serving as vectors (e.g., transporter recognition units, cell-penetrating peptides, tumor-homing peptides, monoclonal antibodies) or as carriers (e.g., monoclonal antibodies, nanoparticles)—into epigenetic modulators may help overcome these delivery barriers. In this narrative review, I discuss the potential and advantages of effective non-invasive delivery of epigenetic drugs using such functionalized accessory unit conjugates.