IPHASE Solutions for siRNA Drug In Vitro Metabolism Research

IPHASE Solutions for siRNA Drug In Vitro Metabolism Research

  Nucleic acid drugs, due to their unique technological characteristics, have become the focus of new drug development in recent years. Nucleic acid drugs include small interfering RNA (siRNA), antisense oligonucleotides (ASO), microRNA (miRNA), small activating RNA (saRNA), messenger RNA (mRNA), aptamers, and antibody-drug conjugates (ADC), are forms of gene therapy. Among these, siRNA drugs, as a hotspot in nucleic acid drug research and development, have been widely used in new drug development due to their high gene silencing efficiency, controllable side effects, and easy synthesis. They are expected to be the most promising drugs for new drug development after small molecule and antibody drugs.

1. 1.  Mechanistic Insights into siRNA Drug Action

  Small interfering RNA (siRNA), also referred to as silencing RNA, short interfering RNA, or non-coding RNA, consists of short double-stranded RNA molecules typically 21–25 base pairs in length. Upon synthesis, siRNA enters the cell via endocytosis. A fraction of the siRNA escapes lysosomal degradation and enters the cytoplasm, where it is incorporated into the RNA-induced silencing complex (RISC). Within the RISC, the siRNA unwinds into two single strands: the sense strand and the antisense strand. The sense strand is rapidly degraded in the cytoplasm, while the RISC, bound to the antisense strand, is activated. The complex then selectively binds to the target mRNA, facilitating its cleavage and subsequent degradation. As a result of mRNA degradation, the expression level of the target gene is significantly reduced, ultimately leading to gene silencing and the inhibition of protein translation.

1. 2.  siRNA Drug Metabolism Research Strategy

 In vivo, siRNA drugs are primarily metabolized by nucleases and exonucleases present in plasma and tissues, rather than by phase I and II metabolic enzymes in the liver. Following structural modifications, currently marketed siRNA drugs exhibit reduced metabolism in the bloodstream. Typically, the majority of siRNA drugs are rapidly taken up by the liver, with a smaller fraction distributed to other tissues, where they are subsequently metabolized by nucleases in the liver or other tissues. For in vivo metabolism studies of siRNA drugs, metabolic products are typically identified and quantitatively analyzed in plasma, urine, feces, and target tissues (such as the liver or kidneys) from animal models.

  However, during the early stages of drug development, the large number of compounds, extended experimental timelines, and high costs associated with in vivo studies pose significant challenges for large-scale compound screening and structural optimization. As a result, in vitro metabolism studies are of particular importance during the early screening phase of siRNA drug development. These studies offer notable advantages, such as high throughput and shorter experimental cycles, which can significantly enhance the efficiency of siRNA drug screening.

                                          Table 1: In Vitro Metabolism Research Systems for SiRNA Drugs

1. 3.  IPHASE Relevant Products