Antisense Oligonucleotides and RNA Interference - Challenges in Delivery of Therapeutic Genomics and Proteomics - page 366

incorporating “inactive/mutant” targeting moieties should be evaluated to provide an
evidence of effective targeting. There should be more than 50% reduction in target
mRNA levels in target tissue at 1 mg/kg dose by target siRNA by 24-48 h and less
than 10% reduction in target mRNA levels in target tissue at 1 mg/kg dose by control
siRNA by 24-48 h. Demonstration of RNAi-induced off-target effects by less than
10-fold cytokine induction in 2 and 24 h at 3 mg/kg and less than 10-fold increases
in ALT and AST at 3 mg/kg with no effect on body weight, blood clinical chemistry,
and hematology data in 48 h is also essential.
7. Targeted Delivery
Prior understanding of the nature of the targeting mechanism (passive or active) helps
to prove the active targeting and cellular internalization in vitro by blocking with the
appropriate soluble ligand or receptor. Incorporated targeted moeity should be able
to compete with the ligands like transferrin, folate, and galactosamine for binding
to the target cell. Controls for in vivo active targeting experiments should include a
nonfunctional targeting moiety of similar class, molecular weight, and pI, like irrele-
vant IgG. Materials without a control targeting ligand are not good controls. In addi-
tion, unrelated cell lines that do not express the receptor are not good controls. There
should be at least fivefold greater in vivo gene silencing in target cells using actively
targeted materials than that observed with the negative targeting controls.
7.12 Patent Trends
A mark of the astonishing potential of antisense technology is the surge in the num-
ber of patents applied for in the past few years, which must take into account the 90
granted US patents and the 745 US applications on siRNA only in the year 2009 itself
[261] . The trend in the patents is toward gene silencing, preparation techniques for
judicious design, and modifications to improve specificity, nuclease resistance, trans-
fection efficiency, and targeting of the molecules. At present, the focus of antisense
research is toward delivering an adequate amount in the right cells at the right time
through an appropriate siRNA design and labeling it with suitable delivery system.
Commercial benefits can be fully exploited with sensible and executed patent strategies
based on an understanding of the existing patent coverage. Many antisense technology-
based formulations are now being developed with a view toward patentability in the
USA, and there are key differences between US and international patent systems that
may be relevant to international patenting of RNAi technology. Patents on most recent
antisense technology based on siRNA can be grasped by analyzing the strengths and
weaknesses of patents of established technologies, such as monoclonal antibodies,
gene therapy, and AS ODNs. Successful patent position is also being addressed in
therapeutics characteristics and platform technologies of antisense technology for the
treatment of various disorders like allergy, ocular angiogenesis, cancer, cardiovascu-
lar problems, CNS disorders, and AIDS. As well, patents for targeting and delivery