Correspondence Gene silencing and related oligonucleotide therapies for TH2-promoting cytokines To the Editor: This letter is with regard to your excellent recent review of the pharmacology and mechanisms of TH2-promoting cytokines.1 The author’s perspective is evidently focused on the proteinprotein interactions and protein/peptide-based therapies, such as humanized mAbs and small molecules, in human clinical trials currently. However, in addressing ‘‘future directions,’’ some mention should be made of the potential of gene-silencing therapies, such as antisense, small interfering RNA, and RNAse P, in which the expression of receptors, cytokines, or both is interrupted at the mRNA level in addition to therapies directed at altering cytokine and receptor interactions.2,3 Elimination of cytokines or cytokine receptors by using gene silencing, although only tested in animal or in vitro systems, has the potential to block not only intercellular or paracrine cytokine signaling but also autocrine signaling, which might not be fully achieved by extracellular blockade of receptors after signaling. Decoy oligonucleotides and interference with downstream transcription factors activated by cytokines also have the potential to block cytokine signaling after receptor activation, also addressing the problem of autocrine signaling loops not blocked by partial inactivation of the cytokine receptors.4 Oligonucleotide-based therapies might have significant advantages in terms of cost and topical administration because oligonucleotides, unlike immunoglobulins and peptides, are mostly effective for topical or local administration to respiratory or other epithelial tissues.2 In the future, the authors would probably agree that some combination of antibody/peptide-based therapy and nucleotide-based gene silencing will be optimal for control of TH2-promoting cytokines. David H. Dreyfus, MD, PhD From Keren Pharmaceutical, New Haven and Clinical Faculty, Yale SOM, New Haven, Conn. E-mail: [email protected]. Disclosure of potential conflict of interest: D. H. Dreyfus has a patent with Yale SOM and has stock/stock options in Keren Pharmaceutical.
REFERENCES 1. Romeo MJ, Agrawal R, Pomes A, Woodfolk JA. A molecular perspective on TH2-promoting cytokine receptors in patients with allergic disease. J Allergy Clin Immunol 2014;133:952-60.e1. 2. Dreyfus DH, Ghoda L. A review of recent patents concerning therapy of respiratory diseases using gene silencing by RNAi (RISC) and EGS (RNAse P). Recent Pat Inflamm Allergy Drug Discov 2007;1:49-55. 3. Lively TN, Kossen K, Balhorn A, Koya T, Zinnen S, Takeda K, et al. Effect of chemically modified IL-13 short interfering RNA on development of airway hyperresponsiveness in mice. J Allergy Clin Immunol 2008;121:88-94. 4. Darcan-Nicolaisen Y, Meinicke H, Fels G, Hegend O, Haberland A, Kuhl A, et al. Small interfering RNA against transcription factor STAT6 inhibits allergic airway inflammation and hyperreactivity in mice. J Immunol 2009;182:7501-8. Available online July 18, 2014. http://dx.doi.org/10.1016/j.jaci.2014.06.008
Reply To the Editor: We would like to thank Dr Dreyfus1 for his comment on our review of TH2-promoting cytokine receptors.2 The objective of our article was to highlight how the molecular features of various 762
forms of these receptors and their associated components affect their function in patients with allergic disease. In particular, we discussed how TH2-promoting cytokines are integral to complex networks because of their overlapping functions and multiple actions. Such networks undoubtedly conspire to undermine the efficacy of therapeutics designed to target specific molecules. In relation to this point, the concept of using combined therapies to attain optimal clinical benefit was mentioned. We agree that extending this notion to include strategies that suppress the expression of genes encoding cytokines and their receptors (or else downstream signaling molecules) might provide an additional weapon in the armory against allergic inflammation. It is important to consider whether experimental evidence supports the ability for gene-silencing approaches to effectively suppress TH2-driven allergic inflammation. The articles cited by Dr Dreyfus1 describe administration of small interfering RNA (siRNA) to silence IL-13 or signal transducer and activator of transcription 6 (STAT6) in vivo by using mouse models of ovalbumin (OVA)–induced airway inflammation.3,4 In both models mice were sensitized intraperitoneally and then challenged repeatedly with aerosolized or intranasal allergen. Results showed that administration of siRNA before each challenge through either the intravenous or intranasal routes ameliorated allergen-induced airway dysfunction or inflammation. However, neither molecule alone inhibited both airway reactivity and infiltrating cells. Moreover, the inhibitory effects observed were incomplete. Indeed, a notable finding in mice treated with IL-13 siRNA was the lack of a reduction in IL-13 levels in bronchoalveolar lavage fluid, despite attenuation of airway hyperresponsiveness.3 Collectively, these observations underscore not only the pleiotropic and overlapping actions of TH2 cytokines but also the need for combined therapies directed against multiple targets. Beyond attaining gene silencing, challenges to developing effective siRNA-based therapies include the design of sequences to avoid ‘‘off-target’’ effects and optimization of delivery routes that are practical in the clinical setting.5 Chemical modification of the siRNA backbone, along with the use of nanoparticles and conjugate delivery systems, might help to direct siRNA molecules to target tissues and prevent their degradation. Nonetheless, tailoring of siRNA therapies will be necessary to optimize safe and effective delivery to sites of allergic inflammation in human subjects. RNA interference strategies are currently being tested in clinical trials for the treatment of diverse diseases, including viral infections and cancers.5 Given the potentially broad applications for gene-silencing therapies, it will be interesting to see where they might fit into the future therapeutic landscape for allergic disease. Martin J. Romeo, PhDa Rachana Agrawal, PhDa Anna Pom es, PhDb Judith A. Woodfolk, MBChB, PhDa From athe Asthma and Allergic Diseases Center, University of Virginia, and bIndoor Biotechnologies Inc, Charlottesville, Va. E-mail: [email protected]. Supported by grants from the National Institutes of Health/National Institute of Allergy and Infectious Diseases (R01 AI-052196) and the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (R01 AR-059058).
REFERENCES 1. Romeo MJ, Agrawal R, Pomes A, Woodfolk JA. A molecular perspective on TH2-promoting cytokine receptors in patients with allergic disease. J Allergy Clin Immunol 2014;133:952-60.e1. 2. Dreyfus DH, Ghoda L. A review of recent patents concerning therapy of respiratory diseases using gene silencing by RNAi (RISC) and EGS (RNAse P). Recent Pat Inflamm Allergy Drug Discov 2007;1:49-55. 3. Lively TN, Kossen K, Balhorn A, Koya T, Zinnen S, Takeda K, et al. Effect of chemically modified IL-13 short interfering RNA on development of airway hyperresponsiveness in mice. J Allergy Clin Immunol 2008;121:88-94. 4. Darcan-Nicolaisen Y, Meinicke H, Fels G, Hegend O, Haberland A, Kuhl A, et al. Small interfering RNA against transcription factor STAT6 inhibits allergic airway inflammation and hyperreactivity in mice. J Immunol 2009;182:7501-8. Available online July 18, 2014. http://dx.doi.org/10.1016/j.jaci.2014.06.008
Reply To the Editor: We would like to thank Dr Dreyfus1 for his comment on our review of TH2-promoting cytokine receptors.2 The objective of our article was to highlight how the molecular features of various 762
forms of these receptors and their associated components affect their function in patients with allergic disease. In particular, we discussed how TH2-promoting cytokines are integral to complex networks because of their overlapping functions and multiple actions. Such networks undoubtedly conspire to undermine the efficacy of therapeutics designed to target specific molecules. In relation to this point, the concept of using combined therapies to attain optimal clinical benefit was mentioned. We agree that extending this notion to include strategies that suppress the expression of genes encoding cytokines and their receptors (or else downstream signaling molecules) might provide an additional weapon in the armory against allergic inflammation. It is important to consider whether experimental evidence supports the ability for gene-silencing approaches to effectively suppress TH2-driven allergic inflammation. The articles cited by Dr Dreyfus1 describe administration of small interfering RNA (siRNA) to silence IL-13 or signal transducer and activator of transcription 6 (STAT6) in vivo by using mouse models of ovalbumin (OVA)–induced airway inflammation.3,4 In both models mice were sensitized intraperitoneally and then challenged repeatedly with aerosolized or intranasal allergen. Results showed that administration of siRNA before each challenge through either the intravenous or intranasal routes ameliorated allergen-induced airway dysfunction or inflammation. However, neither molecule alone inhibited both airway reactivity and infiltrating cells. Moreover, the inhibitory effects observed were incomplete. Indeed, a notable finding in mice treated with IL-13 siRNA was the lack of a reduction in IL-13 levels in bronchoalveolar lavage fluid, despite attenuation of airway hyperresponsiveness.3 Collectively, these observations underscore not only the pleiotropic and overlapping actions of TH2 cytokines but also the need for combined therapies directed against multiple targets. Beyond attaining gene silencing, challenges to developing effective siRNA-based therapies include the design of sequences to avoid ‘‘off-target’’ effects and optimization of delivery routes that are practical in the clinical setting.5 Chemical modification of the siRNA backbone, along with the use of nanoparticles and conjugate delivery systems, might help to direct siRNA molecules to target tissues and prevent their degradation. Nonetheless, tailoring of siRNA therapies will be necessary to optimize safe and effective delivery to sites of allergic inflammation in human subjects. RNA interference strategies are currently being tested in clinical trials for the treatment of diverse diseases, including viral infections and cancers.5 Given the potentially broad applications for gene-silencing therapies, it will be interesting to see where they might fit into the future therapeutic landscape for allergic disease. Martin J. Romeo, PhDa Rachana Agrawal, PhDa Anna Pom es, PhDb Judith A. Woodfolk, MBChB, PhDa From athe Asthma and Allergic Diseases Center, University of Virginia, and bIndoor Biotechnologies Inc, Charlottesville, Va. E-mail: [email protected]. Supported by grants from the National Institutes of Health/National Institute of Allergy and Infectious Diseases (R01 AI-052196) and the National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (R01 AR-059058).
