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Rational design of cationic lipids for siRNA delivery


We adopted a rational approach to design cationic lipids for use in formulations to deliver small interfering RNA (siRNA). Starting with the ionizable cationic lipid 1,2-dilinoleyloxy-3-dimethylaminopropane (DLinDMA), a key lipid component of stable nucleic acid lipid particles (SNALP) as a benchmark, we used the proposed in vivo mechanism of action of ionizable cationic lipids to guide the design of DLinDMA-based lipids with superior delivery capacity. The best-performing lipid recovered after screening (DLin-KC2-DMA) was formulated and characterized in SNALP and demonstrated to have in vivo activity at siRNA doses as low as 0.01 mg/kg in rodents and 0.1 mg/kg in nonhuman primates. To our knowledge, this represents a substantial improvement over previous reports of in vivo endogenous hepatic gene silencing.

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Figure 1: Proposed mechanism of action for membrane disruptive effects of cationic lipids and structural diagram of DLinDMA divided into headgroup, linker and hydrocarbon chain domains.
Figure 2: In vivo evaluation of novel cationic lipids.
Figure 3: Efficacy of KC2-SNALP in rodents and nonhuman primates.

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The authors thank K. McClintock for assistance with animal studies. The authors also thank the Centre for Drug Research and Development at the University of British Columbia for use of the NMR facilities and M. Heller for his expert assistance in setting up the 31P-NMR experiments.

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Authors and Affiliations



J.C., M.A.C., P.R.C., T.D.M., M.J.H. and K.F.W. designed and advised on novel lipids. J.C., K.F.W. and M.S. synthesized novel lipids. M.J.H., T.D.M., J.C., K.F.W., M.M., K.G.R., M.A.M., M.T. and M.J. analyzed and interpreted lipid data. T.D.M., M.J.H. and M.A.T. co-directed novel lipid synthesis and screening program. S.C.S. designed and directed rodent in vivo studies. S.C.S., S.K.K., B.L.M., K.L., M.L.E., M.K., A.P.S., Y.K.T., S.A.B., W.L.C., M.J.W. and E.J.C. generated rodent in vivo data, including Factor VII and tolerability analyses. L.N., V.K., T.B., R.A., Q.C. and D.W.Y.S. developed novel siRNAs targeting TTR. R.A. and A.A. designed and directed NHP in vivo studies. S.C.S., S.K.K., A.A., B.L.M., I.M., A.P.S., Y.K.T., R.A., T.B., D.W. Y. S., S.A.B., J.Q., J.R.D. and A.d.F. analyzed and interpreted in vivo data. B.L.M., K.L., A.P.S., S.K.K., S.C.S. and E.J.C. generated and characterized preformed vesicle formulations with novel lipids. D.S. and C.K.C. developed methods and designed and conducted HPLC lipid analyses of preformed vesicle formulations. E.Y. and L.B.J. prepared SNALP formulations. P.R.C. directed biophysical studies and advised on methods. A.P.S., I.M.H., S.D. and K.W. performed biophysical characterization studies (pKa, NMR, differential scanning calorimetric) of novel lipids and formulations. M.J.H., P.R.C., T.D.M., A.P.S., I.M.H. and K.F.W. analyzed biophysical data. S.C.S., M.J.H., A.A. and P.R.C. co-wrote the manuscript. T.D.M., M.M., M.A.M., M.A.T. and A.D.F. reviewed and edited the manuscript. S.C.S., M.J.H., A.A., P.R.C., I.M. and A.D.F. were responsible for approval of the final draft.

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Correspondence to Sean C Semple or Akin Akinc.

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Authors are employees of Alnylam, Tekmira, or Alcana or receive funding from Alnylam.

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Supplementary Fig. 1, Supplementary Tables 1–4 and Supplementary Syntheses 1 and 2 (PDF 345 kb)

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Semple, S., Akinc, A., Chen, J. et al. Rational design of cationic lipids for siRNA delivery. Nat Biotechnol 28, 172–176 (2010).

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