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High potency of lipid conjugated TLR7 agonist requires nanoparticulate or liposomal formulation

Gadd, A. J. R., Castelletto, V., Kabova, E., Shankland, K., Perrie, Y., Hamley, I., Cobb, A. J. A., Greco, F. and Edwards, A. D. (2018) High potency of lipid conjugated TLR7 agonist requires nanoparticulate or liposomal formulation. European Journal of Pharmaceutical Sciences, 123. pp. 268-276. ISSN 0928-0987

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To link to this item DOI: 10.1016/j.ejps.2018.07.048

Abstract/Summary

Conjugation of small molecule agonists of Toll-like receptor 7 (TLR7) to proteins, lipids, or polymers is known to modulate potency, and the physical form or formulation of these conjugates is likely to have a major effect on their immunostimulatory activity. Here, we studied the effect of formulation on potency of a 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phosphoethanolamine (DOPE) conjugated TLR7 agonist (DOPE-TLR7a) alongside assessing physical form using Dynamic Light Scattering (DLS), Nanosight Particle Tracking (NTA) analysis and Small Angle X-ray Scattering (SAXS). A very high potency of DOPE-TLR7a conjugate (EC50 around 9 nM) was observed either when prepared by direct dilution from DMSO or when formulated into 400-700 nm large multilamella liposomes containing dimethyldioctadecylammonium bromide salt (DDA) and DOPE. When prepared by dissolution in DMSO followed by dilution in aqueous culture medium, 93 ± 5 nm nanoparticles were formed. Without dilution from solution in DMSO, no nanoparticles were observed, and no immunostimulatory activity could be detected without this formulation step. SAXS analysis of the conjugate after DMSO dissolution/water dilution revealed a lamellar order with a layer spacing of 68.7 Å, which correlates with arrangement in groups of 3 bilayers. The addition of another immunostimulatory glycolipid, trehalose-6,6-dibehenate (TDB), to DOPE:DDA liposomes gave no further increase in immunostimulatory activity beyond that provided by incorporating DOPE-TLR7a. Given the importance of nanoparticle or liposomal formulation for activity, we conclude a major mechanism for increase in potency when TLR7 agonists are conjugated to macromolecules is through alteration of physical form.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
Interdisciplinary centres and themes > Chemical Analysis Facility (CAF) > Xray (CAF)
Faculty of Life Sciences > School of Chemistry, Food and Pharmacy > School of Pharmacy > Pharmaceutics Research Group
ID Code:78566
Publisher:Elsevier

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