Semi‐Synthetic Ecdysteroids as Gene‐Switch Actuators: Synthesis, Structure–Activity Relationships, and Prospective ADME Properties

• Published in: ChemMedChem Vol. 4; no. 1; pp. 55 - 68
• Main Authors: Lapenna, Silvia, Dinan, Laurence, Friz, Jennifer, Hopfinger, Anton J., Liu, Jianzhong, Hormann, Robert E.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag 12.01.2009
• Subjects: 3T3 Cells; Aedes aegypti; Animals; Caco-2 Cells; Cells, Cultured; Choristoneura fumiferana; Drosophila melanogaster; Drosophila melanogaster - metabolism; Drug Design; ecdysteroid; Ecdysteroids - chemical synthesis; Ecdysteroids - chemistry; Ecdysteroids - pharmacology; Gene Expression - drug effects; gene switch; gene therapy; Humans; Mice; Receptors, Steroid - chemistry; Receptors, Steroid - genetics; Receptors, Steroid - metabolism; Structure-Activity Relationship; structure–activity relationships
• ISSN: 1860-7179; 1860-7187
• DOI: 10.1002/cmdc.200800280

The ligand‐inducible, ecdysteroid receptor (EcR) gene‐expression system can add critical control features to protein expression in cell and gene therapy. However, potent natural ecdysteroids possess absorption, distribution, metabolism and excretion (ADME) properties that have not been optimised for use as gene‐switch actuators in vivo. Herein we report the first systematic synthetic exploration of ecdysteroids toward modulation of gene‐switch potency. Twenty‐three semi‐synthetic O‐alkyl ecdysteroids were assayed in both a natural insect system (Drosophila BII cells) and engineered gene‐switch systems in mammalian cells using Drosophila melanogaster, Choristoneura fumiferana, and Aedes aegypti EcRs. Gene‐switch potency is maintained, or even enhanced, for ecdysteroids methylated at the 22‐position in favourable cases. Furthermore, trends toward lower solubility, higher permeability, and higher blood–brain barrier penetration are supported by predicted ADME properties, calculated using the membrane‐interaction (MI)‐QSAR methodology. The structure–activity relationship (SAR) of alkylated ecdysteroids indicates that 22‐OH is an H‐bond acceptor, 25‐OH is most likely an H‐bond donor, and 2‐OH and 3‐OH are donors and/or acceptors in network with each other, and with the EcR. The strategy of alkylation points the way to improved ecdysteroidal actuators for switch‐activated gene therapy. Modulating gene behaviour: In a ligand‐inducible gene‐expression (gene‐switch) system, a small‐molecule drug modulates the expression level of the target gene. The strategy of alkylation of natural ecdysteroid receptor (EcR) ligands points the way to improved ecdysteroidal actuators for switch‐activated gene therapy.