¹Department of Medicine/Hematology, Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, USA

Correspondence: Dr CA Blau, Department of Medicine/Hematology, University of Washington, K260, Health Science Building, Mailstop 357710 Seattle, Washington, WA 98195, USA. E-mail: tblau@u.washington.edu

Received 18 February 2008; Accepted 18 February 2008; Published online 20 March 2008.

Abstract

Many recombinant growth factors have failed in clinical trials due to off-target effects. We describe a method for circumventing off-target effects that involves equipping cells with a conditionally active signaling protein that can be specifically activated by an exogenously administered synthetic ligand. We believe that this approach will have many applications in gene and cell therapy.