This invention describes a novel agent for the targeted control of a
mammalian cell activity, in particular the agent is used to control the
interaction of particular cell types with their external environment. The
agent has applications as a pharmaceutical for the treatment of a variety
of disorders. An agent according to the invention comprises three Domains
B, T and E linked together in the following manner: Domain B-Domain
T-Domain E where Domain B is the Binding Domain which binds the agent to
a Binding Site on the cell which undergoes endocytosis to produce an
endosome, Domain T is the Translocation Domain which translocates the
agent (with or without the Binding Site) from within the endosome across
the endosomal membrane into the cytosol of the cell, Domain E is the
Effector Domain which inhibits the ability of the Recyclable Membrane
Vesicles to transport the Integral Membrane Proteins to the surface of
the cell.