Although site-specific direction of drugs within an organism would ben
efit patients with many diseases, active drug targeting is clinically
not yet possible. To overcome some of the problems associated with act
ive drug targeting, we have developed a magnetic fluid to which drugs,
cytokines, and other molecules can be chemically bound to enable thos
e agents to be directed within an organism by high-energy magnetic fie
lds. In the first part of this study, various concentrations of the ma
gnetic fluid were tested in rats and immunosuppressed nude mice with r
egard to subjective and objective tolerance. In the second part, the s
ame parameters were evaluated after administration of the ferrofluid t
o which epirubicin (4'-epidoxorubicin) was chemically)ly bound. Finall
y, two forms of therapy with the magnetic fluid were tested: tumor tre
atment by mechanical occlusion with the ferrofluid in high concentrati
ons; and magnetic drug targeting, using small amounts of the ferroflui
d as a vehicle to concentrate epirubicin locally in tumors. As a resul
t, the ferrofluid did not cause major laboratory abnormalities; there
was no LD(50). With very high concentrations of the ferrofluid, animal
s showed lethargy for 1-2 days. There were no intolerances with the ep
irubicin-bound ferrofluid as well. Both forms of treatment led to comp
lete tumor responses in an experimental human kidney as well as in a x
enotransplanted colon carcinoma model. Thus, the magnetic fluid is a s
afe agent, which can be used in different ways for local forms of canc
er treatment in conjunction with high-energy magnetic fields.