Chemistry Reference
In-Depth Information
Scheme 3 Synthesis of
HPPH-2 Gd(III)DTPA
conjugates
The strategy of employing tumor-specific molecules as a vehicle to carry
radioactive tracers to target tissue turned out to be very successful and has led to
the development of many novel tumor-imaging radiopharmaceuticals [
65
]. In this
regard,
111
In-complexes of certain porphyrins have shown significant potential for
SPECT imaging. Roswell Park group was the first to show the utility of tumor-avid
chlorophyll-
a
-based NIR photosensitizer for dual imaging (PET/fluorescence) with
an option of photodynamic therapy [
66
-
70
]. Most of the porphyrin-based com-
pounds show optimal tumor uptake at 24-48 h post-administration. Therefore, the
radionuclide initially selected was
124
I- with a half-life of 4 days, which provides
several advantages: (1) the
124
I-labeled agent can be synthesized in high yield and
