Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

(e)
(f)
(g)
Determine the RCP as follows. Using a sterile 1 mL syringe, an aliquot
(~0.05 mL) is removed and transferred to a conical tube containing 0.2 mL
of a mixture of avidin and diethylenetetraminopenta acetic acid (DTPA)
(0.4mM avidin and 2.5mM DTPA at pH6.0). The RCP is determined by
spotting an aliquot of the mixture on an instant thin layer chromatographic
(ITLC) silica gel (SG) strip and developing it with saline. Once developed,
the strip is cut in the middle and each portion counted separately. The
90 Y DOTA biotin bound to avidin remains at the origin (bottom counts),
whereas the unbound 90 Y, chelated by DTPA, migrates with the solvent
front (top counts). Caution: The amount of radioactivity at the origin is
expressed as a percentage of the total amount of radioactivity applied to the
strip (RCP).
If the RCP is >98%, add to the reaction mixture 0.2 mL of a sterile solution
of DTPA, 1mM, pH5.0, to bind any possible trace of free 90 Y not bound to
the biotin DOTA and then 1 mL of saline.
Using a sterile 3 mL syringe, withdraw the required patient’s dose and
measure in a dose calibrator that has previously been calibrated for that
counting geometry.
A–5. BIOTINYLATION OF IMMUNOGLOBULINS
(CONTRIBUTION FROM EUROPEAN INSTITUTE OF ONCOLOGY)
A–5.1. Introduction
The biotinylation of monoclonal antibodies (MAbs) represents a useful tool
to prepare in house MAbs containing a number of biotin molecules, which do not
compromise the MAb immunoreactivity (see Section 6 of this Annex), and can
be used as a first step in the pretargeting approach, which foresees as a final step
the intravenous injection of radiolabelled biotin (see Section 4 of this Annex)
[A–10, A–11].
A–5.2. Materials
2X AH biotin NHS (biotinyl aminocapronic acid N-hydroxysuccinimide
ester) containing a six carbon atom spacer between the head of the biotin group
and the activated carboxylic group can be purchased from SPA - Società Prodotti
Antibiotici S.p.A.
293