Comparison of Succinimidyl [125I]Iodobenzoate with Iodogen Iodination Methods to Study Pharmacokinetics and ADME of Biotherapeutics

Abstract

In this study, iodination of proteins using SIB methodology has overcome the dehalogenation problem in vivo which is inherent in Iodogen method, and PK parameters of a protein iodinated via SIB were comparable to the un-labeled protein measured by LBA. The SIB iodination method is an improved labeling approach for biotherapeutics used in studying PK and biodistribution characteristics.

Utility of a human FcRn transgenic mouse model in drug discovery for early assessment and prediction of human pharmacokinetics of monoclonal antibodies

“…Study approach was determined based on available resources (Supplemental Table 1 52 PK Studies using LBA analysis 22/27 mAbs were administered IV and analyzed by LBA. MAbs were prepared in 10 mM histidine, 5% sucrose, pH 6.0 buffer, to a final concentration of 1.25 mg/mL (2.5 mg/mL for Rituximab-US and 0.5 mg/mL for mAb14 and mAb14-FcRnC).…”

“…Radio-iodination ( 125 I) of mAbs for PK studies was performed using the succinimidyl iodobenzoate (SIB) iodination method. 52 Briefly, 2-3 mCi of Na 125 I (Perkin-Elmer, Billerica, MA) was reacted with 5-8 mg N-succinimidyl-3-(tri-n-butylstannyl) benzoate (American Advanced Scientific, College Station, TX) to generate [ 125 I] SIB, which in turn was reacted with 1-2 mg of each test mAb, essentially as described. 52 The labeled proteins were purified by gel filtration over PD-10 desalting columns (GE Healthcare, Piscataway, NJ) to remove unconjugated [ 125 I]SIB and protein concentrations verified by UV spectroscopy.…”

“…52 Briefly, 2-3 mCi of Na 125 I (Perkin-Elmer, Billerica, MA) was reacted with 5-8 mg N-succinimidyl-3-(tri-n-butylstannyl) benzoate (American Advanced Scientific, College Station, TX) to generate [ 125 I] SIB, which in turn was reacted with 1-2 mg of each test mAb, essentially as described. 52 The labeled proteins were purified by gel filtration over PD-10 desalting columns (GE Healthcare, Piscataway, NJ) to remove unconjugated [ 125 I]SIB and protein concentrations verified by UV spectroscopy. Dosing solutions were prepared by mixing unlabeled mAbs with the corresponding 125 I-mAb to a final concentration of 1.25 mg/mL in buffer (PBS-CMF, 1% bovine serum albumin (BSA) or 10 mM histidine, 5% sucrose, 1% BSA, pH 6.0).…”

“…The radioactive specific activity of the dosing solutions was 70-100 mCi/mg for 2 mAbs that utilized a composite plasma sampling approach (mAb04 and mAb17), and 400-500 mCi/mg for all other mAbs using a serial plasma sampling approach. Radiochemical purity of dosing solutions was characterized by trichloroacetic acid (TCA; Sigma-Aldrich, St. Louis, MO) precipitation 52 and sizeexclusion HPLC using an Agilent Bio SEC-3 column (Agilent Technologies, Santa Clara, CA). The percentage of free 125 I was less than 1% in all dosing solution preparations.…”

Poor outcome with anti-programmed death-ligand 1 (PD-L1) antibody due to poor pharmacokinetic properties in PD-1/PD-L1 blockade-sensitive mouse models

“…10 In contrast, Iodine-125 (I-125) containing metabolites, such as the lysine adduct of I-125-iodobenzoate, are rapidly released from cells and eliminated from circulation such that the two radiolabels (In-111 and I-125) differ in their intracellular residence time (figure 1). [11][12][13][14] Therefore, once a labeled antibody is degraded in the endosome/ lysosome space following uptake, the I-125 metabolite is quickly released while the In-111 metabolite remains trapped within the cells. Hence, mAbs labeled with In-111 and I-125 have been used to distinguish between intact and degraded fractions of mAbs in tissues.…”