Stability of Monoclonal Antibodies, Lym-1 and ChL6, and 2IT-BAD-Lym-1 Immunoconjugate with Ultra Freezer Storage

Abstract

Use of a single lot of monoclonal antibody (MoAb) or immunoconjugate for clinical studies provides efficiency of scale and consistent characteristics for MoAb-based pharmaceuticals. Lym-1, an anti-lymphoma mouse IgG _2∞ chimeric L6 (ChL6), an anti-adenocarcinoma mouse IgG_2a-human IgG₁ chimera, and the immunoconjugate 2IT-BAD-Lym-1 were examined for stability following storage. Methods. Lym-1, ChL6, and 2IT-BAD-Lym-1 were aliquotted with filtration and stored at -70 ^°C for up to 8.5 years. 2IT-BAD-Lym-1 stored for 6.3 years (lot A) was compared to freshly prepared 2IT-BAD-Lym-1 (lot B). MoAbs were thawed and examined yearly by gel filtration high performance liquid chromatography (HPLC), polyacrylamide gel electrophoresis (PAGE), cellulose acetate electrophoresis (CAE), and Scatchard analysis of antigen binding. 2IT-BAD-Lym-1 was evaluated by HPLC, CAE, and radioimmunoassay. To assure the in vivo significance of the in vitro studies, 2IT-BAD-Lym-1 lots A and B were labeled with ¹¹¹In and their pharmacokinetics in BALB/c mice were compared. Results. Lym-1 demonstrated stability over 8.5 years, providing the following ranges of data over the interval: 98-100% chemical purity (HPLC), 96-100% monomeric fraction (CAE), 8.18-8.46 antigen binding pKa (Scatchard). Similar results were obtained for ChL6for 7.4 years. HPLC and PAGE of Lym-1 and ChL6 have not changed from original manufacturer specifications, and both MoAbs remain sterile and apyrogenic. No significant differences between 2IT-BAD-Lym-1 lots A and B were observed by in vitro evaluation or pharmacokinetics in mice. Conclusions. Lym-1, ChL6, and 2IT-BAD-Lym-1 as manufactured and stored for 8.5, 7.4, and 6.3 years, respectively, demonstrated retention of structural and functional integrity.