Influence of physiochemical properties on the subcutaneous absorption and bioavailability of monoclonal antibodies

Abstract

Many therapeutic monoclonal antibodies (mAbs) were initially developed for intravenous (IV) administration. As a means to improve mAb drug-ability and the patient experience, subcutaneous (SC) administration is an increasingly important delivery route for mAbs. Unlike IV administration, bioavailability limitations for antibodies have been reported following SC injection and can dictate whether a mAb is administered via this parenteral route. The SC bioavailability of antibodies has been difficult to predict, and it can be variable and partial, with values ranging from ~50% to 100%. The mechanisms leading to the incomplete bioavailability of some mAbs relative to others are not well understood. There are some limited data that suggest the physiochemical properties inherent to a mAb can contribute to its SC absorption, bioavailability, and in vivo fate. In this study, we evaluated the integrated influence of multiple mAb physiochemical factors on the SC absorption and bioavailability of six humanized mAbs in both rats and cynomolgus monkeys. We demonstrate the physiochemical properties of mAbs are critical to their rate and extent of SC absorption. The combination of high positive charge and hydrophobic interaction significantly reduced the rate of the evaluated mAb's SC absorption and bioavailability. Reduction or balancing of both these attributes via re-engineering the mAbs restored desirable properties of the molecules assessed. This included reduced association with SC tissue, improvements in mAb absorption from the SC space and overall SC bioavailability. Our findings point to the importance of evaluating the relative balance between various physiochemical factors, including charge, hydrophobicity, and stability, to improve the SC drug-ability of mAbs for selecting or engineering mAbs with enhanced in vivo absorption and bioavailability following SC administration.

Keywords: Subcutaneous absorption; charge; chemical properties; disposition; drug-ability; hydrophobicity; monoclonal antibody; nonspecific binding; pharmacokinetics; physiochemical characterization; subcutaneous bioavailability; thermal stability.

Figure 1.

Subcutaneous tissue association of the Platform 1 and 3 parent and re-engineered molecules following a single administration of 0.1 mg/kg of each ¹²⁵I labeled mAb. Data show the relative SC tissue association of each re-engineered mAb relative to their respective parental mAb. The 1-h post dose time point skin punctures radioactive count for each mAb was considered 100% bound for data normalization purposes. The 6-h post dose collected radioactivity data were compared reported as a fraction of the percent bound relative to the 1-h post dose time point for calculation, data processing and loss of mAb from the SC site reporting over time. Data are the average of two independent SC tissue assessment from two cynomolgus monkeys for each mAb.

Figure 2.

Correlation plots of the rat pharmacokinetic parameters following SC administration of mAbs 1P and 1RE in Platform 1, mAbs 2P and 2RE in Platform 2 and mAbs 3P and 3RE in Platform 3. Correlation plots for the (a) CL/F, (b) SC bioavailability, (c) rate of SC absorption (k_a), (d) C_max and (e) T_max with the physiochemical properties HpnIP, HIP, T_agg and T_{m onset.}

Figure 3.

Correlation plots of the cynomolgus monkey pharmacokinetic parameters following SC administration of mAbs 1P and 1RE in Platform 1 and mAbs 3P and 3RE in Platform 3. Correlation plots for the (a) CL/F, (b) SC bioavailability, (c) rate of SC absorption (k_a), (d) C_max and (e) T_max with the physiochemical properties HpnIP, HIP, T_agg and T_{m onset.}