Preclinical pharmacokinetics, interspecies scaling, and tissue distribution of humanized monoclonal anti-IL-13 antibodies with different IL-13 neutralization mechanisms

Abstract

Numerous animal and in vitro studies suggest that neutralization of IL-13 is an attractive approach for therapeutic intervention in asthma. In this paper we describe preclinical pharmacokinetics (PK), interspecies scaling, and biodistribution of two humanized anti-IL-13 IgG1 monoclonal antibodies, Ab-01 and Ab-02, with different IL-13 neutralization mechanisms. PK parameters of Ab-01 and Ab-02 following IV or SC dosage to mouse, rat, cynomolgus monkey, and sheep, were similar. After IV administration, the elimination of anti-IL-13 antibodies was slow in all species tested and the serum clearance ranged from 0.13 mL/h/kg in monkeys to 0.81 mL/h/kg in mice. Both anti-IL-13 antibodies appeared to be confined primarily to the vascular space, as volume of distribution was relatively small (< 120 mL/kg) in all species and tissue-to-serum concentration ratios (in mice and rats) were low (< 0.5) in the tissues examined. The elimination half-life ranged from 3–6 days in mice to 14–17 days in monkey and sheep. In monkeys, PK parameters appeared to be approximately linear in the 1–100 mg/kg dose range. Following SC administration, the bioavailability of anti-IL-13 antibodies was 60–90% in all species tested. PK profile of Ab-02 in the model of acute airway inflammation (induced by Ascaris challenge) was, in general, similar to that in unchallenged monkeys; however, volume of distribution and clearance tended to decrease in Ascaris-challenged animals. Allometric scaling suggested that anti-IL-13 antibodies would likely to have a favorable PK profile, such as slow clearance and long terminal half-life, following IV or SC administration to humans.

Introduction

Numerous animal and in vitro studies support a major role for Th2 cytokine, interleukin-13 (IL-13), in asthma pathogenesis [1], [2], [3], [4]. In addition, there are consistent correlations between polymorphism in the IL-13 gene and asthma susceptibility in humans [5]. Neutralization of IL-13 with anti-IL-13 antibodies or with IL-13 receptor α2/Fc fusion protein (IL-13Rα2-Fc) prevents airway hyperresponsiveness and other asthmatic changes in mice [3], [6], [7], [8], [9], [10], sheep [11], and cynomolgus monkeys [12], [13]. Thus, neutralization of IL-13 is an attractive approach for therapeutic intervention in asthma.

IL-13 interacts with cells through a receptor complex consisting of IL-13 receptor α1 (IL-13αR1) and interleukin-4 receptor alpha (IL-4Rα) subunits [1], [2]. IL-13 first undergoes a low affinity interaction with IL-13Rα1, which recruits IL-4Rα to form an active signaling complex with high affinity for IL-13, leading to phosphorylation of STAT6 and downstream cellular activation events.

Ab-01 and Ab-02 are the humanized anti-IL-13 monoclonal antibodies that have been shown to be efficacious in a cynomolgus monkey model of acute airway inflammation induced by lung segmental challenge with Ascaris antigen [12], [13]. Although Ab-01 and Ab-02 have comparable inhibitory activity in vitro and comparable in vivo efficacy, these antibodies neutralize IL-13 bioactivity by different mechanisms [12], [13]. Ab-01 blocks the interaction of IL-13 with the IL-4Rα chain (but not the IL-13Rα1/IL-13Rα2 chains), while Ab-02 blocks binding of IL-13Rα1/IL-13Rα2 and IL-13. Since anti-IL-13 antibodies bind to a soluble ligand, the potential for a direct Fc-mediated activity is low. However, by virtue of its epitope Ab-01 has the potential for an indirect Fc-mediated effector activity on IL-13Rα1/IL-4Rα-expressing cells, while Ab-02 does not. Therefore, two point mutations that reduce potential effector activity were introduced into the lower hinge region of the IgG1Fc tail of both antibodies [13]. Neither Ab-01 nor Ab-02 binds to rodent IL-13. Ab-01 cross-reacts with monkey IL-13 (K_D of 1.4 × 10^− 11 M) and with sheep IL-13, albeit with significantly lower affinity compared to human IL-13, while Ab-02 cross-reacts only with monkey IL-13 (K_D of 9.2 × 10^− 11 M) [13].

To support development of anti-IL-13 antibodies, pharmacokinetic studies were conducted in mice, rats, sheep, and cynomolgus monkeys after IV and SC administration. Tissue distribution of [¹²⁵I]Ab-01 and [¹²⁵I]Ab-02 was studied in mice and rats, respectively. The pharmacokinetic data in animals were used to predict the disposition of anti-IL13 in humans using allometric scaling. In addition, we obtained PK profiles in Ascaris-challenged monkeys and compared to those in normal unchallenged animals.