Pharmacokinetics and immunogenicity investigation of a human anti-interleukin-17 monoclonal antibody in non-naïve cynomolgus monkeys.

The pharmacokinetics (PK) of biologic therapeutics, especially monoclonal antibodies (mAbs), in monkeys generally presents the most relevant predictive PK information for humans. However, human mAbs, xenogeneic proteins to monkeys, are likely to be immunogenic. Monkeys previously treated with a human mAb (non-naïve) may have developed antidrug antibodies (ADAs) that cross-react with another test mAb in subsequent studies. Unlike PK studies for small-molecule therapeutics, in which animals may be reused, naïve monkeys have been used almost exclusively for preclinical PK studies of biologic therapeutics to avoid potential pre-existing immunologic cross-reactivity issues. The propensity and extent of pre-existing ADAs have not been systematically investigated to date. In this study, the PK and immunogenicity of mAb A, a human anti-human interkeukin-17 mAb, were investigated in a colony of 31 cynomolgus monkeys previously exposed to other human mAbs against different targets. We screened the monkeys for pre-existing antibodies to mAb A prior to the PK study and showed that 44% of the monkeys had pre-existing cross-reactive antibodies to mAb A, which could affect the PK characterization of the antibody. In the subcolony of monkeys without measurable pre-existing ADAs, PK and immunogenicity of mAb A were successfully characterized. The impact of ADAs on mAb A PK was also demonstrated in the monkeys with pre-existing ADAs. Here we report the results and propose a pragmatic approach for the use of non-naïve monkeys when conducting PK studies of biologic therapeutics.

4ß-Hydroxycholesterol as an endogenous biomarker of CYP3A activity in cynomolgus monkeys.

It has been proposed that in humans 4ß-hydroxycholesterol is formed mainly by CYP3A-catalyzed metabolism of cholesterol and thus may serve as an endogenous marker for CYP3A activity. The cynomolgus monkey is widely used as one of the nonrodent preclinical safety species in pharmaceutical research. In the current study, the potential application of 4ß-hydroxycholesterol as an endogenous biomarker of CYP3A in response to drug treatment was evaluated in cynomolgus monkeys. Following multiple oral administration of rifampicin (a known CYP3A inducer) at 15 mg/kg/d in cynomolgus monkeys, the mean serum 4ß-hydroxycholesterol levels increased 4-fold from the baseline of 55.3 ± 21.7 to 221 ± 53.4 ng/ml. The mean concentration ratios of 4ß-hydroxycholesterol to cholesterol increased 5-fold. The data suggest that 4ß-hydroxycholesterol formation from cholesterol metabolism was induced by rifampicin treatment in monkeys. This observation correlated with the metabolism of midazolam (a probe substrate of CYP3A activity) monitored in the same study. The serum exposure (area under the curve) of midazolam was markedly decreased by ∼95%, confirming the induction of CYP3A catalytic activity by rifampicin treatment in monkeys. The formation of 4ß-hydroxycholesterol from cholesterol was specifically mediated by recombinant cynomolgus CYP3A8 and CYP3A5. The Km values of CYP3A8 and CYP3A5 for 4ß-hydroxycholesterol formation from cholesterol were 204 and 104 µM, respectively, and Vmax values were 0.600 and 0.310 pg/pmol/min, respectively. The results suggest that 4ß-hydroxycholesterol can be used as an endogenous biomarker to identify strong CYP3A inducers in cynomolgus monkeys, which may help to evaluate drug-drug interaction potential of drug candidates in preclinical settings.

Nonclinical safety assessment of a synthetic peptide thrombopoietin agonist: effects on platelets, bone homeostasis, and immunogenicity and the implications for clinical safety monitoring of adverse bone effects.

RWJ-800088 is a novel, potent polyethylene glycol (PEG)-conjugated thrombopoietin (TPO) mimetic that increases platelet levels and protects against thrombocytopenia. A nonclinical safety program was customized for this peptide that takes into account its protein-like structure, synthetic chemical nature, agonist pharmacologic activity, and mode of administration. In repeat-dose toxicity studies, the salient findings were dose-related increases in circulating platelet counts, mean platelet volume, and megakaryocytes in the bone marrow with no antibody formation. Reversible myelofibrosis and hyperostosis were observed in rats, but not dogs, when the circulating platelet levels exceeded 3× those of vehicle controls. The bone effects were due to the exaggerated pharmacologic effect and excessive stimulation and elevation of megakaryocytes by TPO, which results in intramedullary proliferation of fibroblasts and mesenchymal cells followed by osseous metaplasia. These findings support the use of platelet elevations of >3× as a stopping criterion to prevent potential adverse bone-related effects in humans.