Pharmacokinetics of monoclonal antibodies locally-applied into the middle ear of guinea pigs.

Countless therapeutic antibodies are currently available for the treatment of a broad range of diseases. Some target molecules of therapeutic antibodies are involved in the pathogenesis of sensorineural hearing loss (SNHL), suggesting that SNHL may be a novel target for monoclonal antibody (mAb) therapy. When considering mAb therapy for SNHL, understanding of the pharmacokinetics of mAbs after local application into the middle ear is crucial. To reveal the fundamental characteristics of mAb pharmacokinetics following local application into the middle ear of guinea pigs, we performed pharmacokinetic analyses of mouse monoclonal antibodies to FLAG-tag (FLAG-mAbs), which have no specific binding sites in the middle and inner ear. FLAG-mAbs were rapidly transferred from the middle ear to the cochlear fluid, indicating high permeability of the round window membrane to mAbs. FLAG-mAbs were eliminated from the cochlear fluid 3 h after application, similar to small molecules. Whole-body autoradiography and quantitative assessments of cerebrospinal fluid and serum demonstrated that the biodistribution of FLAG-mAbs was limited to the middle and inner ear. Altogether, the pharmacokinetics of mAbs are similar to those of small molecules when locally applied into the middle ear, suggesting the necessity of drug delivery systems for appropriate mAb delivery to the cochlear fluid after local application into the middle ear.

Pharmacokinetics of trastuzumab deruxtecan (T-DXd), a novel anti-HER2 antibody-drug conjugate, in HER2-positive tumour-bearing mice.

Trastuzumab deruxtecan (T-DXd, DS-8201a) is an antibody-drug conjugate (ADC), comprising an anti-HER2 antibody (Ab) at a drug-to-Ab ratio of 7-8 with the topoisomerase I inhibitor DXd. In this study, we investigated the pharmacokinetics (PK), biodistribution, catabolism, and excretion profiles of T-DXd in HER2-positive tumour-bearing mice.Following intravenous (iv) administration of T-DXd, the PK profiles of T-DXd and total Ab (the sum of conjugated and unconjugated Ab) were almost similar, indicating that the linker is stable during circulation. Biodistribution studies using radiolabelled T-DXd demonstrated tumour-specific distribution and long-term retention. DXd was the main catabolite released from T-DXd in tumours, with exposure levels at least five times higher than those in normal tissues and seven times higher than those achieved by non-targeted control ADC. Following iv administration of DXd, it was rapidly cleared from the circulation (T1/2; 1.35 h) and excreted mainly through faeces as its intact form.The PK profiles reveal that T-DXd effectively delivers the expected payload, DXd, to tumours, while minimising payload exposure to the systemic circulation and normal tissues. The released DXd is rapidly cleared from systemic circulation, presumably via the bile with negligible metabolism, and excreted through the faeces.

Novel comb-shaped PEG modification enhances the osteoclastic inhibitory effect and bone delivery of osteoprotegerin after intravenous administration in ovariectomized rats.

PURPOSE: Recombinant osteoprotegerin (OPG) has been proven to be useful for treating various bone disorders such as osteoporosis. To improve its in vivo pharmacological effect, OPG was conjugated to novel comb-shaped co-polymers of polyethylene glycol (PEG) allylmethylether and maleamic acid (poly(PEG), 5 kDa). Biodistribution and bioactivity were evaluated. METHODS: OPG was conjugated via lysine to poly(PEG) and to linear PEG (0.5 kDa and 5 kDa). Poly(PEG)-OPG was compared with linear PEG0.5k-OPG and PEG5k-OPG in terms of in vitro and in vivo efficacy and bone distribution. RESULTS: The in vitro receptor binding study showed that poly(PEG)-OPG could be the most bioactive among the three PEG-OPG derivatives. Pharmacokinetic studies in ovariectomized (OVX) rats showed that serum half-life and AUC of poly(PEG)-OPG were comparable with those of linear PEG-OPG derivatives. For in vivo pharmacological effect, poly(PEG)-OPG showed the strongest inhibitory effect on bone resorption activity in OVX rats. Poly(PEG)-OPG demonstrated enhanced bone marrow distribution with higher selectivity than linear PEG5k-OPG. CONCLUSION: Poly(PEG) modification could provide longer residence time in serum and higher bone-marrow specific delivery of OPG, leading to a higher in vivo pharmacological effect.

Human pharmacokinetic prediction of UDP-glucuronosyltransferase substrates with an animal scale-up approach.

The aim of the current study was to evaluate the accuracy of allometric scaling methods for drugs metabolized by UDP-glucuronosyltransferases (UGTs), such as ketoprofen, imipramine, lorazepam, levofloxacin, zidovudine, diclofenac, furosemide, raloxifene, gemfibrozil, mycophenolic acid, indomethacin, and telmisartan. Human plasma clearance (CL) predictions were conducted from preclinical in vivo data by using multiple-species allometry with the rule of exponents and single-species allometric scaling (SSS) of mice, rats, monkeys, or dogs. Distribution volume at a steady state (V(ss)) was predicted by multiple-species allometry or SSS of V(ss). Oral plasma clearance (CL(po)) was calculated under the assumption that F(a) × F(g) was equivalent across species. Each of the results was compared with the observed parameter calculated from the clinical data after intravenous or oral administration. Multiple-species allometry and SSS of mice, rats, and dogs resulted in a similar accuracy of CL and CL(po) predictions. Monkeys tended to provide the most accurate predictions of human CL and CL(po). The ability to predict the half-life, which was determined from CL and V(ss) predictions, was more accurate in SSS of rats and monkeys. The in vivo fraction metabolized by glucuronidation (f(m,UGT)) in bile duct-cannulated monkeys was relatively similar to that of humans compared with other animal species, which likely contributed to the highest accuracy of SSS prediction of monkeys. On the basis of the current results, monkeys would be more reliable than other animal species in predicting human pharmacokinetics and f(m,UGT) for drugs metabolized by UGTs.