Antibody-drug conjugate (ADC) is a new class of therapeutics composed of a monoclonal antibody and small cytotoxin moieties conjugated through a chemical linker. ADC molecules bind to the target antigens expressed on the tumor cell surfaces guided by the monoclonal antibody component. The binding ADC molecules can be internalized and subsequently the toxin moieties can be released within the tumor cells via chemical and/or enzymatic reactions to kill the target cells. The conjugation combines the merits of both components, i.e., the high target specificity of the monoclonal antibody and the highly potent cell killing activity of the cytotoxin moieties. However, such complexities make the pharmacokinetic and metabolic studies of ADCs highly challenging. The major challenges should include characterization of absorption, distribution, metabolism and excretion, investigation of underlying mechanisms, assessment of pharmacokinetic- pharmacodynamic relationship, and analytical method development of ADC drugs. This review will discuss common pharmacokinetic issues and considerations, as well as tools and strategies that can be utilized to characterize the pharmacokinetic and metabolic properties of ADCs.

OBJECTIVEInterleukin-27 (IL-27) has been reported to reduce the levels of interleukin-17 (IL-17) and alleviate the severity of experimental autoimmune myocarditis. IL-17, an important tissue-protective cytokine in viral myocarditis (VMC), has been reported to increase synovial expression of IL-27 in rheumatoid arthritis. However, the influence of IL-17 on IL-27 expression in murine model of VMC remains unknown.

METHODSWild-type (WT) and IL-17A-deficient (IL-17A(-/-)) mice on the BALB/c background were intraperitoneally (i.p) injected with coxsackievirus B3 (CVB3) for establishing VMC models. Cardiac tissue was obtained on day 7 after CVB3 injection. Myocardial histopathologic changes were observed by hematoxylin-eosin (HE) stained myocardial sections.Expression of IL-27 in heart and serum was measured by real-time reverse transcription-polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assay (ELISA), respectively. Furthermore, splenic lymphocytes and peritoneal macrophages were purified 1 week after injection from WT mice.Isolated lymphocytes were cultured in the presence of different concentrations (0 and 25 ng/ml) of recombinant IL-17 (rIL-17) for 24 h. Macrophages were cultured with different concentrations of rIL-17 (0 and 10 ng/ml) for 48 h.IL-27 mRNA expression of cultured cells was assayed by RT-PCR, and their protein level in the culture supernatant was measured by ELISA.

RESULTSCompared with WT mice, significantly less cardiac inflammation was evidenced in the heart of IL-17A-/- mice (0.9 ± 0.3 vs.1.9 ± 0.5) , relative cardiac IL-27 p28 mRNA expressions (1.11 ± 0.24 vs.3.1 ± 0.8) and serum IL-27 protein[(72 ± 18) pg/ml vs.(95 ± 25) pg/ml] were also significantly lower in IL-17A-/- mice (all P < 0.05).In the culture lymphocytes, the relative mRNA (1.02 ± 0.13 vs.1.32 ± 0.21) and protein [(49 ± 9) pg/ml vs.(52 ± 11) pg/ml]expressions of IL-27 p28 and were similar post treatment with 0 and 25 ng/ml rIL-17 (all P > 0.05). Compared with 0 ng/ml rIL-17 culture with macrophages, higher relative mRNA (8.5 ± 3.1 vs.2.2 ± 0.7) and protein [(368 ± 95) pg/ml vs.(150 ± 38) pg/ml] expressions of IL-27 p28 were detected in 10 ng/ml rIL-17 group (all P < 0.05).

CONCLUSIONOur data indicates that cytokine IL-17 may contribute to the secretion of IL-27 in VMC mice.Furthermore, macrophages but not lymphocytes may be the important IL-27-producing immune cells and major target cells for IL-17. Thus,IL-27 and IL-17 might be actively involved in the pathogenesis of VMC.

Animals ; Coxsackievirus Infections ; immunology ; metabolism ; Disease Models, Animal ; Interleukin-17 ; immunology ; Interleukin-27 ; metabolism ; Macrophages ; metabolism ; Male ; Mice ; Mice, Inbred BALB C ; Myocarditis ; immunology ; metabolism