Wide application of a novel topoisomerase I inhibitor-based drug conjugation technology.

To establish a novel and widely applicable payload-linker technology for antibody-drug conjugates (ADCs), we have focused our research on applying exatecan mesylate (DX-8951f), a potent topoisomerase I inhibitor, which exhibits extensive antitumor activity as well as significant myelotoxicity, as the payload part. Through this study, we discovered a promising exatecan derivative (DX-8951 derivative, DXd), that has the characteristics of low membrane permeability and shows considerably less myelotoxicity than that shown by exatecan mesylate in an in vitro human colony forming unit-granulocyte macrophage assay. DXd was further used for drug conjugation by using commercially or clinically useful monoclonal antibodies to evaluate the potency of the ADC. The result revealed that the DXd-ADCs targeting CD30, CD33, and CD70 were effective against each of their respective target-expressing tumor cell lines. Moreover, a novel DXd-ADC targeting B7-H3, which is a new target for ADCs, also showed potent antitumor efficacy both in vitro and in vivo. In conclusion, this study showed that this novel topoisomerase I inhibitor-based ADC technology is widely applicable to a diverse number of antibodies and is expected to mitigate myelotoxicity, thereby possibly resulting in better safety profiles than that of existing ADC technologies.

Generation and Characterization of Inhibitory Antibodies Specific to Guinea Pig CXCR1 and CXCR2.

CXCR1 and CXCR2 are chemokine receptors that have different selectivity of chemokine ligands, but the distinct role of each receptor is not clearly understood. This is due to the absence of specific inhibitors in guinea pigs, which are the appropriate species for investigation of CXCR1 and CXCR2 because of their functional similarity to humans. In this study, we generated and evaluated monoclonal antibodies that specifically bound to guinea pig CXCR1 (gpCXCR1) and guinea pig CXCR2 (gpCXCR2) for acquisition of specific inhibitors. To assess the activity of antibodies, we established CHO-K1 cells stably expressing either gpCXCR1 or gpCXCR2 (CHO/gpCXCR1 or CHO/gpCXCR2). CHO/gpCXCR1 showed migration in response to guinea pig interleukin (IL)-8, and CHO/gpCXCR2 showed migration in response to both guinea pig IL-8 and guinea pig growth-regulated oncogene α. The receptor selectivities of the chemokines of guinea pigs were the same as the human orthologs. The inhibitory activities of the anti-gpCXCR1 and anti-gpCXCR2 monoclonal antibodies on cell migration were observed in a concentration-dependent manner. In conclusion, we successfully obtained inhibitory antibodies specific to gpCXCR1 and gpCXCR2. These inhibitory antibodies will be useful to clarify the physiological roles of CXCR1 and CXCR2 in guinea pigs.

[Neoadjuvant intraarterial chemotherapy with nedaplatin, peplomycin and mitomycin C for advanced cervical cancer].

The aim of the present study was to examine the usefulness of neoadjuvant intraarterial chemotherapy (NAC) using nedaplatin as key drug to improve the prognosis in case of advanced cervical cancer. Twenty-five cases of advanced cervical cancer (15 cases of stage II with high risks, 10 of stage III, referred to as the 254-S group) treated by NAC using nedaplatin, mitomycin C and peplomycin were compared with 30 cases (22 cases of stage II with high risks, 8 of stage III, referred to as the CDDP group) treated using cisplatin and mitomycin C which is the conventional regimen, in terms of measurable response, pathological response, rate of lymph node metastasis, cumulative survival rate, side effects and relapse style. According to the evaluation by measurable responses, the response rate was 90% (CR 52%) in the 254-S group and 75% (CR 15%) in the CDDP group. For pathological response of the specimen, the CR rate was 16% in the 254-S group and 23% in the CDDP group. The rate of lymph node metastasis extracted surgically was 33% and 41%, respectively. The cumulative survival rate in the 254-S group was about 10% better than in the CDDP group, but no significant difference was found. Leucopenia of both groups was of the same grade. In the 254-S group, although thrombocytopenia was more critical than in the CDDP group, there was a slight tendency to kidney toxicity. The locoregional recurrence rate was 12% in the 254-S group and 30% in the CDDP group. The distant metastasis rate was 16% and 27%, respectively. Although neoadjuvant intraarterial chemotherapy using nedaplatin as a key drug was useful to improve the prognosis of advanced cervical cancer, measures against recurrence outside the pelvis and individualization of medical treatment were considered to lead to a further improvement of the prognosis.