Niloy Kumar Kulldeep, Horn Jamie, Bhuiyan Nazmul H, Shaaban Khaled A, Bhosale Suhas S, Prisinzano Thomas E, Thorson Jon S, Rohr Jurgen, Leggas Markos
Department of Pharmacy and Pharmaceutical Sciences, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Department of Pharmaceutical Sciences, College of Pharmacy, The University of Tennessee Health Science Center, Memphis, TN 38163, USA.
Pharmaceutics. 2025 Jun 10;17(6):765. doi: 10.3390/pharmaceutics17060765.
: Mithramycin (MTM) is a polyketide anti-cancer natural product previously identified as an EWS-FLI1 inhibitor. This oncogenic transcription factor is a canonical target for drug development in Ewing sarcoma. However, poor pharmacokinetics have been identified as a critical liability of MTM, preventing its further development. Through semisynthetic chemical modifications, we identified mithramycin SA-Trp (MTMSA-Trp) as being a pharmacologically superior congener. To explore their pharmacokinetic (PK) differences, this study examined the plasma PKs and plasma protein binding (PPB) of MTM and MTMSA-Trp in mice, rats, and monkeys. : Protein binding was investigated by rapid equilibrium dialysis in plasma from mice, rats, monkeys, and humans. The pharmacokinetics were investigated at milligram- and microgram-level doses in mice and rats. The pharmacokinetics in monkeys were investigated using the cassette dosing approach at two microgram-level doses. The MTMSA-Trp pharmacokinetic linearity was evaluated in mice at 0.3, 1, 3, and 10 mg/kg doses. All samples were analyzed using LC-MS/MS. : Plasma protein binding was higher for MTMSA-Trp (1-4% unbound) than for MTM (10-30% unbound) across species, except in athymic nude mice (1-4% unbound and <1% for mithramycin and MTMSA-Trp, respectively). In mice and rats, MTMSA-Trp had significantly lower clearance than MTM at both milligram and microgram doses; however, the difference in plasma exposure was more pronounced at milligram doses. Consistent with the rodent PK results, cassette microdosing in monkeys showed that the clearance of MTMSA-Trp was lower than that of MTM, but the differences were less pronounced. In the dose proportionality study, MTMSA-Trp showed linear pharmacokinetics at 1, 3, and 10 mg/kg doses. : MTMSA-Trp has significantly lower clearance than MTM in rodent models. This is a significant improvement compared to the parent drug, MTM, and warrants further evaluation of PKs in non-rodent models to enable the prediction of MTMSA-Trp PK in humans.
光辉霉素（MTM）是一种聚酮类抗癌天然产物，先前被鉴定为EWS-FLI1抑制剂。这种致癌转录因子是尤因肉瘤药物开发的典型靶点。然而，不良的药代动力学已被确定为MTM的一个关键缺陷，阻碍了其进一步开发。通过半合成化学修饰，我们确定了光辉霉素SA-色氨酸（MTMSA-Trp）是一种药理学上更优的同系物。为了探究它们的药代动力学（PK）差异，本研究检测了MTM和MTMSA-Trp在小鼠、大鼠和猴子体内的血浆PK及血浆蛋白结合（PPB）情况。
通过快速平衡透析法研究了小鼠、大鼠、猴子和人类血浆中的蛋白结合情况。在小鼠和大鼠中，以毫克和微克级剂量研究了药代动力学。在猴子中，采用多剂量给药法以两个微克级剂量研究了药代动力学。在小鼠中，以0.3、1、3和10 mg/kg剂量评估了MTMSA-Trp的药代动力学线性。所有样品均采用液相色谱-串联质谱（LC-MS/MS）进行分析。
除无胸腺裸鼠外（MTM和MTMSA-Trp的未结合率分别为1 - 4%和<1%），在所有物种中，MTMSA-Trp的血浆蛋白结合率（未结合率为1 - 4%）高于MTM（未结合率为10 - 30%）。在小鼠和大鼠中，无论毫克剂量还是微克剂量，MTMSA-Trp的清除率均显著低于MTM；然而，在毫克剂量下，血浆暴露差异更为明显。与啮齿动物的PK结果一致，猴子的多剂量微量给药研究表明，MTMSA-Trp的清除率低于MTM，但差异不太明显。在剂量比例研究中，MTMSA-Trp在1、3和10 mg/kg剂量下呈现线性药代动力学。
在啮齿动物模型中，MTMSA-Trp的清除率显著低于MTM。与母体药物MTM相比，这是一个显著的改进，有必要在非啮齿动物模型中进一步评估PK，以便预测MTMSA-Trp在人体内的PK情况。
