Chen Ping, Bordeau Brandon M, Zhang Wenqiu, Balthasar Joseph P
Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo, 452 Pharmacy Building, Buffalo, New York, 14214, USA.
AAPS J. 2025 May 9;27(4):91. doi: 10.1208/s12248-025-01076-z.
The pharmacokinetics of antibodies with varied binding kinetics were simulated to assess the role of affinity and binding microconstants (kon, koff) on tumor exposure and intra-tumoral distribution. Anti-HER2 constructs (trastuzumab, pertuzumab, VK3VH6, and conjugates with DM1 and gelonin) were produced, purified, and tested for binding and cytotoxicity in vitro, and for intra-tumoral distribution and anti-tumor efficacy in mice. Simulations demonstrated that homogeneity in intra-tumoral distribution increases with increases in koff and with decreases in kon. Interestingly, simulations also predicted that homogeneity in tumor distribution may be improved by decreasing kon and koff in parallel (without changing affinity). Relative to trastuzumab, pertuzumab exhibits similar affinity but a ~ fivefold smaller kon and koff, while VK3VH6 exhibits a similar koff but a ~ 30-fold lower kon and affinity. Conjugate concentrations associated with 50% inhibition of cell proliferation (IC50s) were found to vary with affinity, where IC50 values were similar for pertuzumab and trastuzumab, and higher for VK3VH6. Consistent with model simulations, VK3VH6 and pertuzumab demonstrated more homogeneous tumor distribution than trastuzumab. Although treatment differences were not statistically significant, pertuzumab and VK3VH6 conjugates showed trends for increased survival time relative to mice treated with trastuzumab conjugates. Our simulation and experimental results demonstrate complex relationships between antibody-antigen binding kinetics, intratumoral distribution, and efficacy. The rate constant of association, kon, is an underappreciated determinant of intra-tumoral distribution; among high-affinity antibodies, those with lower values of kon may be expected to exhibit improved intra-tumoral distribution and, potentially, efficacy.
模拟了具有不同结合动力学的抗体的药代动力学，以评估亲和力和结合微观常数（kon、koff）对肿瘤暴露和肿瘤内分布的作用。制备、纯化了抗HER2构建体（曲妥珠单抗、帕妥珠单抗、VK3VH6以及与DM1和去甲氧基凝胶毒素的缀合物），并在体外测试其结合和细胞毒性，在小鼠体内测试其肿瘤内分布和抗肿瘤疗效。模拟结果表明，肿瘤内分布的均匀性随着koff的增加和kon的降低而增加。有趣的是，模拟还预测，通过同时降低kon和koff（不改变亲和力），可以改善肿瘤分布的均匀性。相对于曲妥珠单抗，帕妥珠单抗表现出相似的亲和力，但kon和koff约小5倍，而VK3VH6表现出相似的koff，但kon和亲和力约低30倍。发现与50%细胞增殖抑制（IC50）相关的缀合物浓度随亲和力而变化，其中帕妥珠单抗和曲妥珠单抗的IC50值相似，而VK3VH6的IC50值更高。与模型模拟一致，VK3VH6和帕妥珠单抗的肿瘤分布比曲妥珠单抗更均匀。尽管治疗差异无统计学意义，但与用曲妥珠单抗缀合物治疗的小鼠相比，帕妥珠单抗和VK3VH6缀合物显示出生存时间延长的趋势。我们的模拟和实验结果证明了抗体-抗原结合动力学、肿瘤内分布和疗效之间的复杂关系。结合速率常数kon是肿瘤内分布中一个未得到充分重视的决定因素；在高亲和力抗体中，kon值较低的抗体可能会表现出更好的肿瘤内分布，并可能具有更高的疗效。
