Institute of Pharmacy, University of Regensburg, D-93040, Regensburg, Germany.
Institute of Pharmacy, University of Regensburg, D-93040, Regensburg, Germany.
Eur J Med Chem. 2021 Jan 15;210:112958. doi: 10.1016/j.ejmech.2020.112958. Epub 2020 Nov 4.
A good balance between hydrophilicity and lipophilicity is a prerequisite for all bioactive compounds. If the hydrophilicity of a compound is low, its solubility in water will be meager. Many drug development failures have been attributed to poor aqueous solubility. ABCG2 inhibitors are especially prone to be insoluble since they have to address the extremely large and hydrophobic multidrug binding site in ABCG2. For instance, our previous, tariquidar-related ABCG2 inhibitor UR-MB108 (1) showed high potency (79 nM), but very low aqueous solubility (78 nM). To discover novel potent ABCG2 inhibitors with improved solubility we pursued a fragment-based approach. Substructures of 1 were optimized and the fragments 'enlarged' to obtain inhibitors, supported by molecular docking studies. Synthesis was achieved, i.a., via Sonogashira coupling, click chemistry and amide coupling. A kinetic solubility assay revealed that 1 and most novel inhibitors did not precipitate during the short time period of the applied biological assays. The solubility of the compounds in aqueous media at equilibrium was investigated in a thermodynamic solubility assay, where UR-Ant116 (40), UR-Ant121 (41), UR-Ant131 (48) and UR-Ant132 (49) excelled with solubilities between 1 μM and 1.5 μM - an up to 19-fold improvement compared to 1. Moreover, these novel N-phenyl-chromone-2-carboxamides inhibited ABCG2 in a Hoechst 33342 transport assay with potencies in the low three-digit nanomolar range, reversed MDR in cancer cells, were non-toxic and proved stable in blood plasma. All properties make them attractive candidates for in vitro assays requiring long-term incubation and in vivo studies, both needing sufficient solubility at equilibrium. 41 and 49 were highly ABCG2-selective, a precondition for developing PET tracers. The triple ABCB1/C1/G2 inhibitor 40 qualifies for potential therapeutic applications, given the concerted role of the three transporter subtypes at many tissue barriers, e.g. the BBB.
亲水性和疏水性之间的良好平衡是所有生物活性化合物的前提条件。如果化合物的亲水性低，其在水中的溶解度就会很低。许多药物开发失败都归因于水溶性差。ABCG2 抑制剂尤其容易不溶，因为它们必须解决 ABCG2 中非常大且疏水的多药物结合位点。例如，我们之前的与 tariquidar 相关的 ABCG2 抑制剂 UR-MB108（1）表现出高活性（79 nM），但水溶性非常低（78 nM）。为了发现具有改善的溶解度的新型有效 ABCG2 抑制剂，我们采用了基于片段的方法。优化了 1 的亚结构，并通过分子对接研究“扩大”了片段以获得抑制剂。通过 Sonogashira 偶联、点击化学和酰胺偶联等方法实现了合成。动力学溶解度测定表明，1 和大多数新型抑制剂在应用的生物测定的短时间内没有沉淀。在平衡热力学溶解度测定中研究了化合物在水介质中的溶解度，其中 UR-Ant116（40）、UR-Ant121（41）、UR-Ant131（48）和 UR-Ant132（49）的溶解度在 1 μM 和 1.5 μM 之间-与 1 相比提高了 19 倍。此外，这些新型 N-苯基-色酮-2-甲酰胺抑制剂在 Hoechst 33342 转运测定中以低三位数纳摩尔范围的效力抑制 ABCG2，逆转了癌细胞中的 MDR，无毒性，并在血浆中稳定。所有这些特性使它们成为需要长期孵育的体外测定和体内研究的有吸引力的候选物，这两者都需要在平衡时具有足够的溶解度。41 和 49 对 ABCG2 具有高度选择性，是开发 PET 示踪剂的前提条件。鉴于三种转运体亚型在许多组织屏障（如 BBB）中的协同作用，三重 ABCB1/C1/G2 抑制剂 40 有资格用于潜在的治疗应用。
