Explore efflux transporter-associated chemoresistance using a chemical biology approach and develop efflux resistant TOPO I inhibitors as ADC payloads

抗体-药物结合物(ADC)是一类新兴的癌症治疗药物，它由单抗(MAb)通过连接物与细胞毒药物连接而成。抗体成分通过与特定的细胞表面抗原结合来确定ADC的特异性，从而允许选择性地靶向某些类型的细胞1。与传统化疗药物相比，ADC的主要优势是增加了治疗窗口，因为抗体的细胞靶向性减少了非靶标毒性2。到目前为止，FDA已经批准了11种ADC，其中大多数被批准用于液体肿瘤的治疗，只有3种ADC被批准用于实体肿瘤。有效载荷的适当选择对于开发用于临床开发的成功的ADC至关重要。可开发性问题，如外排能力、非选择性毒性、化疗耐药性、现有有效载荷的不良药代动力学和药效学特征，正在导致临床开发的失败。目前在临床评估中的大多数ADC使用微管抑制剂或DNA损伤剂作为有效载荷，但最近，由于Trodelvy R和Enhertu R分别使用拓扑异构酶抑制剂SN-38和Dxd作为有效载荷，大量带有拓扑异构酶I(Topo I)抑制剂的ADC已进入临床开发(图1)。喜树碱及其衍生物与Topo 1/DNA复合体结合以防止复温，复温可由于部分切割的DNA5的积累而导致细胞死亡。SN-38和Dxd都是喜树碱的类似物，与微管抑制剂和DNA结合剂相比，它们的尺寸相对较小，毒性较低，因此被认为是下一代ADC有效载荷。然而，SN-38和Dxd都是P-gp和BCRP外排泵的外排底物，这降低了它们的有效性，伦敦大学国王学院的拉赫曼实验室开发了一种专有的外排耐药破碎器(ERB)技术，该技术允许修改化学支架以降低其外排敏感性，同时保持靶标活性(图2)8，9。这增加了药物的细胞内浓度，可以克服化疗耐药，降低耐药性出现的可能性。本博士项目的目的是使用化学生物学方法探索外排转运体相关耐药现象，并生产ERB修饰的Topo I抑制剂，可进一步开发为ADC有效载荷。

Antibody-drug conjugates (ADCs) are an emerging class of cancer therapeutics that consist of a monoclonal antibody (mAb) connected to a cytotoxic drug via a linker. The antibody component determines the specificity of the ADC by binding to specific cell surface antigens, allowing selective targeting of certain cell types1. The main advantage of ADCs relative to conventional chemotherapeutics is an increased therapeutic window since the cell-targeting properties of antibodies decrease off-target toxicity2. The FDA has approved 11 ADCs to date with majority of them approved for the treatment of liquid tumours and only 3 ADCs have been approved for solid tumours. An appropriate choice of payload is critical to developing a successful ADC for clinical development3. Developability problems such as efflux liability, non-selective toxicity, chemoresistance, poor pharmacokinetic and pharmacodynamic profiles of existing payloads are leading to failures in clinical development. The majority of ADCs currently in clinical evaluation use microtubule inhibitors or DNA damaging agents as the payload, but more recently a significant number of ADCs with Topoisomerase I (TOPO I) inhibitors have entered clinical development due to the approval of Trodelvy R and Enhertu R which utilise Topoisomerase inhibitors SN-38 and Dxd as payloads (Figure 1), respectively4. Camptothecin and its derivatives bind to the TOPO 1/DNA complex to prevent reannealing, which can cause cell death due to the accumulation of partially cleaved DNA5. Both SN-38 and Dxd are Camptothecin analogues and are considered as next generation ADC payloads due to their relatively small-size and lower toxicity compared to microtubule inhibitors and DNA binding agents. However, both SN-38 and Dxd are efflux substrates of P-gp and BCRP efflux pumps which reduces their effectiveness, causing non-selective toxicity and often leading to chemoresistance particularly in cancer stem cells6,7. The Rahman lab at King's College London has developed a proprietary Efflux Resistance Breaker (ERB) Technology that allows modification of chemical scaffolds to reduce their efflux susceptibility while maintaining the on-target activity (Figure 2)8,9. This increases the intracellular concentration of the drugs which can overcome chemoresistance and reduce the likelihood of resistance emergence.The aim of this PhD project is to explore the phenomenon of efflux transporter-associated resistance using a chemical biology approach and produce ERB-modified TOPO I inhibitors that can be further developed as ADC payloads.