Interferon gamma(Hayashibara Co., Ltd.)

During a bout of influenza, B cells interact with other immune cells and then take different paths to defend the body. One path is the B cells that differentiate into lung-resident memory B cells, or lung-BRMs, that are critical for pulmonary immunity. These long-lived, non-circulating lung-BRMs migrate to the lungs from draining lymph nodes and reside there permanently as the first layer of defense that can quickly react to produce antibodies in a future infection. During a bout of influenza, B cells interact with other immune cells and then take different paths to defend the body. One path is the B cells that differentiate into antibody producing cells. Another path is the B cells that differentiate into lung-resident memory B cells, or lung-BRMs, that are critical for pulmonary immunity. Unlike antibody-producing B cells that help fight the current infection, the long-lived, non-circulating lung-BRMs migrate to the lungs from draining lymph nodes. They reside there permanently and lie in wait as the first layer of defense that can quickly react to produce antibodies in a future infection. Understanding the mechanism that creates these lung-BRMs is important for better flu vaccine development. Seasonal influenza kills 290,000 to 650,000 people each year, according to the World Health Organization. Yet flu vaccines are less effective in the elderly -- the most at-risk population -- compared to younger people. Also, there is need for vaccines that are more effective against later variants of a particular virus. André Ballesteros-Tato, Ph.D., and colleagues at the University of Alabama at Birmingham have now published a mouse-model study in the journal Immunity showing that interferon-gamma produced by T follicular helper cells, or Tfh cells, after intranasal influenza infection is required to initiate the path of B cell differentiation into lung-BRMs. Ballesteros-Tato is an associate professor in the UAB Department of Medicine Division of Clinical Immunology and Rheumatology. During influenza infection, both Tfh and B cells are present at germinal centers in the lymph nodes that drain the lungs. Class-switched memory B cells that are primed against the influenza virus begin to appear in the lungs at day 10 of the infection, and their numbers peak at Day 30. However, the UAB researchers found that, if mice were deficient in Tfh cells, or if the Tfh cells were blocked by an antibody, the lung-BRMs did not accumulate. Thus, Tfh cell help is required for class-switched-specific BRM responses to influenza. What role do the Tfh cells play? The UAB researchers found that the preferential differentiation of lung-BRMs early after infection correlated with differences in the Tfh cell response early in the viral infection. They found that the number of Tfh cells increased quickly and peaked between days 10 and 15. By Day 10, early in the flu infection, nearly 40 percent of the Tfh cells were producing interferon-gamma, or INF-γ; but that frequency dropped sharply thereafter. The production of INF-γ by Tfh cells turned out to be key to the lung-BRM response in flu. Ballesteros-Tato and colleagues found that mice whose Tfh cells were unable to produce INF-γ had a dramatically reduced frequency and number of influenza-specific BRMs in the lungs. Furthermore, the absence of INF-γ-producing Tfh cells, and therefore fewer lung-BRMs, was shown to compromise immune protection when mice were later reinfected with a different strain of influenza. The researchers asked whether the requirement for IFN-γ signaling in lung-BRM development was intrinsic to B cells, meaning the interferon was producing effects inside the B cells. They found that mice whose B cells lacked the receptor for INF-γ had significantly diminished numbers of flu-specific BRMs after influenza virus infection. Inside B cells, the transcription factor STAT1 is known to be required for optimal INF-γ signaling. The researchers found that mice whose B cells lacked STAT1 also failed to accumulate flu-specific BRMs after influenza infection. In mechanistic details, the researchers found that intrinsic IFN-γ-STAT1 signaling in B cells in the germinal center of lung-draining lymph nodes promoted expression of the T-bet transcription factor, and T-bet was necessary for differentiation into pre-memory B cells that express the surface marker CXCR3. Subsequently, CXCR3+ pre-memory B cells differentiated into CXCR3+ memory B cells, which exited the mediastinal lymph nodes and homed to the lung to become lung-BRMs. "In this proposed model, CXCR3+ memory B cells in the mediastinal lymph nodes are the precursors of lung-BRMs," said Ballesteros-Tato. "Our data provide evidence of a critical role for IFN-γ-producing Tfh cells in generating lung-BRM responses and provide new insights into the mechanisms that fine-tune germinal center B cell fate decisions after influenza virus infection." "This knowledge is essential for designing new vaccine strategies tailored to elicit potent lung-BRM responses, which have the potential to generate enhanced cross-protection to escape variants." Co-authors with Ballesteros-Tato in the study, "Interferon-γ production by Tfh cells is required for CXCR3+ pre-memory B cell differentiation and subsequent lung-resident memory B cell responses," are Nicole M. Arroyo-Díaz, Holly Bachus, Amber Papillion, Troy D. Randall and Jobaida Akther, UAB Department of Medicine, Division of Clinical Immunology and Rheumatology; and Alexander F. Rosenberg and Beatriz León, UAB Department of Microbiology. Support came from National Institutes of Health grants AI162698, AI150664, AI116584 and AI007051.

fam-Trastuzumab deruxtecan-nxki (Enhertu®)是Daiichi Sankyo开发的一款靶向HER2的ADC药物，又称为DS-8201a或T-DXd，用于HER2+/Low表达/突变的实体瘤，其在业内广为人知。DS-8201a通过可酶切的四肽Linker (GGFG)将人源化抗HER2抗体(IgG1)与拓扑异构酶I抑制剂偶联制备而成。DS-8201a的成功离不开缜密的专利布局(图1)。所用抗体源头专利到期(Tras，WO9222653)和Linker、Payload的专利自有(US5658920/US6436912)，为其消除了大部分的产品侵权问题；ADC各种旧元素的新组合(WO2014057687/WO2015115091)带来了意想不到的活性效果，使得该款药物能在ADC日益激烈的HER2竞速赛道上得到破壁；对DS-8201a的专利进行迭代/衍生、提早布局等，延长了DS-8201a的市场独占期。诚然，不论如何布局，也会存在一定的破壁者(WO2022033578)，不过，DS-8201a本身就是一个破壁者。 图1. DS-8201a的专利布局相关阅读：DS-8201专利大战：第一三共 PK SeagenDS-8201a作为新一代ADC改良的标杆，DS-8201a已在不同肿瘤中体现了其卓越的治疗实力。市场方面也体现了凌厉的销售攻势，2022年销售额涨势如虹，全年营收为1616亿日元，约合12.38亿美元，同比上涨191% (2021年4.26亿美元)。随着其在乳腺癌领域(HER2+, HER2+/Low/HER2 Mutant, Triple-negative BC)的全线推进，以及其他肿瘤治疗领域(mNSCLC, GC)的开发，DS-8201a有可能成为ADC市场的超重磅炸弹(图2)[1]。图2. 已批准ADC的全球销量额预测  01  DS-8201a的成功：离不开早期设计DS-8201a能够如此成功，主要是其具有多项创新性特征[2]：高效的新型Payload (半衰期短、可发挥旁观者效应)，高DAR值，良好的同质性，肿瘤选择性可裂解Linker，血液循环中稳定的Linker-Payload。DS-8201a的Linker-Payload以Exatecan mesylate (DX8951f，8)作为起始原料，经两步成酰胺反应引入GGFG四肽Linker (Glycyn-Glycyn-Phenylalanyn-Glycyn)和可与巯基反应的马来酰亚胺基团(mc-GGFG-DXd，图3)[3]；然后采用传统的半胱氨酸偶联策略，利用TCEP打开链间二硫键，与mc-GGFG-DXd偶联得到DS-8201a (9，图3)。 图3. DS-8201a (9)及其相关衍生物的合成路线与活性评价早期研发阶段，研究人员构建不同种类的Linker-payload并通过控制TCEP、Linker-Payload的反应当量数构建含有不同DAR值的ADC，对其进行理化性质及抑制活性的验证(图3右下)。尽管所有ADC (9-17)在体外均表现出较强的细胞毒性，但与其他ADC相比，ADC (12)和(13)的细胞毒性较低，且ADC (12)的聚集程度较高(26%)。据推测，细胞毒性较低的原因是由于释放的药物部分的空间位阻导致肿瘤细胞中的降解酶可能无法有效发挥切割作用，释放的药物发挥毒性作用。因此，通过在GGFG与DXd之间添加不同长度的亚甲基链[(-CH2-)n]，使得可裂解的酰胺基团在空间上远离Payload，ADC (14-17，n=2-5)释放出具有亚甲基烷基链的烷基胺DXd衍生物，显示出较高的体外活性。然而，ADC (17，n=5)有较高的聚集倾向(20%)，可能是由于亚甲基烷基链的疏水性所导致的，低程度的亚甲基修饰(n=1-4)对聚集程度的影响无明显差异。因此可知DXd衍生物的烷基链的长度影响聚集程度。从ADC的物理化学性质的角度来看，优选烷基链的长度应2≤n≤4。此外，在mc段PEGylation修饰以及在GGFG与DXd之间引入氧亚甲基可显著降低聚集体的产生，ADC (9-11)显示出更低的聚集程度，即便是具有较高DAR值(7.7/6.2)也具有可接受的低聚集性和更高的体外抑制活性。传统观念认为较高的DAR值会导致ADC异源性增加，体内清除加快，导致治疗指数的降低[4]。但在DS-8201a的早期研发过程种并未采取将DAR值控制在4的策略，而是通过控制TCEP、Linker-Payload的反应当量数构建高DAR值(7.7) ADC药物，在提高载药量的同时也可降低ADC的异质性[5]。此外，研究人员也未采用活性最好的ADC进行后续的试验，而是选取ADC (9)的Linker-Payload结构进行后续的优化和临床试验评估。之所以选择ADC (9)进行研究是因为不同亚甲基修饰的ADC经酶切释放的Payload代谢物在结构中含有源自Linker部分的伯氨基(-NH2)，导致其细胞膜通透性受损；而ADC (9)经酶切释放的Payload虽然含有伯氨基(18)，但其作为自降解间隔子氨基亚甲基的一部分会自发消除，产生含有羟基的Payload (DXd，19)，具出膜通透性，使其在肿瘤异质性的环境中具有更高的疗效；然后在体内水解酶的作用下，DXd可能进一步水解产生具有更高活性的依喜替康(Exatecan，推断，图4A)。相较于DXd/SN-38，其母本药物Exatecan拥有诸多的优势：较高的TOP1抑制活性[6, 7](图4B)；对ABCG2G/P-gP等药物外排泵蛋白低敏感性，具有更少的Payload外排[8](图4C)；较高的渗透性和旁观者穿透效应[9, 10]。因此，DS-8201a在肿瘤异质性以及在含有ABCG2G或P-gP等多药耐药转运体的肿瘤中发挥良好的抗肿瘤效果，扩展了相关适应症。 图4. DS-8201a体内降解机制(A)及Exatecan活性(B)、克服耐药性(C)数据在同类靶向HER2的ADC药物中，DS-8201a活性优于T-DM1，其对T-DM1不敏感/耐药(Insensitive/Resistance)的肿瘤细胞有较好的治疗效果。一部分原因是由于Payload造成的，DS-8201a拥有较高的DAR值(~7.7)，T-DM1的DAR值相对较低(~3.5)，DS-8201a内化后所释放的Payload较多，高载药量可发挥更具杀伤力的细胞毒性作用；此外，DM1作为药物外排泵蛋白(ABCC2/ABCG2)的良好底物使肿瘤细胞内DM1浓度相对较低[11, 12]，但DXd/Exatecan的底物敏感性较差，外排较少，胞内浓度较高可以发挥足够的杀伤作用[13]。因此，针对T-DM1不敏感/耐受的肿瘤使用DS-8201a可以展示良好的抗肿瘤活性[14, 15]。DS-8201a与T-DM1进行了头对头临床试验(DESTINY-Breast03，NCT03529110，Phase III)，DS8201组和T-DM1组患者12个月的预估OS率分别为94.1%和85.9%，基于良好的临床试验结果，FDA也正式批准DS8201的二线适应症[14]；此外，用于评估DS8201与T-DM1新辅助治疗高危或有残留浸润性淋巴结的HER2阳性原发性乳腺癌患者的临床试验(DESTINY-Breast05，NCT04622319，Phase III)也正在招募患者中，期望DS-8201a能有良好的治疗效果。  02  DS-8201a：新颖的作用机制+旁观者效应DS-8201a的偶联方式是通过还原剂TCEP•HCl打开抗体链间的二硫键，将Linker-Payload连接到裸露的半胱氨酸残基上，产生高DAR值的偶联物。该种偶联方式可能会影响抗体的结构(Architecture)，从而进一步影响抗体的功能[16]。通过ELISA实验发现DS-8201a的Kd值为7.3 ng/mL，Trastuzumab的Kd值为7.8 ng/mL，表明高DAR值并不会过多的影响DS-8201a与HER2的结合活性(图5A)。Trastuzumab的主要作用机制涉及ADCC[17]以及下调磷酸化Akt (pAkt)水平并抑制细胞增殖[18]。实验表明DS-8201a仍然保留了与Trastuzumab相同的作用机制。DS-8201a在人外周血单核细胞(PBMC)介导的SK-BR-3细胞中显示出ADCC活性，最大ADCC活性可达48.6%，EC50为3.8 ng/mL (图5B)，与Trastuzumab相似。关于Akt磷酸化水平的抑制，DS-8201a以剂量依赖性方式诱导SK-BR-3细胞中胞内pAkt(Ser473)的下调，在相同条件下对照IgG ADC不影响Akt的磷酸化水平(图5C)；Trastuzumab降低了约70%的Akt磷酸化，表明DXd偶联可能增强未缀合的Trastuzumab对pAkt的下调作用。以上数据表明DS-8201a在DXd偶联后仍保留了Trastuzumab的功能。另一方面，DS-8201a (10 mg/mL)可诱导Chk1和组蛋白H2A.X的磷酸化(DNA损伤Marker[19, 20])以及PARP裂解(凋亡Marker[21])，10 mg/mL的抗HER2 Ab在相应时间点都不会引起任何目标蛋白的变化，这些结果表明DS-8201a以与DXd相同的方式诱导DNA损伤和细胞凋亡。因此，DS-8201a通过一种新颖的作用机制表现出HER2特异性细胞生长抑制和抗肿瘤活性。 图5. DS-8201a的作用机制另一部分高抗肿瘤活性的原因则是DS-8201a旁观者效应的加持，通过转移抗原表达肿瘤细胞释放的Payload (DXd/Exatecan，高渗透性)至邻近的抗原阴性细胞发挥“杀”屋及乌的毒性作用[22]；T-DM1由于裂解不完全，导致毒素上残留一个带正电的赖氨酸(Lys-SMCC-DM1，低渗透性)，这使其无法透过肿瘤细胞膜，因此其不会产生旁观者效应(图6A)[23-25]。通过体外共培养细胞实验验证DS-8201a的旁观者效应，将HER2+ KPL-4细胞和HER2- MDA-MB-468细胞以适当比例混合并培养过夜，用ADC处理细胞5天，然后测定活细胞的数量。T-DM1仅完全杀死HER2+ KPL-4细胞，但DS-8201a却可以同时杀死KPL-4和MDA-MB-468细胞；与未处理的孔相比，阴性对照ADC不会诱导细胞死亡(图6B)。以上数据表明MDA-MB-468细胞杀伤是由释放的DXd/Exatecan引起的，说明DS-8201a在细胞水平上具有旁观者杀伤作用。 图6. DS-8201a旁观者效应研究DS-8201a的旁观者效应在体外实验得到验证后，通过MDA-MB-468-Luc细胞构建的肿瘤异种移植模型(PDX)利用体内成像系统检测其体内旁观者效应(图6C)。将每种实验/对照ADC给予共同接种的异种移植小鼠，并测量每只小鼠的肿瘤体积和荧光素酶活性。在DS-8201a实验组中，可观察到荧光素酶信号明显减少，表明MDA-MB-468-Luc细胞被DS-8201a完全根除；其他HER2靶向ADC或对照ADC未观察到类似结果；就肿瘤体积变化而言，T-DM1抑制肿瘤生长，但不如DS-8201a有效，这可能是由于肿瘤消除有限，仅消除HER2+肿瘤(图6C)。免疫组化研究表明，T-DM1治疗组中HER2+细胞被根除，而HER2-癌细胞占据了肿瘤组织的大部分；在DS-8201a治疗组中，几乎所有HER2+和HER2-细胞消失，肿瘤中几乎没有癌细胞残留。这些结果证实，在共同接种条件下，DS-8201a不仅对HER2+肿瘤有效，而且对HER2-肿瘤也显示出抗肿瘤活性，而T-DM1对HER2-肿瘤没有作用。DS-8201a除对邻近HER2-细胞有旁观者作用外，对其远端癌细胞是否拥有旁观者效应进行验证。将NCI-N87和MDA-MB-468-Luc细胞的混合物接种到小鼠的右胁腹中，并且仅将MDA-MB-468-Luc细胞接种到同一小鼠的左胁腹中。DS-8201a治疗14天后，联合接种肿瘤的荧光信号减弱，但单独接种肿瘤的荧光信号没有变化，与未治疗组小鼠荧光信号相当(图6D)。这些结果表明，DS-8201a对HER2-细胞的影响仅在与HER2+细胞相邻的细胞中观察到，而在远端细胞中未观察到抗肿瘤作用。基于旁观者效应可以解决肿瘤异质性的问题[26]，DS-8201a被开发用于多种肿瘤异质性的癌症治疗(表1)。表1. 基于DS-8201a旁观者效应开展的临床试验  03  GGFG四肽Linker功不可没以上所提到高DAR值、旁观者效应均是Payload所贡献的，Payload能发挥如此作用，其多肽Linker发挥着重要的作用。Linker的重要性经常被忽略，大家仅仅认为其是Antibody和Payload中间部分(“the piece in the middle”)，其实Linker是ADC中较为关键的中间部分(Crucial “Part in the Middle”)[27]。Linker的化学和生物物理特性在ADC的设计中起着至关重要的作用，其化学特性会显著影响ADC的生物物理性质和生化稳定性，进而对药效学和药代动力学产生深远的影响[28]。为了使ADC具有选择性和抗肿瘤活性，所采用的Linker应努力实现三个关键特性：(1)循环稳定性高，避免Payload的过早释放；(2)高水溶性，有助于生物偶联并避免形成无活性的ADC聚集体；(3)能够有效地释放高细胞毒性的Linker-Payload代谢物[29, 30]。DS-8201a通过GGFG四肽Linker将抗体和Payload偶联在一起(图3)，该Linker在小鼠、大鼠、猴和人血浆中DS-8201a的DXd释放率为1.2%至3.9%，特别是在人血浆孵育21天后，DXd的释放率低至2.1% (图7A)，与其他ADC (如T-DM1、SGN-38）相当或相对较低[15]；同时在猕猴中研究DS-8201a的药代动力学(Pharmacokinetics，PK)特征，数据显示其与总抗体之间无明显差异(图7B)，即便是在不同的给药剂量下二者PK参数也无明显差异(图7C)[31]，这说明DS-8201a的GGFG四肽Linker即使在DAR=8的情况下在血浆中的稳定性也是极好的，仅在有限的时间点检测到低水平的DXd释放。 图7. DS-8201a体外(A)/体内(B/C)血浆稳定性研究  04  DS-8201a与肿瘤免疫检查点的combo上述数据主要讲述了DS-8201a作为ADC所发挥的抗肿瘤作用，除此之外，DS-8201a还可以引起免疫系统激活，从而提升抗肿瘤免疫[32]。在具有免疫能力的小鼠体内接种人HER2的CT26细胞(CT26.WT-hHER2, s.c.)，荷瘤小鼠使用DS-8201a进行抗肿瘤治疗，将获得完全缓解(Complete Response, CR)的小鼠再次接受CT26.WT-hHER2挑战后发现小鼠可以抵御新接种的肿瘤(图8A)；同时，细胞因子IFNγ (主要有活化的T细胞、自然杀伤细胞产生[33])的分泌也在增加(图8B)。以上数据说明DS-8201a诱导的T细胞不仅可以识别人HER2，还可以识别肿瘤细胞的其他抗原。即使是在对DS-8201a细胞毒活性不太敏感的肿瘤中，适应性免疫也可被激活，CD8+ T细胞(CD45+ CD3+ CD8+细胞)和颗粒酶B+的CD8+ T细胞比率明显增加(图8C)；当采用anti-CD8耗竭Ab消耗掉CD8+T细胞时，DS-8201a的抗肿瘤活性基本上消失(图8D)。与对照组相比，CD8+ T细胞显着增强DS-8201a在免疫活性小鼠模型中的抗肿瘤作用。 图8. DS-8201a引起免疫系统激活提升抗肿瘤免疫由于拓扑异构酶Ⅰ抑制剂可以激活树突状细胞(DC)[34]，所以DS-8201a内化后所释放的DXd也可以使DC成熟/活化标志物(CD86+MHC Ⅱ类)的标志物增加，说明DS-8201a发挥抗肿瘤作用需要DC参与；经DS-8201a处理的小鼠体内DC细胞(CD45+ CD11c+ MHC class II+)占比明显增加，其中CD86+的DC细胞也明显增加(图9A)；这说明DS-8201a除发挥细胞毒性作用外，DC体内激活也是其发挥抗肿瘤作用的重要机制。此外，DS-8201a还可以增加免疫相关分子(PD-L1/ MHC Ⅰ类)的表达(图9B)，MHC I类的表达增加抗原呈递，促进T细胞识别肿瘤[35]；另一方面，PD-L1表达增加可能是一种负性调节的结果，由于T细胞激活或体内产生抑制信号而降低体内抗肿瘤免疫力。因此，采用“万金油”-免疫位点阻断剂(ICI，尤其是抗PD-1/PD-L1阻断剂)与DS-8201a联用可以阻断抑制信号，发挥更好的抗肿瘤效果。利用抗PD-1抗体、DS-8201a或联用疗法治疗荷瘤小鼠(CT26.WT-hHER2, s.c.)，38天后各治疗方案的存活率分别为20%、20%和80% (图9C)；单一疗法虽然能够延长总生存时间，但联合疗法对总生存时间的延长明显增加。基于以上动物实验数据可以说明抗PD-1抗体可以阻断PD-1/PD-L1抑制信号通路，并且能提高DS-8201a的功效。图9. DS-8201a对免疫相关分子表达水平的影响及与抗PD-1抗体联用的抗肿瘤效果受到上述动物实验DS-8201a和抗PD-1抗体联合治疗所产生的良好效果的影响，Daiichi Sankyo和AstraZeneca联合多家药企开展了两项临床试验评估联合疗法的抗肿瘤活性(表2)[36-38]，目前暂未有临床结果披露。基于动物实验的良好活性，期待该种联合疗法能够成为治疗HER2+肿瘤的新的有效疗法。表2. DS-8201a和抗PD-1抗体联合疗法所涉及的临床试验针对DS-8201a临床前体内外抗肿瘤活性的其他研究，以及临床研究梳理，作者不再赘述。相关阅读：ADC“药王”：DS-8201临床研究全面梳理不可忽视！DS-8201a的临床前研究  05  DS-8201a：期待下一个破局者▌ 提高安全性在过去几年里，ADC的设计改进取得了重大进展，重塑了多种晚期实体瘤的治疗方法。ADC的预期原理是将细胞毒性分子与针对肿瘤特异性抗原的抗体连接来实现细胞毒性分子的靶向递送，预计其细胞毒性将低于传统化疗。然而，大多数ADC仍然面临着类似于细胞毒性Payload的脱靶毒性、靶向毒性和其他知之甚少且可能危及生命的不良反应，DS-8201a也不例外。DS-8201a自2019年12月20日批准用于HER2+不可切除或转移性乳腺癌以来，其临床适应症的迅速扩大，随之而来的是其安全性问题(表3)[14, 37, 39-41]，提高其安全性也势在必行。表3. DS-8201a所涉及的毒性副作用如何降低DS-8201a乃至其他FDA批准ADC药物的毒性问题成为目前ADC类药物研发所面临的重要问题。除了可以通过剂量优化策略(剂量封顶、限制性治疗持续时间、分次给药、治疗反应指导剂量调整、随机剂量探索研究)、实时诊断、药物基因组学指导的个体化用药等方法在实现疗效最大化的同时降低其副作用外，优化ADC的设计(抗体部分的创新、Linker化学的创新、Payload方面的创新)，ADC的每个元素组成的设计创新都可以实现药理学特性的微调，并对安全性和耐受性产生潜在影响。▌ 新一代ADC的优化对于ADC中的Linker而言，当然不存在“One size fits all”的情况。迄今为止获批的ADC药物的Linker具有多样性，包括可切割、不可切割的接头，酸敏感、蛋白酶敏感的Linker，在ADC的作用机制中发挥关键作用[42]。GGFG四肽Linker并非是“高山”不可逾越，它更像是一座“灯塔”指引我们前进，站在“药王”的肩膀上让我们走的更远。随着我们对ADC中使用的各种Linker的优化，并深入分析不同Linker的特性，解析其影响ADC功效和副作用的“特征图谱”，终会获得安全有效的ADC用于癌症治疗。对于ADC中的Payload而言，现阶段所批准ADC的Payload均为细胞毒性药物，涉及Calicheamicin、MMAE/F、DM1/4、DXd、SN-38、PBD SG3199、Duocarmycin。临床经验表明，与ADC相关的大多数不良事件(Off-target/Off-tumour)在谱系、发生率和严重程度方面与Payload的不良事件相似[43]，广为流传的治疗窗扩展概念也是不准确的（图10）[44]，并且拥有相同Payload的不同ADC通常具有相似的毒性特征，无论目标抗原有何不同[45]。ADC并非一定要以细胞毒性药物作为Payload，随着研究的深入，大家开始拓展新型Payload，构建了多种新型抗体偶联物-ISAC[46]、IM-ADC[47]、GC-ADC[48]等。随着我们对ADC技术研究的不断革新，采用不同种类Payload的ADC作为肿瘤学以外疾病领域治疗药物的开发也将会增加。图10. 传统版与修正版的ADC治疗优势对于ADC中的Antibody而言，我们似乎已经形成了思维定式：ADC中的Antibody只需要发挥靶向作用将细胞毒性Payload递送至目的细胞即可，其治疗作用可以不用考虑，试问最开始研发抗体药物的出发点是什么，难道只是为了增加靶向性、延长半衰期(部分GLP-1R药物[49])？随着大家对肿瘤生物学研究的深入，非内化(Non-internalising) ADC[50]开始进入我们的眼帘，这消除了对高抗原表达的依赖，避免了潜在的低效内化，并且可以极大地将癌症靶标范围扩大到细胞外肿瘤基质以及其他膜蛋白/胞外蛋白。此外，我们能否构建一种ADC使其既保留抗体的特异性又能维持抗体的活性，同时还能与Payload相辅相成发挥协同作用，这是一个值得深思的问题。结语“Magic Bullet”概念的提出者Paul Ehrlich认为科学的成功需要4G: Geduld、Geschick、Glück und Geld”(德语，耐心、能力、运气和金钱)，希望这4G格言赋能大家ADC药物的研发，在未来开发出更有效的“灵丹妙药”，让“High-hanging Fruit”变得触手可及。最后，借用周恩来总理的一首诗与诸君共勉！《无题·大江歌罢掉头东》大江歌罢掉头东，邃密群科济世穷。面壁十年图破壁，难酬蹈海亦英雄。免责声明：本文仅作信息交流之目的，文中观点不代表个人立场，亦不代表个人支持或反对文中观点。本文并非治疗方案推荐。如需获得治疗方案指导，请前往正规医院就诊。刍荛之作，若有纰漏/不足，欢迎各位批评指正(dyc21@mails.tsinghua.edu.cn)，谢谢！ 参考文献 1. do Pazo, C., K. 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