In January 2020 theFood and Drug Administration (FDA) reviewed its 2017 draft content and published finalized guidance for in vitroandclinical药物互动研究。我们已经总结了在本职位中对体外药物 - 药物相互作用（DDI）测试的关键变化和影响，但如果您希望有关具体变化的更多细节，请审查我们的深入在线白皮书，比较FDA，EMA和PMDA DDI法规。
DDI and associated adverse drug reactions (ADRs) are integral to drug development and can greatly affect how successful a drug is in the market. Severe or highly frequent ADRs suggest an unfavorable risk/benefit profile and can result in limitations such as dose restrictions, ultimately limiting the success of a drug.
Compared to the draft 2017 in vitro FDA DDI guidance, only a few key changes were included in the finalized 2020 publication.
DDI研究现在是IND包的一部分
One of the biggest changes to the updated guidelines is that the FDA now clearly recommends a wider panel of in vitro DDI studies be performed before clinical development begins. As such, DDI studies now form part of the investigational new drug (IND)-enabling program.
这种变化的原因之一是允许的tter characterization of multiple clearance pathways in special populations, helping to ensure the appropriate inclusion or exclusion of all relevant genotypes during clinical trials.
也就是说，即使使用Ind-Package变化，2020 FDA更新也会对开发时间表的影响最小。进行符合FDA的DDI测试，European Medical Agency (EMA)和日本的制药和医疗设备（PMDA）指导方针，您应该允许4-6个月，包括报告时间。但这些研究可以在突出的安全研究方向上运行，以尽量减少延误。yaboapp体育官网
Substrate victim studies: Validated methods & wider range of enzymes
虽然2017年FDA草案DDI指南的基底受害者研究没有重大变化，但在FDA 2020的最终指导下，必须在测量这些研究中的试验项目的浓度时使用拉力解带，并且通常使用（通常通过液相色谱 - 质谱法[LC-MS]除非测试项目是放射性标记的）。该指南被描述为新规定中的“验证方法”，但没有进一步的定义。然而，这种验证的方法被解释为意味着必须开发稳健，精确和可重复的分析方法，并用于测量体外系统中测试项目的浓度。
In addition, the range of enzymes to be included in enzymology phenotyping studies has increased from the standard cytochromes P450 (CYP) and uridine 5′-diphospho-glucuronosyltransferase (UGT) enzymes.
考虑到更大数量的酶允许更大评估潜在的DDIS和药物疗效的间间变化。仅由一种酶代谢的药物具有较高的DDI潜力，作为受害者药物的潜在，而不是多种酶代谢的药物，特别是如果它具有窄的治疗窗口。
| 评估潜在的代谢相互作用的酶 |
|---|
| CYP Aldehyde oxidases (AO) 羧基酯酶（CES） 单胺氧化酶（MAO） Flavin monooxygenase (FMO) Xanthine oxidase (XO) Alcohol dehydrogenase (ADH) 醛脱氢酶（ALDH） UGT磺螺旋转移酶（SULTS） |
Therefore, the primary updates to note for substrate victim studies include:
- Using validated methods for measuring test drug concentrations
- Including appropriate positive controls to show positive enzyme activity when using recombinant enzymes.
肇事者研究：简化的抑制研究
Similar to victim studies, no major changes from the FDA draft DDI guidance in 2017 to the finalized 2020 guidance occurred. The one notable change that will simplify inhibition studies is the use of IC50values for risk assessments instead of Kivalues (under specific experimental conditions), which often involve much larger experiments.
Other minor changes to perpetrator studies include:
- Enzyme activity can now be used as well as, or in place of, mRNA analysis as the index of induction in CYP induction studies
- Cut-off values for being classified as positive for interaction have been aligned for MATE transporters, bringing them in line with other transporter cut-off values
| Box 1: Practical considerations for conducting studies Radiolabeling in victim studies 在早期的体外代谢研究期间，放射性标记的化合物通常是不可用的;但是，它们的可用性确实提供了某些优势。该技术可用于容易地确定在体外测试系统中的未结合/游离药物，溶解度和非特异性结合的浓度，否定使用LC-MS的需要。使用放射性标记物品还允许定量代谢物用于表型/酶鉴定研究，而无需分析标准。 良好的实验室练习（GLP） Typically, in vitro DDI studies do not require GLP status; however, “validated analytical methods” should be used. The use of liquid scintillation counting with a radiolabeled compound fulfils this requirement. |
Finally, a preincubation phase has been added to OATP1B1/1B3 testing to test for potential time-dependent inhibition (a relatively recent phenomenon observed with these anionic uptake transporters).
FDA.now aligns closer with international regulatory agencies for DDI guidance
The finalized FDA 2020 guidance brings more harmony and alignment between international agencies, including the theEMAandPMDA。例如，使用未结合的风险评估试验药物（而不是总药物）和折叠变化的建议作为评估CYP诱导的方法与这些机构更接近。
Therefore, as it stands now, international agency requirements differ only slightly between each other. The improved alignment between international guidance should make it easier to develop a study program acceptable to multiple global regulatory bodies, simplifying filing and reducing development time and costs.
The EMA is currently reviewing their2013 DDI guideline并且，在发出a之后concept document in 2017, the general expectation is that the advice on cut-off values and which enzymes and transporters to test will align even more closely with the 2020 FDA guidelines. In addition, the FDA’s recommendations on the use of IC50values rather than Ki（在特定的实验条件下）（可逆）CYP抑制和转运仪研究的风险评估也可能在最终确定的EMA指导中进一步对准。
Conclusion
Perhaps the most important change to remember from the finalized FDA guidance is thatDDI studies must now be conducted as part of the IND-enabling program before clinical development begins.Other more minor changes will hopefully simplify the process of victim and perpetrator studies, for example, by allowing the use of IC50values in place of Kivalues.
If you want a more in-depth assessment of the finalized in vitro FDA 2020 DDI guidance, please read our全面的网上白皮书，详细介绍了FDA，EMA和PMDA之间的监管差异，用于DDI指导。
