Developing effective anticancer drugs is crucial to address the severity of malignant tumors and the limited efficacy of current treatments. However, the planning and execution of nonclinical studies to support the development of anticancer pharmaceuticals lack globally recognized, calibrated guidelines. This gap arises due to the unique challenges presented by advanced therapies like Antibody Drug Conjugates (ADCs), which often require different considerations than other pharmaceuticals. Nonclinical evaluations of anticancer drugs serve to identify pharmacologic properties, establish safe initial dosing, and understand toxicological profiles. Meanwhile, clinical studies involve patients with fatal and progressive conditions, leading to close proximity of dose levels to adverse effects. Consequently, regulatory bodies face challenges in establishing suitable and harmonized regulations for ADCs. This chapter explores regulations for ADCs and their impact on approval processes. For exemplification purposes examining how Kadcyla, an ADC used to treat HER2-positive breast cancer, aligns with current ADC regulations will be staged in a structured, stepwise manner. The discourse emphasizes the necessity for harmonization initiatives among various regulatory bodies on national, subregional, regional, and international levels. Such initiatives aim to promote informed, transparent, and consistent decision-making processes, enhancing global public health through effective medicine access. However, the proliferation of separate projects can hinder harmonization efforts, highlighting the importance of coordinated collaboration to avoid duplicative work and ensure meaningful standardization. As these initiatives evolve, interdependence among nations and organizations becomes more pronounced, simplifying international collaboration and trade.