This review provides a comprehensive survey of analytical methods for evaluating the tissue distribution of approved antisense oligonucleotides and small interfering RNAs, as well as developmental products still in preclinical and clinical trial stages (hereafter referred to as developmental products), based on original research articles, reviews and regulatory application documents from the US, EU and Japan.

The analytical methods employed for evaluation can be classified into imaging-based and non-imaging-based methods. These can be further subdivided based on the detection strategy: whether they utilize direct labeling for detection, employ detection reagents without direct labeling, or detect directly without the use of detection reagents. The imaging-based methods utilized for approved drugs were limited to quantitative whole-body autoradiography and microautoradiography using radiolabeled substances. In contrast, non-imaging-based methods encompassed various quantitative analytical methods, including liquid chromatography (LC) and capillary gel electrophoresis (CGE) coupled with detectors such as ultraviolet, fluorescence and mass spectrometric detection, as well as ligand-binding assays (LBAs) including enzymelinked immunosorbent assays and electrochemiluminescence. These methods are described and stipulated in bioanalysis guidelines in the US, EU and Japan, enabling an objective demonstration of method validity. For developmental products, the imaging-based methods included radio-imaging, fluorescence imaging, immunohistochemical staining, in situ hybridization and mass spectrometric imaging, in addition to the methods adopted for approved oligonucleotide therapeutics. Non-imaging-based methods encompassed LBAs and analytical separation methods via LC or CGE, in addition to quantitative polymerase chain reaction. While approved oligonucleotide therapeutics typically adhered to stringent analytical method guidelines, employing a limited range of imaging-based methods, developmental products utilized a broader selection of both imaging and non-imaging-based methods tailored to specific objectives.

In case studies utilizing the evaluation methods for tissue distribution, research was undertaken to assess the relationship between tissue distribution in target tissues and pharmacological activity or toxicity, as well as the changes in overall distribution characteristics due to different drug delivery systems. The selection of evaluation methods was determined based on considerations such as whether the distribution assessment focused on the whole body or specific tissues, the desired locations within the tissues, and whether sufficient information could be obtained from a sensitivity viewpoint.

This review of analytical methods available for evaluation of the tissue distribution of oligonucleotide therapeutics is expected to promote an understanding of the characteristics and limitations of the analytical methods and to assist in the selection of appropriate evaluation methods aligned with particular study objectives.

Purpose: To investigate the characteristics and clinical profiles of unintended pregnancies among isotretinoin users in Japan.

Methods: We reviewed the medication counseling records of isotretinoin-exposed pregnant women seen at the Japan Drug Information Institute in Pregnancy (JDIIP) between October 5, 2005, and March 31, 2024. The main outcomes were the proportion of unplanned pregnancies, duration of isotretinoin exposure during pregnancy, and means of accessing isotretinoin.

Results: Of the 10,405 pregnant women seen at the JDIIP, 28 (0.27%) sought medical advice regarding isotretinoin. In 2021, 2022, 2023, and 2024 (January to March), the numbers (percentage) of patients who started medication counseling regarding isotretinoin were 3 (0.77%), 4 (1.31%), 4 (1.25%), and 4 (5.97%), respectively. All the 28 pregnancies among isotretinoin users were unplanned. Twenty-one women discontinued isotretinoin later than 2 weeks and 0 days of gestation. Sixteen women were prescribed isotretinoin by clinicians in Japan, and three by clinicians overseas. Nine women had purchased and used isotretinoin on their own. None of the patients had used oral or emergency contraceptives.

Conclusions: To prevent unplanned pregnancies during isotretinoin use in Japan, awareness should be raised among both patients and physicians regarding the teratogenic risk of isotretinoin. Additionally, guidance on contraception should be provided before prescribing isotretinoin.