Immunohistochemical localization of afatinib in male rat intestines and skin after its oral administration

Localization of Sites of Osimertinib Action in Rat Intestine, Skin, and Lung by Immunohistochemistry

Osimertinib is a third-generation, irreversible tyrosine kinase inhibitor (TKI) of epidermal growth factor receptor (EGFR) that selectively inhibits both EGFR-TKI-sensitizing and EGFR T790M resistance mutations and has shown efficacy in patients with non-small-cell lung cancer. In this study, we created osimertinib-specific antibodies and developed an immunohistochemistry (IHC) for locating the sites of osimertinib action. Moreover, we located osimertinib-protein conjugates in intestinal, dermal, and lung tissues of rats, thereby using our IHC to visualize the sites of the adverse effects of osimertinib, including diarrhea, skin disorder, and interstitial pneumonia. This report is the first to elucidate the localization of the sites of action of osimertinib in the rat intestine, skin, and lung and is expected to help clarify the mechanism of osimertinib-induced adverse effects.

Intestinal Haemorrhage and Colitis Induced by Treatment With Osimertinib for Non-Small-Cell Lung Carcinoma: A Case Report

Background: Osimertinib is recommended either as the first-line therapy for sensitizing EGFR-mutations (FLAURA trial) or at progression to first-/second-generation EGFR inhibitors in the presence of resistance mutation T790M (AURA 3 study). It can effectively improve the prognosis of patients with NSCLC with manageable adverse reactions. Among adverse events, intestinal haemorrhage is rare and requires extensive study on its potential lethality.

Case presentation: A 59-year-old female, diagnosed with relapsed stage IV (cT4N2M1c) NSCLC with T790M mutation of the EGFR gene, received osimertinib treatment. Eight months after osimertinib treatment, she complained of lower abdominal pain and haematochezia without haemorrhoids. Potential causes of intestinal haemorrhage other than osimertinib toxicity were ruled out. Colonoscopy examination showed severe colitis with grade 3 CTCAE. Osimertinib was discontinued, and prednisone 0.5 mg/kg was administered. Follow-up endoscopy showed no pathological findings. A novel third-generation EGFR-TKI, aumolertinib, was administrated. Five months after aumolertinib initiation, CT evaluation showed stable disease (SD), and this patient was free of colitis recurrence.

Conclusion: To our knowledge, this is the first case report of severe colitis as an adverse event associated with osimertinib. Although osimertinib is the standard treatment for NSCLC in patients with T790M mutation and has fewer side effects, colitis may occur after months of treatment. Aumolertinib, a novel third-generation EGFR-TKI, might be an effective alternative for the treatment of patients with NSCLC experiencing colitis from osimertinib.

Click-based amplification: designed to facilitate various target labelling modes with ultralow background amplification

We here describe a fluorescent signal amplification method termed “Click-based amplification” that can be well integrated with various click-labelling modes, including chemical labelling, genetic incorporation and covalent inhibitor probe mediated target labelling. Picolyl azide (pAz) was used as a functional group of a streptavidin-based amplifier to enhance the efficiency of click chemistry. Click-based amplification provided 3.0–12.7 fold amplification on fixed HeLa cells with different click-labelling modes. Click-based amplification has proven to be superior to tyramide signal amplification (TSA) in view of its low nonspecific amplification and high signal-to-noise ratio. Moreover, in terms of the challenging signal amplification of tissue specimens, Click-based amplification successfully achieved remarkable fluorescence enhancement on intestinal tissue slices of afatinib-N₃ treated mice, which provided direct evidence of the presence of afatinib-N₃ in the intestinal tissues and helped in revealing the off-target toxicity of afatinib. Collectively, these results illustrate that Click-based amplification could serve as a promising method for bioimaging studies.

We describe a signal amplification method termed “Click-based amplification” that can be well integrated with various click-labelling modes, including chemical labelling, genetic incorporation and covalent inhibitor probe mediated target labelling.

Localization and Accumulation Studies of Dacomitinib in Rat Intestines and Skin by Immunohistochemistry

Dacomitinib, a second-generation tyrosine kinase inhibitor, was irreversible inhibitor forming covalent bonds with the kinase domains of EGFR and other ErbB family receptors. Dacomitinib has been approved for the treatment of locally advanced or metastatic non-small cell lung cancer. In this study, we aimed to develop an immunohistochemistry to detect dacomitinib-ErbB family receptor conjugates. Immunostaining was performed in rat intestine and skin tissues after oral administration of dacomitinib. Following a single oral dose of dacomitinib, strong staining was observed after 24 hr in the ileum and colon, with only slight staining in the duodenum and jejunum. In the skin, strong staining was observed in the epidermis, hair follicles, and sebaceous glands. Moreover, significant amounts of dacomitinib remained for up to 72 hr post-administration in the ileum, colon, and skin. This report is the first to elucidate the localization and accumulation of dacomitinib in the rat intestine and skin and should be valuable during efforts to clarify the mechanism dacomitinib-induced diarrhea or skin toxicities.