The stem cell growth factor receptor KIT is not expressed on interstitial cells in bladder.

The mast/stem cell growth factor receptor KIT has long been assumed to be a specific marker for interstitial cells of Cajal (ICC) in the bladder, with possible druggable perspectives. However, several authors have challenged the presence of KIT+ ICC in recent years. The aim of this study was therefore to attempt to clarify the conflicting reports on KIT expression in the bladder of human beings, rat, mouse and guinea pig and to elucidate the possible role of antibody-related issues and interspecies differences in this matter. Fresh samples were obtained from human, rat, mouse and guinea pig cystectomies and processed for single/double immunohistochemistry/immunofluorescence. Specific antibodies against KIT, mast cell tryptase (MCT), anoctamin-1 (ANO1) and vimentin were used to characterize the cell types expressing KIT. Gut (jejunum) tissue was used as an external antibody control. Our results revealed KIT expression on mast cells but not on ICC in human, rat, mouse and guinea pig bladder. Parallel immunohistochemistry showed KIT expression on ICC in human, rat, mouse and guinea pig gut, which confirmed the selectivity of the KIT antibody clones. In conclusion, we have shown that KIT+ cells in human, rat, mouse and guinea pig bladder are mast cells and not ICC. The present report is important as it opposes the idea that KIT+ ICC are present in bladder. In this perspective, functional concepts of KIT+ ICC being involved in sensory and/or motor aspects of bladder physiology should be revised.

Phase I Trial of 131I-GMIB-Anti-HER2-VHH1, a New Promising Candidate for HER2-Targeted Radionuclide Therapy in Breast Cancer Patients.

131I-GMIB-anti-human epidermal growth factor receptor type 2 (HER2)-VHH1 is a targeted radionuclide theranostic agent directed at HER2-expressing cancers. VHH1 is a single-domain antibody covalently linked to therapeutic 131I via the linker N-succinimidyl 4-guanidino-methyl-3-iodobenzoate (SGMIB). The phase I study was aimed at evaluating the safety, biodistribution, radiation dosimetry, and tumor-imaging potential of 131I-GMIB-anti-HER2-VHH1 in healthy volunteers and breast cancer patients. Methods: In a first cohort, 6 healthy volunteers were included. The biodistribution of 131I-GMIB-anti-HER2-VHH1 was assessed using whole-body (anterior and posterior) planar images obtained at 40 min and at 2, 4, 24, and 72 h after intravenously administered (38 ± 9 MBq) 131I-GMIB-anti-HER2-VHH1. Imaging data were analyzed using OLINDA/EXM software to determine the dosimetry. Blood and urine samples were obtained over 72 h. In the second cohort, 3 patients with metastatic HER2-positive breast cancer were included. Planar whole-body imaging was performed at 2 and 24 h after injection. Additional SPECT/CT images were obtained after the whole-body images at 2 and 24 h if there was relevant uptake in known cancer lesions. Results: No drug-related adverse events were observed throughout the study. The biologic half-life of 131I-GMIB-anti-HER2-VHH1 in healthy subjects was about 8 h. After intravenous administration, the compound was eliminated from the blood with a 2.5-h half-life. The drug was eliminated primarily via the kidneys. The drug was stable in circulation, and there was no increased accumulation in the thyroid or stomach. The absorbed dose to the kidneys was 1.54 ± 0.25 mGy/MBq, and to bone marrow it was 0.03 ± 0.01 mGy/MBq. SPECT/CT imaging in patients with advanced breast cancer showed focal uptake of 131I-GMIB-anti-HER2-VHH1 in metastatic lesions. Conclusion: Because of its favorable toxicity profile and its uptake in HER2-positive lesions, this radiopharmaceutical can offer new therapeutic options to patients who have progressed on trastuzumab, pertuzumab, or trastuzmab emtansine, given its difference in mode-of-action. A dose escalation is planned in a subsequent phase I/II study to assess the therapeutic window of this compound (NCT04467515).

A prospective randomized controlled multicentre trial comparing intravesical DMSO and chondroïtin sulphate 2% for painful bladder syndrome/interstitial cystitis

ABSTRACT Objective To compare effectiveness of intravesical chondroïtin sulphate (CS) 2% and dimethyl sulphoxide (DMSO) 50% in patients with painful bladder syndrome/interstitial cystitis (PBS/IC). Materials and methods Patients were randomized to receive either 6 weekly instillations of CS 2% or 50% DMSO. Primary endpoint was difference in proportion of patients achieving score 6 (moderately improved) or 7 (markedly improved) in both groups using the Global Response Assessment (GRA) scale. Secondary parameters were mean 24-hours frequency and nocturia on a 3-day micturition dairy, changes from baseline in O’Leary-Sant questionnaire score and visual analog scale (VAS) for suprapubic pain. Results Thirty-six patients were the intention to treat population (22 in CS and 14 in DMSO group). In DMSO group, 57% withdrew consent and only 6 concluded the trial. Major reasons were pain during and after instillation, intolerable garlic odor and lack of efficacy. In CS group, 27% withdrew consent. Compared with DMSO group, more patients in CS group (72.7% vs. 14%) reported moderate or marked improvement (P=0.002, 95% CI 0.05-0.72) and achieved a reduction in VAS scores (20% vs. 8.3%). CS group performed significantly better in pain reduction (-1.2 vs. -0.6) and nocturia (-2.4 vs. -0.7) and better in total O’Leary reduction (-9.8 vs. -7.2). CS was better tolerated. The trial was stopped due to high number of drop-outs with DMSO. Conclusions Intravesical CS 2% is viable treatment for PBS/IC with minimal side effects. DMSO should be used with caution and with active monitoring of side effects. More randomized controlled studies on intravesical treatments are needed.