Investigation of a Pharmacological Approach for Reduction of Renal Uptake of Radiolabeled ADAPT Scaffold Protein

Reduction of renal activity retention of radiolabeled albumin binding domain‑derived affinity proteins using a non‑residualizing label strategy compared with a cleavable glycine‑leucine‑glycine‑lysine‑linker

The feasibility of targeted imaging and therapy using radiolabeled albumin‑binding domain‑derived affinity proteins (ADAPTs) has been demonstrated. However, high renal uptake of radioactivity limits the maximum tolerated dose. Successful reduction of renal retention of radiolabeled Fab fragments has been demonstrated by incorporating a cleavable linker between the targeting agent and the radiometal chelator. The present study investigated if the introduction of a glycine‑leucine‑glycine‑lysine (GLGK)‑linker would reduce the kidney uptake of radiolabeled ADAPT6 and also compared it with the non‑residualizing [125I]I‑[(4‑hydroxyphenyl)ethyl]maleimide ([125I]I‑HPEM) labeling strategy. GLGK was site‑specifically coupled to human epidermal growth factor receptor 2 (HER2)‑targeting ADAPT6. Conjugates without the cleavable linker were used as controls and all constructs were labeled with lutetium‑177 (177Lu). [125I]I‑HPEM was coupled to ADAPT6 at the C‑terminus. Biodistribution of all constructs was evaluated in NMRI mice 4 h after injection. Specific binding to HER2‑expressing cells in vitro was demonstrated for all constructs. No significant difference in kidney uptake was observed between the [177Lu]Lu‑2,2',2",2"'‑(1,4,7,10‑tetraazacyclododecane‑1,4,7,10‑tetrayl)tetraacetic acid‑GLGK‑conjugates and the controls. The renal activity of [125I]I‑HPEM‑ADAPT6 was significantly lower compared with all other constructs. In conclusion, the incorporation of the cleavable GLGK‑linker did not result in lower renal retention. Therefore, the present study emphasized that, in order to achieve a reduction of renal retention, alternative molecular design strategies may be required for different targeting agents.

Use of Radionuclide-Based Imaging Methods in Breast Cancer

Breast cancer is one of the most commonly occurring cancers in women globally and is the primary cause of cancer mortality in females. Thus, early and effective breast cancer diagnosis is crucial for enhancing the survival rate. Current standard diagnostic techniques to assess the hormone receptor status in biopsies include immunohistochemistry and fluorescence in situ hybridization. However, in recent years, there has been an increase in research on noninvasive techniques for molecular imaging of hormone receptors. These methods offer many advantages over conventional imaging, as repeated measurements can be used to capture heterogeneous tumor expression throughout the body, as well as transformations in receptor status during disease progression. Thus, the noninvasive method, as an adjunct to conventional imaging, offers the potential to improve patient selection, optimize dose and schedule, and streamline the assessment of response.

Pharmacological agents for the prevention of colistin-induced nephrotoxicity

Background

Colistin is a polymyxin antibiotic which has been used for treatment of Gram-negative infections, but it was withdrawn due to its nephrotoxicity. However, colistin has gained its popularity in recent years due to the reemergence of multidrug resistant Gram-negative infections and drug-induced toxicity is considered as the main obstacle for using this valuable antibiotic.

Results

In total, 30 articles, including 29 animal studies and one clinical trial were included in this study. These compounds, including aged black garlic extract, albumin fragments, alpha lipoic acid, astaxanthin, baicalein, chrysin, cilastatin, colchicine, curcumin, cytochrome c, dexmedetomidine, gelofusine, grape seed proanthocyanidin extract, hesperidin, luteolin, lycopene, melatonin, methionine, N-acetylcysteine, silymarin, taurine, vitamin C, and vitamin E exhibited beneficial effects in most of the published works.

Conclusions

In this review, the authors have attempted to review the available literature on the use of several compounds for prevention or attenuation of colistin-induced nephrotoxicity. Most of the studied compounds were potent antioxidants, and it seems that using antioxidants concomitantly can have a protective effect during the colistin exposure.

Reducing the renal retention of low- to moderate-molecular-weight radiopharmaceuticals

The field of nuclear imaging and therapy is rapidly progressing with the development of targeted radiopharmaceuticals that show rapid targeting and rapid clearance with minimal background. Unfortunately, they are often reabsorbed in the kidneys, leading to possible nephrotoxicity, limiting the therapeutic dose, and/or reducing imaging quality. The blocking of endocytic receptors has been extensively used as a strategy to reduce kidney radiation. Alternatively, the physicochemical properties of radiotracers can be modulated to either prevent their reuptake or promote the excretion of radiometabolites. Other interesting strategies focus on the insertion of a cleavable linker between the radiolabel and the targeting moiety or pretargeting approaches in which the targeting moiety and radiolabel are administered separately. In the context of this review, we will discuss the latest advances and insights on strategies used to reduce renal retention of low- to moderate-molecular-weight radiopharmaceuticals.