Nintedanib-Containing Dual Conjugates Targeting αVβ6 Integrin and Tyrosine Kinase Receptors as Potential Antifibrotic Agents

Small molecule- and peptide-drug conjugates addressing integrins: A story of targeted cancer treatment

Targeted cancer treatment should avoid side effects and damage to healthy cells commonly encountered during traditional chemotherapy. By combining small molecule or peptidic ligands as homing devices with cytotoxic drugs connected by a cleavable or non-cleavable linker in peptide-drug conjugates (PDCs) or small molecule-drug conjugates (SMDCs), cancer cells and tumours can be selectively targeted. The development of highly affine, selective peptides and small molecules in recent years has allowed PDCs and SMDCs to increasingly compete with antibody-drug conjugates (ADCs). Integrins represent an excellent target for conjugates because they are overexpressed by most cancer cells and because of the broad knowledge about native binding partners as well as the multitude of small-molecule and peptidic ligands that have been developed over the last 30 years. In particular, integrin αVβ3 has been addressed using a variety of different PDCs and SMDCs over the last two decades, following various strategies. This review summarises and describes integrin-addressing PDCs and SMDCs while highlighting points of great interest.

Nintedanib inhibits normal human vitreous-induced epithelial-mesenchymal transition in human retinal pigment epithelial cells

PURPOSE

In this study, we aim to investigate the potential of nintedanib as a therapeutic approach to proliferative vitreoretinopathy (PVR), which is the leading cause of failure in retinal detachment repair. PVR is characterized by the epithelial-mesenchymal transition (EMT) of retinal pigment epithelial (RPE) cells, and understanding the effects of nintedanib on EMT in the normal human vitreous (HV)-induced RPE cells is crucial.

METHODS

Our research focuses on assessing the impact of nintedanib on HV-induced EMT in human retinal pigment epithelial (ARPE-19) cells in vitro. We employed various techniques, including quantitative real-time PCR (qPCR), western blot analysis, and immunofluorescence staining, to evaluate the mRNA and protein expression of EMT biomarkers in HV-induced ARPE-19 cells. Additionally, we measured the proliferation of RPE cells using cell counting, CCK-8, and Ki-67 assays. Migration was assessed through wound healing and transwell migration assays, while contraction was determined using a collagen gel contraction assay. Morphological changes were examined using phase-contrast microscopy.

RESULTS

Our results demonstrate that nintedanib selectively attenuates the upregulation of mesenchymal markers in HV-induced ARPE-19 cells, at both the mRNA and protein levels. Furthermore, nintedanib effectively suppresses the HV-induced proliferation, migration, and contraction of ARPE-19 cells, while maintaining the cells' basal activity. These findings strongly suggest that nintedanib exhibits protective effects against EMT in ARPE-19 cells and could be a promising therapeutic option for PVR.

CONCLUSIONS

By elucidating the anti-EMT effects of nintedanib in HV-induced RPE cells, our study highlights the potential of this oral triple tyrosine kinase inhibitor in the treatment of PVR. These findings contribute to the growing body of research aimed at developing novel strategies to prevent and manage PVR, ultimately improving the success rates of retinal detachment repair.

A Brief Guide to Preparing a Peptide-Drug Conjugate

Peptide-drug conjugates (PDCs) have recently emerged as interesting hybrid constructs not only for targeted therapy, but also for the early diagnosis of different pathologies. In most cases, the crucial step in the PDC synthesis is the final conjugation step, where a specific drug is bound to a particular peptide-/peptidomimetic-targeting unit. Thus, this concept paper aims to give a short guide to determining the finest conjugation reaction, by considering in particular the reaction conditions, the stability of the linker and the major pros and cons of each reaction. Based on the recent PDCs reported in literature, the most common and efficient conjugation methods will be systematically presented and compared, generating a short guide to consult while planning the synthesis of a novel peptide-drug conjugate.

Cell Adhesion Molecules in Fibrotic Diseases

Mechanisms underlying the pathogenesis of tissue fibrosis remain incompletely understood. Emerging evidence suggests that cell adhesion molecules (CAMs) are critical in fibrotic progression in many organs, including lung, kidney, skin, and liver. CAMs promote cell-cell and cell-extracellular matrix (ECM) interactions to maintain tissue architecture and normal function in homeostasis. However, dysregulated expression and function of CAMs can lead to chronic inflammation and tissue fibrosis. The major families of CAMs include integrins, cadherins, selectins, and immunoglobulins. Here, we review the role of the CAMs in fibrosis development across various organs with a focus on integrins and cadherins, and discuss their respective roles in the development of pulmonary fibrosis.

Nintedanib-αVβ6 Integrin Ligand Conjugates Reduce TGFβ-Induced EMT in Human Non-Small Cell Lung Cancer

Growth factors and cytokines released in the lung cancer microenvironment promote an epithelial-to-mesenchymal transition (EMT) that sustains the progression of neoplastic diseases. TGFβ is one of the most powerful inducers of this transition, as it induces overexpression of the fibronectin receptor, αvβ6 integrin, in cancer cells which, in turn, is strongly associated with EMT. Thus, αvβ6 integrin receptors may be exploited as a target for the selective delivery of anti-tumor agents. We introduce three novel synthesized conjugates, in which a selective αvβ6 receptor ligand is linked to nintedanib, a potent kinase inhibitor used to treat advanced adenocarcinoma lung cancer in clinics. The αvβ6 integrin ligand directs nintedanib activity to the target cells of the tumor microenvironment, avoiding the onset of negative side effects in normal cells. We found that the three conjugates inhibit the adhesion of cancer cells to fibronectin in a concentration-dependent manner and that αvβ6-expressing cells internalized the conjugated compounds, thus permitting nintedanib to inhibit 2D and 3D cancer cell growth and suppress the clonogenic ability of the EMT phenotype as well as intervening in other aspects associated with the EMT transition. These results highlight αvβ6 receptors as privileged access points for dual-targeting molecular conjugates engaged in an efficient and precise strategy against non-small cell lung cancer.