• BRAF inhibition
• cyanine 5
• fluorescent probe
• melanoma
• PLX4032
• Vemurafenib

One of the most common skin cancers is Cutaneous Melanoma. This one affects many people per year ranking it on the 15th among most common cancers worldwide. This tumour, as the others, through DNA mutations, lead to a loss control of the homeostasis of cell proliferation, by maintaining certain signal transduction pathways on. One of the most common genome aberrations in such disease is represented by BRAFV600E mutation, which causes the transition from a valine to a glutamic acid at position 600 within the kinase domain. The BRAF protein is a member of the Raf family of serine threonine kinases, which are part of the Ras/RAF/MEK/ERK mitogen activated protein kinase (MAPK) signal transduction cascade that controls cell proliferation and survival. Behind this mutation, the protein remains in the active form with an 800-fold increased kinase activity with respect to its wild-type counterpart, leading to uncontrolled proliferation and growth of cells expressing BRAFV600E. In the past decades, a great deal of research has resulted in the development of a targeted therapy thanks to the discovery of B-Raf inhibitors, represented by their greatest exponent, Vemurafenib. Vemurafenib (Vem, PLX4032, Plexxikon/Roche) was discovered as a highly specific BRAFV600E kinase inhibitor with selectivity against melanoma cells. Vemurafenib is clinically approved for the treatment of metastatic and non-resectable BRAFV600E-mutant melanoma.
In this context, with the aim to develop a fluorescent probe to image therapeutic BRAF inhibition, a modifiable derivative of Vemurafenib was synthesized by replacing p-chlorophenyl with p-aminophenyl ring generating a free NH2 group, which was conjugated with a specially selected fluorophore by means of a polyethylene glycol chain. In addition, a deep spectroscopic characterization of such probe has been also performed.