Rational drug design of VCP inhibitors to enhance nis function in radioiodide therapy

Objective: New approaches are required to improve the efficacy of drugs that have the potential to enhance ablative radioiodide (RAI) uptake, especially in RAI-refractory disease. Our recent experiments in multiple cellular models revealed that valosin-containing protein inhibitors (VCPi), such as clotrimazole and disulfiram, markedly increase sodium iodide symporter (NIS) activity to promote RAI uptake, but poor bioavailability diminished thyroidal impact in vivo. New drug design strategies may therefore be needed to overcome the poor water solubility and rapid metabolism of VCPi in the circulation. Here, our aim was to determine whether rational drug design and reformulation strategies improve the efficacy of VCPi on NIS function in vitro and in vivo.

Methods: Computational iterative drug design was accompanied by de novo drug synthesis. RAI (¹²⁵I) uptake assays were used to monitor NIS function in vitro. Technetium-99m pertechnetate (^99mTc) uptake after intravenous administration was used to evaluate NIS function in wild-type BALB/c mice.

Results: Based on 3D modelling and iterative drug construction, we designed 21 novel analogues based on clotrimazole and the allosteric VCPi UPDC30425, all with improved predicted bioavailability (LogP), and synthesised 4 de novo compounds based on CryoEM high-resolution features of VCPi NMS873 docking to VCP. In parallel, we prepared albumin nano-encapsulated copperdiethyldithiocarbamate [Cu(DDC)₂-alb] - a stabilised reformulation of a disulfiram metabolite. Subsequent testing revealed that while several clotrimazole analogues specifically increased RAI uptake, the greatest impact was observed with Cu(DDC)₂-alb treatment in thyroidal TPC-1-NIS (2.8-fold; P < 0.01) and 8505C-NIS cells (3.0- fold; P < 0.01). Importantly, the intraperitoneal administration of Cu(DDC)₂-alb significantly induced thyroidal ^99mTc-uptake after 30 min (*40%; n = 11; 3 mg/kg dose; P < 0.001) in BALB/c mice, as well as increasing thyroidal NIS (1.9-fold; P < 0.01), thyroid peroxidase (1.8-fold; P < 0.001) and thyroglobulin mRNA (1.3-fold; P < 0.05) expression. A significant positive correlation was apparent between thyroidal ^99mTc-uptake and NIS mRNA (r_s = 0.4477; P = 0.0169) in Cu(DDC)₂-alb treated mice, uniting drug effects on NIS expression and function.

Conclusion: Our study demonstrates a promising drug strategy utilising a disulfiram metabolite to enhance NIS function in vivo, with clinical potential to improve treatment in RAI-refractory thyroid cancer.