Early completed in vitro studies and an in vivo human proof of concept study in a model of UV-induced erythema and pain, showed significant superiority in terms of skin penetration of the diclofenac molecule for TPR100, and indeed efficacy, compared with other commercially available products.
A randomised, double blind, crossover clinical proof of concept study in 20 healthy volunteers was conducted using a model of induced pain. The skin of healthy volunteers was carefully exposed to a controlled amount of ultra-violet light to increase the sensitivity of the skin to pain stimuli. The effect of TPR100, Voltarol® gel and a placebo gel were assessed over a six hour time period post dosing using two criteria: the primary pain measurement was the volunteers' sensation of pain (heat pain tolerance test) and the secondary pain measurement was the level of inflammation (as indicated by erythema, reddening of the skin). The study data was encouraging, with TPR100 meeting its clinical endpoints. The data provides a pathway for the product's further development and formed the basis of the submission for TPR100 for UK marketing approval by Thornton & Ross.