The placebo components are propylene glycol clinical trials

Randomised, double-blind, multicentre clinical trial to evaluate the efficacy and safety of topical metformin in adjuvant to daylight photodynamic therapy in actinic keratoses.

This study is testing a new cream with metformin alongside a light treatment for a skin condition called actinic keratoses. Researchers want to see if the cream helps the light treatment work better and if it's safe. It's a phase 2 study, meaning it's an early look at a new treatment.