Nicotinamide Hydrochloride is a form of vitamin B3 or niacin that inhibits sirtuin 2 ( SIRT2 ) activity in vitro , with an EC 50 of 2 μM. Nicotinamide Hydrochloride inhibits up to 90% melanoma cell number and increases cellular NAD + , ATP, ROS levels. Nicotinamide Hydrochloride inhibts tumor growth in vivo and improves survival of melanoma-bearing mice, which can be used for the research of skin cancers such as melanoma [1] .