CD44 and skin disorder: This led to the exploration of the coumarin moiety due to its versatility and druggability, as seen in the development of warfarin (anti-coagulants), methoxsalen (anti-dermatosis), novobiocin (antibiotics), etc. (+)-Calanolide A, a clinically-evaluated coumarin derivative, inhibits RT, IN, PR, Tat, and Vpr.