Andarine (S-4)

Andarine, also known as S-4, S-40503, or 8, is a SARM developed with the aim of treating osteoporosis and muscle wasting.

SARMs (selective androgen receptor modulators) are drugs that bind to the androgen receptor (AR), which is the main site of action of the hormone testosterone.

In the early days, Andarine was described as the ideal SARM due to high oral bio availability and great muscle- and bone-building effects (studied in animals).

Phase I human trials with this drug have reportedly been successful but no studies have been published. However, further development of the drug was abandoned in favor of Ostarine, another SARM with a similar structure, also known as S-22.

This was likely because of Andarine’s poor safety profile. It caused vision-related side effects, which further adds to the long list of reasons against ever taking this drug.