Prednylidene is a

glucocorticoid Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebr ...

for systemic use. Substitution at position 16 also leads to more potent corticosteroids. The additional steric bulk introduced by such substituents adjacent to the dihydroxyacetone side chain also protects that moiety against metabolic degradation.

References

Glucocorticoids Vinylidene compounds {{systemic-hormonal-drug-stub