The invention provides a pharmaceutical composition comprising a compound of the formula (1): or a pharmaceutically acceptable salt or tautomer thereof; wherein R1 and R2 are each selected from hydrogen and methyl, provided that at least one of R1 and R2 is hydrogen; and X is CHOH or C=O; and a pharmaceutically acceptable carrier. Also provided are novel compounds wherein R1 and R2 are each selected from hydrogen and methyl, wherein at least one of R1 and R2 is hydrogen; and X is CHOH or C=O; provided that the hydrogen atoms in positions 3 and 11b are present in a cis relative orientation when (i) R1 and R2 are both hydrogen, or (ii) R1 is hydrogen and R2 is methyl.