Farheen, this is possible. Not knowing which kind of receptor we are talking, it is hard to be more specific, but in case of GPCR, the efficacy of a ligand (its ability to elicit a response) is not linearly proportional with its affinity, it depends on the conformational state of the receptor which is stabilized by the binding of ligand. In case of inhibitors, similarly, the inhibition activity also depends on the conformer of receptor, not necessarily proportional with the affinity.

Best, Karoly