True about orphan drug is:

Ans. c. Drugs used for rare diseases (Ref: KDT 7/e, p5, 6/e p6)An orphan drug is a pharmaceutical agent that has been developed specifically to treat a rare medical condition, the condition itself being referred to as an orphan disease.Orphan DrugsThese are drugs or biological products for diagnosis/ treatment/ prevention of a rare disease or a more common disease (endemic only in resource poor countries) for which there is no reasonable expectation that the cost of developing and marketing it will be recovered from the sales of that drug.Though these drugs may be life saving for some patients, they are commercially difficult to obtain.Government is developed countries offer tax benefits and other incentives to pharmaceutical companies for developing and marketing orphan drugs.Orphan Drugs* Sodium nitrite* Fomepizole* Liposomal amphotericin B* Ancrod* Rifabutin* Succimer* Somatropin* Digoxin immune Fab (digoxin antibody)* Liothyronnine (T3)