How is orphan drug exclusivity affected when the FDA-approved use for an orphan drug is arguably narrower than the treatment of the rare disease it was designated for?

By way of background, a sponsor can obtain orphan drug exclusivity when the FDA approves an application for a drug that has first been designated under 21 U.S.C. § 360bb of the Orphan Drug Act (ODA) for a “rare disease or condition.”  Id. § 360cc(a).  Except in any of three statutorily prescribed circumstances (§§ 360cc(b), (c)), the FDA cannot approve another application for the “same drug” for “the same disease or condition” for seven years after the first approval.