There's interest in broad spectrum antivirals probably being driven by the emergent corona virus in the middle east. BCRX just got a 5 million contract for their preclinical product under the marburg solicitation. I expect that work is still being done to discover the mechanism of action for 669. I doubt whether they are in a position to take on large R&D efforts on 669 when the Dengue product has potential for partnership. This is pure speculation on my part.
Oh, that's the universal broad-spectrum antiviral that looks super-promising to cure any virus infection including HIV that they have shelved and stopped even talking about while changing their minds about what Dengue therapy to work on.