I'd say that if it's safe and effective, an FDA approval is likely, though that leaves other questions:
1. The FDA will review their BLA and come up with what are called deficiencies. Depending on how major or minor those are, the time to market will be effected. Much of this is based on experience. Has Regeneron ever filed a BLA before?
2. How much does it cost to make the drug vs how big is the dose vs how big is the market? It may be a successful drug, but whether it's profitable remains to be seen.
3. What does the shelf life look like? An important characteristic of any drug is its expiration dating. If it has a stable shelf life of two years or more, that's a good thing. Less than that, and supply gets difficult.