What happened

Momenta Pharmaceuticals (NASDAQ:MNTA) continued its rollercoaster ride on Friday, with shares closing up 10.1%. The move followed a 19% increase last Friday after the company reported positive data for its immune-mediated disorder drug, M281. However, the drugmaker gave the move entirely back by the middle of this week.

So what

Part of the rollercoaster likely has to with investors' inability to value Momenta in the short term. The drugmaker is trying to gain Food and Drug Administration (FDA) approval for Glatopa 40 mg, its generic version of Teva Pharmaceutical's Copaxone 40 mg, which is stuck in regulatory limbo because of issues at a plant run by Pfizer that Momenta's marketing partner Novartis (NYSE:NVS) uses to fill the syringes with the drug.

Freeway sign that reads "expect delays"

Image source: Getty Images.

In November, Momenta said it hoped Pfizer could get clearance after an FDA reinspection that would allow Glatopa 40 mg to be approved in "late 2017 or early 2018." We're in the back half of that guidance, and Pfizer is waiting to hear back from the FDA whether it'll get Voluntary Action Indicated status for the plant, which would allow Glatopa 40 mg to be approved.

Momenta is still hoping for a launch in the first half of 2018, but Novartis is also exploring the possibility of switching to a different contract manufacturer that would allow for launching the drug in the second half of the year.

Now what

Part of the problem here is that Momenta gets its information from Novartis, which gets it from Pfizer. It's not quite as bad as a kid's game of telephone, but there are undoubtedly things that Pfizer knows that Momenta isn't allowed to tell investors.

Without knowing the relative likelihood of a first-half 2018 versus a second-half 2018 launch, or the potential for an even further delay, shares are likely to continue on a rollercoaster until the telephone call comes in that says the drug has been approved.

Brian Orelli has no position in any of the stocks mentioned. The Motley Fool recommends Momenta Pharmaceuticals. The Motley Fool has a disclosure policy.