We have had a pretty interesting start to the week in the biotech space. A number of companies are already movers and promise to bring with them further volatility as the week matures. Here is a look at where the action is right now and what’s causing it.

The companies we’re looking at today are Puma Biotechnology Inc (NASDAQ:PBYI) and Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN).

Regular readers will know that Puma was one of our featured companies in yesterday’s Biotech Movers analysis, but the company continues to move, and it’s well worth revisiting ahead of the US session today. For those that missed yesterday’s coverage, the company has spent the month of May on something of a roller coaster, rising and falling on the back of shifts in sentiment, with each shift induced by an added import into the clinical development pathway of its lead asset – a drug called Neratinib that Puma is trying to get approved as a therapy for patients with breast cancer. The drug is currently at NDA phase with the FDA in the US, and to put it simply, markets can’t decide whether it has a decent chance, or no chance at all, of picking up approval when it comes in front of the agency as part of an (expected) July 2017 PDUFA.

A key member of the executive team (one who dealt with regulatory affairs) resigned earlier this month on the back of health concerns, and while health concerns are a justifiable resignation driver, the situation has spooked markets somewhat. Mounting concerns over safety and efficacy, combined with the fact that the FDA actually suggested the company didn’t submit a registration application based on the data it has in hand prior to Puma’s NDA submission, are weighing heavily on sentiment.

So that’s the bad news.

The good news is that traders and investors are looking to an advisory panel meeting set to take place tomorrow (May 24) as indicative of the drug’s chances come PDUFA and that we just got the briefing for this meeting and it looks, well, pretty good. There doesn’t seem to be any strong suggestion that the panel takes a negative view of the safety and efficacy data as part of the wording of the briefing and, to some degree, this is a win for Puma and its shareholders in and of itself.

In response to the briefing release, therefore, the company has picked up some strength. At last count, puma shares went for $52.60, a close to 40% premium on the company’s pre-briefing capitalization.

Now all eyes are on the meeting itself, and its outcome, as a near-term indication of where this one’s likely to go. If the meeting resolves as indicative of a failure recommendation, chances are we will see the entirety of the Monday session gains given back. If we see an outcome supportive of efficacy, expect some near-term strength to compound yesterday’s action.

Next up, then, Regeneron.

This one is a far simpler situation. The company was developing a drug called Kevzara (sarilumab) for the treatment of adult patients with moderately to severely active rheumatoid arthritis (RA) who have had an inadequate response or intolerance to one or more disease-modifying antirheumatic drugs (DMARDs), such as methotrexate (MTX). The development was carried out in cooperation with biotech peer Sanofi, and PDUFA for the application that served as the final step in the development process for the drug in this indication came at the start of this week.

The outcome?

The FDA has approved the drug in the target indication, and the two companies can now get to work marketing it in this population. The target population, the non-responders to the current standard of care, is pretty large, despite the drug’s not being first-line therapy. As such, and again, in spite of these two companies having pretty expansive portfolios of approved assets, this program meant a lot to both. In turn, on the back of the approval, we have seen both companies pick up strength.

Regeneron currently trades for around $461 a share, which is a 3% run on the company’s Friday close last week. Sanofi is up a percentage point pre-market and will likely strengthen further as the session matures.