What: Shares of Cempra (NASDAQ:MLNT), a clinical-stage biopharma, crashed today following a positive update for the company's late-stage fourth generation macrolide, solithromycin, indicated as a potential treatment for community acquired bacterial pneumonia (CABP). According to the press release, solithromycin met the FDA's primary objective of statistical non-inferiority when pitted against Bayer AG's moxifloxacin, per a statistical analysis performed on the intent-to-treat population. 

So what: The market nonetheless focused on the drug's side effect profile, which comes off as slightly less favorable than moxifloxacin's based on the top-line data released from this study today. Specifically, Cempra reported that "more treatment-related adverse events were observed with solithromycin (34.3%) than with moxifloxacin (13.1%)", mostly consisting of mild to moderate pain at the infusion site. 

On the bright side, the two treatment arms looked comparable in terms of serious adverse events (6.9% of solithromycin patients vs. 5.4% of moxifloxacin patients experienced SAEs), and the number of deaths between arms were similar as well (5 fatalities in the solithromycin arm vs. 7 in the moxifloxacin arm).

Now what: Cempra's management now plans on submitting solithromycin's regulatory application to the FDA as a treatment for CABP in the first half of 2016. So the burning question is whether or not this experimental drug's side effect profile will derail its regulatory application, or perhaps its commercial launch if approved. 

Personally, I think this drop is largely unwarranted. Based on what we know so far, solithromycin's side effects don't appear to be particularly worrisome, especially in light of the fact that only 2.1% of IV solithromycin patients discontinued dosing because of adverse events.

So, given the growing need for need new drugs to treat CABP, I think it's going to be hard for the FDA to nix solithromycin's regulatory filing simply due to some mild to moderate pain at the infusion site. Investors with a decent appetite for risk therefore might want to dig deeper into Cempra following this massive drop in its share price.