What happened

Shares of AnaptysBio Inc. (ANAB 6.97%), a clinical-stage biotech developing therapeutic antibodies, slipped 13.1% in late-day trading and finished Monday's session 9.7% lower. The company has been quiet since announcing data from a recent peanut allergy trial that has been the source of some disagreement. It appears that a second look at the interim data from the mid-stage trial with ANB020 put a bad taste in shareholders' mouths this afternoon.

So what 

AnaptysBio has four partnered drugs in clinical trials and two more that the company owns outright. ANB020 is the wholly-owned candidate furthest along the development timeline. The stock marched up to an all-time high following data from a mid-stage eczema trial released in February but has fallen about 15% since releasing spotty data from a small peanut allergy trial.

Chalkboard with a drawing of a downward sloping chart.

Image source: Getty Images.

Investigators gave ANB020 to 13 adults with moderate to severe peanut allergy symptoms and then essentially made them eat some peanuts a couple weeks later. Six of the 13 showed an improved peanut tolerance, which might be pretty good. There weren't any improvements in peanut tolerance among patients randomized to receive a placebo, but zero out of three isn't a lot to go on.

Now what

While the results warrant further investigation, they failed to impress analysts bullish for potential competitors in the peanut allergy space. The most fearsome source of competition could come from Aimmune Therapeutics Inc. (AIMT) and its lead candidate AR101. During a pivotal study that wrapped up recently, 96% of patients who completed treatment were able to tolerate a 300 mg dose of peanut, while 63% could handle a whole 1,000 mg of peanut protein.

Aimmune's candidate put up arguably better data, but the pivotal study was limited to children between the ages of 4 and 17, while AnaptysBio has its lead candidate aimed at an adult population. If you're still worried about Aimmune's candidate in the peanut allergy space, remember ANB020's main source of value is as a treatment for eczema.