On Tuesday Shares of PTC Therapeutics (PTCT) fell by 60% after it had announced that the FDA deemed the marketing application as insufficient for review. The company’s drug, known as Translarna, is being used to treat patients with a degenerative muscle disease in kids known as Duchenne muscular dystrophy — DMD. 

There are already a few other biotech companies that are developing drugs for DMD. These other biotechs are Sarepta Therapeutics (SRPT) and Biomarin Pharmaceutical (BMRN). There is a difference, however, and that is that they target a different subset of DMD patients. In October of 2015 the company announced that it failed to meet on the primary endpoint of a phase 3 study. 

Despite this the company said that the phase 3 data along with other data would be sufficient to file an NDA to the FDA for marketing approval. At the moment the FDA has only stated that the application wasn’t sufficient enough to merit a review. Analysts do not yet know if this means that the Application was incomplete with missing info, or if the efficacy data is not what the FDA was looking for. Investors should probably remain on the sidelines until it is clear why the FDA didn’t review the company’s drug.