Shares of Prosensa (RNA) fall nearly 9% on the day.
Investors may be getting increasingly nervous about the prospects for drisapersen following dystrophin response data that some regarded as disappointing.
Predictably, shares of Sarepta Therapeutics (SRPT) moved in the exact opposite direction, rising 4.5%.
The two names have been negatively correlated of late as drisapersen is a competitor to SRPT's eteplirsen.
Strength in shares of SRPT may also be attributable to investors reentering the name following Monday's sell-off which was triggered by what looks to be a largely inconsequential photo publication error.