Shares of Vertex Pharmaceuticals declined more than 5 percent on Wednesday after the company said that refills for its cystic fibrosis drug Orkambi have been slow in recent months.
Greater lag time between refills indicates that patients are using less of the drug, the company said on Wednesday. Vertex emphasized that although patients took longer than expected to refill their prescriptions, they are not dropping their prescriptions.
While the stock declined on the report, Jefferies said it continues "to believe in the long-term value of the [cystic fibrosis] franchise" in a research note on Wednesday. The firm has a "buy" rating and a $107 price target on the stock.
Even with Wednesday's losses, Vertex shares are up 5 percent in the past six months, but have lost 33 percent in the past year.
Disclosure: Jefferies makes a market in the securities or ADRs of Vertex Pharmaceuticals.
— CNBC's Berkeley Lovelace contributed to this report.