US health regulators on Friday said they wanted more data on Protalix's and Pfizer Inc's experimental drug for Gaucher disease before deciding whether to approve the therapy for patients with the rare genetic disorder.

Protalix shares on Nasdaq closed nearly 18.5 percent lower at $7.63 after being down as much as 29 percent earlier.

Protalix shares were down 25.1 percent at 27.12 shekels in afternoon trade in Tel Aviv. ($1 = 3.66 shekels)