US seeks more data on Protalix drug, shares fall

US health regulators want more data on Protalix Biotherapeutics Inc'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 closed nearly 18.5 per cent lower after being down as much as 29 per cent earlier.

It also spells some uncertainty for the $2 billion Gaucher market, which has been dogged by shortages of the leading therapy - Genzyme Corp's Cerezyme. In a letter to Protalix on Friday, the Food and Drug Administration did not call for any new clinical trials, the Israeli drugmaker said. However, the FDA did ask for additional data from several existing studies.

While gathering extra data is less onerous than launching an entirely new study, the news still scared off some investors as Wall Street analysts had largely expected approval and decent market share, given the muscle of the company's marketing partner, Pfizer. Jon LeCroy, a senior healthcare analyst for Hapoalim Securities USA Inc, said he now expects at least a 12-month delay before the drug could get approved for the US market.