Drug giant Pfizer has expanded an existing agreement with Israeli drugmaker Protalix BioTherapeutics for the development of Elelyso.

The companies have now signed a Clinical Development Agreement under which Protalix will continue to fund and manage existing clinical trials or the drug, which are assessing its potential in Gaucher's disease, while Pfizer will take on any new studies.

Under the terms of the deal, Protalix stands to receive a milestone payment of $8.3 million when certain near-term clinical development milestones are achieved.

The companies first hooked up in 2009 under an agreement to develop and commercialise Elelyso (taliglucerase alfa), an enzyme replacement therapy for the treatment of Gaucher disease, which gave Pfizer exclusive worldwide rights to the drug.

This new agreement "helps to maintain the continuity of the ongoing clinical trials for Gaucher patients and physicians and reinforces the companies' mutual commitment to the Gaucher community," Protalix said.