(Reuters) – Pfizer Inc and Sangamo Therapeutics Inc said on Thursday their gene therapy helped maintain levels of a vital protein for up to 14 months in patients with a rare genetic disorder in which blood does not clot easily.

All five patients in an early-stage trial given the one-time treatment, giroctocogene fitelparvovec, did not have spontaneous bleeding episodes or require infusions of the blood-clotting protein they otherwise lack, the companies said.

Pfizer and Sangamo’s therapy is one of several treatments being developed for hemophilia A, as an alternative to the current practice that requires regular infusions to replace the missing protein, factor VIII.

On Wednesday, a rival gene therapy by BioMarin Pharmaceutical Inc was found to reduce bleeding episodes by over 90% in patients treated four years ago. The therapy is currently under review by the U.S. drugs regulator, which is expected to announce its decision by Aug. 21.

The therapies are designed to help patients produce the protein on their own, to avoid the painful bleeding in muscles and joints that is typical of the condition and which could result in chronic joint damage over time.

Pfizer and Sangamo expect to begin dosing patients in a late-stage trial in the second half of this year.