Ultragenyx Pharmaceutical (RARE) said Tuesday that its investigational gene therapy UX111 achieved "substantial and durable" biomarker improvements and provided "meaningful" functional benefits in patients with Sanfilippo syndrome type A, or MPS IIIA, through 8.5 years of follow-up.

The company said the improvements compared with natural history were observed across age groups and disease severity, and UX111 continued to be well-tolerated with a favorable safety profile.

Ultragenyx said it included these new data in its biologics license application for UX111, which it resubmitted to the US Food and Drug Administration in January.

The company said it expects a review period of up to six months, with a target action date anticipated in Q3.

Shares of Ultragenyx were up more than 1% in recent premarket activity Tuesday.