By Doc Louallen

Regenxbio shares advanced after the company said the first patient was dosed in its Phase IIb/III Naavigate study of surabgene lomparvovec for diabetic retinopathy and that it will receive a $100 million milestone payment from AbbVie.

Shares were up 10% at $13.14 in midday trading Wednesday. The stock is up more than 50% over the past three months.

The biotechnology company said the study is testing a one-time, in-office gene therapy for diabetic retinopathy, an eye disease tied to diabetes that can lead to vision loss. The primary endpoint is to assess whether the treatment can improve disease severity by two steps or more on the diabetic retinopathy severity scale at one year, Regenxbio said.

The Phase IIb portion is expected to enroll about 135 participants in the U.S., the company said.

Write to Doc Louallen at Doc.Louallen@wsj.com