Shares of Taysha Gene Therapies were down more than 10 percent after a patient’s death marred positive interim data for the company’s experimental gene therapy treatment for Sandhoff and Tay-Sachs diseases, which are two forms of GM2 gangliosidosis.

Passage Bio’s first attempt to develop a GM1 gangliosidosis gene therapy treatment ran into a roadblock in the form of a clinical hold.

Philadelphia-based Passage Bio launched with a Series A financing round valued at $115.5 million, led by OrbiMed Advisors.