RegenxBio highlights positive data for rare disease drug RGX-121

RegenxBio has announced positive long-term results from its pivotal study of RGX-121 for mucopolysaccharidosis type II (MPS II). The September 3 press release revealed that patients receiving the pivotal dose (dose level 3) experienced an 85% median reduction in cerebrospinal fluid (CSF) heparan sulfate D2S6 levels, nearing normal and sustained for up to two years. RGX-121, using the NAV AAV9 vector, delivers a functional copy of the IDS gene to the central nervous system.

The company plans to file a rolling biologics license application (BLA) under the accelerated approval pathway in Q3 2024, using CSF D2S6 as a surrogate endpoint.

The Phase I/II/III CAMPSIITE study (NCT03566043) includes a safety assessment in 16 pediatric patients and a pivotal expansion in 30 pediatric patients. RGX-121 was well tolerated among 25 treated patients. MPS II, caused by a deficiency in the IDS enzyme, is expected to generate $460 million in global sales by 2030.