- An experimental gene therapy did not significantly improve the vision of people with a rare, inherited eye disease that eventually leads to blindness, according to a Friday statement from the treatment's developer, Biogen.
- The drugmaker's conclusion was based on results from a late-stage study of 50 participants with a form of retinitis pigmentosa known as XLRP. After one year, there was no statistically significant difference between the proportion of patient eyes treated with the therapy that had improved compared to patient eyes that weren't treated, as measured by a test of retinal sensitivity.
- While Biogen noted there were "positive trends" in data on secondary study goals, the trial's outcome is a disappointment for a therapy the drugmaker acquired two years ago in a $800 million buyout of Nightstar Therapeutics.
Biogen's acquisition of Nightstar signaled the biotech company's commitment to gene therapy research, an investment it's expanded upon with subsequent deals like a January collaboration with Germany's ViGeneron and another earlier this week with Capsigen.
The Nightstar deal bought Biogen two gene therapies in advanced trials, including the XLRP treatment that's now fallen short in Phase 2/3 testing.
XLRP, short for X-linked retinitis pigmentosa, primarily affects males and is associated with progressive vision loss caused by the degradation of light-sensing cells in the retina. Biogen's treatment is designed to deliver into the eye, via a subretinal injection, a functional gene encoding for a key protein that's missing in XLRP patients.
The study was split into two parts: a Phase 1 portion that enrolled 18 patients and sought to establish a dosing regimen, and a Phase 2/3 portion that enrolled 32 more volunteers over the age of 10. The Phase 2/3 segment split participants into three study arms comparing a high dose and a low dose to no treatment.
Changes in retinal sensitivity were measured at one year via a macular integrity assessment. Researchers sought to establish that treatment would result in improvement from baseline across different locations on the retina.
But results showed no difference between the treated group and control, although Biogen did not detail specific data nor did it break out results from the high dose versus the low dose.
"Although the Phase 2/3 XIRIUS study of cotoretigene toliparvovec did not meet its primary endpoint, we are encouraged by positive trends in other pre-specified clinically relevant endpoints, such as a measure of visual acuity under low light conditions," said Katherine Dawson, head of Biogen's therapeutics development unit, using the treatment's scientific name in a statement.
Dawson said Biogen would wait to decide on next steps for the program until it saw complete data from the study, which the company plans to share at a "future scientific forum."
Testing on another Nightstar therapy, for a rare eye disease called choroideremia, is still ongoing, and Biogen is now working with ViGeneron and Massachusetts Eye and Ear Institute on other gene therapies for the eye.
The disappointing outcome reported Friday, however, could diminish confidence the choroideremia therapy will succeed. "We think these results could serve as a canary in the coal mine given the overlap in technology," wrote Brian Skorney, an analyst at R.W. Baird, in an investor note. Results are expected later this year.
And while Biogen's XLRP work is now set back, other companies including Johnson & Johnson, AGTC and 4D Molecular Therapeutics are testing gene therapies for the disease.
For investors, though, Biogen's gene therapy research is secondary to the looming Food and Drug Administration decision on whether to approve the company's experimental Alzheimer's disease treatment aducanumab. A decision is expected by June 7 and, either positive or negative, will greatly impact the company's future.
Shares in Biogen fell by 2% in mid-morning trading Friday.