Shares in Voyager Therapeutics jumped 35% in after-hours trading on the back of interim data from an early trial of its Parkinson’s disease gene therapy. The surgically delivered gene therapy is aiming to make patients with advanced forms of the disease respond better to levodopa, an old drug that is fairly effective at controlling symptoms in the early stages of the condition.
When people are first diagnosed with Parkinson’s, levodopa can effectively manage symptoms. But as the disease’s effect on the brain increases and more neurons die, it overwhelms the treatment, resulting in patients developing disabling motor complications current therapies are unable to stop. The decline is linked to an inability to turn levodopa to dopamine. Voyager’s gene therapy is designed to facilitate this conversion by increasing expression of aromatic L-amino acid decarboxylase (AADC), an enzyme that catalyzes the reaction.
Cambridge, MA-based Voyager now has early clinical data suggesting the idea has legs. The data come from the first two five-person cohorts to enroll in a phase 1b. The trial is primarily looking at the safety of VY-AADC01 and procedure used to administer it—early signs suggest the MRI-guided delivery and gene therapy vector are tolerable—but Voyager is also collecting early data on AADC activity and its effect on motor function.
These early efficacy data, particularly from the second, higher-dose cohort, are responsible for the uptick in optimism about the program. Among the five patients in cohort two, AADC activity rose by 56% and levodopa dosages fell 34% over the first six months of the study. Data from patients who have completed 12 months of follow up suggest the effect persists at least that long. And the six and 12-month results from a clinical rating scale also suggest VY-AADC01 improves outcomes in the year following administration.
If Voyager can show such improvements continue beyond one year and can be achieved in larger numbers of patients, VY-AADC01 could become a one-time treatment to bring Parkinson’s patients back to a point at which their disease was manageable. Voyager is still a long way from showing VY-AADC01 can achieve this lofty ambition, though.
For now, the focus is on wrapping up enrollment in the next part of the dose-escalation trial—cohort 3—and continuing to gather data on patients treated to date. Voyager expects to complete enrollment in cohort 3 early in 2017, and go on to post an update on the 10 patients analyzed to date in the middle of the year.