Voyager’s AADC Gene Therapy Shows Promise as Maintenance Therapy for Parkinson’s

Voyager Therapeutics’ new clinical data on VY-AADC01 as a maintenance therapy for advanced Parkinson’s disease shows   improvement in patients’ motor function after just one dose, and with meaningfully lower doses of oral levodopa.

The company presented ongoing Phase 1b trial (NCT01973543) results at the Oct. 17-20 Congress of the European Society of Gene and Cell Therapy (ESGCT) in Berlin, in a talk titled “Intraputaminal AADC gene therapy for advanced Parkinson’s disease: Interim Results of a Phase 1b Trial.”

Adendo-associated viruses (AAV) are small viruses that can infect humans and primates without causing disease. AAV gene therapy enables the delivery of specific genetic sequences.

“A core competency of Voyager’s gene therapy platform is vector optimization and a critical component of this is optimizing and choosing the capsid, or outer shell of the gene therapy vector,” Dr. Dinah Sah, Voyager’s chief scientific officer, said in a press release. The outer shell of the AAV is an essential component, and must be customized to ensure correct gene delivery.

In normal conditions, levodopa is converted to dopamine by 1-amino acid decarboxylase (AADC). This enzyme acts on nerve terminals between the substantia nigra and striatum. In Parkinson’s, a severe loss of these nerve terminals is associated with a decrease in AADC activity. As a result, patients’ motor symptoms worsen.

Voyager’s VY-AADC01 was designed to deliver the AADC gene, which codes for the AADC enzyme, directly into neurons of Parkinson’s patients’ putamen. The putamen is part of the striatum that has dopamine receptors. This allows the putamen neurons to restore the conversion of levodopa to dopamine.

Motor function was then measured by patient-reported diaries, Parkinson’s disease rating scales, and activities of daily living.

Results show that after a single intravenous administration of VY-AADC01, motor function improved in a durable dose- and time-dependent way. Interestingly, this also happened with lower doses of oral levodopa.

Despite the promising results, Voyager will continue to monitor this trials’ patients. In addition, the pharmaceutical company already plans a pivotal Phase 2/3 trial, which will likely start enrollment in the first half of 2018.