Prothena Corp. (PRTA) Announces PRX002 Phase 1b Met Primary Objective in PD (RHHBY)

November 9, 2016 4:11 PM EST
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Prothena Corporation plc (Nasdaq: PRTA) announced results from its Phase 1b multiple ascending dose study of PRX002, an antibody under investigation as a potentially disease-modifying treatment for Parkinson’s disease. PRX002, also known as RG7935, is the focus of a worldwide collaboration between Prothena and Roche.

PRX002 was found to have an acceptable safety and tolerability profile in patients with Parkinson’s disease, meeting the primary objective of this study. Robust CNS penetration was demonstrated by a dose-dependent increase in PRX002 levels in CSF, and a mean concentration of PRX002 in CSF of 0.3 percent relative to serum across all dose levels. Additional results showed a rapid, dose- and time dependent mean reduction of free serum alpha-synuclein levels of up to 97 percent after a single dose, which were statistically significant (p < 0.0001), and confirmed after two additional monthly doses.

“These data represent the first reported assessment of an anti-alpha-synuclein antibody in patients with Parkinson’s disease,” stated Gene Kinney, PhD, President and Chief Executive Officer of Prothena. “In this study we observed PRX002 penetration in the CNS that exceeded our expectations based on our preclinical experience, and a highly statistically significant reduction of free serum alpha-synuclein. These Phase 1b data further support our belief that we can choose doses that target and saturate aggregated pathogenic alpha-synuclein in the brain for a Phase 2 study to further explore the potential of PRX002 as a disease-modifying treatment for Parkinson’s disease. Together with Roche, we expect to initiate a Phase 2 study in 2017.”

This Phase 1b double-blind, placebo-controlled multiple ascending dose study enrolled 80 patients with Parkinson’s disease. Patients were randomized into six escalating dose cohorts to receive PRX002 or placebo (2:1 randomization for 0.3, 1, 3 or 10 mg/kg, and 3:1 randomization for 30 or 60 mg/kg). In this six-month study, patients received three monthly doses (intravenous infusion once every 28 days) of PRX002 or placebo and were followed for an observational period of three months. No serious or severe treatment emergent adverse events (TEAEs) were reported in PRX002 treated patients. No TEAEs were observed in ten percent or more of PRX002 treated patients. TEAEs greater than placebo in five percent or more of PRX002 treated patients, regardless of relationship to PRX002, included constipation, infusion related reactions (IRRs), diarrhoea, peripheral oedema, and post lumbar puncture syndrome. Mild-to-moderate IRRs, that all resolved, were limited to the 60 mg/kg dose cohort and were observed in four of 12 treated patients. No dose-limiting toxicities were observed. PRX002 demonstrated acceptable pharmacokinetic properties.

“Developing new therapies for complex neurological diseases such as Parkinson’s requires dedicated and disciplined science,” said Todd Sherer, PhD, CEO of The Michael J. Fox Foundation for Parkinson’s Research. “Targeting alpha-synuclein represents a promising path toward a potentially disease-modifying treatment for Parkinson’s disease, and we are very pleased to see PRX002 advance to the next stage of development.”

Prothena plans to present results from this study at an upcoming scientific conference. A Phase 2 clinical study is expected to begin in 2017.

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