Roche and Prothena Advance Parkinson's Drug to Phase III Despite Mixed Results

Roche and its partner Prothena have announced their decision to move forward with Phase III trials for their experimental Parkinson's disease drug, prasinezumab, despite mixed results in earlier studies. This development marks a significant step in the ongoing quest for disease-modifying treatments in Parkinson's, a field that has seen numerous setbacks in recent years.

Pushing Forward Despite Setbacks

The Swiss pharmaceutical giant Roche, in collaboration with Irish biotech firm Prothena, is advancing prasinezumab into late-stage clinical trials. This decision comes on the heels of two mid-stage studies, Pasadena and Padova, which failed to meet their primary efficacy endpoints. However, Roche's Chief Medical Officer, Levi Garraway, stated that the "totality of the data" suggests prasinezumab "may have the potential to become the first disease-modifying treatment for people with Parkinson's disease."

The move to Phase III trials is based on what Roche describes as "efficacy signals" observed in earlier testing. Specifically, the company points to potential clinical benefits when prasinezumab is used in conjunction with symptomatic treatments in early-stage Parkinson's patients. Additionally, Roche cites "positive trends" in motor progression at two years and biomarker evidence supporting the drug's effect on Parkinson's disease biology.

A Challenging Landscape for Parkinson's Drug Development

Prasinezumab is an antibody targeting alpha-synuclein, a protein that can misfold and accumulate in the brains of Parkinson's patients. This approach has been the focus of numerous drug programs, but success has been elusive. Recent years have seen disappointments from other major players in the field, including Biogen, AbbVie, and a UCB-developed pill licensed to Novartis.

The difficulty in developing effective treatments for Parkinson's is underscored by the cautious outlook from industry analysts. Jefferies analysts give the upcoming Phase III study for prasinezumab only a 25% to 40% probability of success. They highlight concerns about whether an antibody approach is potent enough to "slow the spread" of an intracellular protein like alpha-synuclein.

Financial Implications and Market Response

The continuation of prasinezumab's development represents a significant financial commitment for both Roche and Prothena. The partnership, which began in 2013 with a $600 million deal, has already seen Prothena collect $135 million in milestone payments. The news of the Phase III advancement led to an 11% increase in Prothena's share price on Monday.

However, this positive market response comes against the backdrop of recent challenges for Prothena. The company announced layoffs of 91 employees from its California site last week, following a setback in its Phase III AL amyloidosis program in May.

As Roche and Prothena move forward with the Phase III program for prasinezumab, the pharmaceutical industry will be watching closely. The outcome of these trials could have significant implications not only for Parkinson's disease treatment but also for the broader field of neurodegenerative disease research.