Prothena posts $16.5m quarterly loss; partner-run trials keep its pipeline value years from payoff

Prothena reported a third-quarter 2026 net loss of $16.5 million on 5 November and said it held $272.2 million in cash at quarter-end. The material provided does not break out revenue, operating costs or cash runway, so the figures cannot be read as a guide to how long that balance will last.

The more telling detail is who is running the trials. Novo is advancing coramitug, Roche is developing prasinezumab, and Bristol Myers Squibb is responsible for moponetug. The two Phase 3 studies, for coramitug and prasinezumab, are both expected to finish primary data collection in 2029. For Prothena, any late-stage readout, and any filing that could follow, is therefore several years away.

Near-term news flow comes from two sources. Novo presented a post hoc analysis of its Phase 2 coramitug data at the Heart Failure Society of America meeting. In patients with transthyretin amyloid cardiomyopathy, levels of the inflammation marker high-sensitivity C-reactive protein fell on coramitug and rose on placebo. The summary gives no size for the effect and does not describe the patient population analysed. Because the analysis was run after the trial had reported, it is best treated as exploratory rather than as proof of benefit.

The next scheduled clinical milestone is Bristol Myers Squibb's Phase 2 data for moponetug, which the partner expects in the first half of 2027.