Prothena Corporation — Third Quarter 2026 Earnings Summary

Financial Performance:

• Reported a net loss of $16.5 million for the third quarter of 2026, compared to a net loss of $36.5 million for the same period in 2025; net loss for the first nine months of 2026 was $2.4 million versus $222.5 million in 2025.
• Basic and diluted net loss per share was $0.32 for Q3 2026 and $0.05 for the first nine months of 2026, compared to $0.68 and $4.13, respectively, in the prior year periods.
• Total revenue was $0.6 million for Q3 2026 and $52.7 million for the first nine months of 2026, compared to $2.4 million and $9.7 million, respectively, in 2025.
• Q3 2026 revenue consisted of $0.62 million in collaboration revenue; first nine months 2026 revenue included $50.0 million in milestone payments from Novo and $2.66 million in collaboration revenue from Bristol Myers Squibb.
• Research and development (R&D) expenses were $8.4 million for Q3 2026 and $29.9 million for the first nine months of 2026, down from $28.9 million and $120.3 million, respectively, in 2025.
• General and administrative (G&A) expenses were $10.6 million for Q3 2026 and $34.2 million for the first nine months of 2026, down from $13.2 million and $46.7 million, respectively, in 2025.
• Restructuring expenses were $0.4 million for Q3 2026, while the first nine months of 2026 recorded a restructuring credit of $1.4 million, compared to $0.5 million expense and $33.1 million expense in 2025 periods.
• Total non-cash share-based compensation expense was $6.4 million for Q3 2026 and $21.2 million for the first nine months of 2026, compared to $7.2 million and $30.6 million, respectively, in 2025.
• Net cash used in operating and investing activities was $12.0 million in Q3 2026 and $8.9 million for the first nine months of 2026.
• Cash, cash equivalents, and restricted cash totaled $272.2 million as of September 30, 2026, with no debt outstanding.
• Deferred revenue was $0 as of September 30, 2026, compared to $2.66 million as of December 31, 2025.

Guidance and Future Outlook:

• Full year 2026 net cash used in operating and investing activities is expected to be between $18 million and $23 million.
• The company expects to end 2026 with approximately $259 million (midpoint) in cash, cash equivalents, and restricted cash.
• Estimated full year 2026 net loss is projected between $25 million and $30 million, including approximately $26 million in non-cash share-based compensation expense.

Business Segments and Product Lines:

• Prasinezumab (Parkinson's Disease): Roche is conducting the Phase 3 PARAISO trial in approximately 900 participants with a primary completion expected in 2029; Roche estimates peak sales potential greater than $3.5 billion.
• Coramitug (ATTR-CM): Novo is conducting the Phase 3 CLEOPATTRA trial in approximately 1,280 participants with a primary completion expected in 2029; the drug received Fast Track designation from the U.S. FDA.
• Coramitug Clinical Data: Post hoc analyses from the Phase 2 trial presented at the HFSA Annual Scientific Meeting showed an ~8% decrease in the inflammatory biomarker hsCRP in treated patients versus a ~33% increase in placebo (treatment ratio 0.66; p=0.0269).
• Moponetug (Alzheimer's Disease): Bristol Myers Squibb is conducting the Phase 2 TargetTau-1 trial in approximately 310 patients with a data readout expected in the first half of 2027; the drug received Fast Track designation from the U.S. FDA.
• Preclinical Programs: The company is advancing wholly-owned programs TDP-43 CYTOPE and PRX012-TfR, with ongoing preclinical studies for the latter.
• Technology Partnerships: Multiple research collaborations with industry partners are ongoing to explore the CYTOPE® technology over the next 12 to 24 months.

Other Key Points:

• The company has generated $650 million in upfront, milestone, and equity payments to date and may potentially receive over $2.25 billion in additional milestone payments plus potential royalties from partnered programs.
• Prothena repurchased 501,492 ordinary shares in Q3 2026, bringing the aggregate repurchases for the first nine months of 2026 to 2,745,380 shares for $26.6 million under its $100.0 million share repurchase program expiring December 31, 2026.
• As of October 29, 2026, there were approximately 51.3 million ordinary shares outstanding.
• Novo's acquisition of Prothena's ATTR amyloidosis business and pipeline was valued at up to $1.2 billion.