Prothena Narrows Third-Quarter Loss as Cash Use Slows

The Tip Desk · November 11, 2026 · 4 min read

The late-stage biotech used $12.0 million of cash in operations and investing in the third quarter, after $25.7 million in the second quarter.

Prothena Corporation plc (PRTA) reported a narrower third-quarter net loss as research and development spending fell and cash burn slowed from the prior quarter.

The late-stage clinical biotechnology company recorded a net loss of $16.5 million, or $0.32 a share, for the three months ended September 30, 2026, compared with a net loss of $36.5 million, or $0.68 a share, a year earlier.

Total revenue was $0.6 million in the third quarter, down from $2.4 million in the third quarter of 2025. Collaboration revenue was $620 thousand.

Research and development expenses totaled $8.4 million, down from $28.9 million a year earlier. The company said the decrease was primarily due to lower clinical trial expenses, lower personnel expenses and lower consulting expenses. General and administrative expenses were $10.6 million, compared with $13.2 million a year earlier. Restructuring expenses were $0.4 million.

Net cash used in operating and investing activities was $12.0 million in the third quarter, versus $25.7 million used in the second quarter. Quarter-end cash and restricted cash was $272.2 million as of September 30, 2026, down from $289.1 million at the end of the second quarter. The company had no debt.

For the first nine months of 2026, Prothena reported a net loss of $2.4 million, or $0.05 a share, compared with a net loss of $222.5 million, or $4.13 a share, in the first nine months of 2025. Total revenue for the nine months was $52.7 million, primarily from a $50.0 million milestone payment from Novo related to the ongoing Phase 3 clinical trial for coramitug and collaboration revenue from Bristol Myers Squibb related to partial performance of the PRX019 Phase 1 clinical trial obligation. Research and development expenses were $29.9 million for the nine months. General and administrative expenses were $34.2 million. The company recorded an aggregate restructuring credit of $1.4 million for the nine months.

The company continues to expect full-year 2026 net cash used in operating and investing activities of $18 to $23 million and to end the year with approximately $259 million (midpoint) in cash, cash equivalents and restricted cash. The cash-use range matched the outlook set after the first quarter. The approximately $259 million cash midpoint matched the second-quarter update, which had revised the first-quarter midpoint of approximately $273 million. The estimated cash use is primarily driven by an estimated net loss of $25 to $30 million, which includes an estimated $26 million of non-cash share-based compensation expense. The guidance does not include any potential additional cash utilized as part of a share repurchase program.

Prothena repurchased 501,492 ordinary shares in the third quarter. Together with 788,990 shares in the first quarter and 1,454,898 shares in the second quarter, it repurchased an aggregate of 2,745,380 ordinary shares during the first nine months of 2026 for $26.6 million, excluding commissions and expenses, under its up-to-$100.0 million share repurchase program, which expires on December 31, 2026. As of October 29, 2026, the company had approximately 51.3 million ordinary shares outstanding.

President and Chief Executive Officer Gene Kinney said Roche and Novo highlighted prasinezumab and coramitug at Roche’s Pharma Day and Novo’s Capital Markets Day, respectively. Novo presented a post hoc analysis of its Phase 2 coramitug trial at the Heart Failure Society of America Annual Scientific Meeting showing that the inflammatory biomarker hsCRP decreased from baseline in patients treated with coramitug, while increasing in those receiving placebo. At week 52, the pooled coramitug dose groups (10 and 60 mg/kg) reported an approximately 8% decrease of hsCRP, compared with an approximately 33% increase with placebo (treatment ratio versus placebo: 0.66; nominal p=0.0269).

Roche is conducting the Phase 3 PARAISO trial of prasinezumab in approximately 900 participants with early-stage Parkinson’s disease, with primary completion expected in 2029. Roche has stated that prasinezumab has peak sales potential greater than $3.5 billion (unadjusted). Novo is conducting the Phase 3 CLEOPATTRA trial of coramitug in approximately 1,280 participants with ATTR-CM, with primary completion expected in 2029. Bristol Myers Squibb is conducting the Phase 2 TargetTau-1 trial of moponetug in approximately 310 patients with early Alzheimer’s disease, with data readout expected in the first half of 2027.

Through partnered programs, the company said it has generated $650 million in upfront, milestone and equity payments and may potentially receive over $2.25 billion in additional milestone payments, plus potential royalties. Multiple research collaborations with industry partners are ongoing to explore the potential of CYTOPE technology over the next 12 to 24 months.