Prothena Corporation plc (PRTA) reported nine-month 2026 revenue of $52.714 million, versus $9.663 million a year earlier, including a $50.0 million Novo Nordisk milestone for coramitug’s continued advancement in the Phase 3 CLEOPATTRA trial. Third-quarter revenue was $620,000, compared with $2.415 million a year earlier. Nine-month net loss was $2.371 million, versus $222.503 million, while operating expenses were $62.601 million, down from $200.100 million.
Cash and cash equivalents were $271.368 million at September 30, 2026. Management said this amount was sufficient for obligations for at least the next 12 months under current business plans, while also stating that substantial additional capital will be needed to develop and seek regulatory approval for products. Operating activities used $8.135 million in cash during the nine months; share repurchases used $26.843 million in financing activities. In October 2026, Bristol Myers Squibb told Prothena it would not advance PRX019 and was terminating the license; it will not owe the company potential development, regulatory, and sales milestones of up to $617.5 million or tiered royalties.
Prothena Corporation plc reported third-quarter 2026 revenue of $0.6 million and net loss of $16.5 million, compared with $2.4 million and $36.5 million a year earlier. For the first nine months, revenue was $52.7 million versus $9.7 million, primarily from a $50.0 million Novo milestone payment; net loss was $2.4 million versus $222.5 million. At September 30, 2026, cash, cash equivalents and restricted cash totaled $272.2 million, and Prothena had no debt.
Net cash used in operating and investing activities was $12.0 million in the third quarter and $8.9 million in the first nine months. Prothena repurchased 2,745,380 ordinary shares for $26.6 million during the first nine months, excluding commissions and expenses, under its up to $100.0 million program, which expires December 31, 2026. The company continues to expect full-year 2026 net cash use of $18 million to $23 million and approximately $259 million in year-end cash, cash equivalents and restricted cash at the midpoint. Partner-led Phase 3 trials of prasinezumab and coramitug have primary completion expected in 2029.
Prothena Corporation plc said Bristol Myers Squibb decided not to advance PRX019 further in the clinic; the PRX019 Global License Agreement will terminate on January 28, 2027. Prothena was eligible for up to $617.5 million in development, regulatory, and sales milestones, plus tiered royalties on annual, worldwide net sales. In connection with termination, Bristol Myers Squibb will not owe those milestones or royalties. The agreement included an upfront payment of $80 million in May 2024.
Bristol Myers Squibb continues developing moponetug and conducting the Phase 2 TargetTau-1 trial in patients with early Alzheimer’s disease. It has paid Prothena $135 million in licensing payments for moponetug, and Prothena is eligible for up to $562.5 million in regulatory and sales milestones plus tiered royalties on annual, worldwide net sales.
William P. Scully, a ten percent owner of Prothena Corp Public Ltd Co (PRTA), acquired 566,444 ordinary shares in a bona fide gift transfer on October 27, 2026. His direct holdings afterward were 1,753,444 ordinary shares. The ordinary shares have a par value of $0.01 per share.
Prothena Corp Public Ltd Co (PRTA) ten-percent owner William P. Scully reported direct purchases of 100,000 ordinary shares on October 22, 2026, at a weighted average $8.1852 per share, and 50,000 shares on October 23 at a weighted average $8.0705 per share. No Rule 10b5-1 plan is reported. Indirect holdings included 529,000 shares by his spouse and 187,000 by Manatee Equity Fund LLC; Scully disclaims beneficial ownership of the LLC shares except to the extent of his pecuniary interest.
Prothena Corp Public Ltd Co (PRTA) ten-percent owner William P. Scully directly purchased 100,000 ordinary shares on October 13, 2026, at a weighted average of $8.3548 per share, across prices from $8.2547 to $8.4616. He directly purchased 10,000 shares on October 14, 2026, at a weighted average of $8.4569 per share, across prices from $8.4000 to $8.5600. No Rule 10b5-1 plan is reported. As of October 13, 2026, indirect holdings included 529,000 shares held by his spouse and 187,000 shares held by Manatee Equity Fund LLC; Scully disclaimed beneficial ownership of the LLC shares except to the extent of his pecuniary interest.
William P. Scully, a ten percent owner of Prothena Corp Public Ltd Co (PRTA), reported that his spouse purchased 125,000 ordinary shares on October 7, 2026, at a weighted average price of $8.4012 per share, and 90,000 shares on October 8, 2026, at a weighted average price of $8.5656 per share. The purchases comprised multiple transactions within reported ranges of $8.2100 to $8.6000 and $8.4000 to $8.8063, respectively. No Rule 10b5-1 plan is reported.
Prothena Corp Public Ltd Co (PRTA) reported that ten-percent owner William P. Scully purchased 100,000 ordinary shares indirectly through his spouse on October 2, 2026, at a weighted average price of $8.5724 per share. The reported spouse-held position after the purchase was 314,000 shares. The purchases occurred in multiple transactions at prices from $8.5150 to $8.6098, inclusive; no Rule 10b5-1 plan is reported.
Prothena Corporation plc said Chad J. Swanson, Ph.D., its Chief Development Officer, is resigning effective October 9, 2026, to accept a position with one of the company’s strategic partners.
Prothena Corp Public Ltd Co (PRTA) reports that 10% owner William P. Scully’s spouse purchased 162,000 ordinary shares on September 29, 2026. The reported weighted average price was $8.6770 per share, across multiple transactions from $8.6000 to $8.7550, inclusive. The reported post-transaction holding through his spouse was 214,000 shares. No Rule 10b5-1 plan is reported.