aibioSummit Therapeutics derivative suit over $520 million Duggan notes ends in voluntary dismissal
Tickers SMMT
Rainaldi Revocable Trust sued certain current and former Summit directors in Delaware Chancery in 2025, with Summit a nominal defendant. The parties stipulated to dismissal on May 27, 2026.
Key facts
- Company
- Summit Therapeutics Inc. (NASDAQ: SMMT)
- News type
- Legal
- Primary source
- Summit Therapeutics 10-Q for the quarter ended June 30, 2026 (SEC EDGAR)
A Delaware derivative lawsuit over the $520 million in bridge notes that Summit Therapeutics Inc. (Nasdaq: SMMT) issued to Robert W. Duggan and Dr. Mahkam Zanganeh has ended. Rainaldi Revocable Trust, a purported stockholder, filed the suit on March 17, 2025 in the Delaware Court of Chancery against certain current and former directors, with Summit named only as a nominal defendant. The 10-Q filed July 23, 2026 says the parties stipulated to voluntary dismissal on May 27, 2026, and the court approved it the same day.
The 10-Q does not name the director defendants or give a case number. Summit's annual report filed February 24, 2025, its last annual report before the suit, was signed by nine directors, listed below. That report lists Mr. Duggan and Dr. Zanganeh as Summit's co-chief executive officers.
The case
The suit concerned a Note Purchase Agreement under which Summit issued unsecured promissory notes to Mr. Duggan and Dr. Zanganeh in December 2022, in connection with its license agreement. Summit says the notes totaled $520 million: a $400 million note and a $100 million note to Mr. Duggan, and a $20 million note to Dr. Zanganeh. The notes carried interest at 7.5% through February 15, 2023, with prepaid interest paid in shares valued at $0.7913 per share.
The complaint asserted claims for breach of fiduciary duty and unjust enrichment. It sought, among other things, unspecified damages, rescission of the shares that Mr. Duggan and Dr. Zanganeh received as prepaid interest, and attorneys' fees and costs.
Defendants
Summit is a nominal defendant. The 10-Q names no individual defendants and says only that the defendants are certain current and former directors. It does not say that Mr. Duggan or Dr. Zanganeh is a defendant. The 2025 annual report was signed by these nine directors: Robert W. Duggan, co-chief executive officer and executive chairman; Mahkam Zanganeh, co-chief executive officer, president and director; Manmeet S. Soni, chief operating officer, chief financial officer and director; and directors Robert F. Booth, Alessandra Cesano, Kenneth Clark, Jeff Huber, Mostafa Ronaghi and Yu Xia. That is the board when the suit was filed, not a statement of who was sued. It does not show who the former directors are.
Where it stands
Defendants moved to dismiss on May 16, 2025. The plaintiff moved on May 29, 2025 to certify constitutional questions to the Delaware Supreme Court. The parties stayed the briefing until that court decided another case with substantially the same questions, and the court granted the stay on June 18, 2025. The Delaware Supreme Court decided that case on February 27, 2026, and the parties filed a briefing schedule for the motion to dismiss on April 16, 2026.
On May 27, 2026, the plaintiff and defendants stipulated to dismissal of the plaintiff's claims with prejudice as to the plaintiff and without prejudice as to any other stockholder. The court approved that the same day. Summit's later filings, through a proxy statement filed October 19, 2026, do not mention the case.
Why it matters to shareholders
The 10-Q reports no payment, accrual or estimated loss for the suit, and it does not say whether insurance covered the defense. The dismissal was with prejudice only as to the Rainaldi trust and without prejudice as to any other Summit stockholder.
Summit says the notes were repaid. Mr. Duggan's $400 million note and Dr. Zanganeh's $20 million note were repaid after the $500 million 2023 rights offering. The $75.5 million repayment of the extended $100 million note was funded through a September 2024 private placement, and the remaining $24.5 million was repaid in full on October 1, 2024, with $7.3 million in accrued interest.
Related matters
Summit also reports a European patent opposition. On June 18, 2025, an unknown third party filed a notice of opposition against the in-licensed EP3882275B1 patent, which covers ivonescimab, in the European Patent Office. It asserts the patent lacks inventive step. Summit says it contests the assertions and has filed responses with its collaboration partner, Akeso, including on June 22, 2026.