Summit Therapeutics Announces $2.0B Private Placement with AstraZeneca

What Happened
Summit Therapeutics Inc. announced on Sept. 28, 2026 (filed 8‑K on Sept. 29, 2026) that it entered a securities purchase agreement with AstraZeneca Holdings B.V. for a $2.0 billion private placement. Summit will issue 108,955.3686 shares of newly designated Class A Convertible Preferred Stock at $18,356.14 per preferred share (implying $18.3561 per common share). Each preferred share converts into 1,000 shares of Summit common stock.

Key Details

• Investor: AstraZeneca Holdings B.V., a subsidiary of AstraZeneca plc.
• Amount: $2.0 billion gross proceeds; 108,955.3686 Class A Convertible Preferred Shares issued at $18,356.14 each.
• Conversion: Each preferred share converts into 1,000 common shares → ~108.96 million common shares would be issuable upon full conversion.
• Timing & mechanics: Closing expected within five business days of the Sept. 28, 2026 Purchase Agreement, subject to customary conditions. Securities issued under exemptions (Section 4(a)(2) and/or Rule 506).
• Registration & rights: Summit will enter a Registration Rights Agreement to file a resale registration statement for the conversion shares within 60 days after closing and has agreed to use reasonable best efforts to have it declared effective. The Purchase Agreement also grants AstraZeneca certain preemptive and third‑party acquisition participation rights.
• Other: Summit disclosed a separate clinical trial collaboration between a Summit subsidiary and AstraZeneca to evaluate sonesitatug vedotin (sone‑ve) with ivonescimab; a press release was issued (Exhibit 99.1).

Why It Matters
This transaction provides Summit with $2.0 billion in immediate capital, which can support clinical programs and operations. However, the convertible structure creates potential substantial dilution: if all preferred shares convert, roughly 108.96 million new common shares could be issued. The filing also gives AstraZeneca contractual rights (preemptive and acquisition‑related) and sets a near‑term timetable for registration of the conversion shares, which may affect liquidity and trading of Summit’s common stock once the registration statement is effective.