AstraZeneca commits $2.0B preferred equity to Summit Therapeutics

Summit Therapeutics said that on September 28, 2026 it entered into a securities purchase agreement with AstraZeneca Holdings B.V. for a $2.0 billion Class A convertible preferred Private Placement, with closing expected within five business days subject to customary conditions, alongside a clinical collaboration to test ivonescimab with AstraZeneca's Claudin 18.2 ADC sonesitatug vedotin (Form 8-K AccNo 0001193125-26-405776).

Summit Therapeutics locked in a $2.0 billion preferred-equity commitment from AstraZeneca — a signed securities purchase agreement dated September 28, 2026 that is still expected to close within days, not a completed investment that already put AstraZeneca on the common register.

$2.0 billion preferred Private Placement

On September 28, 2026, Summit Therapeutics Inc. (Nasdaq: SMMT) entered into a securities purchase agreement with AstraZeneca Holdings B.V., a subsidiary of AstraZeneca plc (LSE/STO/NYSE: AZN), for the issuance and sale of 108,955.3686 shares of newly designated Class A Convertible Preferred Stock at $18,356.14 per preferred share. Aggregate gross proceeds are $2.0 billion.

Each preferred share converts into 1,000 shares of Summit common stock. The preferred purchase price is based on $18.3561 per common share — about $18.36 in the press release — equal to the volume-weighted average price for the five trading days from the prior week plus 10%. AstraZeneca's release says that after completion it will hold rights equivalent to about 12% of Summit's outstanding common stock, or about 10.6% on a fully diluted basis.

The Form 8-K says closing of the Private Placement is expected within five business days of the purchase agreement, subject to customary closing conditions. Summit's press release says the close is expected by the end of this week; AstraZeneca's release says within one week. None of those sources says the preferred shares have already been issued or paid for.

Clinical collaboration — and a non-binding broader plan

Separately, a Summit subsidiary entered a clinical trial collaboration with AstraZeneca to evaluate sonesitatug vedotin (sone-ve), a Claudin 18.2-targeting antibody-drug conjugate, in combination with ivonescimab, Summit's investigational PD-1/VEGF bispecific antibody, in gastrointestinal cancer settings. The companies say they intend to start those studies imminently.

They also signed a non-binding memorandum of understanding to pursue a wider programme combining ivonescimab with multiple AstraZeneca cancer medicines, including other ADCs. That MOU is intent language, not a second definitive collaboration agreement in the 8-K.

Why the preferred agreement matters

A $2.0 billion strategic preferred check from one of the largest oncology franchises is a direct capital and validation event for ivonescimab — and it is still contingent on closing conditions. Readers should keep the preferred close, the GI combination trials, and the non-binding broader MOU on separate tracks: only the first is a funded equity commitment with a stated close window measured in business days.

What the filings do not settle

The Form 8-K and press releases do not report that the Private Placement has closed, do not show a post-close beneficial-ownership filing for the converted common, and do not convert the non-binding MOU into a definitive multi-ADC collaboration agreement.

Sources & evidence

- Form 8-K AccNo 0001193125-26-405776 — Item 1.01 securities purchase agreement for 108,955.3686 Class A Convertible Preferred shares at $18,356.14 each ($2.0 billion aggregate); conversion 1,000:1; close expected within five business days; Items 3.02/5.03/8.01/9.01. - Exhibit 99.1 press release — $2.0 billion preferred investment at $18.36 common-equivalent (five-day VWAP + 10%); close expected by end of week; clinical collaboration on ivonescimab + sone-ve; non-binding MOU for broader ADC combinations. - AstraZeneca Cision release (29 September 2026) — confirms $2 billion equity investment; ~12% outstanding / ~10.6% fully diluted after completion; close anticipated within one week.