Co-CEO Mahkam Zanganeh (SMMT) reports spouse’s 3.81M-share open-market buy

Rhea-AI Filing Summary

Summit Therapeutics Inc. Co-CEO Mahkam Zanganeh reported a large indirect open-market purchase of 3,810,000 shares of Common Stock at $13.12 per share on behalf of her spouse. The filing also lists existing holdings, including 31,000 direct shares and substantial indirect stakes through family trusts and an immediate family member. A footnote states she disclaims beneficial ownership beyond her pecuniary interest.

Insights

Insider transactions analyst

Large open-market buy reported indirectly through the co-CEO’s spouse.

Mahkam Zanganeh, Co-Chief Executive Officer, director, and more-than-10% owner of Summit Therapeutics Inc., reported an indirect open-market purchase of 3,810,000 Common Stock shares at $13.12 per share by her spouse. Open-market purchases typically reflect a deliberate decision to increase exposure.

The same report lists sizable indirect holdings through the Mahkam Zanganeh Revocable Trust, the Shaun Zanganeh Irrevocable Trust, and an immediate family member, plus 31,000 shares held directly. A footnote clarifies she disclaims beneficial ownership beyond her pecuniary interest in these accounts.

There are no derivative positions shown, and no sales or tax-related dispositions reported in this filing. Future company disclosures may provide more context on how these large family and trust holdings relate to overall ownership and governance at Summit Therapeutics.

Insider Trade Summary

Net Buyer: 3,810,000 shares ($49,987,200)

Net Buy 5 txns

Insider Zanganeh Mahkam

Role Co-Chief Executive Officer

Bought 3,810,000 shs ($49.99M)

Type	Security	Shares	Price	Value
Purchase	Common Stock	3,810,000	$13.12	$49.99M
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 573,883,879 shares (Indirect, By Spouse); Common Stock — 31,000 shares (Direct, null)

Footnotes (1)

1. [object Object]

Key Figures

Open-market purchase: 3,810,000 shares Purchase price: $13.12 per share Direct shares held: 31,000 shares +4 more

7 metrics

Open-market purchase 3,810,000 shares Common Stock bought indirectly via spouse on 2026-06-12

Purchase price $13.12 per share Price for 3,810,000-share open-market or private purchase

Direct shares held 31,000 shares Direct Common Stock ownership after transactions

Revocable trust holding 25,824,474 shares Held by Mahkam Zanganeh Revocable Trust after transactions

Irrevocable trust holding 10,199,776 shares Held by Shaun Zanganeh Irrevocable Trust after transactions

Immediate family holding 76,680 shares Indirect ownership through an immediate family member

Spouse holding after purchase 573,883,879 shares Common Stock held indirectly by spouse following the 3,810,000-share buy

Key Terms

open-market purchase, indirect, pecuniary interest, beneficial ownership, +1 more

5 terms

open-market purchase financial

"transaction_action: open-market purchase"

An open-market purchase is when an investor or a company buys shares on a public stock exchange at the going market price, rather than through a private deal. It matters to investors because these purchases change how many shares are available, can push the stock price up or signal confidence from large buyers, and often affect per-share metrics like earnings—think of it like someone buying lots of apples off a grocery shelf, reducing supply and potentially raising the price.

indirect financial

"ownership_type: indirect and nature_of_ownership: By Spouse"

pecuniary interest financial

"disclaims beneficial ownership of these securities, except to the extent of her pecuniary interest therein"

beneficial ownership financial

"shall not be deemed an admission of beneficial ownership of all of the reported securities"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

Section 16 regulatory

"for purposes of Section 16 or for any other purpose"

Section 16 is a U.S. securities law rule that governs the trading and disclosure obligations of company insiders — typically officers, directors and large shareholders — to promote transparency and deter unfair profit-taking. It requires insiders to publicly report their stock trades and allows companies or the issuer to reclaim quick, short-term profits from certain insider trades, like a scoreboard and a refund policy that help investors see and limit possible insider advantage.

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Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Zanganeh Mahkam

(Last) (First) (Middle)

C/O SUMMIT THERAPEUTICS INC.

601 BRICKELL KEY DRIVE, SUITE 1000

(Street)

MIAMI FLORIDA 33131

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Summit Therapeutics Inc. [ SMMT ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
X	Officer (give title below)		Other (specify below)
	Co-Chief Executive Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/12/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	06/12/2026		P		3,810,000	A	$13.12	573,883,879(1)	I	By Spouse
Common Stock								25,824,474(1)	I	By the Mahkam Zanganeh Revocable Trust, with the Reporting Person as Trustee
Common Stock								76,680(1)	I	Immediate family member
Common Stock								10,199,776(1)	I	By the Shaun Zanganeh Irrevocable Trust, with the Reporting Person as Trustee
Common Stock								31,000	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The Reporting Person disclaims beneficial ownership of these securities, except to the extent of her pecuniary interest therein, if any, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

Remarks:

	/s/ Mahkam Zanganeh	06/12/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transaction did SMMT Co-CEO Mahkam Zanganeh report on this Form 4?

Mahkam Zanganeh reported an indirect open-market purchase of 3,810,000 Summit Therapeutics Common Stock shares by her spouse at $13.12 per share. The filing characterizes the transaction as a purchase in the open market or a private transaction.

At what price were the 3,810,000 SMMT shares purchased in the reported transaction?

The 3,810,000 Common Stock shares associated with Mahkam Zanganeh’s Form 4 were purchased at $13.12 per share. This price is disclosed as the transaction price per share for the open-market or private purchase carried out through her spouse’s indirect ownership.

Are Mahkam Zanganeh’s reported SMMT holdings direct or indirect ownership?

Mahkam Zanganeh holds 31,000 Summit Therapeutics shares directly, while additional large positions are held indirectly. These include shares held by her spouse, two family trusts where she is trustee, and an immediate family member, reflecting substantial indirect ownership across related accounts.

What trusts and family accounts related to Mahkam Zanganeh hold SMMT shares?

The filing lists the Mahkam Zanganeh Revocable Trust, the Shaun Zanganeh Irrevocable Trust, an immediate family member, and her spouse as indirect holders of Summit Therapeutics shares. Zanganeh is trustee for both trusts, giving her a pecuniary interest in those trust-held shares.

Does Mahkam Zanganeh claim full beneficial ownership of all reported SMMT shares?

No. A footnote states she disclaims beneficial ownership of the reported securities except to the extent of her pecuniary interest. This means inclusion of trust, spouse, and family holdings does not represent an admission of full beneficial ownership under Section 16 rules.

Were any derivative securities or option exercises reported in this SMMT Form 4?

No derivative transactions or option exercises are reported. The derivativeSummary section is empty, and the transactionSummary shows zero exerciseCount and exerciseShares, indicating only Common Stock holdings and an open-market or private purchase, with no listed options or other derivatives exercised.