[Form 4] Adaptimmune Therapeutics plc American Insider Trading Activity

Rhea-AI Filing Summary

EcoR1 Capital, LLC, a 10% owner of Adaptimmune Therapeutics plc (ADAP), filed a Form 4 disclosing three consecutive open-market sales of American Depositary Shares (ADSs) between 28-30 Jul 2025.

• 28 Jul 2025: sold 5,655,290 ADSs (33,931,740 ordinary shares) at a $0.1125 weighted-average price.
• 29 Jul 2025: sold 447,910 ADSs (2,687,460 shares) at $0.1012.
• 30 Jul 2025: sold 4,572,223 ADSs (27,433,338 shares) at $0.1021.

The aggregate disposal totals 10,675,423 ADSs, equivalent to 64,052,538 ordinary shares. Post-transaction, EcoR1’s beneficial ownership stands at 16,728,647 ADSs (100,371,882 ordinary shares) held indirectly through its funds.

No derivative transactions were reported. The filing signals a sizable reduction in EcoR1’s stake, though the firm remains an insider owning more than 10% of ADAP’s equity.

Positive

• None.

Negative

• EcoR1 Capital sold 10.7 M ADSs (64 M ordinary shares) within three days, cutting its ADAP stake nearly in half.
• Sales occurred at ~$0.10–$0.11 per ADS, indicating limited price support and potentially weak confidence at current valuation.
• No simultaneous insider purchases or derivative conversions were disclosed to offset the negative sentiment.

Insights

Securities Analyst

TL;DR: Large insider sells (~$1.1 M) at penny-level prices cut EcoR1’s ADAP stake nearly in half—generally a bearish governance signal.

EcoR1 trimmed 10.68 M ADSs over three days, reducing holdings from roughly 32.4 M to 16.7 M ADSs. At weighted prices near $0.11, the sales grossed about $1.1 million. The magnitude and rapid cadence suggest active portfolio repositioning and may pressure already depressed share prices. While EcoR1 still owns 100 M+ ordinary shares, the reduction weakens perceptions of long-term sponsor support and could amplify liquidity concerns. No offsetting purchases or option exercises were disclosed, reinforcing a negative read-through for sentiment.

Portfolio Manager

TL;DR: Position reduction is material but EcoR1 remains a strategic holder; impact skewed negative for short-term flows.

EcoR1’s disposals equate to ~64 M ordinary shares—significant float supply that could weigh on ADAP’s micro-cap liquidity. The remaining 100 M shares still align EcoR1 with long-term upside, yet the timing near 52-week lows raises questions on risk-reward perceptions. Unless offset by catalysts (not addressed here), investors may interpret the move as diminished conviction. From a portfolio construction view, EcoR1 freed cash with minimal market value loss due to the stock’s low absolute price, hinting at reallocation priorities elsewhere.

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

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X

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^*

EcoR1 Capital, LLC

(Last) (First) (Middle)

357 TEHAMA STREET #3

(Street)

SAN FRANCISCO CA 94103

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Adaptimmune Therapeutics PLC [ ADAP ]

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

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
07/28/2025

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

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

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

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
Ordinary Shares(1)	07/28/2025		S		33,931,740(3)	D	$0.1125(4)	130,492,680(5)	I	See Note(2)
Ordinary Shares(1)	07/29/2025		S		2,687,460(6)	D	$0.1012(7)	127,805,220(8)	I	See Note(2)
Ordinary Shares(1)	07/30/2025		S		27,433,338(9)	D	$0.1021(7)	100,371,882(10)	I	See Note(2)

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. These Ordinary Shares are held through American Depositary Shares ("ADS") of the Issuer. Each ADS represents 6 Ordinary Shares.

2. The reporting persons are EcoR1 Capital, LLC ("Ecor1"), Oleg Nodelman and EcoR1 Capital Fund Qualified, L.P. ("Qualified Fund"). EcoR1 is the general partner and investment adviser of private funds, including Qualified Fund (the "Fund"). Mr. Nodelman is the manager and controlling owner of EcoR1. EcoR1 is filing this Form 4 for itself, Mr. Nodelman and Qualified Fund. The filers are filing this Form 4 jointly, but not as a group, and each expressly disclaims membership in a group within the meaning of Rule 13d-5(b) under the Securities Exchange Act of 1934. The Funds hold these securities directly for the benefit of their investors. EcoR1 may be deemed to indirectly beneficially own them as the investment adviser to the Funds. Mr. Nodelman may be deemed to indirectly beneficially own them as the control person of EcoR1. The filers disclaim beneficial ownership of the securities except to the extent of their respective pecuniary interests therein.

3. The reporting persons sold 5,655,290 ADSs representing 33,931,740 Ordinary Shares. Qualified Fund sold 5,281,476 of those ADSs, representing 31,688,856 Ordinary Shares.

4. The price reported in Column 4 is the price per ADS sold by the reporting persons. This price is a weighted average price. These ADSs were sold in multiple transactions at prices ranging from $0.1086 to $0.1184, inclusive. The reporting person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission upon request, full information regarding the number of ADSs sold at each separate price within the ranges set forth in this footnote.

5. After this transaction, the reporting persons beneficially owned 21,748,780 ADSs, including 20,569,634 ADS held by Qualified Fund representing 123,417,804 Ordinary Shares.

6. The reporting persons sold 447,910 ADSs representing 2,687,460 Ordinary Shares. Qualified Fund sold 418,303 of those ADSs, representing 2,509,818 Ordinary Shares.

7. The price reported in Column 4 is the price per ADS sold by the reporting persons.

8. After this transaction, the reporting persons beneficially owned 21,300,870 ADSs, including 20,151,331 ADSs held by Qualified Fund representing 120,907,986 Ordinary Shares.

9. The reporting persons sold 4,572,223 ADSs representing 27,433,338 Ordinary Shares. Qualified Fund sold 4,270,000 of those ADSs, representing 25,620,000 Ordinary Shares.

10. After this transaction, the reporting persons beneficially owned 16,728,647 ADSs, including 15,881,331 ADSs held by Qualified Fund representing 95,287,986 Ordinary Shares.

	/s/ Oleg Nodelman	07/30/2025
	** Signature of Reporting Person	Date
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FAQ

How many Adaptimmune (ADAP) shares did EcoR1 Capital sell in July 2025?

EcoR1 disposed of 10,675,423 ADSs, equal to 64,052,538 ordinary shares, between 28–30 July 2025.

What prices did EcoR1 receive for its ADAP ADS sales?

Weighted-average prices were $0.1125 on 28 Jul, $0.1012 on 29 Jul, and $0.1021 on 30 Jul 2025.

How many ADAP shares does EcoR1 Capital still own after the transactions?

The filing shows remaining holdings of 16,728,647 ADSs, representing 100,371,882 ordinary shares.

Does EcoR1 remain a 10% owner of Adaptimmune after the sales?

Yes. Despite the reduction, EcoR1 is still marked as a 10% owner in the Form 4.

Were any derivative securities involved in EcoR1’s filing?

No. Table II was empty; the filing reports only open-market stock sales.

Why is insider selling significant to ADAP investors?

Large insider sales can signal lower confidence and may add downward pressure due to increased float supply.