CUSIP No. 589492107

SCHEDULE 13G/A

Page 4 of 8 Pages

Item 1. (a) Name of Issuer

Mereo BioPharma Group Plc (the “Issuer”)

(b) Address of Issuer’s Principal Executive Offices

Fourth Floor, One Cavendish Place

London W1G 0QF

United Kingdom

Item 2. (a) Names of Person Filing

This Statement is filed on behalf of each of the following persons (collectively, the “Reporting Persons”):

i. Rock Springs Capital Management LP (“RSCM”);

ii. Rock Springs Capital LLC (“RSC”)

This Statement relates to Shares (as defined herein) held directly by the Rock Springs Capital Master Fund LP, which is a Cayman Island exempted limited partnership, and Four Pines Master Fund LP (“Four Pines”), which is a Cayman Islands exempted limited partnership, and indirectly held by RSCM, a Delaware limited partnership, and RSC, a Delaware limited liability company. RSCM serves as the investment manager to each of the Rock Springs Capital Master Fund LP (the “Master Fund”) and Four Pines. RSC is the general partner of RSCM.



(b) Address of Principal Business Office, or, if none, Residence

Rock Springs Capital Management LP and Rock Springs Capital LLC

650 South Exeter, Suite 1070

Baltimore, MD 21202

(c) Citizenship

Rock Springs Capital Management LP - Delaware

Rock Springs Capital LLC - Delaware

(d) Title of Class of Securities

Ordinary Shares, nominal value £0.003, per ordinary share (the “Shares”)

(e) CUSIP No.:

There is no CUSIP number assigned to the Ordinary Shares. CUSIP number 589492107 has been assigned to the American Depository Receipts (“ADRs”) of the Issuer, which are quoted on the Nasdaq Global Market under the symbol “MREO.” Each ADR represents 5 Ordinary Shares.

CUSIP No.  589492107

SCHEDULE 13G/A

Page 5 of 8 Pages

Item 3. If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a) ¨ Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b) ¨ Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c) ¨ Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d) ¨ Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e) x An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f) ¨ An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g) x A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G);

(h) ¨ A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i) ¨ A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j) ¨ A non-U.S. institution in accordance with §240.13d-1(b)(1)(ii)(J);

(k) ¨ A group, in accordance with §240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with §240.13d-1(b)(1)(ii)(J), please specify the type of institution:

CUSIP No. 589492107

SCHEDULE 13G/A

Page 6 of 8 Pages

Item 4. Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

As of the date of this filing, the Reporting Persons may be deemed to be the beneficial owners of 6,244,897 ADRs (translates to 31,224,485 shares), which amount includes 5,600,000 ADRs (translates to 28,000,000 shares) directly beneficially owned by the Master Fund, and 644,897 ADRs (translates to 3,224,485 shares) directly beneficially owned by Four Pines. The percent of class is determined by dividing the number of Shares beneficially owned by the Reporting Persons by 544,510,263, as reported on the Issuer’s 6-K Exhibit 99.1 filed on November 2, 2022.

(a) Amount beneficially owned:

Rock Springs Capital Management LP: 6,244,897 ADRs (translates to 31,224,485 shares)

Rock Springs Capital LLC: 6,244,897 ADRs (translates to 31,224,485 shares)

(b) Percent of Class:

Rock Springs Capital Management LP: 5.34%

Rock Springs Capital LLC: 5.34%

(c) Number of shares as the which the person has:

(i) Sole power to vote or to direct the vote:

Rock Springs Capital Management LP: 0

Rock Springs Capital LLC: 0

(ii) Shared power to vote or to direct the vote:

Rock Springs Capital Management LP: 6,244,897 ADRs (translates to 31,224,485 shares)

Rock Springs Capital LLC: 6,244,897 ADRs (translates to 31,224,485 shares)

(iii) Sole power to dispose or to direct the disposition of:

Rock Springs Capital Management LP: 0

Rock Springs Capital LLC: 0

(iv) Shared power to dispose or to direct the disposition of:

Rock Springs Capital Management LP: 6,244,897 ADRs (translates to 31,224,485 shares)

Rock Springs Capital LLC: 6,244,897 ADRs (translates to 31,224,485 shares)

Item 5. Ownership of Five Percent or Less of a Class

Not Applicable.

Item 6. Ownership of More Than Five Percent on Behalf of Another Person

See disclosure in Items 2 and 4 hereof. Certain funds listed in Item 2(a) are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Shares covered by this Statement that may be deemed to be beneficially owned by the Reporting Persons.

Item 7. Identification and Classification of the Subsidiary which Acquired the Security Being Reported on by the Parent Holding Company or Control Person

Please see response to Item 2.

Item 8. Identification and Classification of Members of the Group

Not Applicable.

Item 9. Notice of Dissolution of Group

Not Applicable.

Item 10. Certification

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than the activities solely in connection with a nomination under §240.14a-11.

CUSIP No. 589492107

SCHEDULE 13G/A

Page 7 of 8 Pages

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: February 14, 2023


	Rock Springs Capital Management LP By: Rock Springs Capital LLC, General Partner

	By:	Graham McPhail
		Name: Graham McPhail Title: Member

	Rock Springs Capital LLC

	By:	Graham McPhail
		Name: Graham McPhail Title: Member


1	NAME OF REPORTING PERSONS Rock Springs Capital Management LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) o (b) o
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 31,224,485 ordinary shares (represented by 6,244,897 ADRs)
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 31,224,485 ordinary shares (represented by 6,244,897 ADRs)
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 31,224,485 ordinary shares (represented by 6,244,897 ADRs)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.34%
12	TYPE OF REPORTING PERSON IA


1	NAME OF REPORTING PERSONS Rock Springs Capital LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (a) o (b) o
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION Delaware
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER 0
		6	SHARED VOTING POWER 31,224,485 ordinary shares (represented by 6,244,897 ADRs)
		7	SOLE DISPOSITIVE POWER 0
		8	SHARED DISPOSITIVE POWER 31,224,485 ordinary shares (represented by 6,244,897 ADRs)
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 31,224,485 ordinary shares (represented by 6,244,897 ADRs)
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES			o
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.34%
12	TYPE OF REPORTING PERSON OO; HC

(a)	¨	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b)	¨	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c)	¨	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d)	¨	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e)	x	An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)	¨	An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)	x	A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G);

(h)	¨	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)	¨	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)	¨	A non-U.S. institution in accordance with §240.13d-1(b)(1)(ii)(J);

(k)	¨	A group, in accordance with §240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with §240.13d-1(b)(1)(ii)(J), please specify the type of institution: