Mereo BioPharma Group plc - Ordinary Shares, par value GBP 0.003 per share (MREO) Institutional Ownership

13F Institutional Holders and Ownership History from Q2 2019 to Q4 2025

Type / Class: Equity / Ordinary Shares, par value GBP 0.003 per share
Symbol: MREO on Nasdaq
Shares outstanding: 792,553,191
Price per share: $0.44
All holders as of 31 Dec 2025: Q4 2025
Total 13F shares: 62,027,627
Total reported value: $25,825,711
% of total 13F portfolios: 0%
Share change: -37,447,485
Value change: -$114,799,457
Number of holders: 68

Reported Shares, Excluding Options vs Price

Reported Value, Excluding Options

Total Investors

Significant Owners of Mereo BioPharma Group plc - Ordinary Shares, par value GBP 0.003 per share (MREO) based on Schedule 13D/G filings

Filer	Ownership	Holdings Value	Nb Shares	Reporting Name	Report Period
EcoR1 Capital, LLC	9.4%	$31,044,150	74,500,000	EcoR1 Capital, LLC	02 Jan 2026
683 Capital Management, LLC	8.2%	$27,120,426	65,083,815	683 Capital Management, LLC	29 Dec 2025
ADAGE CAPITAL PARTNERS GP, L.L.C.	5.6%	$113,730,920	43,575,065	Adage Capital Management, L.P.	31 Dec 2024
MANGROVE PARTNERS IM, LLC	4.9%	$80,242,974	38,952,900	Mangrove Partners IM, LLC	30 Sep 2025
Rock Springs Capital Management LP	4.2%	$87,229,423	33,421,235	Rock Springs Capital Management LP	31 Mar 2025
Adage Capital Management, L.P.	1.1%	$22,194,866	8,503,780	Adage Capital Management, L.P.	31 Mar 2025

As of 31 Dec 2025, 68 institutional investors reported holding 62,027,627 shares of Mereo BioPharma Group plc - Ordinary Shares, par value GBP 0.003 per share (MREO). This represents 7.8% of the company’s total 792,553,191 outstanding shares.

Institutional Holders of Mereo BioPharma Group plc - Ordinary Shares, par value GBP 0.003 per share (MREO) across Reporting Periods

Period	Reported Shares, Excl. Options	Value, Excl. Options	Value Change	Puts Notional Value	Calls Notional Value	Price (Median)	Investors
2025 Q4	62,027,627	$25,825,711	-$114,799,457	$418,445	$1,547,170	$0.42	68
2025 Q3	99,471,712	$204,984,259	-$1,910,639	$368,534	$4,601,010	$2.06	82
2025 Q2	98,647,167	$267,511,231	-$28,666,960	$2,062,852	$6,181,364	$2.71	85
2025 Q1	110,598,225	$250,098,919	-$12,622,883	$1,502,775	$2,253,600	$2.25	87
2024 Q4	115,193,969	$403,099,510	+$29,662,675	$1,593,550	$527,100	$3.50	90
2024 Q3	105,735,860	$434,698,726	+$21,814,008	$1,969,101	$857,757	$4.11	76
2024 Q2	100,520,356	$361,910,507	+$59,834,784	$748,080	$435,240	$3.60	76
2024 Q1	84,006,001	$277,272,467	+$19,427,852	$821,700	$601,260	$3.30	77
2023 Q4	78,538,884	$181,392,642	+$20,402,688	$83,391	$725,109	$2.31	60
2023 Q3	69,934,611	$90,216,596	+$9,888,781	$17,802	$137,772	$1.29	52
2023 Q2	63,630,062	$83,982,713	+$9,810,717	$26,796	$372,240	$1.32	48
2023 Q1	60,813,068	$42,992,107	-$604,492	$0	$24,279	$0.71	56
2022 Q4	61,433,344	$46,074,279	-$7,738,535	$66,300	$69,675	$0.75	57
2022 Q3	67,994,550	$58,546,462	-$7,128,601	$187,000	$107,000	$0.86	56
2022 Q2	73,625,094	$82,466,840	-$16,891,885	$200,000	$303,000	$1.12	58
2022 Q1	88,907,613	$99,569,590	-$3,071,799	$0	$70,000	$1.12	54
2021 Q4	90,856,815	$145,372,152	-$12,163,504	$69,000	$25,000	$1.60	67
2021 Q3	87,544,301	$211,861,957	-$26,671,615	$270,000	$186,000	$2.42	58
2021 Q2	89,643,356	$284,079,000	-$2,186,471	$289,000	$424,000	$3.17	68
2021 Q1	90,226,943	$304,106,740	+$110,829,354	$575,000	$479,000	$3.37	64
2020 Q4	57,138,262	$204,527,659	+$139,354,322			$3.58	44
2020 Q3	14,275,529	$38,070,000	+$18,635,267			$2.62	22
2020 Q2	7,275,071	$22,263,000	+$12,610,604			$3.06	20
2020 Q1	3,279,730	$3,419,000	+$2,078,837			$1.04	8
2019 Q4	1,243,651	$4,079,000	-$2,385,808			$3.28	10
2019 Q3	1,781,796	$5,210,000	-$42,868			$2.98	14
2019 Q2	1,799,585	$4,384,000	+$4,384,000			$2.52	15