Mereo BioPharma Announces Pricing of $50 Million Underwritten Registered Direct Offering of American Depository Shares, Priced At-the-Market London

Mereo BioPharma Announces Pricing of $50 Million Underwritten Registered Direct Offering of American Depository Shares, Priced At-the-Market

London, June 14, 2024 - Mereo

BioPharma Group plc (NASDAQ: MREO) ( Mereo or the Company ), a clinical-stage biopharmaceutical company focused on rare diseases, today announced the pricing of an underwritten offering of 12,531,300 of its American Depositary

Shares ( ADSs ). Each ADS is being sold at a price of $3.99 per ADS in an underwritten registered direct offering priced at-the-market under Nasdaq rules. The

gross proceeds from the offering, before deducting underwriting discounts and commissions and offering expenses, are expected to be approximately $50.0 million. Each ADS represents five ordinary shares of Mereo. The net proceeds of this

offering are expected to be used to fund the setrusumab program, including supply and pre-launch activities in Europe, and for working capital and other general corporate purposes. The offering is expected to

close on or about June 17, 2024, subject to the satisfaction of customary closing conditions.

Participants in the offering include new investors

Frazier Life Sciences, Deerfield Management, and Perceptive Advisors, and existing Mereo shareholders, including Rubric Capital Management, Rock Springs Capital, and Janus Henderson Investors along with other leading healthcare-focused institutional

Jefferies, Leerink Partners and Cantor are acting as joint book-running managers for the offering.

A shelf registration statement on Form S-3 (File No. 333-279433) relating

to the offering of the ADSs described above was declared effective by the Securities and Exchange Commission ( SEC ) on May 22, 2024. The offering is being made only by means of a prospectus supplement and the accompanying prospectus

that form a part of the registration statement. A final prospectus supplement relating to and describing the terms of the offering will be filed with the SEC and will be available on the SEC s website at www.sec.gov. When available, copies of

the final prospectus supplement and accompanying prospectus relating to these securities may also be obtained by sending a request to: Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, New York, NY 10022, by

telephone at (877) 821-7388, or by email at prospectus_department@jefferies.com; Leerink Partners LLC, Attention: Syndicate Department, 53 State Street, 40th Floor, Boston, MA 02109, by telephone at (800) 808-7525, ext. 6105 or by email at syndicate@leerink.com; or Cantor Fitzgerald & Co., Attention: Capital Markets, 110 East 59th Street, 6th Floor, New

York, New York 10022, or by email at prospectus@cantor.com.

This press release does not constitute an offer to sell or a solicitation of an offer

to buy any of these securities, nor will there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale is not permitted.

About Mereo BioPharma

Mereo BioPharma is a

biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has two rare disease product candidates, setrusumab for the treatment of osteogenesis imperfecta (OI) and alvelestat primarily for the

treatment of severe alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD). The Company s partner,

Ultragenyx Pharmaceutical, Inc., has completed enrollment in the Phase 3 portion of a pivotal Phase 2/3 pediatric study in young adults (5 to 25 years old) for setrusumab in OI and in the Phase 3 study in pediatric patients (2 to <7 years old) in

the first half of 2024. The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights

and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the EMA and FDA, PRIME designation from the EMA and has pediatric disease designation from the

FDA. Alvelestat has received U.S. Orphan Drug Designation for the treatment of AATD and Fast Track designation from the FDA. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the

primary endpoints for a Phase 3 pivotal study which if successful could enable full approval in both the U.S. and Europe.

Forward-Looking Statements

This press release contains forward-looking statements that involve substantial risks and uncertainties. All statements other than

statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934,

as amended. Forward-looking statements usually relate to future events and anticipated revenues, earnings, cash flows or other aspects of our operations or operating results. Forward-looking statements are often identified by the words

believe, expect, anticipate, plan, intend, foresee, should, would, could, may, estimate, outlook and

similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company s current expectations, beliefs and

assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future

developments affecting the Company will be those that it anticipates.

All of the Company s forward-looking statements involve known and unknown

risks and uncertainties some of which are significant or beyond its control and assumptions that could cause actual results to differ materially from the Company s historical experience and its present expectations or projections. Such risks

and uncertainties include, among others, the uncertainties inherent in the clinical development process; the Company s reliance on third parties to conduct and provide funding for its clinical trials; the Company s dependence on enrollment

of patients in its clinical trials; and the Company s dependence on its key executives. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company s business, including those described

in the Risk Factors section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company s subsequent filings with

the Securities and Exchange Commission. The Company wishes to caution you not to place undue reliance on any forward-

looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking

statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law.