RNA

EX-99.1

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EX-99.1

EX-99.1

Exhibit 99.1

Atrium Therapeutics Reports Second Quarter 2026 Financial Results

— IND clearance for ATR 1072 and launch of Corventis Phase 1/2 trial in

PRKAG2 syndrome —

— Achieved second milestone payment under global cardiovascular collaboration

with Bristol Myers Squibb —

SAN DIEGO, August 13, 2026 / PRNewswire/ – Atrium Therapeutics, Inc. (Nasdaq: RNA) (“Atrium,” “Atrium Therapeutics,” or the “Company”), a biopharmaceutical company advancing precision cardiology by developing RNA therapeutics targeted to the heart, today reported financial results for the second quarter ended June 30, 2026, and highlighted recent corporate progress including FDA clearance of its Investigational New Drug (IND) application for ATR 1072 and continued achievements under its collaboration with Bristol Myers Squibb (BMS).

“Our team continues to execute well, achieving FDA clearance of our IND for ATR 1072 and launching Corventis — Atrium’s first Phase 1/2 trial and the first clinical study to evaluate a potential disease-modifying treatment for people living with PRKAG2 syndrome,” said Kathleen Gallagher, President and Chief Executive Officer of Atrium Therapeutics. “Atrium’s precision approach to genetic cardiomyopathies is part of a burgeoning frontier in medicine. Our experienced team is well-positioned to continue advancing and efficiently expanding our pipeline with urgency on behalf of patients and clinicians.”

Recent Highlights

•

Received FDA clearance of IND application and Health Canada No Objection Letter for ATR 1072. FDA cleared Atrium’s IND application for ATR 1072, allowing the Company to proceed with Corventis, a Phase 1/2 open-label, multicenter clinical trial designed to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy of ATR 1072 in participants living with PRKAG2 syndrome. Additionally, the Company has received a No Objection Letter from Health Canada enabling the activation of planned Corventis study sites in Canada. The study will enroll approximately 37 participants across two parts: Part A, multiple ascending dose cohorts to characterize safety and support dose selection, and Part B, a single-arm expansion cohort at the recommended Phase 2 dose to further evaluate efficacy trends in cardiac structure and function. ATR 1072 is Atrium’s first precision cardiology program to enter the clinic.

•

Initiated clinical site activities for Corventis. Atrium continues to expect the first participant to be enrolled by the end of 2026.

•

Earned a second milestone payment from Bristol Myers Squibb. Atrium achieved a second milestone under its global cardiovascular collaboration with BMS in August, triggering a payment of $15 million which will be accounted for in the third quarter financial statements.

Anticipated Upcoming Milestones

•

Enroll first participant in the Corventis Phase 1/2 trial for ATR 1072 by the end of 2026.

•

Report initial trial data from Corventis demonstrating proof of concept in the second half of 2027.

•

File IND application for ATR 1086 in 2027, with IND-enabling studies initiating in 2026.

•

We are also advancing two undisclosed pipeline programs in rare cardiomyopathy targets and expect to select our next development candidate in 2027.

Second Quarter 2026 Financial Results

•

Collaboration Revenue: Collaboration revenue was $3.0 million for the second quarter of 2026, primarily related to R&D services under Atrium’s research collaboration and license agreement with Bristol Myers Squibb.

•

Research and Development (R&D) Expenses: R&D expenses were $15.3 million for the second quarter of 2026, primarily reflecting clinical trial preparations, IND-enabling activities, and continued development of the Company’s overall research capabilities.

•

General and Administrative (G&A) Expenses: G&A expenses were $10.3 million for the second quarter of 2026, driven by employee-related expenses, professional fees, and costs to support the Company’s expanded operations.

•

Cash, Cash Equivalents, and Short-term Investments: As of June 30, 2026, Atrium $263.9 million in cash, cash equivalents and short-term investments. The Company believes its current cash resources, inclusive of the receipt of the second milestone payment from had BMS earned in August, are sufficient to fund planned operations through mid-2028.

About Atrium Therapeutics

Atrium Therapeutics, Inc. (Nasdaq: RNA) is pioneering targeted delivery of ribonucleic acid (RNA) therapeutics to the heart to transform the standard of care for people living with cardiomyopathies. With the U.S. Food and Drug Administration’s (FDA) recent clearance of its Investigational New Drug (IND) application for ATR 1072 for PRKAG2 (Protein Kinase AMP-activated non-catalytic subunit Gamma 2) syndrome, Atrium is advancing its first precision cardiology program into the clinic through the Corventis Phase 1/2 clinical trial. The Company’s proprietary technolog

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rna-202511100001599901FALSE00015999012025-11-102025-11-10

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of report (Date of earliest event reported): November 10, 2025

AVIDITY BIOSCIENCES, INC.

(Exact name of registrant as specified in its charter)

Delaware001-3932146-1336960 (State or other jurisdiction of incorporation or organization) (Commission File Number) (I.R.S. Employer Identification No.)

3020 Callan Road San Diego, California 92121 (Address of principal executive offices) (Zip Code) (858) 401-7900 (Registrant’s telephone number, include area code) N/A (Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

oWritten communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

oSoliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

oPre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

oPre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each classTrading Symbol(s) Name of each exchange on which registered

Common Stock, par value $0.0001 per shareRNAThe Nasdaq Global Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company o If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 2.02. Results of Operations and Financial Condition. On November 10, 2025, Avidity Biosciences, Inc. issued a press release announcing its financial results for the quarter ended September 30, 2025. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference. In accordance with General Instruction B.2 of Form 8-K, the information in Item 2.02 of this Current Report on Form 8-K, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, whether made before or after the date hereof, except as expressly set forth by specific reference in such filing.

Item 9.01. Financial Statements and Exhibits. (d) Exhibits

Exhibit Number Description

99.1Press Release issued on November 10, 2025.

104Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

AVIDITY BIOSCIENCES, INC.

Date: November 10, 2025 By:/s/ Michael F. MacLean Michael F. MacLean Chief Financial Officer