Molecular Partners Presents New Preclinical Data Highlighting Radio-DARPins’ Amenability to Multiple Isotopes

Highly comparable biodistribution profiles of Radio-DARPin candidates labeled with imaging isotopes 177 Lu or 203 Pb allows for rapid expansion of pipeline with multiple therapeutic isotopes

ZURICH-SCHLIEREN, Switzerland and CONCORD, Mass., March 19, 2026 (GLOBE NEWSWIRE) -- Molecular Partners AG (SIX: MOLN; NASDAQ: MOLN), a clinical-stage biotech company developing a novel class of custom-built protein drugs known as DARPin therapeutics (“Molecular Partners” or the “Company”), today announced it will hold an oral presentation outlining new preclinical data on Radio-DARPins at the 3rd Global Radiopharmaceuticals Development Summit, taking place in Shanghai, China on March 19–20, 2026.

The presentation will outline the Radio-DARPins’ suitability to different isotopes with data on two Radio-DARPin candidates, each specific for a different tumor target. The results of studies in tumor-bearing mice show highly comparable biodistribution profiles for both Radio-DARPin candidates labeled with Lutetium-177 ( 177 Lu) or with Lead-203 ( 203 Pb), with similar uptake and washout rates. Imaging with 177 Lu can be indicative of behavior with the therapeutic isotope Actinium-225 ( 225 Ac), and similarly with 203 Pb for 212 Pb.

“Our recent data confirms that our Radio-DARPin-vector design allows interchangeability of alpha-isotopes, including 212 Pb and 225 Ac,” said Patrick Amstutz, Ph.D., CEO of Molecular Partners . “This feature offers us the opportunity and flexibility to evaluate Radio-DARPin candidates in an isotope-agnostic manner and to choose the most suitable therapeutic isotope, as late as with initial clinical data, without having to restart the entire drug discovery and development process – a significant advantage to tailor our candidates to patient needs.”

Details of the presentation

DARPins for targeted alpha therapy: from promising MP0712 first in-human data to opportunities for next Radio-DARPin candidates Presenter: Daniel Steiner, Ph.D., SVP of Technology and Research Time: 9:25 am CST, Friday, March 20 Location: Meeting Room B – IND Filing and Clinical Development Progress

The full presentation can be found here .

MP0712, Molecular Partners’ DLL3-targeted 212 Pb-based Radio-DARPin candidate co-developed with strategic partner Orano Med, is in an ongoing Phase 1/2a trial in the US (NCT07278479). Imaging data of MP0712 carrying the diagnostic isotope 203 Pb under compassionate care are supportive of clinical development plans of MP0712 carrying the therapeutic isotope 212 Pb for patients with small cell lung cancer (SCLC) and other DLL3-expressing neuroendocrine cancers.

In February 2026, Molecular Partners entered into an agreement with Eckert & Ziegler, leading specialist in isotope-related components for nuclear medicine and radiation therapy, to enable the development and manufacturing of Radio-DARPin therapeutics. Eckert & Ziegler will support Molecular Partners with a comprehensive range of services covering development activities for Radio-DARPins with 225 Ac as therapeutic payload and 177 Lu as imaging payload.

About Radio-DARPins Molecular Partners’ Radio-DARPins are designed as ideal vectors for precise delivery of potent alpha-emitting isotopes to tumor lesions and have the potential to unlock a broad range of tumor targets for targeted radiopharmaceuticals. Building on the DARPins’ unique properties, Molecular Partners has developed a proprietary Radio-DARPin platform to address historic limitations of radioligand therapy, such as kidney accumulation and toxicity, and suboptimal tumor uptake. Molecular Partners’ Radio-DARPins addresses these limitations through half-life extension technologies and surface engineering approaches, while preserving the advantages of the small protein format.

About DARPin Therapeutics DARPin (Designed Ankyrin Repeat Protein) therapeutics are a novel class of protein drugs based on natural binding proteins, which have been clinically validated across several therapeutic areas and developed through to the registrational stage. The key properties of DARPins – intrinsic high affinity and specificity, small size, flexible architecture, and high stability – offer unmatched advantages to drug design, such as multispecificity, broad target range, and tunable half-life. The Company’s Radio-DARPins enable highly effective and specific delivery of potent radioactive payloads to tumor lesions while sparing healthy tissues. Molecular Partners’ Switch-DARPins allow conditional, tumor-localized immune activation, which enables increased safety and potency for next-generation immune cell engagers. Powered by twenty years of DARPin leadership in the clinic, Molecular Partners has built an innovative, rapid and cost-effective DARPin drug design engine, including proprietary DARPin libraries and platforms, for candidates produced with optimized properties and tailored to therapeutic needs.

About Molecular Partners AG Molecular Partners AG (SIX: MOLN, NASDAQ: MOLN) is a clinical-stage biotech company pioneering a novel class of protein drugs known as DARPin therapeutics, for medical challenges other treatment modalities cannot readily address. Molecular Partners leverages the key properties of DARPins to design and develop differentiated therapeutics for cancer patients, including targeted radiopharmaceuticals and next-generation immune cell engagers. The Company has proprietary programs in various stages of pre-clinical and clinical development, as well as programs developed through partnerships with leading pharmaceutical companies and academic centers. Molecular Partners, founded in 2004, has offices in both Zurich, Switzerland and Concord, MA, USA. For more information, visit www.molecularpartners.com and find us on LinkedIn and Twitter / X @MolecularPrtnrs

For further details, please contact: Seth Lewis, EVP Corporate Finance Concord, Massachusetts, U.S. [email protected] Tel: +1 781 420 2361

Laura Jeanbart, Ph.D., Head of Portfolio Management & Communications Zurich-Schlieren, Switzerland [email protected] Tel: +41 44 575 19 35

Cautionary Note Regarding Forward-Looking Statements

This press release contains forward-looking statements. Any statements contained in this press release that do not describe historical facts may constitute forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995, as amended, including without limitation: implied and express statements regarding the clinical development of Molecular Partners’ current or future product candidates; expectations regarding timing for reporting data from ongoing clinical trials or the initiation of future clinical trials; the potential therapeutic and clinical benefits of Molecular Partners’ product candidates and its RDT and Switch-DARPin platforms; the selection and development of future programs; Molecular Partners’ collaboration with Orano Med including the benefits and results that may be achieved through the collaboration; the expected benefits of the strategic review; and Molecular Partners’ expected business and financial outlook, including anticipated expenses and cash utilization for 2026 and its expectation of its current cash runway. These statements may be identified by words such as “aim”, “anticipate”, “expect”, “guidance”, “intend”, “outlook”, “plan”, “potential”, “will” and similar expressions, and are based on Molecular Partners’ current beliefs and expectations. These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements. Some of the key factors that could cause actual results to differ from Molecular Partners’ expectations include, but are not limited to, those set forth in under the heading “Risk Factors” in Molecular Partners’ Annual Report on Form 20-F for the year ended December 31, 2025 and other filings Molecular Partners makes with the SEC from time to time. These documents are available on the Investors page of Molecular Partners’ website at www.molecularpartners.com . In addition, this press release contains information relating to interim data as of the relevant data cutoff date, results of which may differ from topline results that may be obtained in the future.

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