Biogen Partners with City Therapeutics in $1B RNAi CNS Drug Deal

Highlights

• Biogen invests $16 million upfront and $30 million via convertible note in City Therapeutics, an RNAi-focused biotech.
• Potential milestone payments in the deal could reach up to $1 billion, plus royalties.
• Partnership targets CNS diseases using City’s RNAi platform to create a systemic "trigger molecule."
• Biogen will lead clinical development, regulatory, and commercialization activities.
• The deal follows Biogen’s strategic restructuring and external investment emphasis earlier in 2025.
• City Therapeutics, founded with $135 million Series A funding, is led by RNAi industry veterans John Maraganore and Andy Orth.
• City also collaborates with Bausch + Lomb on retinal disease treatments and is backed by Arch Venture Partners.

Biogen Invests in RNAi Technology to Advance CNS Drug Development

Biogen, a leading biotechnology company based in Cambridge, Massachusetts, has entered into a strategic partnership with RNA interference (RNAi) specialist City Therapeutics, marking a significant step into next-generation therapies targeting central nervous system (CNS) diseases. The collaboration involves an initial cash payment of $16 million and a $30 million convertible note investment in City Therapeutics, granting Biogen a minority equity stake upon conversion, according to a May 27 company release.

Potential for Up to $1 Billion in Milestones

Under the terms of the agreement, Biogen could receive up to approximately $1 billion in milestone payments related to the initial RNAi program, in addition to royalties. The deal also allows Biogen to add a second therapeutic target through an extra payment to City Therapeutics. The partners aim to develop a "trigger molecule" leveraging City’s RNAi engineering platform, which is designed to facilitate systemic administration of RNAi therapies for CNS indications.

Roles and Responsibilities in the Collaboration

Biogen will take the lead on investigational new drug (IND) enabling studies, clinical trials, regulatory submissions, and commercialization efforts. Jane Grogan, Ph.D., Biogen’s Head of Research, emphasized the strategic nature of the collaboration, stating, “This collaboration underscores Biogen’s new strategic research approach of balancing our differentiated internal capabilities with external investments in cutting-edge science. With this effort, we are further expanding the modalities in our R&D toolbox to potentially reach our targets of interest more precisely by adding an RNAi-based approach.”

Context: Biogen’s Strategic Shift and Previous Investments

This partnership aligns with Biogen’s recent organizational restructuring earlier this year, which included workforce reductions and a renewed focus on external collaborations. Soon after the restructure announcement, Biogen invested $165 million upfront to acquire ex-U.S. rights to a Phase 3-ready molecule from Stoke Therapeutics, aimed at becoming the first disease-modifying treatment for Dravet syndrome.

City Therapeutics: A New RNAi Innovator with Experienced Leadership

City Therapeutics, a privately held biotech launched last fall with $135 million in Series A funding, is helmed by co-founder and executive chair John Maraganore, Ph.D., who is renowned for founding RNAi pioneer Alnylam Pharmaceuticals. CEO Andy Orth, also an Alnylam veteran and former chief commercial officer at gene therapy company Krystal Biotech, joined City in January and is driving the company’s mission to develop a diverse pipeline of RNAi therapeutics. The first City program is anticipated to enter clinical trials near the end of 2025.

Additional Partnerships and Backing

Backed by Arch Venture Partners, City Therapeutics has already secured a collaboration with Bausch + Lomb to develop novel treatments for retinal diseases, further underscoring the company’s commitment to expanding the therapeutic applications of RNAi technology.