Primrose Bio® Raises Significant Growth Capital Investment Led by Signet Healthcare Partners

SAN DIEGO, Sept. 22, 2026 /PRNewswire/ -- Primrose Bio, Inc. ("Primrose"), a provider of production solutions for next-generation biologics, today announced the closing of a financing round led by new investor Signet Healthcare Partners ("Signet"), with significant participation from existing investors 1315 Capital, Ligand Pharmaceuticals Incorporated (Nasdaq: LGND), LDV Partners, and Agent Capital. In conjunction with the financing, James Gale, Founding Partner and Managing Director of Signet, has joined Primrose's Board of Directors.

The proceeds will help Primrose continue to expand the reach and capabilities of its differentiated technology portfolio:

• Pfenex Expression Technology^® ("Pfenex"), a scalable microbial expression platform for efficient, high-yield production of complex, engineered proteins used in six approved biologics
• Prima RNApols^®, proprietary RNA polymerases for consistent, scalable, high-quality mRNA manufacturing (available in RUO- and GMP-grade)
• PeliCRM197^®, a validated carrier protein used in multiple approved vaccines (RUO and GMP) 

"This financing marks an important next step for Primrose and reflects confidence in our technologies, team and commercial opportunity," said Andrew Burch, Chief Executive Officer of Primrose Bio. "As the engineering of biologic and nucleic acid medicines advances, developers need more robust production systems that also improve quality, yield, speed, scalability and cost. This capital will help us broaden adoption, enhance capabilities and accelerate customers moving therapeutic and vaccine programs forward toward clinical trials." 

"Signet sees a compelling opportunity across Primrose's portfolio," said James Gale. "Having partnered with The Dow Chemical Company to establish Pfenex Inc. in 2009, we have seen the platform's commercial value firsthand. Primrose is building on that foundation with further advances in Pfenex technology as well as Prima RNApols and PeliCRM197. We are pleased to invest in this next phase of growth and support the team as they scale the business and help more customers improve manufacturing performance across multiple therapeutic modalities."

About Primrose Bio, Inc.

Primrose Bio develops and commercializes manufacturing technologies that close gaps in biologics, mRNA and vaccine production. Primrose's major offerings include Pfenex Expression Technology^®: a proprietary microbial production system used in six approved products with up to 20x higher yields and a strong record across diverse protein modalities; Prima RNApols^®: improved enzymes for mRNA manufacturing; and PeliCRM197^®: a commercially validated CRM197 carrier protein used for conjugate vaccines.  Several of the world's leading pharmaceutical companies use Primrose's technologies in marketed products, including Merck, Jazz Pharmaceuticals, Alvogen, and Serum Institute of India. For more information, please visit: www.primrosebio.com.

About Signet Healthcare Partners

Signet Healthcare Partners is a healthcare growth equity firm that invests in commercial-stage pharmaceutical (pharma services and therapeutics) and medical technology companies. Founded in 1998 and based in New York, Signet has invested in more than 60 companies, supporting entrepreneurs with capital, strategic guidance, and deep industry networks. For more information, please visit: www.signethealthcarepartners.com.

SOURCE Primrose Bio