ParcelBio Raises $13M in Seed Funding Led by Breyer Capital

The company will use the funds to develop its APEXm (Amplified and Prolonged EXpression mRNA) platform and advance its pipeline, including its lead in vivo CAR-T program for autoimmune diseases, as well as additional programs in cancer treatment and protein-based therapies.

ParcelBio is developing a new category of mRNA medicines using its APEXm™ platform, which enhances RNA stability by engaging the cell’s natural machinery to produce higher, longer-lasting protein expression, enabling stronger biological effects and achieving therapeutic levels previously difficult to achieve with mRNA therapies.

Current mRNA technologies struggle to deliver both high protein production and long lasting effects, often forcing tradeoffs between strength, duration and ease of manufacturing. Because of these limitations, mRNA has mostly been used for vaccines and short-term treatments.

ParcelBio uses a simple linear mRNA design, unlike some newer circular RNA approaches that can be more complex or reduce peak output, and it delivers both strong and long-lasting protein expression. The platform is flexible and can be used across different proteins and cell types, supporting a range of treatments, including immune system reprogramming and protein replacement therapies.

The company’s lead program focuses on in vivo CAR-T therapies to target harmful B cells in autoimmune diseases, aiming for long lasting remission without ongoing treatment. By enabling sustained CAR expression without viral delivery or complex cell processing, ParcelBio is working toward scalable, off the shelf therapies with curative potential while also developing additional programs in cancer, and protein based treatments.

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“ParcelBio's durable, tunable expression is designed to collapse the tradeoffs that have constrained mRNA in chronic, deep-tissue disease, bringing durable, controllable immune reset within reach in refractory autoimmunity, and beyond,” said Dr. Morgan Cheatham, Partner and Head of Healthcare and Life Sciences at Breyer Capital. “Breyer Capitals life sciences thesis is organized around the technologies that redefine what medicine can reach: programmable biology, controllable expression and durable therapeutic impact. ParcelBio is built to advance all three.”

“Most RNA platforms force a tradeoff between potency, durability, and manufacturability,” said Chris Carlson, Ph.D., Chief Scientific Officer and Co-Founder of ParcelBio. “Our approach eliminates that tradeoff, enabling both higher peak expression and longer duration within a manufacturable system, and opening the door to entirely new classes of medicines.”

“mRNA has transformed medicine, but todays technologies are fundamentally limited in how much protein they can produce, and for how long,” said David Weinberg, Ph.D., Chief Executive Officer and Co-Founder of ParcelBio. “We engineered RNA to work with the cell’s machinery rather than against it, enabling meaningful improvements in both expression and durability that we believe are essential for true disease modification.”

About ParcelBio

Founded in 2024 by David Weinberg, PhD, and Chris Carlson, PhD, ParcelBio is developing a new class of mRNA medicines designed to deliver stronger and longer-lasting effects. APEXm™ platform uses specialized RNA designs to boost protein production and extend activity, helping enable therapies that could achieve meaningful, potentially curative outcomes. The company is currently working on programs in autoimmune diseases, cancer, and protein-based therapies.

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