ParcelBio raised $13 million in seed financing led by Breyer Capital, with participation from General Catalyst, Y Combinator, Metaplanet, SurgePoint Capital, and others. The company will use the funding to develop its APEXm (Amplified and Prolonged EXpression mRNA) platform and advance a pipeline that includes an in vivo CAR T program for autoimmune disease plus additional oncology and encoded protein therapeutics. ParcelBio said APEXm is designed to recruit the cell’s native RNA-stabilizing machinery to achieve higher and more durable protein expression than conventional mRNA design approaches. The company also emphasized a linear RNA architecture intended to reduce manufacturing complexity. David Weinberg, ParcelBio’s CEO and co-founder, said the goal is to overcome today’s limits in how much protein mRNA can produce and for how long, positioning the platform for disease modification. Chris Carlson, the company’s CSO, added that the platform aims to reduce tradeoffs between potency, durability, and manufacturability. For the durable-mRNA field, the round highlights investor appetite for new designs that claim both biological performance and manufacturability, with early-stage data planned for ASGCT’s annual meeting in Boston.