Passage Bio is a clinical-stage gene therapy company focused on neurodegenerative diseases, with no approved products and no revenue. Its entire value rests on PBFT02, a one-time gene therapy that delivers a functional copy of the GRN gene via an AAV1 viral vector administered directly into the brain's fluid system. PBFT02 raises levels of progranulin, a protein critical to lysosomal function, and is designed to treat frontotemporal dementia caused by GRN mutations (FTD-GRN), a rapidly progressive dementia with no approved disease-modifying therapies. PBFT02 is in a Phase 1/2 trial, with nine patients dosed as of mid-2025, and Passage Bio expects to seek regulatory feedback on registrational trial design in the first half of 2026. Beyond FTD-GRN, Passage Bio is pursuing PBFT02 in FTD-C9orf72 and ALS, based on evidence that elevated progranulin reduces TDP-43 pathology common across these diseases. Passage Bio also has a preclinical Huntington's disease program in collaboration with Gemma Biotherapeutics. If approved, PBFT02 would be sold as a one-time treatment to a small, well-defined rare disease population, likely at a high per-patient price. Manufacturing is outsourced to Catalent. Passage Bio owes the University of Pennsylvania mid-single-digit tiered royalties on net sales plus up to $55M in sales milestones per product upon commercialization. Until then, the company depends on cash on hand and capital raises to fund operations.