Scientific Drivers Technology in Development Issues Viral vectors rAAV 2, 4, 5 Physical stability, small size; Transduction efficiency; Chromosome integration Helper virus contamination, immune response eliminated Long-term transgene expression Linear dose-response Initial Phase 1 study results Issues Safety Efficiency Manufacturing

Porous biomaterial scaffolds - natural polymers, e.g. collagen Scientific Drivers Porous biomaterial scaffolds - natural polymers, e.g. collagen Technology in Development Recombinant collagen Issues Safety Efficiency Manufacturing Formulation

Scientific Drivers 2 6 12 18 Technology in Development Multiple genes Potential synergies between DNA vectors and porous biomaterial scaffolds Technology in Development Multiple genes Printing Scaffold composites MEMS Weeks in-life 2 6 12 18 100.0-mg pMat-1

Key Challenge Safety Interaction between gene-based therapy and tissue at delivery site Vector persistence and bioavailability Interaction between gene-based therapy and immune system Local and systemic PK/PD of vector-encoded protein

Regulated transgene expression Key Challenge Regulated transgene expression Low baseline expression High induction ratio Positive control by small molecule drug

DNA vector and porous biomaterial scaffold Control Parameters DNA vector and porous biomaterial scaffold Variation associated with site and extent of tissue injury Rate constants for cell proliferation-migration within biomaterial scaffold Gene transfer efficiency Rate constants for therapeutic protein production Pharmacokinetics and pharmacodynamics of vector-encoded protein Safety factors that influence gene transfer efficiency Transgene silencing