Upstream process optimization and its critical role in chimpanzee adenoviral vector clinical drug development: lessons learned from VRON-0200 manufacturing.

Chimpanzee adenoviral (AdC) vectors represent a powerful platform for immunotherapies due to their strong immunogenicity, excellent safety profile, low human seroprevalence, and minimal cross-neutralization to prevalent human serotypes. Despite these advantages, AdC manufacturing presents unique challenges, including elevated infectivity ratios, transgene-dependent replication kinetics, and higher impurity burdens compared to well-characterized human adenovirus systems. During VRON-0200 development, a first-in-class heterologous AdC-based immunotherapy targeting functional cure in chronic hepatitis B, we found that upstream process optimization, rather than downstream purification, is the main driver of crude harvest quality and final drug product attributes. Iterative refinement of permissive cell growth cycles, time of harvest, and multiplicity of infection, guided by a robust, tiered analytical strategy, delivered high-purity harvests with superior infectivity ratios, reduced host cell residuals, minimized product-related impurities, and diminished downstream processing demands. These manufacturing refinements supported GMP production and Phase 1b clinical outcomes demonstrating safety, tolerability, and significant anti-HBV activity in chronically infected patients. We contend that the bioprocessing community's longstanding emphasis on downstream polishing overlooks the foundational role of upstream control in addressing AdC-specific hurdles. Reprioritizing upstream-first strategies holds transformative potential to improve vector quality, enhance safety profiles, accelerate development timelines, and increase cost-effectiveness for AdC and related vector platforms.