Re-administration of high dose AAV gene therapy vectors enabled by ImmTOR nanoparticles combined with B cell-targeted agents

Abstract Tolerogenic ImmTOR nanoparticles encapsulating rapamycin have been demonstrated to mitigate immunogenicity of adeno-associated virus (AAV) gene therapy vectors, enhance levels of transgene expression and enable redosing of AAV at moderate vector doses of 2-5E12 vg/kg. However, recent clinical trials have often pushed AAV vector doses 10-50-fold higher, with serious adverse events observed at the upper range. Here we assessed combination therapy of ImmTOR with B cell-targeting drugs for the ability to increase the efficiency of re-dosing at high vector doses. The combination of ImmTOR with a monoclonal antibody against B cell activation factor (aBAFF) exhibited strong synergy leading to more than a 5-10-fold reduction of splenic mature B cells and plasmablasts while increasing the fraction of pre-/pro-B cells. In addition, this combination dramatically reduced anti-AAV IgM and IgG antibodies, thus enabling four successive AAV administrations at doses up to 5E12 vg/kg and at least two AAV doses at 5E13 vg/kg, with the transgene level in the latter case being equal to that observed in control animals receiving a single vector dose of 1E14 vg/kg. Similar synergistic effects were seen with a combination of ImmTOR and a Bruton’s tyrosine kinase inhibitor, ibrutinib. These results suggest that ImmTOR could be combined with B cell targeting agents to enable repeated vector administrations as a potential strategy to avoid toxicities associated with vector doses above 1E14 vg/kg.