Vivovec™ Surface-Engineered Lentiviral Particles Mediate In Vivo CAR T Generation with Potent and Highly Durable Activity in Non-Human Primates
Authors: Parker Maura H. , Mittelsteadt Kristen L. , Ulrich-Lewis Justin T. , Tang Weiliang , McDonnell Mollie M. , Manivanh Richard , Brandes Alissa H. , Ericson Nolan , Koo Angela Soo Min , Hamilton Greyson , Youn Yong Ha , Wu Chang-Chih , Shin Seungjin , Gottschalk Rebecca J , Lynch Kelsey L , Cavanaugh Eric , Kiem Hans-Peter , Scharenberg Andrew M. , Larson Ryan P. , Beitz Laurie O. , Ryu Byoung Y. 
Published: December 2024

Introduction:
Autologous CAR T cell therapy has transformed the treatment of hematologic malignancies, driving durable responses in patients refractory to conventional therapies. CAR T therapy has great potential beyond blood-borne cancers, such as resetting the immune system in autoimmunity; however, multiple challenges including complex manufacturing, high cost, and toxic pre-conditioning regimens limits access to these therapies. The VivoVec™ platform is designed to overcome these challenges and provide an off-the-shelf solution for generation of CAR T cells in vivo. We previously presented data demonstrating potent and specific generation of functional CAR T cells in vivo following intralymphatic delivery in immune competent NHPs (Macaca nemestrina). Here we demonstrate the performance of VivoVec particles following intralymphatic delivery in Macaca fascicularis and intravenous (IV) delivery in both NHP species. Following a single IV dose of VivoVec particles, CAR T cells are efficiently generated in vivo, expand in response to cognate antigen and eradicate target antigen expressing cells in the absence of lymphodepleting chemotherapy.
Methods:
VivoVec surface engineered lentiviral particles with NHP-specific T cell targeting multi-domain fusion (MDF) ligand and carrying a human/NHP cross-reactive αCD20 CAR payload were generated for Macaca nemestrina (HIV particles) and Macaca fascicularis (SHIV particles). VivoVec was administered via IV infusion or intralymphatic delivery to 5 animals at various doses. αCD20 CAR T expansion and B-cell depletion were evaluated by flow cytometry approximately weekly for up to ~4 months. Body weight, body temperature, neurological exams, serum chemistry panels, and complete blood counts were assessed weekly for the duration of the study.
Results:
VivoVec was well-tolerated in all animals following delivery via both routes of administration with no evidence of toxicity associated within, or shortly after the period of administration. Mild CRS was observed in association with CAR T cell expansions. αCD20 CAR T cells were detected in peripheral blood by flow cytometry following intralymphatic administration of 2.4e9 transducing units (TU) in two Macaca fascicularis animals (representing 5.7% and 34.2% of total T cells), consistent with observations in Macaca nemestrina. B-cell aplasia, starting on day 7, persisted for the duration of the study (28 days). At the same dose, IV VivoVec particle delivery in Macaca fascicularis resulted in detection of αCD20 CAR T cells in the peripheral blood with peak expansion at day 7 representing up to 41.6% of total T cells. IV delivery in a Macaca nemestrina animal resulted in a peak expansion of αCD20 CAR T cells by day 8, representing 42.3% of total T cells. In this animal, persistent B-cell aplasia was observed starting on day 6 and the animal continues to be monitored.
Conclusions:
VivoVec™ with MDF surface engineering enables potent and specific generation of functional CAR T cells in vivo following delivery by intralymphatic and IV routes of administration in immune competent NHP models. Peak CAR T expansion observed in NHP following VivoVec administration mirrors peak expansion of ex vivo manufactured CAR T cells in human patients. Given the association between ex vivo CAR T expansion and efficacy, the results in NHP support potential VivoVec efficacy in human patients. Importantly, the generation and expansion of CAR T cells occurs in the absence of lymphodepleting chemotherapy or supportive exogenous cytokines; thus, MDF engineering could impart properties consistent with a natural T cell effector response followed by formation of functional memory T cells. VivoVec represents a transformative therapeutic platform in oncology and autoimmunity that has the potential to overcome many of the challenges associated with the current ex vivo CAR T cell approaches. Additional data from ongoing NHP studies will be provided at the time of presentation.