Development of Allogeneic CAR T Cell Therapy for a Functional Cure of HIV Infection

Abstract: Antiretroviral therapy (ART) dramatically reduces HIV-associated morbidity and mortality (1). However, it is not a practical cure as eradication of HIV through ART alone is estimated to require over 60 years of treatment (1, 2). Numerous studies support that HIV-specific T cell responses are critical for efficient targeting and elimination of HIV infected cells that are the source of chronic infection (3-10). Unfortunately, viral escape and a limited presence of functional virus-specific effector CD8+ T cells undermine the potency of these responses in chronically infected individuals (11-17). As such, there is growing interest in the development of novel immunotherapeutic approaches to target and eliminate HIV-infected cells to achieve viral suppression in the absence of ART, a “functional cure”. Chimeric antigen receptor (CAR) T cell immunotherapies have demonstrated great promise against blood cancers (18-20), and now also demonstrate the potential to mitigate HIV/SIV infection in rhesus macaques (21, 22) and humanized mice (23-28). We recently showed that HIV-specific Dual CD4-based CAR T cells co- expressing independent 4-1BB and CD28 costimulatory domains restrict HIV replication and reduce viral burden in humanized mice (23). However, current limitations of using autologous T cells to derive CAR T cell products (TCPs), including time-consuming and costly manufacturing, insufficient or dysfunctional patient-derived T cells, and the inter-patient heterogeneity of TCPs, are barriers to their widespread application to human diseases. Development of allogeneic TCPs derived from healthy human donors, could, however, provide an ‘off-the-shelf’ treatment option to overcome these hurdles, as well as accelerate the use of CAR T cell therapies (29-38). Unfortunately, post-infusion elimination by the recipient’s immune system remains a major hurdle (39-41). Here we propose to leverage our expertise in CAR T cell biology (21, 23, 25, 26, 42, 43), base editing (44-49), and a humanized mouse model of HIV infection (50-58) to develop an allogeneic CAR T cell therapy against HIV. Building on our preliminary data applying efficient multiplex base editing to CAR T cells, we hypothesize that both base editing approaches and identification of an optimal allogenic donor will enable the development of an allorejection-resistant CD4-based CAR TCP with enhanced efficacy to eliminate HIV-infected cells and suppress HIV in the absence of ART. To test this hypothesis, we propose the following specific aims: Aim 1: Determine whether genetic modifications to allogeneic T cells can augment their in vivo persistence. Aim 2: Identify characteristics of allogeneic HIV-specific CD4CAR T cells that associate with enhanced persistence and antiviral efficacy. Aim 3: Compare the in vivo HIV efficacy of allogeneic versus autologous HIV-specific CD4CAR T cells, incorporating Aim 1 and 2’s signatures of improved allogeneic functionality.