Safety and tolerability of AAV8 delivery of a broadly neutralizing antibody in adults living with HIV: a phase 1, dose-escalation trial

Abstract

Adeno-associated viral vector-mediated transfer of DNA coding for broadly neutralizing anti-HIV antibodies (bnAbs) offers an alternative to attempting to induce protection by vaccination or by repeated infusions of bnAbs. In this study, we administered a recombinant bicistronic adeno-associated virus (AAV8) vector coding for both the light and heavy chains of the potent broadly neutralizing HIV-1 antibody VRC07 (AAV8-VRC07) to eight adults living with HIV. All participants remained on effective anti-retroviral therapy (viral load (VL) <50 copies per milliliter) throughout this phase 1, dose-escalation clinical trial ( NCT03374202 ). AAV8-VRC07 was given at doses of 5 × 10¹⁰, 5 × 10¹¹ and 2.5 × 10¹² vector genomes per kilogram by intramuscular (IM) injection. Primary endpoints of this study were to assess the safety and tolerability of AAV8-VRC07; to determine the pharmacokinetics and immunogenicity of in vivo VRC07 production; and to describe the immune response directed against AAV8-VRC07 vector and its products. Secondary endpoints were to assess the clinical effects of AAV8-VRC07 on CD4 T cell count and VL and to assess the persistence of VRC07 produced in participants. In this cohort, IM injection of AAV8-VRC07 was safe and well tolerated. No clinically significant change in CD4 T cell count or VL occurred during the 1-3 years of follow-up reported here. In participants who received AAV8-VRC07, concentrations of VRC07 were increased 6 weeks (P = 0.008) and 52 weeks (P = 0.016) after IM injection of the product. All eight individuals produced measurable amounts of serum VRC07, with maximal VRC07 concentrations >1 µg ml^-1 in three individuals. In four individuals, VRC07 serum concentrations remained stable near maximal concentration for up to 3 years of follow-up. In exploratory analyses, neutralizing activity of in vivo produced VRC07 was similar to that of in vitro produced VRC07. Three of eight participants showed a non-idiotypic anti-drug antibody (ADA) response directed against the Fab portion of VRC07. This ADA response appeared to decrease the production of serum VRC07 in two of these three participants. These data represent a proof of concept that adeno-associated viral vectors can durably produce biologically active, difficult-to-induce bnAbs in vivo, which could add valuable new tools to the fight against infectious diseases.

Fig. 1 ∣. Schematic representation of the AAV8-VRC07 vector cassette.

The AAV8-VRC07 vector uses a single open reading frame design packaged between two inverted terminal repeats (ITRs) with a CASI promoter, a truncated woodchuck hepatitis post-translational regulatory element (WPRE) and a single SV40 poly-A sequence (SV40 polyA). The CASI promoter is 1.05 kb and consists of a CMV enhancer; a chicken β-actin promoter; a splice donor (SD) inserted between the β-actin promoter and a human ubiquitin C enhancer element; and a splice acceptor (SA). The VRC07 coding cassette contains the VRC07 IgG heavy chain (VRC07 IgG HC) and the VRC07 IgG light chain (VRC07 LC) coding sequences. Between the heavy chain and light chain sequences is an F2A self-processing sequence (2A), which contains a picornavirus-derived ribosomal skip sequence preceded by a furin cleavage site.

Fig. 2 ∣. VRC 603 CONSORT diagram.

Study enrollment, AAV8-VRC07 administration, participant follow-up and data analysis are shown for the three study groups.

Fig. 3 ∣. Concentrations of post-product administration of AAV8-VRC07 plasma DNA.

Longitudinal plasma AAV8-VRC07 DNA from 2 weeks after injection until two sequential longitudinal samples of less than 200 copies per milliliter of AAV8-VRC07 plasma DNA were found. Participants A–C received IM injections of 5 × 10¹⁰ vg kg⁻¹ of AAV8-VRC07; Participants D and E received 5 × 10¹¹ vg kg⁻¹; and Participants F–H received 2.5 × 10¹² vg kg⁻¹.

Fig. 4 ∣. Longitudinal serum VRC07 concentration and tier 1 and tier 2 ADA from immediately before IM injection of AAV8-VRC07 to 80–156 weeks after IM injection of 5 × 10¹⁰, 5 × 10¹¹ and 2.5 × 10¹² vg kg⁻¹.

Participants without tier 1 and tier 2 ADA are shown in the left column; participants with tier 1 and tier 2 ADA are shown in the right column. Serum VRC07 concentrations for different participants are as shown by colored lined as indicated in the figure legend. Tier 1 ADA is as indicated by black lines, with tier 2 ADA as indicated by solid colored bars over the time at which they were identified. No tier 3 ADA was identified for any participants. For VRC07 concentration data, all data points represent the results of a single assay performed in triplicate. Tier 2 and tier 3 ADA responses represent the average of a single assay done in quadruplicate.

Fig. 5 ∣. Longitudinal neutralization data and the effect of VRC07 paratope binding by 5C9 on neutralization by purified IgG from study participants.

a, Neutralization of five different tier 2 pseudoviruses as shown in the figure legend by purified IgG for the first seven trial participant enrolled in VRC 603. Participants A–C received 5 × 10¹⁰ vg kg⁻¹; Participants D and E received 5 × 10¹¹ vg kg⁻¹; and Participants F and G received 2.5 × 10¹² vg kg⁻¹ of AAV8-VRC07 by IM injection. Longitudinal IgG IC₅₀s are reported as μg ml⁻¹ of purified IgG on the left y axis for each pseudoviral strain. VRC07 concentration as determined by 5C9 titration is reported as ng ml⁻¹ of 1 mg ml⁻¹ of purified IgG on the right y axis. Data points represent single determinations. Data points in the shaded area are below the limits of accurate quantitation. b, Neutralization curves adjusted for the concentration of VRC07 in purified IgG serum samples are shown for Participant C at 0, 6, 12, 24 and 52 weeks after IM injection of AAV8-VRC07, as indicated in the figure legend. Neutralization curves for purified in vitro produced VRC07 for each pseudoviral species are overlaid on each plot. Data points for neutralization assays of ex vivo produced VRC07 represent the average of six replicate assays; error bars are ± s.d. Data points for in vitro produced VRC07 represent a single assay, These data are representative of data for Participants A, B and D–G. c, Representative neutralization curve showing the failure of in vitro produced VRC07 to neutralize pseudoviral strain CAP210.E8.SG3 at weeks 6,12, 28 and 52. Each data point represents a single determination. d, From left to right, neutralization of TZBD by purified IgG from Participant C containing the amount of VRC07 indicated on the x axis from week 28 purified IgG; neutralization of TZBD by purified in vitro produced VRC07; and neutralization of TZBD by in vitro produced VRC13, in the presence or absence of 10 μg ml⁻¹ of the VRC07 paratope-binding monoclonal antibody 5C9, as shown in the figure legend. These data are representative of neutralization curves for Participants A, B and D–G. Each data point represents a single determination.