AKS-452 is a biologically-engineered vaccine comprising an Fc fusion protein of the SARS-CoV-2 viral spike protein receptor binding domain antigen (Ag) and human IgG1 Fc (SP/RBD-Fc) in clinical development for the induction and augmentation of neutralizing IgG titers against SARS-CoV-2 viral infection to address the COVID-19 pandemic. The Fc moiety is designed to enhance immunogenicity by increasing uptake via Fc-receptors (FcγR) on Ag-presenting cells (APCs) and prolonging exposure due to neonatal Fc receptor (FcRn) recycling. AKS-452 induced approximately 20-fold greater neutralizing IgG titers in mice relative to those induced by SP/RBD without the Fc moiety and induced comparable long-term neutralizing titers with a single dose vs. two doses. To further enhance immunogenicity, AKS-452 was evaluated in formulations containing a panel of adjuvants in which the water-in-oil adjuvant, Montanide™ ISA 720, enhanced neutralizing IgG titers by approximately 7-fold after one and two doses in mice, including the neutralization of live SARS-CoV-2 virus infection of VERO-E6 cells. Furthermore, ISA 720-adjuvanted AKS-452 was immunogenic in rabbits and non-human primates (NHPs) and protected from infection and clinical symptoms with live SARS-CoV-2 virus in NHPs (USA-WA1/2020 viral strain) and the K18 human ACE2-trangenic (K18-huACE2-Tg) mouse (South African B.1.351 viral variant). These preclinical studies support the initiation of Phase I clinical studies with adjuvanted AKS-452 with the expectation that this room-temperature stable, Fc-fusion subunit vaccine can be rapidly and inexpensively manufactured to provide billions of doses per year especially in regions where the cold-chain is difficult to maintain.

In order to address the increasing demand for biologics, cell culture intensification using perfusion offers significantly higher productivities while also reducing manufacturing costs, especially when part of an integrated, continuous bioprocess. An initial study of a long‐duration perfusion process using a cell‐bleed to maintain a target cell density observed a 2.1‐fold higher cell‐specific productivity and a gradual decline in the culture growth rate when perfused at an overall lower rate. Subsequent studies sought an alternative process that largely reduced the overall volume of media needed by first perfusing at a high cell‐specific perfusion rate (CSPR) to support a high cell density followed by continued perfusion at a low CSPR to promote a more productive stationary phase. This high intensity, low‐volume perfusion (HILVOP) process achieved cumulative volumetric productivities of 1.5–1.6 g/L/day with two CHO cell lines. When compared to each cell line's respective commercial‐ready, fed‐batch process, a 3.1–3.8‐fold productivity increase was demonstrated while yielding similar product quality. Furthermore, the higher productivity achieved with HILVOP used 6.6–12.3‐fold less media than a similarly productive long‐duration process. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1472–1481, 2018

To address the coronavirus disease 2019 (COVID-19) pandemic caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a recombinant subunit vaccine, AKS-452, is being developed comprising an Fc fusion protein of the SARS-CoV-2 viral spike protein receptor binding domain (SP/RBD) antigen and human IgG1 Fc emulsified in the water-in-oil adjuvant, Montanide™ ISA 720. A single-center, open-label, phase I dose-finding and safety study was conducted with 60 healthy adults (18–65 years) receiving one or two doses 28 days apart of 22.5 µg, 45 µg, or 90 µg of AKS-452 ( i.e. , six cohorts, N = 10 subjects per cohort). Primary endpoints were safety and reactogenicity and secondary endpoints were immunogenicity assessments. No AEs ≥ 3, no SAEs attributable to AKS-452, and no SARS-CoV-2 viral infections occurred during the study. Seroconversion rates of anti-SARS-CoV-2 SP/RBD IgG titers in the 22.5, 45, and 90 µg cohorts at day 28 were 70%, 90%, and 100%, respectively, which all increased to 100% at day 56 (except 89% for the single-dose 22.5 µg cohort). All IgG titers were Th1-isotype skewed and efficiently bound mutant SP/RBD from several SARS-CoV-2 variants with strong neutralization potencies of live virus infection of cells (including alpha and delta variants). The favorable safety and immunogenicity profiles of this phase I study ( ClinicalTrials.gov: NCT04681092 ) support phase II initiation of this room-temperature stable vaccine that can be rapidly and inexpensively manufactured to serve vaccination at a global scale without the need of a complex distribution or cold chain.

A novel, alternative intensified cell culture process comprised of a linked bioreactor system is presented. An N-1 perfusion bioreactor maintained cells in a highly proliferative state and provided a continuous inoculum source to a second bioreactor operating as a continuous-flow stirred-tank reactor (CSTR). An initial study evaluated multiple system steady-states by varying N-1 steady-state viable cell densities, N-1 to CSTR working volume ratios, and CSTR dilution rates. After identifying near optimum system steady-state parameters yielding a relatively high volumetric productivity while efficiently consuming media, a subsequent lab-scale experiment demonstrated the startup and long-term operation of the envisioned manufacturing process for 83 days. Additionally, to compensate for the cell-specific productivity loss over time due to cell line instability, the N-1 culture was also replaced with younger generation cells, without disturbing the steady-state of the system. Using the model cell line, the system demonstrated a two-fold volumetric productivity increase over the commercial-ready, optimized fed-batch process.

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