ASP-0113

Cytomegalovirus (CMV) infection causes significant morbidity and mortality in immunocompromised transplant patients. ASP0113, a first‐in‐class DNA vaccine containing plasmids encoding CMV phosphoprotein 65 and glycoprotein B (gB), was evaluated in a phase 1b, subject‐blinded study in CMV‐seropositive (n = 13) and CMV‐seronegative (n = 12) healthy and CMV‐seronegative dialysis subjects (n = 12) randomized to ASP0113 or placebo. End points included pharmacokinetics, anti‐gB antibody levels, phosphoprotein 65–specific T‐cell responses measured by ex vivo enzyme‐linked immune absorbent spot (ELISpot) assay and 10‐day cultured ELISpot and Stat T‐cell activation assays, and safety. ASP0113 concentrations peaked at 2‐10 and 24‐48 hours; the pharmacokinetics were similar across groups. No group demonstrated significant anti‐gB antibody responses. T‐cell responder rates in the cultured ELISpot assay were 8/12 (66.7%, 95%CI 35% to 90%) and 4/12 (33.3%, 95%CI 10% to 65%) in CMV‐seronegative healthy subjects and dialysis patients, respectively, whereas ex vivo ELISpot assay response rates were 4/11 (36.4%, 95%CI 11% to 69%) and 0/12, respectively. Responses peaked at week 27, with lower magnitude observed in CMV‐seronegative dialysis patients versus CMV‐seronegative healthy subjects. No serious adverse events occurred; the most common adverse event in ASP0113‐vaccinated patients was injection‐site pain (64.9%). Some CMV‐seronegative healthy subjects and dialysis patients had T‐cell responses; no humoral responses were detected.

Cytomegalovirus (CMV) is a latent infection in most infected individuals, but can be pathogenic in immunocompromised kidney transplant recipients. ASP0113 is a DNA-based vaccine for the prevention of CMV-related mortality and end-organ disease in transplant recipients. The efficacy, safety, and immunogenicity of ASP0113 was assessed in a phase 2, double-blind, placebo-controlled study in CMV-seronegative kidney transplant recipients receiving a kidney from a CMV-seropositive donor. Transplant recipients were randomized (1:1) to receive 5 doses of ASP0113 (5 mg; n = 75) or placebo (n = 74) on Days 30/60/90/120/180 posttransplant, and they received prophylactic valganciclovir/ganciclovir 10-100 days posttransplant. The primary endpoint was the proportion of transplant recipients with CMV viremia ≥1000 IU/mL from Day 100 through to 1 year after the first study vaccine injection. There was no statistically significant difference in the primary endpoint between the ASP0113 and placebo groups (odds ratio 0.79, 95% confidence interval 0.43-1.47; P = .307). There were similar numbers of transplant recipients with treatment-emergent adverse events between groups; however, more transplant recipients reported injection site pain in the ASP0113 group compared with placebo. ASP0113 did not demonstrate efficacy in the prevention of CMV viremia in this CMV-seronegative kidney transplant population, but demonstrated a safety profile similar to placebo. ClinicalTrials.gov registration number: NCT01974206.