On Jun. 29, 2021, Altimmune provided an update on its AdCOVID investigational vaccine for the prevention of COVID-19. The Company also provided an update on its T-COVID Phase 1/2 clinical trial to evaluate the potential of T-COVID to prevent clinical worsening in patients with early COVID-19.

The Phase 1 AdCOVID clinical trial is evaluating the safety and immunogenicity of the intranasally administered vaccine candidate in approximately 80 healthy adult volunteers between the ages of 18 and 55. Subjects received either 1 or 2 doses of AdCOVID as a nasal spray at 3 dose levels. In addition to the primary study endpoint of safety and tolerability, the immunogenicity evaluation of AdCOVID included serum binding and neutralizing antibody titers and mucosal IgA antibody from nasopharyngeal swabs post-vaccination.

AdCOVID appeared to be well tolerated with an overall adverse event profile similar to intranasal saline placebo. The immunogenicity data demonstrated lower than expected immune responses for each of the immune parameters tested. Although antibodies were detected that bound the SARS-CoV-2 Spike protein and neutralized the virus in a subset of subjects, the magnitude of the response and the percent of subjects responding to AdCOVID were substantially lower than what had been demonstrated for other vaccines already authorized for emergency use. Based on these data, and in view of the highly competitive COVID-19 vaccine landscape, Altimmune is discontinuing further development of AdCOVID beyond the completion of this Phase 1 trial.

The Phase 1/2 trial completed dosing in 2 of the 3 planned dose cohorts. The first 2 cohorts were designed to assess the safety of T-COVID treatment and were comprised of COVID-19 infected patients 49 years or younger with a low risk of progression to serious disease. In these cohorts, T-COVID was well tolerated without any serious adverse events observed. The 3^rd cohort was intended to evaluate the efficacy of treatment and enroll patients over the age of 65 or with increased risk of serious sequelae by virtue of pre-existing comorbidities. However, the effective rollout in the United States of authorized COVID-19 vaccines and decreasing incidence of disease significantly reduced the number of patients meeting these criteria, and Altimmune has been unable to enroll subjects in the final cohort.

As a result of these enrollment challenges, the Company has decided to terminate further enrollment and evaluate options for future T-COVID development following an assessment of the available data and discussions with its partners, the U.S. Army Medical Research & Development Command (USAMRDC) and the Medical Technology Enterprise Consortium (MTEC).