ImmunityBio Announces 12-Month Overall Survival Probability of 83% in NCI-Led Phase 1 Study of Multi-Targeted hAd5 Immunotherapy Vaccine in Patients with Advanced Metastatic Prostate Cancer

ImmunityBio, Inc. (NASDAQ: IBRX), a clinical-stage immunotherapy company, today announced the publication of Phase I data in The Journal of ImmunoTherapy of Cancer (JITC). The publication, titled “Phase I study of a multitargeted recombinant Ad5 PSA/MUC-1/ brachyury-based immunotherapy vaccine in patients with metastatic castration-resistant prostate cancer (mCRPC)” highlighted the safety, T-cell immunogenicity, and clinical activity of ImmunityBio’s second-generation human adenovirus (hAd5) in patients with incurable mCRPC. ImmunityBio’s hAd5 is designed to deliver tumor-associated antigens, or TAAs, and neoepitopes (expressed only by cancer cells) and has the capability to induce T-cell memory due to the activation of both CD4+ and CD8+ T cells along with antibody (or humoral) responses.

“The finding of T-cell-mediated immunity induced in 100% of 17 prostate cancer patients whose white blood cells were evaluated in the study validates the ability of our hAd5 vaccine platform to generate a potent response to antigens delivered,” said Patrick Soon-Shiong, M.D., Founder and Executive Chairman of ImmunityBio. “Furthermore, the demonstration that the vaccine can be administered repeatedly, without adverse effects at the dose of 5x 10¹¹ viral particles, supports the application of this hAd5 platform in both cancer and infectious diseases such as COVID-19. These early results, which include signals of clinical activity and durable stable disease, are encouraging for patients with highly resistant advanced metastatic prostate cancer and warrants further study.”

Study Highlights:

• Eligible patients had to have incurable metastatic castration-resistant metastatic prostate cancer with radiologic evidence of progression or PSA progression
• The vaccine was safe and well tolerated with no grade >3 treatment-related adverse events or dose-limiting toxicities (DLTs) observed
• The recommended Phase II dose was 5×10¹¹ viral particles (VPs) administered three times repeatedly every 3 weeks
• One patient achieved a partial response (PR), 5 patients had confirmed stable disease (SD) for greater than 6 months, with confirmed PSA decline
• Median progression-free survival (PFS) was 22 weeks (95% confidence interval: 19.1 to 34)
• Median overall survival (OS) was not reached, and the 12-month OS probability for all patients was 83.3% (95% confidence interval: 56.8% to 94.3%)
• 100% (17 out of 17) of patients mounted T-cell responses to at least one tumor-associated antigen and 16 of 17 (94%) patients developed T-cell responses to >1 antigen encoded by the vaccine

In the Phase 1 study undertaken in collaboration with Investigators at the Genitourinary Malignancy Branch of the National Cancer Institute, 18 patients with mCRPC who had advanced, incurable disease were given concurrently three hAd5 vaccines targeting PSA, brachyury, and MUC-1 at 5×10¹¹ (VPs) each, subcutaneously every 3 weeks for a maximum of three doses (dose de-escalation cohort), followed by a booster vaccine every 8 weeks for 1 year (dose-expansion cohort only). Additional trial details can be found at clinicaltrials.gov-NCT03481816.