This study tests an investigational cancer vaccine called ITI-5000 in people who have completed standard treatment for early-stage triple-negative breast cancer (TNBC).
ITI-5000 is a self-amplifying RNA (saRNA) vaccine that instructs the immune system to recognize and attack cancer cells expressing two proteins found on TNBC cells-HERV-K and CT83-fused with a molecule called LAMP-1 that helps the immune system respond more strongly. The vaccine is delivered inside lipid nanoparticles (LNPs), similar to other approved mRNA vaccines.
The study has two parts:
* Part A: Participants receive ITI-5000 alone at one of two dose levels (1 µg or 10 µg), given as an injection into the upper arm muscle every 28 days for 3 doses total. The goal is to find the safest dose. * Part B: Participants receive ITI-5000 at the best dose identified in Part A, combined with an approved immunotherapy drug called pembrolizumab (Keytruda®), every 21 days for 3 doses total.
Age: Adults aged 18 years or over.
Consent: Provided a signed and dated informed consent form (ICF).
Diagnosis: Histologically confirmed stage 2-3 triple-negative breast cancer (TNBC), defined as HER2-negative, ER-negative, and PgR-negative by immunohistochemistry. BRCA mutations are allowed.
Prior Treatment: Completed all planned standard therapy (surgery, chemotherapy, radiation, and/or pembrolizumab as applicable) and be within 36 months of definitive surgery.
Part B only: Discontinued prior treatment with an immune checkpoint inhibitor (ICI) due to immune-related adverse events (irAEs).
Recent Surgery/Therapy: Major surgery within 4 weeks before vaccination #1 or received cancer-directed therapy or investigational drug/device within 4 weeks or 5 half-lives before vaccination #1.
Part B only: Received other PD-1/PD-L1 inhibitors (besides pembrolizumab) without proper washout.
Toxicities: Unresolved toxicities from prior immunotherapy or chemotherapy (must be ≤ Grade 1 or baseline, or deemed irreversible and not worsened by immunotherapy).