Multipeptide + XS15

The drug "multipeptide + XS15" is a personalized cancer vaccine that combines multiple peptides with the TLR1/2 ligand XS15 as an adjuvant. This combination is being investigated in several clinical trials for different types of cancer, particularly acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and glioblastoma. ## Drug Composition and Mechanism The vaccine consists of: - A cocktail of multiple peptides derived from cancer-associated antigens - XS15 (Pam3Cys-GDPKHPKSF), a water-soluble synthetic Pam3Cys-derivative that functions as a TLR1/2 ligand - Montanide ISA 51 VG, which forms a water-in-oil emulsion with the peptide and XS15 mixture XS15 serves as a potent adjuvant that stimulates the immune system by activating Toll-like receptors 1 and 2 (TLR1/2)[1][2]. This activation helps generate strong and long-lasting T-cell responses against the cancer-associated peptides included in the vaccine[5][6]. The formulation creates a depot at the injection site where the vaccinated peptides persist, facilitating continuous immune stimulation without causing significant systemic side effects[5]. ## Clinical Development The multipeptide + XS15 combination is currently being evaluated in several Phase 1 clinical trials: 1. **AML-VAC-XS15-01**: A first-in-human trial for acute myeloid leukemia patients in complete remission, using a vaccine comprising two mutated HLA class I-restricted peptides and seven HLA class II-restricted peptides[2][7]. 2. **iVAC-XS15-CLL01**: A personalized multi-peptide vaccination for chronic lymphocytic leukemia patients undergoing BTK-inhibitor-based regimens[5][6]. 3. **Glioblastoma trial**: A completed Phase 1 trial testing the vaccine in newly diagnosed HLA-A2-positive MGMT-methylated glioblastoma patients, in addition to standard postoperative radiation therapy and temozolomide chemotherapy[3][4][9]. ## Dosing and Administration In the clinical trials, each peptide is typically administered at a dose of 300 μg, with XS15 included at a dose of 50 μg[5][6]. The peptide cocktail and XS15 are reconstituted in 33% dimethyl sulfoxide (DMSO)/water solution and then emulsified in a 1:1 ratio with Montanide ISA 51 VG before subcutaneous injection[2][5]. The vaccination schedule varies by trial but generally involves 2-3 doses spaced several weeks apart, with the option for booster vaccinations in some protocols[2][6]. ## Safety Profile According to the available data, the multipeptide + XS15 combination has demonstrated a favorable safety profile in previous trials. No significant systemic side effects have been reported in healthy volunteers or cancer patients, particularly no allergic or anaphylactic reactions or immune-related adverse events[5]. This innovative cancer vaccine approach represents a promising strategy for personalized immunotherapy, especially for patients with hematological malignancies and brain tumors.