Personalised multipeptide-based T-cell activator for chronic lymphocytic leukaemia: an open-label, single-centre,...

Therapeutic T-cell activation to induce tumour-specific immune responses promises sustainable cancer control. However, this treatment is not yet widely used because of the challenges of personalised drug design and a shortage of mutation-derived neoepitopes. This study aimed to evaluate the immunogenicity, safety, and toxicity of iTAC-XS15-CLL01, a personalised warehouse-based multipeptide T-cell activator combined with the Toll-like receptor 1/2 ligand XS15, in patients with chronic lymphocytic leukaemia who were undergoing Bruton's tyrosine kinase inhibitor (BTKi)-based regimes.

This open-label, single-centre, phase 1 study, conducted in Germany, enrolled patients aged 18 years or older who had chronic lymphocytic leukaemia with an Eastern Cooperative Oncology Group score of 2 or lower and were due to receive a BTKi-based regimen either as monotherapy or in combination (eg, with anti-CD20). The patients' HLA allotype had to match at least one of the corresponding HLA alleles of peptides included in the peptide warehouse. To begin treatment with iTAC-XS15-CLL01, patients had to have reached at least partial remission with remaining minimal residual disease after 6-8 months of BTKi therapy. iTAC-XS15-CLL01 comprised eight chronic lymphocytic leukaemia-specific peptides, selected for the individual patient from a peptide warehouse on the basis of HLA allotyping and immunopeptidomics. Participants received three monthly doses of iTAC-XS15-CLL01 (consisting of 300 μg of each peptide plus 50 μg XS15, emulsified in Montanide ISA 51 VG), injected subcutaneously. The primary endpoints were induction of a T-cell response after application of iTAC-XS15-CLL01 compared with baseline, as assessed with IFNγ ELISpot assays, and the frequency and severity of adverse events from the first application of iTAC-XS15-CLL01 to end of treatment. All analyses were done per protocol. This study was registered with ClinicalTrials.gov (NCT04688385) and is now closed.

Between Jan 21, 2021, and July 7, 2023, 30 patients with chronic lymphocytic leukaemia were screened, and 20 were recruited to enter the iTAC-XS15-CLL01 treatment phase and followed up for 6 months. All patients were of White ethnicity; six (30%) patients were female, and 14 (70%) were male. Median age was 56·5 years (IQR 49·5-65·5). The most common grade 3 adverse events were injection-site erythema (three [15%] of 20 patients), granuloma (two [10%] of 20), and ulceration (one [5%] of 20). There were no grade 4 adverse events, treatment-related serious adverse events, or deaths. T-cell responses targeting multiple peptides were induced in 19 (95% [95% CI 75·1-99·9]) of 20 patients at end of treatment and persisted in 16 (84%) of 19 at 6 months follow-up, with the intensity of responses increasing until end of study.

Our findings indicate that iTAC-XS15-CLL01 could be a potent immunotherapeutic agent in patients with chronic lymphocytic leukaemia and should be further evaluated in phase 2 trials.

Medical Faculty, Tübingen University.