Abstract: Systems and methods for determining the likely responsiveness of a human cancer subject to a checkpoint blockade immunotherapy regimen are provided. Sequencing reads are obtained from samples from the subject representative of the cancer. A human leukocyte antigen type and a plurality of clones is determined from the sequencing reads. For each clone, an initial frequency X? in the one or more samples is determined and a corresponding clone fitness score of the clone is computed, thereby computing clone fitness scores. Each such fitness score is computed by identifying neoantigens in the respective clone, computing a recognition potential for each neoantigen, and determining the corresponding clone fitness score of the respective clone as an aggregate of these recognition potentials. A total fitness, quantifying the likely responsiveness of the subject to the regimen, is computed by summing the clone fitness scores across the plurality of clones.