Fig. 5. Combination therapy with anti-PD-1 increases initial antitumor efficacy but not durability of response in vivo.

a Mice were engrafted with 1.5 × 10⁶ WT MM.1 S cells. Tumor-bearing animals were treated with 1.5 × 10⁶ EGFRt- or CAR-expressing T cells on day 8 (8 days after tumor injection) and day 16. Tumor progression was monitored by bioluminescence imaging and shown for individual animals in each test group (n = 6). On day 133, animals that had been tumor-free for at least 7 weeks (3 each in the huLuc63-c11D5.3 Short groups with and without anti-PD-1) were rechallenged with 1.5 × 10⁶ WT MM.1 S cells. Black arrows indicate time of cell injections; red arrows indicate instances of CAR-T cells eradicating palpable tumor nodules. The endpoint for each animal is marked with an “X.” b CD38 and PD-1 expression on T cells persisting in mice at time of animal sacrifice. Each data point in b corresponds to an individual tumor mass, tissue (e.g., brain and spleen), or cardiac blood sample recovered. For PD-1 expression: 23 samples were collected from six mice in the group not treated with anti-PD-1, and 26 samples were collected from six mice in the group treated with anti-PD-1. For CD38 expression: seven samples were collected from two mice in the group not treated with anti-PD-1, and nine samples were collected from three mice in the group treated with anti-PD-1. Only samples that contained at least 10 human CD45⁺ cells as detected by flow cytometry were included for analysis. P-values were calculated by unpaired two-tailed Student’s t-test. Source data are provided as a Source Data File.