Immuno-PET Detects Antibody–Drug Potency on Coadministration with Statins

(A) Schematic illustrating T-DM1 and statin dose administration in single-dose ADC regime. NCIN87 gastric xenografts were established in female nude mice (≥8 per group). Once tumors reached 200–300 mm³, intravenous T-DM1 administration at 5 mg/kg weekly (for 1 wk—single-treatment regime) was started on day 1. Lovastatin (4.15 mg/kg) was orally administered 12 h before and simultaneously with intravenous injection of T-DM1. [⁸⁹Zr]Zr-DFO-trastuzumab was intravenously administered on day 39, and PET images were collected at 41 d after treatment. Immediately after PET imaging, organs were harvested for ex vivo biodistribution. Tumors were excised at 43 d after initiating therapy and used for Western blot analyses. Schematic was created with Biorender.com. (B) Tumor volumes (mm³) measured across 60 d for control, T-DM1 single-treatment regime, and T-DM1/statin single-treatment regime. Mean ± SD for at least 8 mice is shown. ****P < 0.0001 based on 2-way repeated measures ANOVA. (C) Fold-change in NCIN87 tumor volume for T-DM1 or T-DM1/statin (1 wk of therapy, single-treatment regime) and for T-DM1 or T-DM1/statin (5 wk, multiple-treatment regime reported (21)). Fold-change between day 0 and day 60 is displayed as mean ± SD (n ≥ 8). ****P < 0.0001 based on 1-way ANOVA.

(A and B) Representative PET images (A) and biodistribution (B) of [⁸⁹Zr]Zr-DFO-trastuzumab displaying %ID/g acquired 48 h after radiolabeled trastuzumab injection on day 39 for T-DM1 single-treatment regime, T-DM1/statin single-treatment regime, T-DM1 multiple-treatment regime, and T-DM1/statin multiple-treatment regime. Tumor location is indicated by arrow. Data are mean ± SD (n = 4). Significant P values (<0.05) are displayed for tumor mean comparisons and were calculated by unpaired Student t test. (C) Scatterplot of mean %ID/g of [⁸⁹Zr]Zr-DFO-trastuzumab in tumor regions against tumor volume (mm³). Pearson correlation coefficient (r) and P value are displayed. Line of best fit is displayed (solid black line) with 95% CIs (dotted black lines).

(A) Schematic illustrating T-DXd and statin dose administration across single-dose regime. NCIN87 gastric xenografts were established in female nude mice (9 per group). Once tumors reached about 200 mm³, mice were intravenously administered T-DXd, 5 mg/kg weekly (for 1 wk—single-treatment regime). Lovastatin (4.15 mg/kg) was orally administrated 12 h before and simultaneously with intravenous injection of T-DXd. [⁶⁴Cu]Cu-NOTA-trastuzumab was intravenously administered on days 1 and 29, and PET images were collected before (day 2) and after (day 30) therapy. Mice were sacrificed 34–63 d after initiating therapy. Schematic was created with Biorender.com. (B) Tumor volumes (mm³) were measured across 34 d for T-DXd and T-DXd/statin. Mean ± SD of 9 mice per group is shown. **P = 0.006 at endpoint based on 2-way repeated-measures ANOVA. (C) Tumor volume fold-change in NCIN87 tumor volume in T-DXd or T-DXd/statin. Fold-change between days 0 and 34 is displayed as mean ± SD. **P = 0.008 calculated by unpaired Student t test. (D) Representative PET images of [⁶⁴Cu]Cu-NOTA-trastuzumab displaying %ID/g acquired at 24 h after radiolabeled trastuzumab injection before therapy (day 2) and after therapy (day 30) for T-DXd and T-DXd/statin. Two different mice with varying tumor sizes from 73 to 384 mm³ are displayed for each group and each time point. Tumors are encircled.

(A) Schematic displaying establishment of HER-positive gastric cancer PDX from patient tumor. Tumor fragments were implanted subcutaneously into NSG mice (≥8 per group). T-DM1/statin multiple- and single-dose schedules were administered as described in Figure 1. T-DXd/statin single-dose schedule was administered as described in Figure 3. Schematic was created with Biorender.com. (B) Tumor volumes (mm³) were measured across 40 d for control, T-DM1 single-dose regime, and T-DM1/statin single-dose regime. Mean ± SD is shown (n ≥ 8 per group). ****P < 0.0001 based on 2-way repeated measures ANOVA. (C) Tumor volume fold-change in gastric PDX for T-DM1 or T-DM1/statin (1 wk of therapy, single-treatment regime) and for T-DM1 or T-DM1/statin (5 wk, multiple-treatment regime reported (21)). Fold-change between first and last tumor volume measurements is displayed as mean ± SD (n ≥ 5 per group). ns = not significant. ****P < 0.0001 based on 1-way ANOVA. (D) Tumor volumes (mm³) were measured across 21 d for T-DXd single-dose regime and T-DXd/statin single-dose regime. Mean ± SD is shown (n ≥ 8 per group). *P = 0.02 based on 2-way repeated measures ANOVA. (E) Tumor volume fold-change in gastric PDX for T-DXd or T-DXd/statin. Fold-change between first and last tumor volume measurements is displayed as mean ± SD (n ≥ 8 per group). **P = 0.007 based on unpaired Student t test.