ABSTRACT Camizestrant is the next‐generation oral selective estrogen receptor degrader and complete estrogen receptor antagonist in Phase 3 development for hormone receptor‐positive breast cancer. To investigate the impact of manufacturing changes during pivotal Phase 3 studies, this open‐label, randomized crossover study of 32 postmenopausal healthy volunteers determined the relative bioavailability of a tablet used in early clinical studies (Phase 1 tablet), a tablet designed for late‐phase development (prototype Phase 3 tablet), and an oral solution. Absolute oral bioavailability in the fasted state (using a 14 C camizestrant intravenous microtracer) and effects of a high‐fat meal on the prototype Phase 3 tablet were also determined. The geometric mean ratios (GMRs) of the prototype Phase 3/Phase 1 tablets (% 90% CI) for C max and AUC, respectively were 98.7 (87.4–111.5) and 97.4 (92.6–102.5) at 75 mg ( n = 15), and 96.6 (86.9–107.5) and 100.4 (96.2–104.9) at 300 mg ( n = 15). GMRs of the prototype Phase 3 tablet/oral solution for C max and AUC were 96.2 (85.3–108.7) and 99.5 (94.6–104.6) at 75 mg ( n = 15). Fed‐to‐fasted C max and AUC GMRs were 106.2 (94.3–119.7) ( n = 16) and 109.8 (104.4–115.5) ( n = 15) at 75 mg ( n = 16), and 115.9 (104.3–128.7) and 102.3 (98.0–106.8) at 300 mg ( n = 15). Absolute oral bioavailability at 75 mg ( n = 6) and 300 mg ( n = 6) was 42.5% (36.8%–49.0%) and 55.1% (48.5%–62.5%). The formulations showed similar exposures, supporting the planned manufacturing changes. Camizestrant exhibited moderate bioavailability; exposures were similar under fasted and high‐fat meal conditions, supporting its administration with or without food.
Sykes et al. (Tue,) studied this question.