Pilot Study of Bazedoxifene Plus Conjugated Estrogen on Imaging and Blood Biomarkers

Duavee® which is the combination of the selective estrogen receptor modulator (SERM) bazedoxifene plus conjugated estrogens is an FDA approved drug for treatment of hot-flashes and prevention of osteoporosis in postmenopausal women. In a single arm pilot study 6 months of Duavee® was associated with improvement in several risk biomarkers including benign breast tissue proliferation, mammographic fibroglandular volume, and progesterone in women in late menopause transition and at high risk for development of breast cancer. Prior to opening a planned randomized Phase IIB trial of 6 months of Duavee® vs placebo in high risk women with hot-flashes followed by open label Duavee®, a pilot trial was initiated of 6 months of Duavee® vs wait-list control in symptomatic women (Study00145121; NCT04379024). This trial was also intended to provide additional imaging biomarker information from MRI which was not performed in the previous prior study. A finding on MRI of greater background parenchymal enhancement (BPE) in high risk women is positively associated with higher probability of developing breast cancer and is independent of fibroglandular volume. BPE is reduced by selective estrogen receptor modulators including tamoxifen. Change in MRI BPE over time was also investigated for women randomly assigned to either receive Duavee® or not (wait-list control), as well as exploration of fully automated breast MRI volumetric density measures. Unfortunately, midway through the trial, Duavee® became no longer available due to an issue with packaging and dissolution of the active agents. As an alternative, this current protocol will utilize separate agents of bazedoxifene (as Vivant® available from Japan) plus conjugated estrogens (available in the US as Premarin®). The specific objectives are identical to those in Study00145121, with the exception that Duavee® has been replaced by BZA+CE. The intent is to combine the results of both trials for analysis.