This study is for subjects that have been diagnosed with HR+, HER2-negative breast cancer while still being in a premenopausal hormone status (i.e. females with active ovaries that produce hormones that cause menstrual cycles (even if they are not regular). The investigational drug that will be used is TOL2506. The drug will be given as an injection. The study is to assess suppression of ovarian function
following administration of TOL2506 in premenopausal subjects with HR+, HER2-negative breast cancer. Participants can expect to be in this study for 24 months.