Inclusion Criteria:

          -  Females

               1. Able to understand the investigational nature of this study and provide written
                  informed consent prior to the participation in the trial

               2. Age 18 to 55, inclusive

               3. Diagnosis of Stage I, II, or III HR+, HER2-negative breast cancer (ER>1% and/or,
                  PR>1%, HER2-negative per ASCO CAP guidelines)

               4. Is a candidate for endocrine therapy + ovarian suppression

               5. Is premenopausal at the time of study entry.

                    -  E2 > 30 pg/mL

                    -  Follicle stimulating hormone (FSH) < 40 IU/L

                    -  Last menstrual period within the 3 months prior to first dose of TOL2506

                  Exclusion Criteria:

          -  Females

               1. Body mass index (BMI) < 18.00 kg/m2 or > 35.00 kg/m2

               2. Breastfeeding

               3. Life expectancy < 12 months

               4. Eastern Cooperative Oncology Group (ECOG) performance status ≥ 3

               5. Unacceptable hepatic function as determined by any of the following:

                    1. Alanine aminotransferase (ALT) ≥ 2X upper limit of normal (ULN)

                    2. Aspartate aminotransferase (AST) ≥ 2X ULN

                    3. Bilirubin ≥ 2X ULN

                    4. Alkaline phosphatase ≥ 2X ULN

                    5. Severe hepatic impairment (Child-Pugh Class C)

               6. Unacceptable renal function as determined by any of the following:

                    1. Creatinine ≥ 3X ULN

                    2. Creatinine clearance ≤ 30 mL/minute

                    3. Creatinine clearance ≤ 60 mL/minute in subjects with bone density 1.5
                       standard deviations below the young adult normal mean

               7. History of significantly abnormal ECG or screening 12-lead ECG demonstrating any
                  of the following:

                    1. HR > 100 BPM

                    2. QRS > 120 msec

                    3. QTc > 450 msec

                    4. PR > 220 msec

               8. Prior (within 28 days prior to Day 0) and/or concomitant use of medications known
                  to prolong the QT/QTc interval

               9. Prior use of tamoxifen, other SERMs (eg, raloxifene) or antagonists (eg,
                  fulvestrant), aromatase inhibitor, mammalian target of rapamycin (mTOR)
                  inhibitors, or hormone replacement therapy within 3 months before breast cancer
                  diagnosis

              10. Prior neoadjuvant or adjuvant endocrine therapy since diagnosis of breast cancer

              11. History of treatment for osteopenia/osteoporosis

              12. Prior or current use of drugs or supplements known to increase bone mineral
                  density (ie, bisphosphonates, denosumab, teriparatide, abaloparatide,
                  romosozumab, calcitonin, fluoride, strontium)

              13. Low trauma fracture(s) occurring within 12 months prior to Screening (defined as
                  a fracture that results from a fall from a standing height or less, excluding
                  fingers, toes, face and skull)

              14. Conditions that preclude bone mineral density measurement (lumbar spine/bilateral
                  hip surgery with hardware in place, abdominal clips, umbilical ring [not willing
                  to remove] or weight that exceeds the DEXA machine limitation)

              15. Any other medical condition or serious illness, presence of a second malignancy
                  under current treatment or follow-up, or the presence of clinically significant
                  findings on the physical exam, laboratory testing, medical history (including
                  conditions that may be associated with low bone mass), that in the opinion of the
                  Investigator may interfere with trial conduct, subject safety, or interpretation
                  of study results

              16. Already receiving and/or previously received GnRH analogs within 1 year before
                  breast cancer diagnosis

              17. Psychiatric, addictive, or other disorders that would preclude study compliance

              18. Use of medications that may impact subject safety and/or affect the PK of the
                  drug and hormonal assessments including but not limited to:

                    1. Oral or transdermal hormonal therapy within 30 days prior to Screening

                    2. Estrogen, progesterone, or androgens within 30 days prior to Screening

                    3. Hormonal contraceptives within 30 days prior to Screening

                    4. Medications known to result in clinically important decreases in bone mass
                       taken within 6 months prior to Screening

              19. Known hypersensitivity, idiosyncratic, or allergic reactions to GnRH, GnRH
                  agonist/analogs or to any of the components of the IP

              20. Sexually active with a male partner and not willing to use non-hormonal
                  contraceptive methods throughout the study

              21. Is of childbearing potential with a positive serum pregnancy test at Screening or
                  urine pregnancy test at Day 0

              22. Exposure to any investigational agent within 30 days prior to the first dose of
                  TOL2506

        See contact information to obtain inclusion/exclusion criteria for males