Pivotal Study in HER2 Negative, Locally Recurrent or Metastatic Breast Cancer

Key Inclusion Criteria:

   - Histologically confirmed Breast cancer

   - Metastatic Breast Cancer currently of stage IV disease or unresectable locoregionally
   recurrent breast cancer

   - refractory to the most recent chemotherapy, documented by progression on or within six
   (6) months of therapy

   - At least 14 days from the completion of any previous cancer therapy

   - Adequate organ function

   - Life expectancy of 3 months or more

   - Willing and able to comply with the protocol and able to understand and willing to
   sign an informed consent

Key Exclusion Criteria:

   - Previously treated with eribulin

   - Peripheral neuropathy Grade ≥3

   - Receipt of prior CXCR4 therapy

   - Receipt of colony stimulating factors (CSFs) filgrastim, pegfilgrastim, or
   sargramostim, or radiation therapy within 14 days prior to study Day 1

   - History of allergic reactions attributed to compounds of similar chemical or biologic
   composition to balixafortide or eribulin or other agents used in the study

   - Breast feeding or pregnant

   - Patients with congestive heart failure, electrolyte abnormalities, bradyarrhythmias,
   known congenital long QT syndrome, QT interval corrected with Fridericia's formula
   (QTcF) ≥470 msec at baseline in the absence of bundle branch block, or currently
   taking drugs at known risk of prolonging the QT interval or causing torsades de
   pointes