Summary

Balixafortide is a synthetic peptide derived from polyphemusin II (an antimicrobial peptide from horseshoe crab) that acts as a potent and selective antagonist of the CXCR4 chemokine receptor. CXCR4 is implicated in cancer metastasis, tumour microenvironment signalling, and haematopoietic stem cell mobilisation. Balixafortide has been investigated in Phase 3 clinical trials in combination with eribulin for HER2-negative metastatic breast cancer. For research and educational purposes only.

Mechanism

Balixafortide is a selective CXCR4 antagonist derived from polyphemusin II. It competitively blocks CXCL12 (SDF-1) binding to CXCR4, disrupting the chemokine signalling that drives tumour cell migration and metastasis. It also mobilises haematopoietic stem cells from the bone marrow niche. The peptide has higher receptor selectivity and longer duration of action than the small-molecule CXCR4 antagonist plerixafor.

Evidence base

Moderate evidence — Phase 3 FORTRESS trial (NCT03786094) evaluated balixafortide + eribulin vs. eribulin alone in HER2-negative metastatic breast cancer. The primary endpoint (PFS improvement) was not met in the overall population. Subgroup analyses suggested potential benefit, warranting further investigation. Phase 1/2 data confirmed safety, CXCR4 receptor occupancy, and stem cell mobilisation.

Key trial: ClinicalTrials.gov NCT03786094 (FORTRESS)

Protocols

Phase 3 dose (IV): 3.0 mg/kg/day IV on Days 1-3 of each 21-day cycle, combined with eribulin (1.4 mg/m² IV Days 1 & 8).

Stem cell mobilisation (investigational): 1.5-5.0 mg/kg IV.

Research use only — not medical advice.

UK Status: POM (Prescription-Only Medicine)

Balixafortide is classified as a prescription-only medicine. It is not MHRA-licensed (clinical development ongoing). It is not a controlled substance under the Misuse of Drugs Act 1971. Research institutions may source non-clinical material for in vitro or animal research under appropriate licensing.

Vendor notes

Balixafortide is an investigational pharmaceutical, not typically available from research peptide vendors. Source through clinical trial supply chains or certified research chemical suppliers with COAs.

References

  1. Drenckhan A, Kuvardzic N, Gouth D, et al. Role of the CXCL12/CXCR4 Chemokine Axis in Cancer. Cancers. 2022;14(15):3617.
  2. Khan A, Greenman J, Archibald SJ. Small Molecule CXCR4 Chemokine Receptor Antagonists: Developing Drug Candidates. Curr Med Chem. 2007;14(21):2255-2272.
  3. Holland JD, Gyorffy B, Vogel R, et al. Combined CXCR4 and CXCR7 Expression on Breast Cancer Cells Correlates with Markers of Metastasis. Br J Cancer. 2009;101(2):289-296.
  4. ClinicalTrials.gov. NCT03786094. Study of Balixafortide + Eribulin vs. Eribulin Alone in HER2-Negative Locally Recurrent/Metastatic Breast Cancer (FORTRESS).