Heart & blood CXCR4 antagonist peptide
Balixafortide
Regulatory status
Status at a glance
503A compounding status
Not nominated
We found no pending nomination for the 503A bulks list. Unless the substance has another legal pathway (for example, a USP monograph or use in an FDA-approved drug), 503A pharmacies generally may not compound with it.
- FDA approval
- Not FDA-approved for any use
- 503B outsourcing
- Not determined
- Anti-doping (WADA)
- Not on the WADA Prohibited List
- DEA schedule
- Not a controlled substance
About peptide status
Most peptides discussed here are not FDA-approved for any use, and products labeled “research use only” are not for human use. Removal from Category 2 does not authorize compounding. PCAC votes are non-binding recommendations; FDA and HHS make the final decisions.
This is not medical or legal advice, and we do not publish dosing, sourcing or reconstitution information. Talk with a licensed clinician before using any peptide.
If you think you are having a medical emergency, call 911.
Key takeaway
Balixafortide is an investigational peptide that blocks the CXCR4 receptor, studied by Polyphor in combination with chemotherapy for metastatic breast cancer. An early single-arm trial suggested activity, but the pivotal Phase 3 trial did not show a benefit over chemotherapy alone, and development has effectively stopped. As of 2026 it is not approved.
At a glance
- FDA status
- Investigational peptide, not approved by the FDA
- What it is
- CXCR4 antagonist studied with the chemotherapy eribulin in metastatic breast cancer
- Research
- A Phase 1 trial suggested activity, but the Phase 3 trial (FORTRESS) failed to show benefit
- Development
- Effectively ceased
- Evidence strength
- Low research
Summary
Balixafortide is an investigational CXCR4-blocking peptide studied with chemotherapy for breast cancer. See how it works and why Phase 3 showed no benefit.
What is balixafortide?
Balixafortide is an experimental peptide that blocks CXCR4, a receptor involved in how cells move through the body and interact with their surroundings. It was developed by Polyphor (later Spexis) and studied intravenously together with the chemotherapy drug eribulin for HER2-negative metastatic breast cancer. It is investigational and not approved, and its development has effectively ended. It is also known as POL6326.
How does it work?
Balixafortide blocks the CXCR4 receptor and interrupts its signaling with a partner molecule called CXCL12 (SDF-1α). This pathway influences the trafficking of tumor cells, the tumor's surrounding environment, and immune cell behavior. In laboratory work, blocking CXCR4 was proposed to make tumors more responsive to chemotherapy, which is the rationale for combining it with eribulin. This describes the proposed mechanism, separate from the patient outcomes below.
Is it FDA-approved?
Safety note
Status: Investigational peptide, not approved by the FDA
Category: In clinical trials · Primary body area: Heart & blood
No. Balixafortide is investigational and not approved, and the program is effectively discontinued after its pivotal trial.
What does the research show?
Editor’s note
Evidence strength: Low research (2 human · 0 animal/cell studies)
A randomized Phase 3 trial failed to show benefit over standard chemotherapy, which outweighs the earlier uncontrolled Phase 1 signal.
The decisive evidence is negative. Two trials tested balixafortide plus eribulin in metastatic breast cancer:
| Trial | Design | Result |
|---|---|---|
| Phase 1 trial, according to PubMed | Early single-arm study in heavily pretreated metastatic breast cancer | Partial responses in about 30% of evaluable patients, encouraging for an uncontrolled study |
| Phase 3 FORTRESS trial, reported by the company in 2021 | Randomized, compared with eribulin alone | Did not meet its primary endpoint; response and clinical-benefit rates were similar to eribulin alone, showing no meaningful improvement from adding balixafortide |
The controlled evidence does not support a benefit.
Sources: the Phase 1 dose-escalation trial (Pernas et al., The Lancet Oncology, 2018, DOI: 10.1016/S1470-2045(18)30147-5), indexed on PubMed; and company reporting of the Phase 3 FORTRESS result. This document is educational, is not medical advice or a health claim, and is not an offer to sell any product.
Registered human trials
2 registered human trials on ClinicalTrials.gov that we reviewed
Sources
- [1]
- [2]
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