Balixafortide
A CXCR4 blocker tested for stem cell mobilisation and breast cancer
Balixafortide is an investigational peptide that blocks the CXCR4 receptor. In healthy volunteers it released blood stem cells from the bone marrow, and with the chemotherapy drug eribulin it shrank tumours in 30% of women with metastatic breast cancer in a phase 1 trial. The phase 3 trial was halted early after failing its primary endpoint.
What is it?
CXCR4 holds blood stem cells in the bone marrow and helps tumour cells survive and spread. Blocking it releases stem cells into the blood, which is how the approved peptide motixafortide is used before stem cell collection. In healthy volunteers, balixafortide mobilised stem cells at every dose, reaching about 38 CD34+ cells/µL at the higher doses, and was rated more favourably than G-CSF by participants. Compared with G-CSF, it raised B lymphocytes more and neutrophils and monocytes less, producing a mixed rise in white cells in the mid-20,000 per microlitre range.
In cancer it was combined with eribulin. A phase 1 trial in 56 women with HER2-negative metastatic breast cancer found no dose-limiting toxicities, and partial responses in 16 of 54 evaluable patients (30%). In mice with prostate cancer in bone, it enhanced docetaxel's effect on tumour burden.
The pivotal phase 3 trial, with 432 participants, was terminated: ClinicalTrials.gov records that it was halted early because it failed its primary endpoint. A further trial with nab-paclitaxel or eribulin was withdrawn by the funder, and a new phase 1 study with cosibelimab in pancreatic cancer is registered. It is not approved anywhere. A completed phase 2 trial of 120 participants also tested CXCR4 blockade with it for cell mobilisation and healing after acute myocardial infarction; no results paper was found.
At a Glance
Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Published Research
Studies of balixafortide, from their PubMed abstracts.
Phase 1 with eribulin in breast cancer
In 56 women with HER2-negative metastatic breast cancer, no dose-limiting toxicities were confirmed and the maximum tolerated dose was not reached; 16 of 54 evaluable patients (30%) had partial responses.
Stem cell mobilisation in healthy volunteers
Balixafortide mobilised stem and progenitor cells at all doses, reaching 38.2 CD34+ cells/µL at 1,500-2,500 µg/kg, was well tolerated and was rated favourably over G-CSF.
Prostate cancer in bone, with docetaxel
In mice, adding balixafortide to docetaxel lowered tumour burden compared with docetaxel alone and reduced the area of bone lesions compared with vehicle.
Side Effects & Contraindications
Reported Side Effects
From the studies above.
Contraindications & Cautions
No label; it is investigational.
Legal Status
Balixafortide is investigational.
Frequently Asked Questions
?What is balixafortide?
An investigational peptide that blocks the CXCR4 receptor, tested for releasing blood stem cells and, with eribulin, for metastatic breast cancer.
?Why was the phase 3 trial stopped?
ClinicalTrials.gov records that it was halted early because it failed to meet its primary endpoint.
?How does it relate to motixafortide?
Both are CXCR4-blocking peptides. Motixafortide is approved in the US for mobilising stem cells before collection in multiple myeloma; balixafortide is not approved.
?What did the phase 1 breast cancer trial show?
With eribulin, 30% of evaluable women had partial responses, no dose-limiting toxicities were confirmed, and the maximum tolerated dose was not reached.
?How does it compare with G-CSF for releasing stem cells?
In healthy volunteers it mobilised stem cells at every dose and was rated more favourably than G-CSF; it raised B lymphocytes more, and neutrophils and monocytes less, than G-CSF.
?Is balixafortide still being studied?
A phase 1 study combining it with the antibody cosibelimab in metastatic pancreatic cancer is registered on ClinicalTrials.gov as not yet recruiting, but no new breast cancer trials are active after the phase 3 termination.
?Can I buy balixafortide?
It is not approved anywhere, so anything sold under its name is an untested research chemical with no verified purity.
References
- [registry] ClinicalTrials.gov API v2, read October 3, 2026: NCT03786094 (phase 3, HER2-negative metastatic breast cancer, 432, terminated for failing primary endpoint), NCT01837095 (phase 1 with eribulin, 54, completed), NCT01905475 (phase 2, acute myocardial infarction, 120, completed), NCT04826016 (phase 1/2, withdrawn: funder decision).
- [clinical-trial] Pernas S, et al. "Balixafortide plus eribulin in HER2-negative metastatic breast cancer: a phase 1, single-arm, dose-escalation trial." Lancet Oncol, 2018;19(6):812-824. PMID: 29706375.
- [clinical-trial] Karpova D, et al. "Mobilization of hematopoietic stem cells with the novel CXCR4 antagonist POL6326 (balixafortide) in healthy volunteers-results of a dose escalation trial." J Transl Med, 2017;15(1):2. PMID: 28049490.
- [pubmed] Robinson T, et al. "A CXCR4 inhibitor (balixafortide) enhances docetaxel-mediated antitumor activity in a murine model of prostate cancer bone metastasis." Prostate, 2023;83(13):1247-1254. PMID: 37244751.
Sources & Citations
Studies were read from their PubMed records; trial registrations from ClinicalTrials.gov, read October 3, 2026.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.