Is balixafortide FDA-approved, and what does the research show?

What is balixafortide?

Balixafortide is an investigational drug that has been tested in people with cancer and in stem-cell donors ¹, ². A 2017 research paper calls it "a peptidic CXCR4 antagonist," a peptide-based molecule that blocks a receptor called CXCR4 ². Amino acids, the links in a peptide's chain, are the units that proteins are built from. Its early trials used the code name POL6326 ², ⁶.

A receptor is a protein on a cell that receives chemical signals. Together with its signaling partner, CXCR4 "regulates function and trafficking of immune cells and the tumour microenvironment," the authors of the first breast cancer trial wrote ¹. The tumor microenvironment is the tissue and cells that surround a tumor.

Its breast cancer trials gave balixafortide with eribulin, a chemotherapy drug, for HER2-negative cancers ¹, ⁴. The phase 1 trial required a negative result on laboratory tests for the protein HER2 ⁶. Phase 1 is the first, small stage of testing in people.

Is balixafortide FDA-approved?

Balixafortide is not FDA-approved: Drugs@FDA lists no approved balixafortide product as of November 9, 2026 ³. It is an investigational drug whose late-stage (phase 3) trial, FORTRESS, the registry ClinicalTrials.gov records as "Terminated" (last update posted November 1, 2023) ⁴. Drugs@FDA is FDA's public database of approved drug products. With no approved product there, there is no FDA-approved label for balixafortide to quote ³.

ClinicalTrials.gov is the U.S. government's registry of clinical studies. On November 10, 2026, it listed nine records for the search "balixafortide OR POL6326" ⁴, ⁶, ⁷, ⁸, ⁹, ⁵, ¹⁰, ¹¹, ¹². Five read "Completed," with last updates posted between April 23, 2014 and September 14, 2018 ⁶, ⁵, ¹⁰, ¹¹, ¹². One, a breast cancer study that enrolled no participants, read "Withdrawn" (last update posted March 20, 2023) ⁸.

FORTRESS is the record that reads "Terminated"; it gives a completion date of October 19, 2021, and its last update was posted on November 1, 2023 ⁴. Under the heading for why it stopped, the record says: "The study was halted early due to failure to meet the primary endpoint" ⁴. A primary endpoint is the main result a trial is designed to measure. Polyphor, its maker, announced on April 19, 2018 that FDA had granted Fast Track designation to balixafortide with eribulin for HER2-negative metastatic breast cancer ¹³.

One record, a phase 1 study of balixafortide with the immunotherapy drug cosibelimab in metastatic pancreatic cancer, read "Not yet recruiting" at its last update, posted November 19, 2025 ⁷. Metastatic means the cancer has spread to distant parts of the body. Its sponsor is an investigator at Cedars-Sinai Medical Center, and that update gave an estimated start of January 2026 ⁷. None of the sources cited here shows whether the study has begun.

The record that read "Recruiting" at its last update, posted December 3, 2024, is an observational study of a fluorescent probe it names ICG-POL6326 ⁹. A fluorescent probe is a marker that glows under special light. The probe is applied to breast tissue and lymph nodes after surgeons have removed them, and no participant receives balixafortide ⁹.

Outside a clinical trial, none of the sources cited here shows a route to balixafortide. FDA keeps lists of bulk drug substances nominated for use in compounding under sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act ¹⁴, ¹⁵. Compounding is the making of a medicine by a licensed pharmacy from a bulk ingredient. The 503A list, updated May 14, 2026, does not name balixafortide or POL6326 ¹⁴. Neither does the 503B list, updated March 21, 2025 ¹⁵.

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How does balixafortide work?

Balixafortide is an antagonist of CXCR4: it blocks the receptor instead of switching it on ¹, ². For cancer, the reasoning comes from laboratory work, so the benefit is proposed, not shown in people. "CXCR4 antagonists have been shown to enhance the activity of different anticancer treatments in preclinical models," the phase 1 authors wrote ¹. Preclinical means tested in cells or animals before any trial in people.

CXCR4 also helps hold blood-forming stem cells in the bone marrow ². Blocking it lets those cells move into the bloodstream, where they can be collected for a transplant, a process called mobilization ². The authors of a study in healthy volunteers describe this as "a rather short-lived interference with stem cell retention in the bone marrow" ². In that study the drug left the blood with a half-life of about five hours, the time for its level to halve ². Its clearance suggested to the authors "that balixafortide is mainly cleared through the kidney" ².

What does the research show?

Studied in people: a single-arm, dose-escalation phase 1 trial of balixafortide plus eribulin ¹. Single-arm means every participant received the combination, so the trial had no comparison group. Dose-escalation means successive groups received higher doses to find the highest one tolerated. The paper, published online on April 26, 2018, reports 56 patients enrolled; the registry record gives an actual enrollment of 54 ¹, ⁶.

Participants were women with HER2-negative metastatic breast cancer whose tumor cells showed CXCR4 ¹. They had already received one to three chemotherapy regimens for metastatic disease ¹. The primary endpoints were "dose-limiting toxicities and adverse events, and the establishment of a maximum tolerated dose or recommended phase 2 dose, and pharmacokinetic parameters" ¹. A dose-limiting toxicity is a side effect severe enough to stop the dose being raised; pharmacokinetics is how the body takes up and clears a drug. On those endpoints the paper reports: "No dose-limiting toxicities were confirmed and the maximum tolerated dose was not reached" ¹.

Tumor response was a preliminary measure in this trial ¹. Of 54 patients who could be assessed for antitumor activity, 16 had an objective response, 30% (95% confidence interval 18 to 44), all of them partial responses ¹. An objective response is measured tumor shrinkage, and a partial response is shrinkage short of disappearance. A 95% confidence interval is the range in which the true figure is likely to lie.

These are that trial's figures alone: with no comparison group, they cannot show what balixafortide added to eribulin. The authors wrote that the combination "warrants further investigation in randomised trials" ¹.

Studied in people: FORTRESS, a randomized, open-label phase 3 trial comparing balixafortide plus eribulin with eribulin alone, 432 participants ⁴. Randomized means chance decided each person's treatment; open-label means participants and doctors knew which one it was. The trial assigned 219 people to balixafortide plus eribulin and 213 to eribulin alone, starting in May 2019 ⁴.

They had HER2-negative breast cancer, metastatic or locally recurrent, that had progressed during or within six months of their most recent chemotherapy ⁴. Locally recurrent means the cancer has come back in or near the breast; the trial took such cancers when surgery could not remove them ⁴. None had received eribulin before ⁴.

The record names two primary outcomes: "Progression Free Survival (2nd Line+ Population)" and "Progression Free Survival (3rd Line+ Population)" ⁴. It defines progression-free survival as "the time from the date of randomization to the earliest evidence of documented progressive disease or death from any cause" ⁴. An independent review committee judged progression ⁴. In cancer care a line is one course of treatment in a sequence. The protocol defines 2nd Line+ as study treatment given as the second to fifth line of therapy, and 3rd Line+ as the third to fifth ¹⁶.

In the 2nd Line+ population, all 432 participants, median progression-free survival was 3.5 months (95% confidence interval 2.8 to 4.2) with balixafortide plus eribulin ⁴. With eribulin alone it was 4.0 months (3.0 to 4.3) ⁴. The median is the point by which half of a group had progressed or died.

The hazard ratio, which compares the rate of progression or death between the arms, was 1.10 (96% confidence interval 0.85 to 1.41; p = 0.4450) ⁴. A ratio of 1 means no difference. A p-value is the chance of seeing a difference at least this large if the treatments did not truly differ. The ratio compares the combination with eribulin alone, so a ratio above 1 means a higher rate of progression or death on the combination ¹⁷.

In the 3rd Line+ population, median progression-free survival was 3.5 months (2.8 to 4.2) among 175 participants given the combination ⁴. Among 173 given eribulin alone it was 4.0 months (2.9 to 4.2) ⁴. The hazard ratio was 1.07 (96% confidence interval 0.81 to 1.41; p = 0.6158) ⁴. The record's stated reason for the early halt is "failure to meet the primary endpoint" ⁴.

The one secondary outcome posted is overall survival, the time from randomization to death from any cause, in the 3rd Line+ population ⁴. Its median was 11.0 months (95% confidence interval 8.9 to 12.3) with balixafortide plus eribulin and 11.2 months (8.9 to 14.0) with eribulin alone ⁴. The hazard ratio was 1.08 (99.9% confidence interval 0.66 to 1.77; p = 0.6126) ⁴. The results were first posted on November 1, 2023, and no journal paper on FORTRESS is among the sources cited here ⁴.

Studied in people: an open phase 1 study in 27 healthy male volunteers, all stem-cell donors, who received 39 infusions of balixafortide between them ², ¹⁰. Stem cells in the blood rose at every dose tested ². Each volunteer had earlier taken G-CSF, the standard drug for this purpose ². At the higher doses, the authors found, "the G-CSF regimen was about three times as effective as the CXCR4 antagonist" ². Polyphor, the drug's maker, sponsored and largely funded the study, and several authors were its employees ².

The registry also holds three more Polyphor studies whose records read "Completed," none with results posted there when read on November 10, 2026 ¹¹, ¹², ⁵. Two tested stem-cell mobilization ¹¹, ¹². One was a phase 2 study in 21 patients with multiple myeloma, a blood cancer; the other was a phase 1/2 study of 38 sibling donors and transplant recipients ¹¹, ¹². Phase 2 is the middle stage of testing, and a phase 1/2 study combines the first two stages.

The third, CATCH-AMI, was a randomized phase 2 trial comparing the drug with a placebo, a dummy infusion, in 120 patients after a large heart attack ⁵. None of the sources cited here reports the results of these three studies.

None of the sources cited here studies balixafortide for weight loss, wellness, immune boosting or athletic performance. Nor does any of them report balixafortide given on its own as a cancer treatment.

What are the side effects?

Of the studies cited here, FORTRESS has the largest safety record: 218 people given balixafortide plus eribulin and 204 given eribulin alone ⁴. Those counts are lower than the 219 and 213 people assigned to the two arms ⁴. The trial's statistical plan counts safety among randomized people who received at least one dose, by the treatment they actually received ¹⁷.

Serious adverse events were recorded in 62 of the 218 and in 54 of the 204 ⁴. Deaths from any cause numbered 17 of 218 and 13 of 204 ⁴. The record does not say which deaths, if any, were judged related to treatment ⁴.

Reactions to the infusion set the two arms apart. Infusion-related reactions that were not serious were recorded in 95 of 218 people on the combination and in none of 204 on eribulin alone ⁴. Serious ones were recorded in 5 of 218 on the combination and in none of 204 on eribulin alone ⁴.

Among events not classed as serious, itching was recorded in 55 of 218 people on the combination, rash in 23 and a sore mouth, called stomatitis, in 25 ⁴. On eribulin alone, the counts were 1, none and 11 of 204 ⁴. The eribulin-alone arm received no balixafortide infusion, and the trial was open-label ⁴.

Other common events appeared in both arms. Among events not classed as serious, neutropenia was recorded in 57 of 218 people on the combination and 68 of 204 on eribulin alone ⁴. Hair loss was recorded in 59 of 218 and 62 of 204, and nausea in 44 of 218 and 40 of 204, combination first ⁴. Neutropenia is a low count of the white blood cells that fight infection.

Among serious events, febrile neutropenia, a low white-cell count with fever, occurred in 5 of 218 people on the combination and 9 of 204 on eribulin alone ⁴. Pneumonia occurred in 5 of 218 on the combination and 5 of 204 on eribulin alone ⁴. A blood clot in the lung occurred in 4 of 218 on the combination and 1 of 204 on eribulin alone ⁴.

In the phase 1 trial every participant received both drugs, so its events cannot be assigned to one of them ¹. After "a treatment-related fatal adverse event" in the first group treated, the protocol was amended, and some later groups started on reduced doses ¹. The most common events of any grade were fatigue in 44 of 56 patients (79%), neutropenia in 32 (57%) and infusion-related reactions in 27 (48%) ¹. Hair loss and constipation each occurred in 26 (46%), and nausea in 25 (45%) ¹.

Serious adverse events occurred in 21 of the 56 patients (38%), among them febrile neutropenia in 5 (9%) ¹. Two patients (4%) died while receiving study treatment, one from septic shock and one from pneumonia ¹. Septic shock is a dangerous fall in blood pressure caused by a severe infection. The authors wrote that safety and tolerability "seems to be similar to that of eribulin or balixafortide monotherapy," meaning either drug given alone ¹.

In the 27 healthy volunteers, the paper reports that "No severe adverse events (SAEs) were observed" ². Mild skin reactions "such as flushing, urticaria or local itching" were reported in every dose group ². They affected 1 of 3 volunteers in the lowest dose group, and 8 of 9 and 7 of 10 in the two highest ². Urticaria is hives. The reactions were rated likely related to the drug and eased quickly with antihistamines ².

Three kinds of event were rated possibly related to the drug ². They were mild bone pain in one volunteer, a raised level of the muscle enzyme creatine kinase in two, and a systolic blood-pressure reading above 150 mmHg in two ². Systolic pressure is the higher of the two blood-pressure numbers, and mmHg is the unit it is measured in.

FORTRESS excluded people who were pregnant or breastfeeding ⁴. It also excluded people with congestive heart failure, slow heart rhythms or a long QT interval, and those taking drugs that prolong it ⁴. The QT interval is a measure of the heartbeat's electrical timing.

In sport

Balixafortide is not named on the 2026 Prohibited List of WADA, the World Anti-Doping Agency ¹⁸. The list contains neither its code name, POL6326, nor the term CXCR4 ¹⁸. The trials gave balixafortide by infusion into a vein, and the list has a rule on infusions ¹, ⁴. Section M2.2 prohibits "Intravenous infusions and/or injections of more than a total of 100 mL per 12-hour period except for those legitimately received in the course of hospital treatments, surgical procedures or clinical diagnostic investigations" ¹⁸.

Section S0 of the list reads: "Any pharmacological substance which is not addressed by any of the subsequent sections of the List and with no current approval by any governmental regulatory health authority for human therapeutic use (e.g. drugs under pre-clinical or clinical development or discontinued, designer drugs, substances approved only for veterinary use) is prohibited at all times" ¹⁸. FDA is the only regulator whose records were read, and its Drugs@FDA database lists no approved balixafortide product ³.

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JumpstartMD does not prescribe balixafortide. Our peptide library covers it so you have the facts on its FDA status and the evidence, current as of November 10, 2026.

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