FDA Alert: Long-Term Azithromycin After Donor Stem Cell Transplant Increases Cancer Relapse, Death Risk


The FDA cautions long-term azithromycin after donor stem cell transplant may increase risk of relapse or death in patients with cancers affecting the blood and lymph nodes.

Officials with the FDA are warning against the long-term use of azithromycin (Zithromax, Zmax) for the prevention of an inflammatory lung condition after a donor stem cell transplant in patients with certain cancers, according to a safety announcement.

The safety alert is based on results from a clinical trial that found an increased rate of relapse and death in patients with cancers of the blood or lymph nodes. The trial was terminated early after increased risk of relapse was seen in patients taking azithromycin compared with placebo.

The trial, called ALLOZITHRO, investigated long-term azithromycin exposure to prevent bronchiolitis obliterans syndrome (BOS) in patients who underwent allogenic hematopoietic stem cell transplantation (HSCT) for hematological malignancy.

According to the FDA, long-term azithromycin should not be used to prevent bronchiolitis obliterans syndrome in these patients.

Patients with cancer who undergo stem cell transplants from donors are at risk of BOS, which is caused by inflammation and scarring in the airways of the lungs. Although azithromycin is approved to treat many types of infections, it is not approved for preventing BOS. There are currently no available antibiotic treatments for the prevention of the condition.

In the ALLOZITHRO study, an unexpected increase in the rate of both cancer relapses and death was observed in patients taking the antibiotic, causing researchers to stop the trial approximately 13 months after completing enrollment. According to the data, the researchers observed cancer relapse in 32.9% of patients who were treated with azithromycin compared with 20.8% patients who took a placebo. Overall, 95 patients died in the azithromycin treatment group compared with 70.1% of patients receiving a placebo.

In a Dear Healthcare Provider letter, Pfizer stated that, “Although it is not clear how azithromycin could have contributed to the observed higher rate of hematological relapses, in the study, it is concluded that long-term azithromycin exposure following HSCT may include risks that exceed the anticipated benefits.”

The FDA is advising health care professionals against prescribing long-term azithromycin for prophylaxis of bronchiolitis obliterans syndrome to patients who undergo donor stem cell transplants due to the increased risk of cancer relapse and death. Additionally, patients who have had a stem cell transplant should not discontinue their azithromycin without first consulting with their provider, the agency stated.


FDA warns about increased risk of cancer relapse with long-term use of azithromycin (Zithromax, Zmax) antibiotic after donor stem cell transplant [safety announcement]. FDA’s website. https://www.fda.gov/Drugs/DrugSafety/ucm614085.htm?utm_campaign=New%20FDA%20Drug%20Safety%20Communication%20on%20azithromycin&utm_medium=email&utm_source=Eloqua. Accessed August 3, 2018.

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