Yes. 1 FDA-approved labels for Natalizumab carry a boxed warning, and its subject is progressive multifocal leukoencephalopathy. A boxed warning is the most serious warning the FDA requires on a prescription label. It is applied to the drug and to the situations in which it is used, not to any particular person taking it.
What the warning says
Below is how the Natalizumab warning opens on one specific label, identified underneath it. Only one Natalizumab label carrying a boxed warning is currently in the FDA database, so there is no second version to compare this wording against.
WARNING: PROGRESSIVE MULTIFOCAL LEUKOENCEPHALOPATHY TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML), an opportunistic viral infection of the brain that usually leads to death or severe disability. Risk factors for the development of PML include the presence of anti-JCV antibodies, duration of therapy, and prior use of immunosuppressants. These factors should be considered in the context of expected benefit when initiating and continuing treatment with TYSABRI [ see Warnings and Precautions ( 5.1 ) ]. Healthcare professionals should monitor patients on TYSABRI for any new sign or symptom that may be suggestive of PML.
NATALIZUMAB, Biogen Inc., label version effective 21 March 2025. Opening of the warning; read the full label on DailyMed.Only one label carries this warning
There is no single official text of a boxed warning: the FDA sets what a warning must cover and each manufacturer writes its own label within that, so most drugs in this section carry several different wordings. Natalizumab is a case where only one label carrying a boxed warning is currently in the FDA database, so the wording quoted above is simply the wording, with nothing to compare it against.
That usually reflects a single supplier rather than any special agreement about the text. If another manufacturer begins producing Natalizumab, its label may word the progressive multifocal leukoencephalopathy warning differently while describing the same hazard, and this page would then show more than one version.
Natalizumab is dispensed under 1 current FDA labels despite this warning, which is the point worth holding onto: a boxed warning is a disclosure requirement, not a verdict. What a boxed warning does and does not mean sets out the distinction.
Common questions
Does Natalizumab have a black box warning?
Yes. 1 FDA-approved labels for Natalizumab carry a boxed warning, and its subject is progressive multifocal leukoencephalopathy. A boxed warning is the strongest warning the FDA requires on a prescription label, and it is applied to the drug, not to any individual taking it.
What does the Natalizumab boxed warning say?
The wording is set by each manufacturer within FDA requirements, so it varies. In the version quoted on this page, taken from a label effective 21 March 2025, the warning concerns progressive multifocal leukoencephalopathy. The full text is linked so the exact version can be read rather than summarised.
Does the Natalizumab boxed warning mean the drug is unsafe or being withdrawn?
No. It means the FDA requires the risk of progressive multifocal leukoencephalopathy to be communicated prominently so prescribers weigh it explicitly. Natalizumab remains FDA-approved and is dispensed under 1 current labels. A boxed warning is a disclosure requirement, not a judgement that a drug should not be used.
Is this the only version of the Natalizumab warning?
It is the only one currently in the FDA label database. Most drugs have several manufacturers, each writing its own label within the FDA's requirements, which is why their warning text varies. Only one Natalizumab label carrying a boxed warning is published at present, so there is no second wording to compare against.
Should I stop taking Natalizumab because of this warning?
This page does not answer that and cannot. The warning about progressive multifocal leukoencephalopathy is written for a prescriber deciding whether Natalizumab suits a particular patient, and stopping a prescribed medicine carries its own risks that this page knows nothing about. Raise it with the prescriber or a pharmacist, who can see the whole picture.
Where this page's information comes from
The quotation above is from one Natalizumab label, linked below by its DailyMed set identifier so the exact version can be opened rather than taken on trust. The figure of 1 labels, and the count of 1 distinct wordings among 1 sampled, were computed from the openFDA labelling API on 30 August 2026.
- NATALIZUMAB prescribing information, Biogen Inc., effective 21 March 2025.
- openFDA drug labelling API, the source of the label counts and variant counts on this page.
Labels are revised over time. The version linked above is the one this page was written against, and a newer revision may differ. Counts reflect the labels present in openFDA on the retrieval date.