PML Not Fatal if Caught Early

SAN DIEGO – All multiple sclerosis patients taking natalizumab (Tysabri) who were diagnosed with progressive multifocal leukoencephalopathy (PML) before symptoms appeared were still alive a year later, researchers said.

In contrast, nearly a quarter of patients in whom PML was diagnosed on the basis of clinical symptoms died, according to Tuan Dong-Si, MD, of Biogen Idec, natalizumab’s manufacturer.

They suggested that MRI data for all patients on natalizumab should be examined carefully for signs of PML, including those who are asymptomatic.

The retrospective study of 319 patients developing natalizumab-associated PML worldwide was reported in an abstract to be presented at the American Academy of Neurology’s annual meeting, which begins here on March 16.

PML is a severe brain inflammation resulting from reactivation of latent infection with the JC virus.

The latter is extremely common and causes no symptomatic disease in most people. However, it can become dangerously active in individuals with suppression of certain aspects of their immune function.

PML was first noticed in patients receiving immunosuppressive cancer therapies and then in connection with AIDS. It appeared in multiple sclerosis (MS) patients treated with natalizumab, a monoclonal antibody targeting a leukocyte adhesion factor, shortly after the drug was approved in 2004.

The drug was removed from the U.S. market for 16 months, then relaunched with a strict distribution and registry program. However, PML cases continue to appear. Because of the risk, natalizumab is generally used as second-line therapy for MS.

As of Jan. 1, 2013, a total of 319 cases associated with natalizumab have been tracked by Biogen Idec and its marketing partner, Elan Pharmaceuticals, according to Dong-Si and colleagues.

In their review of records for these cases, the researchers identified 21 in whom PML was diagnosed prior to onset of symptoms, on the basis of routine MRI scans conducted for MS patients.

They found that all 21 were still living 12 months after diagnosis, whereas 228 of the 298 diagnosed with symptomatic PML had survived.

Dong-Si and colleagues also examined data on the trajectory of disability prior to and after PML diagnosis, finding that the patients with early PML diagnosis appeared to fare much better.

In particular, mean Expanded Disability Status Scale (EDSS) scores were substantially higher in the patients diagnosed symptomatically and Karnofsky Performance Scale (KPS) scores were significantly lower, although these data were available for only a minority of patients.

At the patients’ last clinic visit prior to diagnosis of PML, mean EDSS and KPS scores were similar between those subsequently diagnosed with asymptomatic versus symptomatic PML (EDSS 3.2 versus 3.8, respectively, P=0.263; KPS 88.0 versus 80.1, respectively, P=0.144).

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