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.
Action Points
- This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
- All multiple sclerosis patients taking natalizumab who were diagnosed with progressive multifocal leukoencephalopathy (PML) before symptoms appeared were still alive a year later.
- Point out that in contrast, nearly a quarter of patients in whom PML was diagnosed on the basis of clinical symptoms died, suggesting that MRIs for all patients on natalizumab should be examined carefully for signs of PML even when 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).
At diagnosis, EDSS scores were significantly different between the two groups and the KPS scores also had begun to diverge (EDSS 3.6 asymptomatic versus 5.3 symptomatic, P=0.020; KPS 66.7 asymptomatic versus 53.6 symptomatic, P=0.129).
At month 12 post diagnosis, mean EDSS scores had returned to baseline in the asymptomatic group (although data were available for only three of these patients) whereas in the 39 symptomatic PML patients they remained high (3.7 versus 6.5, P=0.066).
KPS scores at month 12 differed significantly, with means of 70.0 in four asymptomatic patients and 46.9 in 50 symptomatic patients (P=0.021).
The study was limited by the small numbers of patients with EDSS and KPS scores available as well as the retrospective design.
PML incidence is expected to decline with screening of MS patients for JC virus exposure prior to natalizumab's initiation, which has only recently become routine.
Disclosures
The study was funded by Biogen Idec and Elan Pharmaceuticals. Dong-Si and other authors are Biogen Idec employees.
Primary Source
American Academy of Neurology
Source Reference: Dong-Si T, et al "Natalizumab-associated progressive multifocal leukoencephalopathy (PML) in multiple sclerosis patients: survival and functional outcome when asymptomatic at diagnosis" AAN 2013; Abstract P04.268.