Natalizumab to fingolimod washout in patients at risk of PML: When good intentions yield bad outcomes.

Jokubaitis et al. Fingolimod after natalizumab and the risk of short-term relapse. Neurology. 2014 Mar. [Epub ahead of print]

OBJECTIVE: To determine early risk of relapse after switch from natalizumab to fingolimod; to compare the switch experience to that in patients switching from interferon-β/glatiramer acetate (IFN-β/GA) and those previously treatment naive; and to determine predictors of time to first relapse on fingolimod.

METHODS: Data were obtained from the MSBase Registry. Relapse rates (RRs) for each patient group were compared using adjusted negative binomial regression. Survival analyses coupled with adjusted Cox regression were used to model predictors of time to first relapse on fingolimod.

RESULTS: A total of 536 patients (natalizumab-fingolimod [n = 89]; IFN-β/GA-fingolimod [n = 350]; naive-fingolimod [n = 97]) were followed up for a median 10 months. In the natalizumab-fingolimod group, there was a small increase in RR on fingolimod (annualized RR [ARR] 0.38) relative to natalizumab (ARR 0.26; p = 0.002). RRs were generally low across all patient groups in the first 9 months on fingolimod (RR 0.001-0.13). However, 30% of patients with disease activity on natalizumab relapsed within the first 6 months on fingolimod. Independent predictors of time to first relapse on fingolimod were the number of relapses in the prior 6 months (hazard ratio [HR] 1.59 per relapse; p = 0.002) and a gap in treatment of 2-4 months compared to no gap (HR 2.10; p = 0.041).

CONCLUSIONS: RRs after switch to fingolimod were low in all patient groups. The strongest predictor of relapse on fingolimod was prior relapse activity. Based on our data, we recommend a maximum 2-month treatment gap for switches to fingolimod to decrease the hazard of relapse.

With more choices for multiple sclerosis (MS) disease-modifying therapies, data are urgently required to support clinical decisions regarding safe transitioning and sequencing of therapies. With over 7 years of clinical experience, natalizumab has been confirmed as highly effective in reducing MS disease activity. However, natalizumab carries a risk of progressive multifocal leukoencephalopathy (PML). The optimal length of natalizumab washout became the subject of intense consternation and debate. This study suggests a maximum of  of 8 weeks but on this subject ProfG has recently posted

MSBase and several smaller studies, which show that if you have a wash-out period when switching from natalizumab you are more likely to have a relapse than if you don't have a washout. Why? Natalizumab has a circulating half-life close to 2 weeks; the half-life describes the period of time it takes for the levels to drop by 50%. It therefore takes about 10-12 weeks (5-6 half lives) for natalizumab levels to drop to low enough levels to allow lymphocytes to start trafficking back into the brain and spinal cord. If these cells are autoimmune cells they will set-up an local inflammatory response and trigger a relapse. This process takes several weeks. This is why we see rebound disease activity (relapses or MRI activity) about 3-4 months after stopping natalizumab. Therefore it is not a good idea to stop natalizumab without starting another DMT to prevent this rebound. Unfortunately, interferon beta and GA have not proven to be very effective post-natalizumab. What about oral drugs? We don't have data yet on teriflunomide (Aubagio) or BG12 (Tecfidera). However, fingolimod has been studied and provided it is started with 8 weeks of stopping natalizumab it can prevent most of the rebound. The sooner you start it the better. At the Royal London Hospital we have adopted this practice for sometime now. If the switch is in a JCV positive MSers we do an MRI for new white matter lesions and lumbar puncture to analyse the spinal fluid for JCV DNA. If these test are clear the likelihood of asymptomatic PML is low and we start fingolimod. This typically occurs at around week 3 or 4 after the last infusion of natalizumab. As it takes about 6 weeks for fingolimod to take an effect by the time natalizumab is out of your system fingolimod is working."

"If you are being switched from natalizumab to fingolimod and your neurologist wants to do a prolonged washout ask him/her why?"

"What is most intriguing about stopping natalizumab is the rebound activity that is often very severe and greater than that what was seen prior to starting natalizumab. Why? I suggest you read my post from last year on this topic; it generated a lot of discussion about MS and its potential cause."

CoI: None