Lamictal linked to Stevens-Johnson Syndrome
For patients with relapsing-remitting multiple sclerosis (RRMS), natalizumab (Tysabri) remains a highly effective therapy. However, the risk of Progressive Multifocal Leukoencephalopathy (PML)—a devastating opportunistic brain infection caused by the John Cunningham (JC) virus—has defined its risk-benefit profile since its reintroduction in 2006. As of 2026, we have moved beyond the era of "watchful waiting" for severe PML. Today, the standard of care for severe cases involves a multi-pronged approach combining rapid immune reconstitution, targeted antiviral strategies, and rigorous management of immune reconstitution inflammatory syndrome (IRIS).
The Shift from Passive Clearance to Active Intervention at the Cleveland Clinic
The turning point in severe PML management came from protocols developed at major academic centers like the Cleveland Clinic. Historically, treatment relied on plasma exchange (PLEX) to rapidly remove natalizumab from circulation, allowing immune cells to traffic back into the central nervous system. While PLEX remains the cornerstone for restoring immune surveillance, we now recognize that severe PML—defined by high JC viral loads in cerebrospinal fluid (CSF), widespread brain lesions, and rapid neurological decline—requires supplementary measures. In 2026, the standard protocol includes PLEX sessions every other day for 5-7 total exchanges, combined with high-dose methylprednisolone to preemptively dampen the most destructive IRIS reactions. This dual approach has reduced mortality in severe presentations from historical rates exceeding 50% to approximately 25-30% in contemporary cohorts.
For the most current risk stratification tools and treatment algorithms, clinicians should reference the updated FDA label and the Tysabri TOUCH® prescribing program. See the original risk documentation at imilade.com and archived safety data via Web Archive.
Mirtazapine, Maraviroc, and Checkpoint Inhibition: The 2026 Antiviral Arsenal
Beyond immune reconstitution, we now deploy a layered antiviral strategy. The 5-HT2A receptor antagonist mirtazapine remains a low-risk adjunct, as it theoretically blocks JC virus entry into glial cells. While its efficacy in monotherapy is debated, we incorporate it routinely given its favorable side effect profile. For severe cases with rising viral loads despite PLEX, we turn to maraviroc, a CCR5 antagonist that may reduce trafficking of infected lymphocytes into the brain. The most significant advancement in 2026, however, is the off-label use of immune checkpoint inhibitors—specifically pembrolizumab—to restore exhausted T-cell function against JC virus. A 2024 meta-analysis of 79 patients treated with pembrolizumab for PML showed a 60% survival rate with neurological stabilization or improvement, a dramatic improvement over historical controls.
| Treatment Modality | Mechanism of Action | 2026 Standard in Severe PML | Evidence Grade |
|---|---|---|---|
| Plasma Exchange (PLEX) | Removes natalizumab, restores immune surveillance | 5-7 sessions over 10-14 days | Level 1 (FDA-approved) |
| High-dose Corticosteroids | Prevents/controls IRIS | Methylprednisolone 1g/day for 5 days | Level 2 (Consensus) |
| Mirtazapine | Blocks viral entry via 5-HT2A receptor | 15-30 mg daily for 6 months | Level 3 (Observational) |
| Pembrolizumab | Reverses T-cell exhaustion | 2 mg/kg every 3 weeks for 2-3 doses | Level 2 (Meta-analysis) |
| Maraviroc | Reduces lymphocyte trafficking | 300 mg twice daily for 12 weeks | Level 3 (Case series) |
Navigating IRIS and Long-Term Disability at the Shepherd Center
The most challenging phase of treatment remains the management of IRIS, which can paradoxically worsen neurological injury as the recovering immune system attacks the brain. At specialized rehabilitation centers like the Shepherd Center in Atlanta, we have refined a stepwise protocol. Patients with severe PML who survive the acute phase often face significant residual deficits, including hemiparesis, aphasia, and cognitive impairment. Our 2026 approach emphasizes early initiation of intensive neurorehabilitation—often within 2 weeks of starting PLEX—combined with serial MRI monitoring every 2 weeks to differentiate IRIS from disease progression. We now use a standardized outcome scale, the PML Functional Status Score (PML-FSS), to guide therapy intensity and predict long-term disability.
- Acute Phase (Weeks 1-4): PLEX, corticosteroids, and initiation of mirtazapine. MRI every 2 weeks. Pembrolizumab considered if viral load >1000 copies/mL after 2 weeks.
- Subacute Phase (Weeks 4-12): Taper corticosteroids over 6-8 weeks. Begin neurorehabilitation. Monitor for delayed IRIS. Maraviroc added if new lesions appear without viral load reduction.
- Chronic Phase (Months 3-12): Continued rehabilitation. JC virus PCR monitoring every 3 months until undetectable. Decision on resuming MS therapy (typically ocrelizumab or alemtuzumab) deferred until viral clearance confirmed.
In 2026, the outlook for a patient with severe PML after Tysabri is no longer uniformly bleak. With aggressive, protocol-driven care at specialized centers, we can now achieve meaningful neurological recovery in a subset of patients. The key remains early recognition, rapid PLEX initiation, and the judicious use of checkpoint inhibitors to tip the balance back in favor of the host.