Status epilepticus is a rare complication of bispecific T-cell engager (BiTE) therapy as part of immune effector cell-associated neurotoxicity syndrome (ICANS), but seizures are usually generalized and non-convulsive in nature. Here we describe a case of super-refractory focal status epilepticus from talquetamab, a BiTE therapy targeting CD3 and GPRC5D.

67-year-old male with treatment-refractory multiple myeloma on maintenance talquetamab at 0.8 mg/kg who presented 15 days after receiving his first maintenance dose with encephalopathy, new-onset right upper extremity weakness, continuous rhythmic shaking of the right arm, and lip-smacking movements. He was diagnosed with epilepsia partialis continua arising from the left hemisphere. MRI brain with and without contrast showed diffusion-weighted imaging (DWI) restriction along the left frontal, temporal, and parietal cortices without enhancement, likely due to prolonged focal status epilepticus. He was intubated and placed on intravenous propofol. Continuous electroencephalography (EEG) showed frequent bursts of lateralized periodic discharges at 1 Hz over the left temporo-parietal region every 5-10 seconds. Lumbar puncture was remarkable for opening pressure 32 cm H₂O, 0 nucleated cells, protein 47 mg/mL, negative meningoencephalitis panel, negative oligoclonal bands, and myelin basic protein 8.67 ng/mL. He was placed on maximal doses of intravenous levetiracetam, lacosamide, and fosphenytoin, however continued to exhibit frequent clonic seizures of the right arm over the next 72 hours. He was treated with intravenous methylprednisolone 1000 mg daily for 5 days, intravenous immune globulin (IVIg) 1g/kg for 2 days, and anakinra 100 mg every 6 hours for 4 doses without meaningful recovery. Due to refractory ICANS, family elected to withdraw care and he passed away on day 24 after presentation.

Focal status epilepticus is a complication of advanced ICANS from talquetamab use, and it may respond poorly to steroids, IVIg, and anakinra.