As of August 31, 2022, 17 patients with R/R MM received zevor-cel infusion in the Phase 2 portion of the clinical trial and have been followed for a median of 113 days (range: 9 to 373). Of these 17 patients, five patients (29.4%) had extramedullary disease (EMD; ≥1 plasmacytoma) and nine patients (52.9%) had high-risk cytogenetic features. Patients were heavily pretreated with a median of six prior lines of therapy (range: 4 to 17). All patients were refractory to their last line of therapy. Prior to zevor-cel infusion, patients received lymphodepletion regimen of fludarabine (30mg/m² for three consecutive days) and cyclophosphamide (500mg/m² for two consecutive days).

Efficacy

In the 11 evaluable patients who had at least eight weeks follow-up, including four patients with EMD, the objective response rate was 100% (very good partial response, complete response, or stringent complete response) and responses deepened for patients with longer follow-up. Since all responses are ongoing, the median progression-free survival, median overall survival and median duration of response have not been reached, and the complete response/stringent complete response rate is not mature. All patients with available MRD results at week 4 were MRD negative by next-generation of sequencing.

Safety

No death occurred and no patient experienced Grade 3 or higher cytokine release syndrome. Cytokine release syndrome was observed in 10 of 17 patients (59%), all reported as Grade 1 or 2. One transient Grade 3 immune effector cell-associated neurotoxicity syndrome event was reported and the patient fully recovered; no neurological toxicity with parkinsonian features was observed. For the management of post-infusion symptoms, five of 17 patients (29%) received tocilizumab and one patient (5.9%) received corticosteroids. Notably, three patients have received outpatient zevor-cel treatment in this study, and the two patients were admitted into the hospital for symptom management for 1 or 2 days.