Ethnic Sensitivity Assessment of Mosunetuzumab Pharmacokinetics and Pharmacodynamics in Chinese Patients With Relapsed or Refractory Follicular Lymphoma

Mosunetuzumab, a CD20 × CD3 T-cell-engaging bispecific antibody, redirects T cells to eliminate malignant B cells. The purpose of YO43555 was to assess the pharmacokinetics (PK), safety, tolerability, and efficacy of mosunetuzumab as a single agent in Chinese patients with relapsed/refractory follicular lymphoma (R/R FL). The impact of ethnicity/region on the PK disposition of mosunetuzumab was assessed by non-compartmental analysis (NCA) as well as a population PK (popPK) approach. A previously established popPK model for intravenous mosunetuzumab, built from the global Phase I/II study GO29781, was externally validated with the PK data from study YO43555. Results from the PK analysis showed that the global popPK model adequately captured the individual PK of the Chinese population. The model predicted mosunetuzumab exposure metrics in Chinese patients were similar to those observed in Asian patients in the GO29781 R/R FL subpopulation with the same dose regimen, while the exposure differences between Chinese and Non-Asians from the global population were < 20%. An overlay of the exposure levels for Chinese patients on the established E-R relationship in global patients indicated that the mosunetuzumab exposure of Chinese patients remained within the established bounds for clinical safety and efficacy. The cytokine biomarkers IL-6 and TNF-α showed similar time-course patterns of release as observed in globally enrolled patients. In summary, mosunetuzumab PK disposition did not show significant ethnic sensitivity that would impact patient outcomes. Therefore, dose adjustment of the globally approved mosunetuzumab regimen is not warranted for Chinese patients with R/R FL. Trial Registration: ClinicalTrials.gov identifier: NCT02500407.