Table 2

Levels of free drug release in CD21high and CD21low lymphoma cell lines

Cell lineRituximab-resistantPercentage of total ADC turnover
Ramos (CD21low)No22
R-Ramos (CD21low)Yes21
Daudi (CD21high)No26
Raji (CD21high)No25
Raji-2R (CD21high)Yes19
Raji-4RH (CD21high)Yes26
  • Rituximab-resistant (Raji-2R, -4RH, R-Ramos) or -sensitive (Ramos, Daudi) cells were treated with hBU12-vcMMAE made with radioactively labeled MMAE (hBU12-vcMMAE*, ∼ 4 drugs/mAb). The total amount of released MMAE over time was determined by methanol precipitation and liquid scintillation counting, providing the nmol of drug released per volume of cell culture. Data are expressed as percentage ADC cleaved relative to the total amount of ADC added to the cells. Comparable levels of released free MMAE and total ADC turned over were observed in all cell lines tested. Data shown represent the mean of 2 replicates of one representative of 2 independent experiments.