Table 2. Surface expression of CD19 and EC₅₀ values for RDL by SPM-1 with different malignant B lymphoid cell lines as targets.

Cell Line	Subtype of malignancy	CD19 density [#]	EC50 (range) [pM]
SEM	Pro-B (mixed lineage)	42,600 ± 10,700	5.6 (2.5 – 10)
NALM-6	Pre-B	26,700 ± 11,400	6.1 (1.8 – 17.3)
RAJI	Burkitt's Lymphoma	31,900 ± 22,800	16.5 (5.4 – 38.5)
ARH-77	Mature B (myeloma)	2,400 ± 1,200	79.4 (38 – 645.3)

Antigen densities are given in copy numbers per cell.