Table 1.

Characteristics of low- and high-molecular-weight Rituximab/saporin-S6 immunotoxins.

Cnjugates	RIP/mAb Molar Ratio	Average Mw (kDa)	IC50 1 (M × 10−11)	Yield (%) 2
				mAb	RIP
LMW	1.93	210	7.31	37	5
HMW	3.60	510	19.9	16	4

¹ Concentration causing 50% inhibition of protein synthesis in a cell-free system (rabbit reticulocyte lysate). The IC₅₀ of native saporin-S6 is 5.24 × 10⁻¹¹ M. ² Amount of mAb and ribosome-inactivating protein (RIP) recovered in the conjugates, each expressed as a percentage of the starting protein amount.