Table 1. In Vitro Cytotoxicities of S-Methylated ADC Metabolites and the Oxidation Products of 12a (12a′ and 12a″).

	Cell Line IC50 (M)
metabolite	H1703	H1975	COLO-704
12a (n = 5)	2.3 × 10–12	2.5 × 10–12	3.0 × 10–12
12b (n = 3)	5.9 × 10–12	5.6 × 10–12	6.9 × 10–12
3b	3.7 × 10–12	4.1 × 10–12	5.1 × 10–12
12a′	3.1 × 10–10	8.4 × 10–10	8.2 × 10–10
12a″	6.3 × 10–10	2.1 × 10–10	3.6 × 10–10