Table 1.

Guanidinium hit series 1 SAR determined in the human sperm calcium influx assay.

Compound	R1	R2	IC50, μM
1a		H	5.4 ± 0.6
1b		H	9.1 ± 0.4
1c		H	67 ± 12
1d		H	> 100
1e			23 ± 6
1f			7.8*
1g			> 100
1h			26*
1i			8.1*
1j			> 100*

CatSper activated by 3 μM progesterone. IC₅₀ values are means ± SEM of 3 independent experiments.

^*IC₅₀ values are means of 2 independent experiments.