These bookish vishkanya are not satisfied with the potency of their natural venom, and seek alchemical means to enhance the poisonous properties found in their various bodily fluids.
Toxigen: Once per day, a venomyst can create a toxigen that increases the damage of their toxin to 1d6 dex (instead of the normal 1d2). A venomyst under the effect of a toxigen may envenom a weapon an additional number of times per day equal to her Intelligence bonus and gains no negative effects when she makes a successful save versus poison. The toxigen lasts for ten minutes per alchemist level. This replaces Mutagen.
Seems pretty powerful, especially targeting a stat like that. Even the plague bringer archetype which can coat weapons with a disease only causes sickness. If you're doing stat damage like that, then the opponent should get a good save against it or it should require a certain level (like 10) before the character can get it.
What you've got here is an ability to coat a weapon with poisons for a number of times per day equal to con modifier + int modifier, that does 1d6 dex damage per round for 6 rounds on a fort save DC 10 + 1/2 level + con mod. A few mutagens that up con can easily make this DC in the high teens or even into the 20s at mid range levels. That could kill full PCs with one hit, especially wizards and other non fort save classes. Too powerful for a poison, in my opinion; especially compared to other poisons in pathfinder. The closest in game poison that does this cost 2500gp per dose; and this ability is free for multiple times per day.
How about eliminating the Int bonus addition and making it so the Toxigen can't be used with a mutagen?
With that adjustment, I'd probably allow it in my game. Just remember that poisons on weapons go away after the first attack (even if you miss).
Another option would be to make it require 2 saves, but keep it at 1d2; or increase the duration and lee it at 1d2. Or scale it; damage increases to 1d4, and at some higher level it goes up to 1d6.