Can Kench's W save allies from Karthus ult?

I was playing Tahm Kench support against a Karthus the other day. The Karthus ended up being quite far behind, so he didn't really have enough damage to kill anyone, but it made me wonder whether or not Kench's W can save allies from Karthus's ult. Nobody seems to really play Karthus so I've never had the chance to see if it's actually effective in negating the damage.