Fastest we have every had a manned spacecraft travel is 600,000 miles per day. That would take around 112 years to get to Proxima Centauri. Obviously a planet four times further is that much more difficult.
Bear in mind that our technology is so primitive we have trouble feeding and providing air for the lunar expeditions, and nobody can quite figure out how we could supply the Martian expedition which wold take over a year. Don't hold ya breath.
