Catalyzes the NADPH-dependent reduction of ketopantoate into pantoic acid. (R)-pantoate + NADP(+) = 2-dehydropantoate + H(+) + NADPH Cofactor biosynthesis; (R)-pantothenate biosynthesis; (R)-pantoate from 3-methyl-2-oxobutanoate: step 2/2. Monomer. Belongs to the ketopantoate reductase family.