You can use complete.cases in the following manner:
final[complete.cases(final), ]
             u       v    w    x    y    z
2 ABCD00000198674    0    2    2    2    2
6 ABCD00000220312    0    1    2    3    2
na.omit can also be chosen to remove all NA's. Also it is better than complete.cases as complete.cases allows partial selection i.e. it includes certain columns of the dataframe:
final[complete.cases(final[ , 5:6]),]
             u       v    w    x    y    z
2 ABCD00000198674    0    2    2    2    2
4 ABCD00000200604    0   NA   NA    1    2
6 ENSG00000220312    0    1    2    3    2
This is not the solution you want right? So to use is.na you have to use something like this:
final[rowSums(is.na(final[ , 5:6])) == 0, ]
             u       v    w    x    y    z
2 ABCD00000198674    0    2    2    2    2
4 ABCD00000200604    0   NA   NA    1    2
6 ABCD00000220312    0    1    2    3    2