simple code to collapse rows in bash

Hello to the experts! I have a file that I'd like to collapse based on a common ID column, separated by a character delimiter.
example input

a 1 6 word1 uniq1
b 2 7 WORD2 uniq2
b 2 7 WORD2 uniq3
b 2 7 WORD2 uniq4
c 3 8 word4 uniq5
d 4 9 word5 uniq6
e 5 1 word6 uniq7

desired output

a 1 6 word1 uniq1
b 2 7 WORD2 uniq2;uniq3;uniq4
c 3 8 word4 uniq5
d 4 9 word5 uniq6
e 5 1 word6 uniq7

Note that column 4 contains the ID used to collapse, and column 5 are the strings to actually collapse with the delimter ";"
Help is sincerely appreciated!
Many thanks.

awk '{idx=$1 OFS $2 OFS $3 OFS $4}{a[idx]=(idx in a)?a[idx]";"$NF:$NF}END{for(i in a) print i,a}' myFile

vgersh99, thank you so much that works exactly as I wanted. Is it easily adaptable to choose any two columns, one as the ID column as one as the column to collapse?
Thank you.

you'll need to change the code for the 'idx' - right now I' taking columns/fields 1,2,3, and 4 as the unique key to 'merge/collapse' on.