For first comma:
sed '/,//' < file
If first comma is first character:
sed '/^,//' < file
REFERENCES
http://stackoverflow.com/questions/2478232/how-to-remove-first-comma-on-each-line-in-a-file
remove-last-character-line
:%s/.$//g
this will delete every last char on each line.
Replace bracket
:%s/(//g
REFERENCES
http://www.unix.com/shell-programming-scripting/10133-remove-last-character-line.html