How to get rid of the repetitive commas of a R string

I have an R string looks like:

0B5P4ZZ, 0B9P40Z, , , , , , , , , , , , , , , , , , , , , , , , , , , ,

How can I get rid of the space-commas at the end of this string so that it looks like the following?

0B5P4ZZ, 0B9P40Z

Thanks!

>Solution :

Another solution:

str_remove_all(s, "(, )+$")