Several lawsuits pending. Congress actually screwed up and left a loophole that may well leave them vulnerable here.
Dime store version: usually can’t mAke out a takings claim in context of voluntary program. Here, an incredibly confiscatory excise tax applies (1600% of all sales for failure to negotiate or agree to price on a single drug) unless you agree to cms final offer or get out of all programs. But, they wrote it in a way that essentially you can’t get out of all programs before the tax applies, for at least some period of time.