ELYM - I didn't notice until your post. No PR, or anything on the news front. Just the SEC filing. The company being acquired is this (which is no detail at all...):
"representatives of the Issuer and a development stage private biotechnology company that is majority-owned by funds affiliated with RA Capital (“Tango”)"
So another biotech company. After they issue shares, they say the enterprise value will be ~$110M, so "Tango" is worth $20M (according to them). And then ELYM had $107M cash on hand (at the end of last Q at least). So could be trading for cash.
Price action probably all depends on the PR they put out and what type of biotech the acquisition is.
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