What happened

Shares of BioNTech (BNTX -2.07%) were sinking 14.5% as of 2:48 p.m. EDT on Thursday. The decline came after the German biotech announced the pricing of an upsized stock offering Wednesday evening.

So what

BioNTech said on Wednesday that it plans to sell 5.5 million American depositary shares (ADSs) at $93 per share. The transaction will generate gross proceeds of $511.5 million. The company had previously indicated that its stock offering would include 5 million ADSs.

$1 bill folded into an arrow that is pointing down

Image source: Getty Images.

The price tag reflects a 10.7% discount from the closing price of the biotech stock on Wednesday. This lower price virtually guaranteed a sell-off today.

However, BioNTech has enjoyed plenty of good news recently. The company and its partner, Pfizer (PFE 0.66%), announced positive results on Monday from a phase 1/2 study of COVID-19 vaccine candidate BNT162b1. On Wednesday, the two companies announced a deal to sell 100 million doses of its COVID-19 vaccine to the U.S. government for $1.95 billion, pending Food and Drug Administration authorization or approval.

Now what

BioNTech's stock offering is expected to close on July 27. The main thing to watch with the company, though, is the clinical progress for its BNT162 program. Pfizer and BioNTech plan to begin a phase 2b/3 clinical study later in July. The two companies hope to file for regulatory approval as early as October of this year.